Source file src/go/types/api_test.go

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package types_test
     6  
     7  import (
     8  	"errors"
     9  	"fmt"
    10  	"go/ast"
    11  	"go/importer"
    12  	"go/parser"
    13  	"go/token"
    14  	"internal/goversion"
    15  	"internal/testenv"
    16  	"slices"
    17  	"strings"
    18  	"sync"
    19  	"testing"
    20  
    21  	. "go/types"
    22  )
    23  
    24  // nopos indicates an unknown position
    25  var nopos token.Pos
    26  
    27  func mustParse(fset *token.FileSet, src string) *ast.File {
    28  	f, err := parser.ParseFile(fset, pkgName(src), src, parser.ParseComments)
    29  	if err != nil {
    30  		panic(err) // so we don't need to pass *testing.T
    31  	}
    32  	return f
    33  }
    34  
    35  func typecheck(src string, conf *Config, info *Info) (*Package, error) {
    36  	fset := token.NewFileSet()
    37  	f := mustParse(fset, src)
    38  	if conf == nil {
    39  		conf = &Config{
    40  			Error:    func(err error) {}, // collect all errors
    41  			Importer: importer.Default(),
    42  		}
    43  	}
    44  	return conf.Check(f.Name.Name, fset, []*ast.File{f}, info)
    45  }
    46  
    47  func mustTypecheck(src string, conf *Config, info *Info) *Package {
    48  	pkg, err := typecheck(src, conf, info)
    49  	if err != nil {
    50  		panic(err) // so we don't need to pass *testing.T
    51  	}
    52  	return pkg
    53  }
    54  
    55  // pkgName extracts the package name from src, which must contain a package header.
    56  func pkgName(src string) string {
    57  	const kw = "package "
    58  	if i := strings.Index(src, kw); i >= 0 {
    59  		after := src[i+len(kw):]
    60  		n := len(after)
    61  		if i := strings.IndexAny(after, "\n\t ;/"); i >= 0 {
    62  			n = i
    63  		}
    64  		return after[:n]
    65  	}
    66  	panic("missing package header: " + src)
    67  }
    68  
    69  func TestValuesInfo(t *testing.T) {
    70  	var tests = []struct {
    71  		src  string
    72  		expr string // constant expression
    73  		typ  string // constant type
    74  		val  string // constant value
    75  	}{
    76  		{`package a0; const _ = false`, `false`, `untyped bool`, `false`},
    77  		{`package a1; const _ = 0`, `0`, `untyped int`, `0`},
    78  		{`package a2; const _ = 'A'`, `'A'`, `untyped rune`, `65`},
    79  		{`package a3; const _ = 0.`, `0.`, `untyped float`, `0`},
    80  		{`package a4; const _ = 0i`, `0i`, `untyped complex`, `(0 + 0i)`},
    81  		{`package a5; const _ = "foo"`, `"foo"`, `untyped string`, `"foo"`},
    82  
    83  		{`package b0; var _ = false`, `false`, `bool`, `false`},
    84  		{`package b1; var _ = 0`, `0`, `int`, `0`},
    85  		{`package b2; var _ = 'A'`, `'A'`, `rune`, `65`},
    86  		{`package b3; var _ = 0.`, `0.`, `float64`, `0`},
    87  		{`package b4; var _ = 0i`, `0i`, `complex128`, `(0 + 0i)`},
    88  		{`package b5; var _ = "foo"`, `"foo"`, `string`, `"foo"`},
    89  
    90  		{`package c0a; var _ = bool(false)`, `false`, `bool`, `false`},
    91  		{`package c0b; var _ = bool(false)`, `bool(false)`, `bool`, `false`},
    92  		{`package c0c; type T bool; var _ = T(false)`, `T(false)`, `c0c.T`, `false`},
    93  
    94  		{`package c1a; var _ = int(0)`, `0`, `int`, `0`},
    95  		{`package c1b; var _ = int(0)`, `int(0)`, `int`, `0`},
    96  		{`package c1c; type T int; var _ = T(0)`, `T(0)`, `c1c.T`, `0`},
    97  
    98  		{`package c2a; var _ = rune('A')`, `'A'`, `rune`, `65`},
    99  		{`package c2b; var _ = rune('A')`, `rune('A')`, `rune`, `65`},
   100  		{`package c2c; type T rune; var _ = T('A')`, `T('A')`, `c2c.T`, `65`},
   101  
   102  		{`package c3a; var _ = float32(0.)`, `0.`, `float32`, `0`},
   103  		{`package c3b; var _ = float32(0.)`, `float32(0.)`, `float32`, `0`},
   104  		{`package c3c; type T float32; var _ = T(0.)`, `T(0.)`, `c3c.T`, `0`},
   105  
   106  		{`package c4a; var _ = complex64(0i)`, `0i`, `complex64`, `(0 + 0i)`},
   107  		{`package c4b; var _ = complex64(0i)`, `complex64(0i)`, `complex64`, `(0 + 0i)`},
   108  		{`package c4c; type T complex64; var _ = T(0i)`, `T(0i)`, `c4c.T`, `(0 + 0i)`},
   109  
   110  		{`package c5a; var _ = string("foo")`, `"foo"`, `string`, `"foo"`},
   111  		{`package c5b; var _ = string("foo")`, `string("foo")`, `string`, `"foo"`},
   112  		{`package c5c; type T string; var _ = T("foo")`, `T("foo")`, `c5c.T`, `"foo"`},
   113  		{`package c5d; var _ = string(65)`, `65`, `untyped int`, `65`},
   114  		{`package c5e; var _ = string('A')`, `'A'`, `untyped rune`, `65`},
   115  		{`package c5f; type T string; var _ = T('A')`, `'A'`, `untyped rune`, `65`},
   116  
   117  		{`package d0; var _ = []byte("foo")`, `"foo"`, `string`, `"foo"`},
   118  		{`package d1; var _ = []byte(string("foo"))`, `"foo"`, `string`, `"foo"`},
   119  		{`package d2; var _ = []byte(string("foo"))`, `string("foo")`, `string`, `"foo"`},
   120  		{`package d3; type T []byte; var _ = T("foo")`, `"foo"`, `string`, `"foo"`},
   121  
   122  		{`package e0; const _ = float32( 1e-200)`, `float32(1e-200)`, `float32`, `0`},
   123  		{`package e1; const _ = float32(-1e-200)`, `float32(-1e-200)`, `float32`, `0`},
   124  		{`package e2; const _ = float64( 1e-2000)`, `float64(1e-2000)`, `float64`, `0`},
   125  		{`package e3; const _ = float64(-1e-2000)`, `float64(-1e-2000)`, `float64`, `0`},
   126  		{`package e4; const _ = complex64( 1e-200)`, `complex64(1e-200)`, `complex64`, `(0 + 0i)`},
   127  		{`package e5; const _ = complex64(-1e-200)`, `complex64(-1e-200)`, `complex64`, `(0 + 0i)`},
   128  		{`package e6; const _ = complex128( 1e-2000)`, `complex128(1e-2000)`, `complex128`, `(0 + 0i)`},
   129  		{`package e7; const _ = complex128(-1e-2000)`, `complex128(-1e-2000)`, `complex128`, `(0 + 0i)`},
   130  
   131  		{`package f0 ; var _ float32 =  1e-200`, `1e-200`, `float32`, `0`},
   132  		{`package f1 ; var _ float32 = -1e-200`, `-1e-200`, `float32`, `0`},
   133  		{`package f2a; var _ float64 =  1e-2000`, `1e-2000`, `float64`, `0`},
   134  		{`package f3a; var _ float64 = -1e-2000`, `-1e-2000`, `float64`, `0`},
   135  		{`package f2b; var _         =  1e-2000`, `1e-2000`, `float64`, `0`},
   136  		{`package f3b; var _         = -1e-2000`, `-1e-2000`, `float64`, `0`},
   137  		{`package f4 ; var _ complex64  =  1e-200 `, `1e-200`, `complex64`, `(0 + 0i)`},
   138  		{`package f5 ; var _ complex64  = -1e-200 `, `-1e-200`, `complex64`, `(0 + 0i)`},
   139  		{`package f6a; var _ complex128 =  1e-2000i`, `1e-2000i`, `complex128`, `(0 + 0i)`},
   140  		{`package f7a; var _ complex128 = -1e-2000i`, `-1e-2000i`, `complex128`, `(0 + 0i)`},
   141  		{`package f6b; var _            =  1e-2000i`, `1e-2000i`, `complex128`, `(0 + 0i)`},
   142  		{`package f7b; var _            = -1e-2000i`, `-1e-2000i`, `complex128`, `(0 + 0i)`},
   143  
   144  		{`package g0; const (a = len([iota]int{}); b; c); const _ = c`, `c`, `int`, `2`}, // go.dev/issue/22341
   145  		{`package g1; var(j int32; s int; n = 1.0<<s == j)`, `1.0`, `int32`, `1`},        // go.dev/issue/48422
   146  	}
   147  
   148  	for _, test := range tests {
   149  		info := Info{
   150  			Types: make(map[ast.Expr]TypeAndValue),
   151  		}
   152  		name := mustTypecheck(test.src, nil, &info).Name()
   153  
   154  		// look for expression
   155  		var expr ast.Expr
   156  		for e := range info.Types {
   157  			if ExprString(e) == test.expr {
   158  				expr = e
   159  				break
   160  			}
   161  		}
   162  		if expr == nil {
   163  			t.Errorf("package %s: no expression found for %s", name, test.expr)
   164  			continue
   165  		}
   166  		tv := info.Types[expr]
   167  
   168  		// check that type is correct
   169  		if got := tv.Type.String(); got != test.typ {
   170  			t.Errorf("package %s: got type %s; want %s", name, got, test.typ)
   171  			continue
   172  		}
   173  
   174  		// if we have a constant, check that value is correct
   175  		if tv.Value != nil {
   176  			if got := tv.Value.ExactString(); got != test.val {
   177  				t.Errorf("package %s: got value %s; want %s", name, got, test.val)
   178  			}
   179  		} else {
   180  			if test.val != "" {
   181  				t.Errorf("package %s: no constant found; want %s", name, test.val)
   182  			}
   183  		}
   184  	}
   185  }
   186  
   187  func TestTypesInfo(t *testing.T) {
   188  	// Test sources that are not expected to typecheck must start with the broken prefix.
   189  	const broken = "package broken_"
   190  
   191  	var tests = []struct {
   192  		src  string
   193  		expr string // expression
   194  		typ  string // value type
   195  	}{
   196  		// single-valued expressions of untyped constants
   197  		{`package b0; var x interface{} = false`, `false`, `bool`},
   198  		{`package b1; var x interface{} = 0`, `0`, `int`},
   199  		{`package b2; var x interface{} = 0.`, `0.`, `float64`},
   200  		{`package b3; var x interface{} = 0i`, `0i`, `complex128`},
   201  		{`package b4; var x interface{} = "foo"`, `"foo"`, `string`},
   202  
   203  		// uses of nil
   204  		{`package n0; var _ *int = nil`, `nil`, `untyped nil`},
   205  		{`package n1; var _ func() = nil`, `nil`, `untyped nil`},
   206  		{`package n2; var _ []byte = nil`, `nil`, `untyped nil`},
   207  		{`package n3; var _ map[int]int = nil`, `nil`, `untyped nil`},
   208  		{`package n4; var _ chan int = nil`, `nil`, `untyped nil`},
   209  		{`package n5; var _ interface{} = nil`, `nil`, `untyped nil`},
   210  		{`package n6; import "unsafe"; var _ unsafe.Pointer = nil`, `nil`, `untyped nil`},
   211  
   212  		{`package n10; var (x *int; _ = x == nil)`, `nil`, `untyped nil`},
   213  		{`package n11; var (x func(); _ = x == nil)`, `nil`, `untyped nil`},
   214  		{`package n12; var (x []byte; _ = x == nil)`, `nil`, `untyped nil`},
   215  		{`package n13; var (x map[int]int; _ = x == nil)`, `nil`, `untyped nil`},
   216  		{`package n14; var (x chan int; _ = x == nil)`, `nil`, `untyped nil`},
   217  		{`package n15; var (x interface{}; _ = x == nil)`, `nil`, `untyped nil`},
   218  		{`package n15; import "unsafe"; var (x unsafe.Pointer; _ = x == nil)`, `nil`, `untyped nil`},
   219  
   220  		{`package n20; var _ = (*int)(nil)`, `nil`, `untyped nil`},
   221  		{`package n21; var _ = (func())(nil)`, `nil`, `untyped nil`},
   222  		{`package n22; var _ = ([]byte)(nil)`, `nil`, `untyped nil`},
   223  		{`package n23; var _ = (map[int]int)(nil)`, `nil`, `untyped nil`},
   224  		{`package n24; var _ = (chan int)(nil)`, `nil`, `untyped nil`},
   225  		{`package n25; var _ = (interface{})(nil)`, `nil`, `untyped nil`},
   226  		{`package n26; import "unsafe"; var _ = unsafe.Pointer(nil)`, `nil`, `untyped nil`},
   227  
   228  		{`package n30; func f(*int) { f(nil) }`, `nil`, `untyped nil`},
   229  		{`package n31; func f(func()) { f(nil) }`, `nil`, `untyped nil`},
   230  		{`package n32; func f([]byte) { f(nil) }`, `nil`, `untyped nil`},
   231  		{`package n33; func f(map[int]int) { f(nil) }`, `nil`, `untyped nil`},
   232  		{`package n34; func f(chan int) { f(nil) }`, `nil`, `untyped nil`},
   233  		{`package n35; func f(interface{}) { f(nil) }`, `nil`, `untyped nil`},
   234  		{`package n35; import "unsafe"; func f(unsafe.Pointer) { f(nil) }`, `nil`, `untyped nil`},
   235  
   236  		// comma-ok expressions
   237  		{`package p0; var x interface{}; var _, _ = x.(int)`,
   238  			`x.(int)`,
   239  			`(int, bool)`,
   240  		},
   241  		{`package p1; var x interface{}; func _() { _, _ = x.(int) }`,
   242  			`x.(int)`,
   243  			`(int, bool)`,
   244  		},
   245  		{`package p2a; type mybool bool; var m map[string]complex128; var b mybool; func _() { _, b = m["foo"] }`,
   246  			`m["foo"]`,
   247  			`(complex128, p2a.mybool)`,
   248  		},
   249  		{`package p2b; var m map[string]complex128; var b bool; func _() { _, b = m["foo"] }`,
   250  			`m["foo"]`,
   251  			`(complex128, bool)`,
   252  		},
   253  		{`package p3; var c chan string; var _, _ = <-c`,
   254  			`<-c`,
   255  			`(string, bool)`,
   256  		},
   257  
   258  		// go.dev/issue/6796
   259  		{`package issue6796_a; var x interface{}; var _, _ = (x.(int))`,
   260  			`x.(int)`,
   261  			`(int, bool)`,
   262  		},
   263  		{`package issue6796_b; var c chan string; var _, _ = (<-c)`,
   264  			`(<-c)`,
   265  			`(string, bool)`,
   266  		},
   267  		{`package issue6796_c; var c chan string; var _, _ = (<-c)`,
   268  			`<-c`,
   269  			`(string, bool)`,
   270  		},
   271  		{`package issue6796_d; var c chan string; var _, _ = ((<-c))`,
   272  			`(<-c)`,
   273  			`(string, bool)`,
   274  		},
   275  		{`package issue6796_e; func f(c chan string) { _, _ = ((<-c)) }`,
   276  			`(<-c)`,
   277  			`(string, bool)`,
   278  		},
   279  
   280  		// go.dev/issue/7060
   281  		{`package issue7060_a; var ( m map[int]string; x, ok = m[0] )`,
   282  			`m[0]`,
   283  			`(string, bool)`,
   284  		},
   285  		{`package issue7060_b; var ( m map[int]string; x, ok interface{} = m[0] )`,
   286  			`m[0]`,
   287  			`(string, bool)`,
   288  		},
   289  		{`package issue7060_c; func f(x interface{}, ok bool, m map[int]string) { x, ok = m[0] }`,
   290  			`m[0]`,
   291  			`(string, bool)`,
   292  		},
   293  		{`package issue7060_d; var ( ch chan string; x, ok = <-ch )`,
   294  			`<-ch`,
   295  			`(string, bool)`,
   296  		},
   297  		{`package issue7060_e; var ( ch chan string; x, ok interface{} = <-ch )`,
   298  			`<-ch`,
   299  			`(string, bool)`,
   300  		},
   301  		{`package issue7060_f; func f(x interface{}, ok bool, ch chan string) { x, ok = <-ch }`,
   302  			`<-ch`,
   303  			`(string, bool)`,
   304  		},
   305  
   306  		// go.dev/issue/28277
   307  		{`package issue28277_a; func f(...int)`,
   308  			`...int`,
   309  			`[]int`,
   310  		},
   311  		{`package issue28277_b; func f(a, b int, c ...[]struct{})`,
   312  			`...[]struct{}`,
   313  			`[][]struct{}`,
   314  		},
   315  
   316  		// go.dev/issue/47243
   317  		{`package issue47243_a; var x int32; var _ = x << 3`, `3`, `untyped int`},
   318  		{`package issue47243_b; var x int32; var _ = x << 3.`, `3.`, `untyped float`},
   319  		{`package issue47243_c; var x int32; var _ = 1 << x`, `1 << x`, `int`},
   320  		{`package issue47243_d; var x int32; var _ = 1 << x`, `1`, `int`},
   321  		{`package issue47243_e; var x int32; var _ = 1 << 2`, `1`, `untyped int`},
   322  		{`package issue47243_f; var x int32; var _ = 1 << 2`, `2`, `untyped int`},
   323  		{`package issue47243_g; var x int32; var _ = int(1) << 2`, `2`, `untyped int`},
   324  		{`package issue47243_h; var x int32; var _ = 1 << (2 << x)`, `1`, `int`},
   325  		{`package issue47243_i; var x int32; var _ = 1 << (2 << x)`, `(2 << x)`, `untyped int`},
   326  		{`package issue47243_j; var x int32; var _ = 1 << (2 << x)`, `2`, `untyped int`},
   327  
   328  		// tests for broken code that doesn't type-check
   329  		{broken + `x0; func _() { var x struct {f string}; x.f := 0 }`, `x.f`, `string`},
   330  		{broken + `x1; func _() { var z string; type x struct {f string}; y := &x{q: z}}`, `z`, `string`},
   331  		{broken + `x2; func _() { var a, b string; type x struct {f string}; z := &x{f: a, f: b,}}`, `b`, `string`},
   332  		{broken + `x3; var x = panic("");`, `panic`, `func(interface{})`},
   333  		{`package x4; func _() { panic("") }`, `panic`, `func(interface{})`},
   334  		{broken + `x5; func _() { var x map[string][...]int; x = map[string][...]int{"": {1,2,3}} }`, `x`, `map[string]invalid type`},
   335  
   336  		// parameterized functions
   337  		{`package p0; func f[T any](T) {}; var _ = f[int]`, `f`, `func[T any](T)`},
   338  		{`package p1; func f[T any](T) {}; var _ = f[int]`, `f[int]`, `func(int)`},
   339  		{`package p2; func f[T any](T) {}; func _() { f(42) }`, `f`, `func(int)`},
   340  		{`package p3; func f[T any](T) {}; func _() { f[int](42) }`, `f[int]`, `func(int)`},
   341  		{`package p4; func f[T any](T) {}; func _() { f[int](42) }`, `f`, `func[T any](T)`},
   342  		{`package p5; func f[T any](T) {}; func _() { f(42) }`, `f(42)`, `()`},
   343  
   344  		// type parameters
   345  		{`package t0; type t[] int; var _ t`, `t`, `t0.t`}, // t[] is a syntax error that is ignored in this test in favor of t
   346  		{`package t1; type t[P any] int; var _ t[int]`, `t`, `t1.t[P any]`},
   347  		{`package t2; type t[P interface{}] int; var _ t[int]`, `t`, `t2.t[P interface{}]`},
   348  		{`package t3; type t[P, Q interface{}] int; var _ t[int, int]`, `t`, `t3.t[P, Q interface{}]`},
   349  		{broken + `t4; type t[P, Q interface{ m() }] int; var _ t[int, int]`, `t`, `broken_t4.t[P, Q interface{m()}]`},
   350  
   351  		// instantiated types must be sanitized
   352  		{`package g0; type t[P any] int; var x struct{ f t[int] }; var _ = x.f`, `x.f`, `g0.t[int]`},
   353  
   354  		// go.dev/issue/45096
   355  		{`package issue45096; func _[T interface{ ~int8 | ~int16 | ~int32  }](x T) { _ = x < 0 }`, `0`, `T`},
   356  
   357  		// go.dev/issue/47895
   358  		{`package p; import "unsafe"; type S struct { f int }; var s S; var _ = unsafe.Offsetof(s.f)`, `s.f`, `int`},
   359  
   360  		// go.dev/issue/50093
   361  		{`package u0a; func _[_ interface{int}]() {}`, `int`, `int`},
   362  		{`package u1a; func _[_ interface{~int}]() {}`, `~int`, `~int`},
   363  		{`package u2a; func _[_ interface{int | string}]() {}`, `int | string`, `int | string`},
   364  		{`package u3a; func _[_ interface{int | string | ~bool}]() {}`, `int | string | ~bool`, `int | string | ~bool`},
   365  		{`package u3a; func _[_ interface{int | string | ~bool}]() {}`, `int | string`, `int | string`},
   366  		{`package u3a; func _[_ interface{int | string | ~bool}]() {}`, `~bool`, `~bool`},
   367  		{`package u3a; func _[_ interface{int | string | ~float64|~bool}]() {}`, `int | string | ~float64`, `int | string | ~float64`},
   368  
   369  		{`package u0b; func _[_ int]() {}`, `int`, `int`},
   370  		{`package u1b; func _[_ ~int]() {}`, `~int`, `~int`},
   371  		{`package u2b; func _[_ int | string]() {}`, `int | string`, `int | string`},
   372  		{`package u3b; func _[_ int | string | ~bool]() {}`, `int | string | ~bool`, `int | string | ~bool`},
   373  		{`package u3b; func _[_ int | string | ~bool]() {}`, `int | string`, `int | string`},
   374  		{`package u3b; func _[_ int | string | ~bool]() {}`, `~bool`, `~bool`},
   375  		{`package u3b; func _[_ int | string | ~float64|~bool]() {}`, `int | string | ~float64`, `int | string | ~float64`},
   376  
   377  		{`package u0c; type _ interface{int}`, `int`, `int`},
   378  		{`package u1c; type _ interface{~int}`, `~int`, `~int`},
   379  		{`package u2c; type _ interface{int | string}`, `int | string`, `int | string`},
   380  		{`package u3c; type _ interface{int | string | ~bool}`, `int | string | ~bool`, `int | string | ~bool`},
   381  		{`package u3c; type _ interface{int | string | ~bool}`, `int | string`, `int | string`},
   382  		{`package u3c; type _ interface{int | string | ~bool}`, `~bool`, `~bool`},
   383  		{`package u3c; type _ interface{int | string | ~float64|~bool}`, `int | string | ~float64`, `int | string | ~float64`},
   384  
   385  		// reverse type inference
   386  		{`package r1; var _ func(int) = g; func g[P any](P) {}`, `g`, `func(int)`},
   387  		{`package r2; var _ func(int) = g[int]; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
   388  		{`package r3; var _ func(int) = g[int]; func g[P any](P) {}`, `g[int]`, `func(int)`},
   389  		{`package r4; var _ func(int, string) = g; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
   390  		{`package r5; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
   391  		{`package r6; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
   392  
   393  		{`package s1; func _() { f(g) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func(int)`},
   394  		{`package s2; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
   395  		{`package s3; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g[int]`, `func(int)`},
   396  		{`package s4; func _() { f(g) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
   397  		{`package s5; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
   398  		{`package s6; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
   399  
   400  		{`package s7; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `g`, `func(int, int)`},
   401  		{`package s8; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func(int, string)`},
   402  		{`package s9; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
   403  		{`package s10; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h[int]`, `func(int, string)`},
   404  
   405  		// go.dev/issue/68639
   406  		// parenthesized and pointer type expressions in various positions
   407  		// - as variable type, not generic
   408  		{`package qa1; type T int; var x T`, `T`, `qa1.T`},
   409  		{`package qa2; type T int; var x (T)`, `T`, `qa2.T`},
   410  		{`package qa3; type T int; var x (T)`, `(T)`, `qa3.T`},
   411  		{`package qa4; type T int; var x ((T))`, `T`, `qa4.T`},
   412  		{`package qa5; type T int; var x ((T))`, `(T)`, `qa5.T`},
   413  		{`package qa6; type T int; var x ((T))`, `((T))`, `qa6.T`},
   414  		{`package qa7; type T int; var x *T`, `T`, `qa7.T`},
   415  		{`package qa8; type T int; var x *T`, `*T`, `*qa8.T`},
   416  		{`package qa9; type T int; var x (*T)`, `T`, `qa9.T`},
   417  		{`package qa10; type T int; var x (*T)`, `*T`, `*qa10.T`},
   418  		{`package qa11; type T int; var x *(T)`, `T`, `qa11.T`},
   419  		{`package qa12; type T int; var x *(T)`, `(T)`, `qa12.T`},
   420  		{`package qa13; type T int; var x *(T)`, `*(T)`, `*qa13.T`},
   421  		{`package qa14; type T int; var x (*(T))`, `(T)`, `qa14.T`},
   422  		{`package qa15; type T int; var x (*(T))`, `*(T)`, `*qa15.T`},
   423  		{`package qa16; type T int; var x (*(T))`, `(*(T))`, `*qa16.T`},
   424  
   425  		// - as ordinary function parameter, not generic
   426  		{`package qb1; type T int; func _(T)`, `T`, `qb1.T`},
   427  		{`package qb2; type T int; func _((T))`, `T`, `qb2.T`},
   428  		{`package qb3; type T int; func _((T))`, `(T)`, `qb3.T`},
   429  		{`package qb4; type T int; func _(((T)))`, `T`, `qb4.T`},
   430  		{`package qb5; type T int; func _(((T)))`, `(T)`, `qb5.T`},
   431  		{`package qb6; type T int; func _(((T)))`, `((T))`, `qb6.T`},
   432  		{`package qb7; type T int; func _(*T)`, `T`, `qb7.T`},
   433  		{`package qb8; type T int; func _(*T)`, `*T`, `*qb8.T`},
   434  		{`package qb9; type T int; func _((*T))`, `T`, `qb9.T`},
   435  		{`package qb10; type T int; func _((*T))`, `*T`, `*qb10.T`},
   436  		{`package qb11; type T int; func _(*(T))`, `T`, `qb11.T`},
   437  		{`package qb12; type T int; func _(*(T))`, `(T)`, `qb12.T`},
   438  		{`package qb13; type T int; func _(*(T))`, `*(T)`, `*qb13.T`},
   439  		{`package qb14; type T int; func _((*(T)))`, `(T)`, `qb14.T`},
   440  		{`package qb15; type T int; func _((*(T)))`, `*(T)`, `*qb15.T`},
   441  		{`package qb16; type T int; func _((*(T)))`, `(*(T))`, `*qb16.T`},
   442  
   443  		// - as method receiver, not generic
   444  		{`package qc1; type T int; func (T) _() {}`, `T`, `qc1.T`},
   445  		{`package qc2; type T int; func ((T)) _() {}`, `T`, `qc2.T`},
   446  		{`package qc3; type T int; func ((T)) _() {}`, `(T)`, `qc3.T`},
   447  		{`package qc4; type T int; func (((T))) _() {}`, `T`, `qc4.T`},
   448  		{`package qc5; type T int; func (((T))) _() {}`, `(T)`, `qc5.T`},
   449  		{`package qc6; type T int; func (((T))) _() {}`, `((T))`, `qc6.T`},
   450  		{`package qc7; type T int; func (*T) _() {}`, `T`, `qc7.T`},
   451  		{`package qc8; type T int; func (*T) _() {}`, `*T`, `*qc8.T`},
   452  		{`package qc9; type T int; func ((*T)) _() {}`, `T`, `qc9.T`},
   453  		{`package qc10; type T int; func ((*T)) _() {}`, `*T`, `*qc10.T`},
   454  		{`package qc11; type T int; func (*(T)) _() {}`, `T`, `qc11.T`},
   455  		{`package qc12; type T int; func (*(T)) _() {}`, `(T)`, `qc12.T`},
   456  		{`package qc13; type T int; func (*(T)) _() {}`, `*(T)`, `*qc13.T`},
   457  		{`package qc14; type T int; func ((*(T))) _() {}`, `(T)`, `qc14.T`},
   458  		{`package qc15; type T int; func ((*(T))) _() {}`, `*(T)`, `*qc15.T`},
   459  		{`package qc16; type T int; func ((*(T))) _() {}`, `(*(T))`, `*qc16.T`},
   460  
   461  		// - as variable type, generic
   462  		{`package qd1; type T[_ any] int; var x T[int]`, `T`, `qd1.T[_ any]`},
   463  		{`package qd2; type T[_ any] int; var x (T[int])`, `T[int]`, `qd2.T[int]`},
   464  		{`package qd3; type T[_ any] int; var x (T[int])`, `(T[int])`, `qd3.T[int]`},
   465  		{`package qd4; type T[_ any] int; var x ((T[int]))`, `T`, `qd4.T[_ any]`},
   466  		{`package qd5; type T[_ any] int; var x ((T[int]))`, `(T[int])`, `qd5.T[int]`},
   467  		{`package qd6; type T[_ any] int; var x ((T[int]))`, `((T[int]))`, `qd6.T[int]`},
   468  		{`package qd7; type T[_ any] int; var x *T[int]`, `T`, `qd7.T[_ any]`},
   469  		{`package qd8; type T[_ any] int; var x *T[int]`, `*T[int]`, `*qd8.T[int]`},
   470  		{`package qd9; type T[_ any] int; var x (*T[int])`, `T`, `qd9.T[_ any]`},
   471  		{`package qd10; type T[_ any] int; var x (*T[int])`, `*T[int]`, `*qd10.T[int]`},
   472  		{`package qd11; type T[_ any] int; var x *(T[int])`, `T[int]`, `qd11.T[int]`},
   473  		{`package qd12; type T[_ any] int; var x *(T[int])`, `(T[int])`, `qd12.T[int]`},
   474  		{`package qd13; type T[_ any] int; var x *(T[int])`, `*(T[int])`, `*qd13.T[int]`},
   475  		{`package qd14; type T[_ any] int; var x (*(T[int]))`, `(T[int])`, `qd14.T[int]`},
   476  		{`package qd15; type T[_ any] int; var x (*(T[int]))`, `*(T[int])`, `*qd15.T[int]`},
   477  		{`package qd16; type T[_ any] int; var x (*(T[int]))`, `(*(T[int]))`, `*qd16.T[int]`},
   478  
   479  		// - as ordinary function parameter, generic
   480  		{`package qe1; type T[_ any] int; func _(T[int])`, `T`, `qe1.T[_ any]`},
   481  		{`package qe2; type T[_ any] int; func _((T[int]))`, `T[int]`, `qe2.T[int]`},
   482  		{`package qe3; type T[_ any] int; func _((T[int]))`, `(T[int])`, `qe3.T[int]`},
   483  		{`package qe4; type T[_ any] int; func _(((T[int])))`, `T`, `qe4.T[_ any]`},
   484  		{`package qe5; type T[_ any] int; func _(((T[int])))`, `(T[int])`, `qe5.T[int]`},
   485  		{`package qe6; type T[_ any] int; func _(((T[int])))`, `((T[int]))`, `qe6.T[int]`},
   486  		{`package qe7; type T[_ any] int; func _(*T[int])`, `T`, `qe7.T[_ any]`},
   487  		{`package qe8; type T[_ any] int; func _(*T[int])`, `*T[int]`, `*qe8.T[int]`},
   488  		{`package qe9; type T[_ any] int; func _((*T[int]))`, `T`, `qe9.T[_ any]`},
   489  		{`package qe10; type T[_ any] int; func _((*T[int]))`, `*T[int]`, `*qe10.T[int]`},
   490  		{`package qe11; type T[_ any] int; func _(*(T[int]))`, `T[int]`, `qe11.T[int]`},
   491  		{`package qe12; type T[_ any] int; func _(*(T[int]))`, `(T[int])`, `qe12.T[int]`},
   492  		{`package qe13; type T[_ any] int; func _(*(T[int]))`, `*(T[int])`, `*qe13.T[int]`},
   493  		{`package qe14; type T[_ any] int; func _((*(T[int])))`, `(T[int])`, `qe14.T[int]`},
   494  		{`package qe15; type T[_ any] int; func _((*(T[int])))`, `*(T[int])`, `*qe15.T[int]`},
   495  		{`package qe16; type T[_ any] int; func _((*(T[int])))`, `(*(T[int]))`, `*qe16.T[int]`},
   496  
   497  		// - as method receiver, generic
   498  		{`package qf1; type T[_ any] int; func (T[_]) _() {}`, `T`, `qf1.T[_ any]`},
   499  		{`package qf2; type T[_ any] int; func ((T[_])) _() {}`, `T[_]`, `qf2.T[_]`},
   500  		{`package qf3; type T[_ any] int; func ((T[_])) _() {}`, `(T[_])`, `qf3.T[_]`},
   501  		{`package qf4; type T[_ any] int; func (((T[_]))) _() {}`, `T`, `qf4.T[_ any]`},
   502  		{`package qf5; type T[_ any] int; func (((T[_]))) _() {}`, `(T[_])`, `qf5.T[_]`},
   503  		{`package qf6; type T[_ any] int; func (((T[_]))) _() {}`, `((T[_]))`, `qf6.T[_]`},
   504  		{`package qf7; type T[_ any] int; func (*T[_]) _() {}`, `T`, `qf7.T[_ any]`},
   505  		{`package qf8; type T[_ any] int; func (*T[_]) _() {}`, `*T[_]`, `*qf8.T[_]`},
   506  		{`package qf9; type T[_ any] int; func ((*T[_])) _() {}`, `T`, `qf9.T[_ any]`},
   507  		{`package qf10; type T[_ any] int; func ((*T[_])) _() {}`, `*T[_]`, `*qf10.T[_]`},
   508  		{`package qf11; type T[_ any] int; func (*(T[_])) _() {}`, `T[_]`, `qf11.T[_]`},
   509  		{`package qf12; type T[_ any] int; func (*(T[_])) _() {}`, `(T[_])`, `qf12.T[_]`},
   510  		{`package qf13; type T[_ any] int; func (*(T[_])) _() {}`, `*(T[_])`, `*qf13.T[_]`},
   511  		{`package qf14; type T[_ any] int; func ((*(T[_]))) _() {}`, `(T[_])`, `qf14.T[_]`},
   512  		{`package qf15; type T[_ any] int; func ((*(T[_]))) _() {}`, `*(T[_])`, `*qf15.T[_]`},
   513  		{`package qf16; type T[_ any] int; func ((*(T[_]))) _() {}`, `(*(T[_]))`, `*qf16.T[_]`},
   514  
   515  		// For historic reasons, type parameters in receiver type expressions
   516  		// are considered both definitions and uses and thus also show up in
   517  		// the Info.Types map (see go.dev/issue/68670).
   518  		{`package t1; type T[_ any] int; func (T[P]) _() {}`, `P`, `P`},
   519  		{`package t2; type T[_, _ any] int; func (T[P, Q]) _() {}`, `P`, `P`},
   520  		{`package t3; type T[_, _ any] int; func (T[P, Q]) _() {}`, `Q`, `Q`},
   521  	}
   522  
   523  	for _, test := range tests {
   524  		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
   525  		var name string
   526  		if strings.HasPrefix(test.src, broken) {
   527  			pkg, err := typecheck(test.src, nil, &info)
   528  			if err == nil {
   529  				t.Errorf("package %s: expected to fail but passed", pkg.Name())
   530  				continue
   531  			}
   532  			if pkg != nil {
   533  				name = pkg.Name()
   534  			}
   535  		} else {
   536  			name = mustTypecheck(test.src, nil, &info).Name()
   537  		}
   538  
   539  		// look for expression type
   540  		var typ Type
   541  		for e, tv := range info.Types {
   542  			if ExprString(e) == test.expr {
   543  				typ = tv.Type
   544  				break
   545  			}
   546  		}
   547  		if typ == nil {
   548  			t.Errorf("package %s: no type found for %s", name, test.expr)
   549  			continue
   550  		}
   551  
   552  		// check that type is correct
   553  		if got := typ.String(); got != test.typ {
   554  			t.Errorf("package %s: expr = %s: got %s; want %s", name, test.expr, got, test.typ)
   555  		}
   556  	}
   557  }
   558  
   559  func TestInstanceInfo(t *testing.T) {
   560  	const lib = `package lib
   561  
   562  func F[P any](P) {}
   563  
   564  type T[P any] []P
   565  `
   566  
   567  	type testInst struct {
   568  		name  string
   569  		targs []string
   570  		typ   string
   571  	}
   572  
   573  	var tests = []struct {
   574  		src       string
   575  		instances []testInst // recorded instances in source order
   576  	}{
   577  		{`package p0; func f[T any](T) {}; func _() { f(42) }`,
   578  			[]testInst{{`f`, []string{`int`}, `func(int)`}},
   579  		},
   580  		{`package p1; func f[T any](T) T { panic(0) }; func _() { f('@') }`,
   581  			[]testInst{{`f`, []string{`rune`}, `func(rune) rune`}},
   582  		},
   583  		{`package p2; func f[T any](...T) T { panic(0) }; func _() { f(0i) }`,
   584  			[]testInst{{`f`, []string{`complex128`}, `func(...complex128) complex128`}},
   585  		},
   586  		{`package p3; func f[A, B, C any](A, *B, []C) {}; func _() { f(1.2, new(string), []byte{}) }`,
   587  			[]testInst{{`f`, []string{`float64`, `string`, `byte`}, `func(float64, *string, []byte)`}},
   588  		},
   589  		{`package p4; func f[A, B any](A, *B, ...[]B) {}; func _() { f(1.2, new(byte)) }`,
   590  			[]testInst{{`f`, []string{`float64`, `byte`}, `func(float64, *byte, ...[]byte)`}},
   591  		},
   592  
   593  		{`package s1; func f[T any, P interface{*T}](x T) {}; func _(x string) { f(x) }`,
   594  			[]testInst{{`f`, []string{`string`, `*string`}, `func(x string)`}},
   595  		},
   596  		{`package s2; func f[T any, P interface{*T}](x []T) {}; func _(x []int) { f(x) }`,
   597  			[]testInst{{`f`, []string{`int`, `*int`}, `func(x []int)`}},
   598  		},
   599  		{`package s3; type C[T any] interface{chan<- T}; func f[T any, P C[T]](x []T) {}; func _(x []int) { f(x) }`,
   600  			[]testInst{
   601  				{`C`, []string{`T`}, `interface{chan<- T}`},
   602  				{`f`, []string{`int`, `chan<- int`}, `func(x []int)`},
   603  			},
   604  		},
   605  		{`package s4; type C[T any] interface{chan<- T}; func f[T any, P C[T], Q C[[]*P]](x []T) {}; func _(x []int) { f(x) }`,
   606  			[]testInst{
   607  				{`C`, []string{`T`}, `interface{chan<- T}`},
   608  				{`C`, []string{`[]*P`}, `interface{chan<- []*P}`},
   609  				{`f`, []string{`int`, `chan<- int`, `chan<- []*chan<- int`}, `func(x []int)`},
   610  			},
   611  		},
   612  
   613  		{`package t1; func f[T any, P interface{*T}]() T { panic(0) }; func _() { _ = f[string] }`,
   614  			[]testInst{{`f`, []string{`string`, `*string`}, `func() string`}},
   615  		},
   616  		{`package t2; func f[T any, P interface{*T}]() T { panic(0) }; func _() { _ = (f[string]) }`,
   617  			[]testInst{{`f`, []string{`string`, `*string`}, `func() string`}},
   618  		},
   619  		{`package t3; type C[T any] interface{chan<- T}; func f[T any, P C[T], Q C[[]*P]]() []T { return nil }; func _() { _ = f[int] }`,
   620  			[]testInst{
   621  				{`C`, []string{`T`}, `interface{chan<- T}`},
   622  				{`C`, []string{`[]*P`}, `interface{chan<- []*P}`},
   623  				{`f`, []string{`int`, `chan<- int`, `chan<- []*chan<- int`}, `func() []int`},
   624  			},
   625  		},
   626  		{`package t4; type C[T any] interface{chan<- T}; func f[T any, P C[T], Q C[[]*P]]() []T { return nil }; func _() { _ = (f[int]) }`,
   627  			[]testInst{
   628  				{`C`, []string{`T`}, `interface{chan<- T}`},
   629  				{`C`, []string{`[]*P`}, `interface{chan<- []*P}`},
   630  				{`f`, []string{`int`, `chan<- int`, `chan<- []*chan<- int`}, `func() []int`},
   631  			},
   632  		},
   633  		{`package i0; import "lib"; func _() { lib.F(42) }`,
   634  			[]testInst{{`F`, []string{`int`}, `func(int)`}},
   635  		},
   636  
   637  		{`package duplfunc0; func f[T any](T) {}; func _() { f(42); f("foo"); f[int](3) }`,
   638  			[]testInst{
   639  				{`f`, []string{`int`}, `func(int)`},
   640  				{`f`, []string{`string`}, `func(string)`},
   641  				{`f`, []string{`int`}, `func(int)`},
   642  			},
   643  		},
   644  		{`package duplfunc1; import "lib"; func _() { lib.F(42); lib.F("foo"); lib.F(3) }`,
   645  			[]testInst{
   646  				{`F`, []string{`int`}, `func(int)`},
   647  				{`F`, []string{`string`}, `func(string)`},
   648  				{`F`, []string{`int`}, `func(int)`},
   649  			},
   650  		},
   651  
   652  		{`package type0; type T[P interface{~int}] struct{ x P }; var _ T[int]`,
   653  			[]testInst{{`T`, []string{`int`}, `struct{x int}`}},
   654  		},
   655  		{`package type1; type T[P interface{~int}] struct{ x P }; var _ (T[int])`,
   656  			[]testInst{{`T`, []string{`int`}, `struct{x int}`}},
   657  		},
   658  		{`package type2; type T[P interface{~int}] struct{ x P }; var _ T[(int)]`,
   659  			[]testInst{{`T`, []string{`int`}, `struct{x int}`}},
   660  		},
   661  		{`package type3; type T[P1 interface{~[]P2}, P2 any] struct{ x P1; y P2 }; var _ T[[]int, int]`,
   662  			[]testInst{{`T`, []string{`[]int`, `int`}, `struct{x []int; y int}`}},
   663  		},
   664  		{`package type4; import "lib"; var _ lib.T[int]`,
   665  			[]testInst{{`T`, []string{`int`}, `[]int`}},
   666  		},
   667  
   668  		{`package dupltype0; type T[P interface{~int}] struct{ x P }; var x T[int]; var y T[int]`,
   669  			[]testInst{
   670  				{`T`, []string{`int`}, `struct{x int}`},
   671  				{`T`, []string{`int`}, `struct{x int}`},
   672  			},
   673  		},
   674  		{`package dupltype1; type T[P ~int] struct{ x P }; func (r *T[Q]) add(z T[Q]) { r.x += z.x }`,
   675  			[]testInst{
   676  				{`T`, []string{`Q`}, `struct{x Q}`},
   677  				{`T`, []string{`Q`}, `struct{x Q}`},
   678  			},
   679  		},
   680  		{`package dupltype1; import "lib"; var x lib.T[int]; var y lib.T[int]; var z lib.T[string]`,
   681  			[]testInst{
   682  				{`T`, []string{`int`}, `[]int`},
   683  				{`T`, []string{`int`}, `[]int`},
   684  				{`T`, []string{`string`}, `[]string`},
   685  			},
   686  		},
   687  		{`package issue51803; func foo[T any](T) {}; func _() { foo[int]( /* leave arg away on purpose */ ) }`,
   688  			[]testInst{{`foo`, []string{`int`}, `func(int)`}},
   689  		},
   690  
   691  		// reverse type inference
   692  		{`package reverse1a; var f func(int) = g; func g[P any](P) {}`,
   693  			[]testInst{{`g`, []string{`int`}, `func(int)`}},
   694  		},
   695  		{`package reverse1b; func f(func(int)) {}; func g[P any](P) {}; func _() { f(g) }`,
   696  			[]testInst{{`g`, []string{`int`}, `func(int)`}},
   697  		},
   698  		{`package reverse2a; var f func(int, string) = g; func g[P, Q any](P, Q) {}`,
   699  			[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
   700  		},
   701  		{`package reverse2b; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g) }`,
   702  			[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
   703  		},
   704  		{`package reverse2c; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g[int]) }`,
   705  			[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
   706  		},
   707  		// reverse3a not possible (cannot assign to generic function outside of argument passing)
   708  		{`package reverse3b; func f[R any](func(int) R) {}; func g[P any](P) string { return "" }; func _() { f(g) }`,
   709  			[]testInst{
   710  				{`f`, []string{`string`}, `func(func(int) string)`},
   711  				{`g`, []string{`int`}, `func(int) string`},
   712  			},
   713  		},
   714  		{`package reverse4a; var _, _ func([]int, *float32) = g, h; func g[P, Q any]([]P, *Q) {}; func h[R any]([]R, *float32) {}`,
   715  			[]testInst{
   716  				{`g`, []string{`int`, `float32`}, `func([]int, *float32)`},
   717  				{`h`, []string{`int`}, `func([]int, *float32)`},
   718  			},
   719  		},
   720  		{`package reverse4b; func f(_, _ func([]int, *float32)) {}; func g[P, Q any]([]P, *Q) {}; func h[R any]([]R, *float32) {}; func _() { f(g, h) }`,
   721  			[]testInst{
   722  				{`g`, []string{`int`, `float32`}, `func([]int, *float32)`},
   723  				{`h`, []string{`int`}, `func([]int, *float32)`},
   724  			},
   725  		},
   726  		{`package issue59956; func f(func(int), func(string), func(bool)) {}; func g[P any](P) {}; func _() { f(g, g, g) }`,
   727  			[]testInst{
   728  				{`g`, []string{`int`}, `func(int)`},
   729  				{`g`, []string{`string`}, `func(string)`},
   730  				{`g`, []string{`bool`}, `func(bool)`},
   731  			},
   732  		},
   733  	}
   734  
   735  	for _, test := range tests {
   736  		imports := make(testImporter)
   737  		conf := Config{Importer: imports}
   738  		instMap := make(map[*ast.Ident]Instance)
   739  		useMap := make(map[*ast.Ident]Object)
   740  		makePkg := func(src string) *Package {
   741  			pkg, err := typecheck(src, &conf, &Info{Instances: instMap, Uses: useMap})
   742  			// allow error for issue51803
   743  			if err != nil && (pkg == nil || pkg.Name() != "issue51803") {
   744  				t.Fatal(err)
   745  			}
   746  			imports[pkg.Name()] = pkg
   747  			return pkg
   748  		}
   749  		makePkg(lib)
   750  		pkg := makePkg(test.src)
   751  
   752  		t.Run(pkg.Name(), func(t *testing.T) {
   753  			// Sort instances in source order for stability.
   754  			instances := sortedInstances(instMap)
   755  			if got, want := len(instances), len(test.instances); got != want {
   756  				t.Fatalf("got %d instances, want %d", got, want)
   757  			}
   758  
   759  			// Pairwise compare with the expected instances.
   760  			for ii, inst := range instances {
   761  				var targs []Type
   762  				for i := 0; i < inst.Inst.TypeArgs.Len(); i++ {
   763  					targs = append(targs, inst.Inst.TypeArgs.At(i))
   764  				}
   765  				typ := inst.Inst.Type
   766  
   767  				testInst := test.instances[ii]
   768  				if got := inst.Ident.Name; got != testInst.name {
   769  					t.Fatalf("got name %s, want %s", got, testInst.name)
   770  				}
   771  				if len(targs) != len(testInst.targs) {
   772  					t.Fatalf("got %d type arguments; want %d", len(targs), len(testInst.targs))
   773  				}
   774  				for i, targ := range targs {
   775  					if got := targ.String(); got != testInst.targs[i] {
   776  						t.Errorf("type argument %d: got %s; want %s", i, got, testInst.targs[i])
   777  					}
   778  				}
   779  				if got := typ.Underlying().String(); got != testInst.typ {
   780  					t.Errorf("package %s: got %s; want %s", pkg.Name(), got, testInst.typ)
   781  				}
   782  
   783  				// Verify the invariant that re-instantiating the corresponding generic
   784  				// type with TypeArgs results in an identical instance.
   785  				ptype := useMap[inst.Ident].Type()
   786  				lister, _ := ptype.(interface{ TypeParams() *TypeParamList })
   787  				if lister == nil || lister.TypeParams().Len() == 0 {
   788  					t.Fatalf("info.Types[%v] = %v, want parameterized type", inst.Ident, ptype)
   789  				}
   790  				inst2, err := Instantiate(nil, ptype, targs, true)
   791  				if err != nil {
   792  					t.Errorf("Instantiate(%v, %v) failed: %v", ptype, targs, err)
   793  				}
   794  				if !Identical(inst.Inst.Type, inst2) {
   795  					t.Errorf("%v and %v are not identical", inst.Inst.Type, inst2)
   796  				}
   797  			}
   798  		})
   799  	}
   800  }
   801  
   802  type recordedInstance struct {
   803  	Ident *ast.Ident
   804  	Inst  Instance
   805  }
   806  
   807  func sortedInstances(m map[*ast.Ident]Instance) (instances []recordedInstance) {
   808  	for id, inst := range m {
   809  		instances = append(instances, recordedInstance{id, inst})
   810  	}
   811  	slices.SortFunc(instances, func(a, b recordedInstance) int {
   812  		return CmpPos(a.Ident.Pos(), b.Ident.Pos())
   813  	})
   814  	return instances
   815  }
   816  
   817  func TestDefsInfo(t *testing.T) {
   818  	var tests = []struct {
   819  		src  string
   820  		obj  string
   821  		want string
   822  	}{
   823  		{`package p0; const x = 42`, `x`, `const p0.x untyped int`},
   824  		{`package p1; const x int = 42`, `x`, `const p1.x int`},
   825  		{`package p2; var x int`, `x`, `var p2.x int`},
   826  		{`package p3; type x int`, `x`, `type p3.x int`},
   827  		{`package p4; func f()`, `f`, `func p4.f()`},
   828  		{`package p5; func f() int { x, _ := 1, 2; return x }`, `_`, `var _ int`},
   829  
   830  		// Tests using generics.
   831  		{`package g0; type x[T any] int`, `x`, `type g0.x[T any] int`},
   832  		{`package g1; func f[T any]() {}`, `f`, `func g1.f[T any]()`},
   833  		{`package g2; type x[T any] int; func (*x[_]) m() {}`, `m`, `func (*g2.x[_]).m()`},
   834  
   835  		// Type parameters in receiver type expressions are definitions.
   836  		{`package r0; type T[_ any] int; func (T[P]) _() {}`, `P`, `type parameter P any`},
   837  		{`package r1; type T[_, _ any] int; func (T[P, Q]) _() {}`, `P`, `type parameter P any`},
   838  		{`package r2; type T[_, _ any] int; func (T[P, Q]) _() {}`, `Q`, `type parameter Q any`},
   839  	}
   840  
   841  	for _, test := range tests {
   842  		info := Info{
   843  			Defs: make(map[*ast.Ident]Object),
   844  		}
   845  		name := mustTypecheck(test.src, nil, &info).Name()
   846  
   847  		// find object
   848  		var def Object
   849  		for id, obj := range info.Defs {
   850  			if id.Name == test.obj {
   851  				def = obj
   852  				break
   853  			}
   854  		}
   855  		if def == nil {
   856  			t.Errorf("package %s: %s not found", name, test.obj)
   857  			continue
   858  		}
   859  
   860  		if got := def.String(); got != test.want {
   861  			t.Errorf("package %s: got %s; want %s", name, got, test.want)
   862  		}
   863  	}
   864  }
   865  
   866  func TestUsesInfo(t *testing.T) {
   867  	var tests = []struct {
   868  		src  string
   869  		obj  string
   870  		want string
   871  	}{
   872  		{`package p0; func _() { _ = x }; const x = 42`, `x`, `const p0.x untyped int`},
   873  		{`package p1; func _() { _ = x }; const x int = 42`, `x`, `const p1.x int`},
   874  		{`package p2; func _() { _ = x }; var x int`, `x`, `var p2.x int`},
   875  		{`package p3; func _() { type _ x }; type x int`, `x`, `type p3.x int`},
   876  		{`package p4; func _() { _ = f }; func f()`, `f`, `func p4.f()`},
   877  
   878  		// Tests using generics.
   879  		{`package g0; func _[T any]() { _ = x }; const x = 42`, `x`, `const g0.x untyped int`},
   880  		{`package g1; func _[T any](x T) { }`, `T`, `type parameter T any`},
   881  		{`package g2; type N[A any] int; var _ N[int]`, `N`, `type g2.N[A any] int`},
   882  		{`package g3; type N[A any] int; func (N[_]) m() {}`, `N`, `type g3.N[A any] int`},
   883  
   884  		// Uses of fields are instantiated.
   885  		{`package s1; type N[A any] struct{ a A }; var f = N[int]{}.a`, `a`, `field a int`},
   886  		{`package s2; type N[A any] struct{ a A }; func (r N[B]) m(b B) { r.a = b }`, `a`, `field a B`},
   887  
   888  		// Uses of methods are uses of the instantiated method.
   889  		{`package m0; type N[A any] int; func (r N[B]) m() { r.n() }; func (N[C]) n() {}`, `n`, `func (m0.N[B]).n()`},
   890  		{`package m1; type N[A any] int; func (r N[B]) m() { }; var f = N[int].m`, `m`, `func (m1.N[int]).m()`},
   891  		{`package m2; func _[A any](v interface{ m() A }) { v.m() }`, `m`, `func (interface).m() A`},
   892  		{`package m3; func f[A any]() interface{ m() A } { return nil }; var _ = f[int]().m()`, `m`, `func (interface).m() int`},
   893  		{`package m4; type T[A any] func() interface{ m() A }; var x T[int]; var y = x().m`, `m`, `func (interface).m() int`},
   894  		{`package m5; type T[A any] interface{ m() A }; func _[B any](t T[B]) { t.m() }`, `m`, `func (m5.T[B]).m() B`},
   895  		{`package m6; type T[A any] interface{ m() }; func _[B any](t T[B]) { t.m() }`, `m`, `func (m6.T[B]).m()`},
   896  		{`package m7; type T[A any] interface{ m() A }; func _(t T[int]) { t.m() }`, `m`, `func (m7.T[int]).m() int`},
   897  		{`package m8; type T[A any] interface{ m() }; func _(t T[int]) { t.m() }`, `m`, `func (m8.T[int]).m()`},
   898  		{`package m9; type T[A any] interface{ m() }; func _(t T[int]) { _ = t.m }`, `m`, `func (m9.T[int]).m()`},
   899  		{
   900  			`package m10; type E[A any] interface{ m() }; type T[B any] interface{ E[B]; n() }; func _(t T[int]) { t.m() }`,
   901  			`m`,
   902  			`func (m10.E[int]).m()`,
   903  		},
   904  		{`package m11; type T[A any] interface{ m(); n() }; func _(t1 T[int], t2 T[string]) { t1.m(); t2.n() }`, `m`, `func (m11.T[int]).m()`},
   905  		{`package m12; type T[A any] interface{ m(); n() }; func _(t1 T[int], t2 T[string]) { t1.m(); t2.n() }`, `n`, `func (m12.T[string]).n()`},
   906  
   907  		// For historic reasons, type parameters in receiver type expressions
   908  		// are considered both definitions and uses (see go.dev/issue/68670).
   909  		{`package r0; type T[_ any] int; func (T[P]) _() {}`, `P`, `type parameter P any`},
   910  		{`package r1; type T[_, _ any] int; func (T[P, Q]) _() {}`, `P`, `type parameter P any`},
   911  		{`package r2; type T[_, _ any] int; func (T[P, Q]) _() {}`, `Q`, `type parameter Q any`},
   912  	}
   913  
   914  	for _, test := range tests {
   915  		info := Info{
   916  			Uses: make(map[*ast.Ident]Object),
   917  		}
   918  		name := mustTypecheck(test.src, nil, &info).Name()
   919  
   920  		// find object
   921  		var use Object
   922  		for id, obj := range info.Uses {
   923  			if id.Name == test.obj {
   924  				if use != nil {
   925  					panic(fmt.Sprintf("multiple uses of %q", id.Name))
   926  				}
   927  				use = obj
   928  			}
   929  		}
   930  		if use == nil {
   931  			t.Errorf("package %s: %s not found", name, test.obj)
   932  			continue
   933  		}
   934  
   935  		if got := use.String(); got != test.want {
   936  			t.Errorf("package %s: got %s; want %s", name, got, test.want)
   937  		}
   938  	}
   939  }
   940  
   941  func TestGenericMethodInfo(t *testing.T) {
   942  	src := `package p
   943  
   944  type N[A any] int
   945  
   946  func (r N[B]) m() { r.m(); r.n() }
   947  
   948  func (r *N[C]) n() {  }
   949  `
   950  	fset := token.NewFileSet()
   951  	f := mustParse(fset, src)
   952  	info := Info{
   953  		Defs:       make(map[*ast.Ident]Object),
   954  		Uses:       make(map[*ast.Ident]Object),
   955  		Selections: make(map[*ast.SelectorExpr]*Selection),
   956  	}
   957  	var conf Config
   958  	pkg, err := conf.Check("p", fset, []*ast.File{f}, &info)
   959  	if err != nil {
   960  		t.Fatal(err)
   961  	}
   962  
   963  	N := pkg.Scope().Lookup("N").Type().(*Named)
   964  
   965  	// Find the generic methods stored on N.
   966  	gm, gn := N.Method(0), N.Method(1)
   967  	if gm.Name() == "n" {
   968  		gm, gn = gn, gm
   969  	}
   970  
   971  	// Collect objects from info.
   972  	var dm, dn *Func   // the declared methods
   973  	var dmm, dmn *Func // the methods used in the body of m
   974  	for _, decl := range f.Decls {
   975  		fdecl, ok := decl.(*ast.FuncDecl)
   976  		if !ok {
   977  			continue
   978  		}
   979  		def := info.Defs[fdecl.Name].(*Func)
   980  		switch fdecl.Name.Name {
   981  		case "m":
   982  			dm = def
   983  			ast.Inspect(fdecl.Body, func(n ast.Node) bool {
   984  				if call, ok := n.(*ast.CallExpr); ok {
   985  					sel := call.Fun.(*ast.SelectorExpr)
   986  					use := info.Uses[sel.Sel].(*Func)
   987  					selection := info.Selections[sel]
   988  					if selection.Kind() != MethodVal {
   989  						t.Errorf("Selection kind = %v, want %v", selection.Kind(), MethodVal)
   990  					}
   991  					if selection.Obj() != use {
   992  						t.Errorf("info.Selections contains %v, want %v", selection.Obj(), use)
   993  					}
   994  					switch sel.Sel.Name {
   995  					case "m":
   996  						dmm = use
   997  					case "n":
   998  						dmn = use
   999  					}
  1000  				}
  1001  				return true
  1002  			})
  1003  		case "n":
  1004  			dn = def
  1005  		}
  1006  	}
  1007  
  1008  	if gm != dm {
  1009  		t.Errorf(`N.Method(...) returns %v for "m", but Info.Defs has %v`, gm, dm)
  1010  	}
  1011  	if gn != dn {
  1012  		t.Errorf(`N.Method(...) returns %v for "m", but Info.Defs has %v`, gm, dm)
  1013  	}
  1014  	if dmm != dm {
  1015  		t.Errorf(`Inside "m", r.m uses %v, want the defined func %v`, dmm, dm)
  1016  	}
  1017  	if dmn == dn {
  1018  		t.Errorf(`Inside "m", r.n uses %v, want a func distinct from %v`, dmm, dm)
  1019  	}
  1020  }
  1021  
  1022  func TestImplicitsInfo(t *testing.T) {
  1023  	testenv.MustHaveGoBuild(t)
  1024  
  1025  	var tests = []struct {
  1026  		src  string
  1027  		want string
  1028  	}{
  1029  		{`package p2; import . "fmt"; var _ = Println`, ""},           // no Implicits entry
  1030  		{`package p0; import local "fmt"; var _ = local.Println`, ""}, // no Implicits entry
  1031  		{`package p1; import "fmt"; var _ = fmt.Println`, "importSpec: package fmt"},
  1032  
  1033  		{`package p3; func f(x interface{}) { switch x.(type) { case int: } }`, ""}, // no Implicits entry
  1034  		{`package p4; func f(x interface{}) { switch t := x.(type) { case int: _ = t } }`, "caseClause: var t int"},
  1035  		{`package p5; func f(x interface{}) { switch t := x.(type) { case int, uint: _ = t } }`, "caseClause: var t interface{}"},
  1036  		{`package p6; func f(x interface{}) { switch t := x.(type) { default: _ = t } }`, "caseClause: var t interface{}"},
  1037  
  1038  		{`package p7; func f(x int) {}`, ""}, // no Implicits entry
  1039  		{`package p8; func f(int) {}`, "field: var  int"},
  1040  		{`package p9; func f() (complex64) { return 0 }`, "field: var  complex64"},
  1041  		{`package p10; type T struct{}; func (*T) f() {}`, "field: var  *p10.T"},
  1042  
  1043  		// Tests using generics.
  1044  		{`package f0; func f[T any](x int) {}`, ""}, // no Implicits entry
  1045  		{`package f1; func f[T any](int) {}`, "field: var  int"},
  1046  		{`package f2; func f[T any](T) {}`, "field: var  T"},
  1047  		{`package f3; func f[T any]() (complex64) { return 0 }`, "field: var  complex64"},
  1048  		{`package f4; func f[T any](t T) (T) { return t }`, "field: var  T"},
  1049  		{`package t0; type T[A any] struct{}; func (*T[_]) f() {}`, "field: var  *t0.T[_]"},
  1050  		{`package t1; type T[A any] struct{}; func _(x interface{}) { switch t := x.(type) { case T[int]: _ = t } }`, "caseClause: var t t1.T[int]"},
  1051  		{`package t2; type T[A any] struct{}; func _[P any](x interface{}) { switch t := x.(type) { case T[P]: _ = t } }`, "caseClause: var t t2.T[P]"},
  1052  		{`package t3; func _[P any](x interface{}) { switch t := x.(type) { case P: _ = t } }`, "caseClause: var t P"},
  1053  	}
  1054  
  1055  	for _, test := range tests {
  1056  		info := Info{
  1057  			Implicits: make(map[ast.Node]Object),
  1058  		}
  1059  		name := mustTypecheck(test.src, nil, &info).Name()
  1060  
  1061  		// the test cases expect at most one Implicits entry
  1062  		if len(info.Implicits) > 1 {
  1063  			t.Errorf("package %s: %d Implicits entries found", name, len(info.Implicits))
  1064  			continue
  1065  		}
  1066  
  1067  		// extract Implicits entry, if any
  1068  		var got string
  1069  		for n, obj := range info.Implicits {
  1070  			switch x := n.(type) {
  1071  			case *ast.ImportSpec:
  1072  				got = "importSpec"
  1073  			case *ast.CaseClause:
  1074  				got = "caseClause"
  1075  			case *ast.Field:
  1076  				got = "field"
  1077  			default:
  1078  				t.Fatalf("package %s: unexpected %T", name, x)
  1079  			}
  1080  			got += ": " + obj.String()
  1081  		}
  1082  
  1083  		// verify entry
  1084  		if got != test.want {
  1085  			t.Errorf("package %s: got %q; want %q", name, got, test.want)
  1086  		}
  1087  	}
  1088  }
  1089  
  1090  func TestPkgNameOf(t *testing.T) {
  1091  	testenv.MustHaveGoBuild(t)
  1092  
  1093  	const src = `
  1094  package p
  1095  
  1096  import (
  1097  	. "os"
  1098  	_ "io"
  1099  	"math"
  1100  	"path/filepath"
  1101  	snort "sort"
  1102  )
  1103  
  1104  // avoid imported and not used errors
  1105  var (
  1106  	_ = Open // os.Open
  1107  	_ = math.Sin
  1108  	_ = filepath.Abs
  1109  	_ = snort.Ints
  1110  )
  1111  `
  1112  
  1113  	var tests = []struct {
  1114  		path string // path string enclosed in "'s
  1115  		want string
  1116  	}{
  1117  		{`"os"`, "."},
  1118  		{`"io"`, "_"},
  1119  		{`"math"`, "math"},
  1120  		{`"path/filepath"`, "filepath"},
  1121  		{`"sort"`, "snort"},
  1122  	}
  1123  
  1124  	fset := token.NewFileSet()
  1125  	f := mustParse(fset, src)
  1126  	info := Info{
  1127  		Defs:      make(map[*ast.Ident]Object),
  1128  		Implicits: make(map[ast.Node]Object),
  1129  	}
  1130  	var conf Config
  1131  	conf.Importer = importer.Default()
  1132  	_, err := conf.Check("p", fset, []*ast.File{f}, &info)
  1133  	if err != nil {
  1134  		t.Fatal(err)
  1135  	}
  1136  
  1137  	// map import paths to importDecl
  1138  	imports := make(map[string]*ast.ImportSpec)
  1139  	for _, s := range f.Decls[0].(*ast.GenDecl).Specs {
  1140  		if imp, _ := s.(*ast.ImportSpec); imp != nil {
  1141  			imports[imp.Path.Value] = imp
  1142  		}
  1143  	}
  1144  
  1145  	for _, test := range tests {
  1146  		imp := imports[test.path]
  1147  		if imp == nil {
  1148  			t.Fatalf("invalid test case: import path %s not found", test.path)
  1149  		}
  1150  		got := info.PkgNameOf(imp)
  1151  		if got == nil {
  1152  			t.Fatalf("import %s: package name not found", test.path)
  1153  		}
  1154  		if got.Name() != test.want {
  1155  			t.Errorf("import %s: got %s; want %s", test.path, got.Name(), test.want)
  1156  		}
  1157  	}
  1158  
  1159  	// test non-existing importDecl
  1160  	if got := info.PkgNameOf(new(ast.ImportSpec)); got != nil {
  1161  		t.Errorf("got %s for non-existing import declaration", got.Name())
  1162  	}
  1163  }
  1164  
  1165  func predString(tv TypeAndValue) string {
  1166  	var buf strings.Builder
  1167  	pred := func(b bool, s string) {
  1168  		if b {
  1169  			if buf.Len() > 0 {
  1170  				buf.WriteString(", ")
  1171  			}
  1172  			buf.WriteString(s)
  1173  		}
  1174  	}
  1175  
  1176  	pred(tv.IsVoid(), "void")
  1177  	pred(tv.IsType(), "type")
  1178  	pred(tv.IsBuiltin(), "builtin")
  1179  	pred(tv.IsValue() && tv.Value != nil, "const")
  1180  	pred(tv.IsValue() && tv.Value == nil, "value")
  1181  	pred(tv.IsNil(), "nil")
  1182  	pred(tv.Addressable(), "addressable")
  1183  	pred(tv.Assignable(), "assignable")
  1184  	pred(tv.HasOk(), "hasOk")
  1185  
  1186  	if buf.Len() == 0 {
  1187  		return "invalid"
  1188  	}
  1189  	return buf.String()
  1190  }
  1191  
  1192  func TestPredicatesInfo(t *testing.T) {
  1193  	testenv.MustHaveGoBuild(t)
  1194  
  1195  	var tests = []struct {
  1196  		src  string
  1197  		expr string
  1198  		pred string
  1199  	}{
  1200  		// void
  1201  		{`package n0; func f() { f() }`, `f()`, `void`},
  1202  
  1203  		// types
  1204  		{`package t0; type _ int`, `int`, `type`},
  1205  		{`package t1; type _ []int`, `[]int`, `type`},
  1206  		{`package t2; type _ func()`, `func()`, `type`},
  1207  		{`package t3; type _ func(int)`, `int`, `type`},
  1208  		{`package t3; type _ func(...int)`, `...int`, `type`},
  1209  
  1210  		// built-ins
  1211  		{`package b0; var _ = len("")`, `len`, `builtin`},
  1212  		{`package b1; var _ = (len)("")`, `(len)`, `builtin`},
  1213  
  1214  		// constants
  1215  		{`package c0; var _ = 42`, `42`, `const`},
  1216  		{`package c1; var _ = "foo" + "bar"`, `"foo" + "bar"`, `const`},
  1217  		{`package c2; const (i = 1i; _ = i)`, `i`, `const`},
  1218  
  1219  		// values
  1220  		{`package v0; var (a, b int; _ = a + b)`, `a + b`, `value`},
  1221  		{`package v1; var _ = &[]int{1}`, `[]int{…}`, `value`},
  1222  		{`package v2; var _ = func(){}`, `(func() literal)`, `value`},
  1223  		{`package v4; func f() { _ = f }`, `f`, `value`},
  1224  		{`package v3; var _ *int = nil`, `nil`, `value, nil`},
  1225  		{`package v3; var _ *int = (nil)`, `(nil)`, `value, nil`},
  1226  
  1227  		// addressable (and thus assignable) operands
  1228  		{`package a0; var (x int; _ = x)`, `x`, `value, addressable, assignable`},
  1229  		{`package a1; var (p *int; _ = *p)`, `*p`, `value, addressable, assignable`},
  1230  		{`package a2; var (s []int; _ = s[0])`, `s[0]`, `value, addressable, assignable`},
  1231  		{`package a3; var (s struct{f int}; _ = s.f)`, `s.f`, `value, addressable, assignable`},
  1232  		{`package a4; var (a [10]int; _ = a[0])`, `a[0]`, `value, addressable, assignable`},
  1233  		{`package a5; func _(x int) { _ = x }`, `x`, `value, addressable, assignable`},
  1234  		{`package a6; func _()(x int) { _ = x; return }`, `x`, `value, addressable, assignable`},
  1235  		{`package a7; type T int; func (x T) _() { _ = x }`, `x`, `value, addressable, assignable`},
  1236  		// composite literals are not addressable
  1237  
  1238  		// assignable but not addressable values
  1239  		{`package s0; var (m map[int]int; _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
  1240  		{`package s1; var (m map[int]int; _, _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
  1241  
  1242  		// hasOk expressions
  1243  		{`package k0; var (ch chan int; _ = <-ch)`, `<-ch`, `value, hasOk`},
  1244  		{`package k1; var (ch chan int; _, _ = <-ch)`, `<-ch`, `value, hasOk`},
  1245  
  1246  		// missing entries
  1247  		// - package names are collected in the Uses map
  1248  		// - identifiers being declared are collected in the Defs map
  1249  		{`package m0; import "os"; func _() { _ = os.Stdout }`, `os`, `<missing>`},
  1250  		{`package m1; import p "os"; func _() { _ = p.Stdout }`, `p`, `<missing>`},
  1251  		{`package m2; const c = 0`, `c`, `<missing>`},
  1252  		{`package m3; type T int`, `T`, `<missing>`},
  1253  		{`package m4; var v int`, `v`, `<missing>`},
  1254  		{`package m5; func f() {}`, `f`, `<missing>`},
  1255  		{`package m6; func _(x int) {}`, `x`, `<missing>`},
  1256  		{`package m6; func _()(x int) { return }`, `x`, `<missing>`},
  1257  		{`package m6; type T int; func (x T) _() {}`, `x`, `<missing>`},
  1258  	}
  1259  
  1260  	for _, test := range tests {
  1261  		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
  1262  		name := mustTypecheck(test.src, nil, &info).Name()
  1263  
  1264  		// look for expression predicates
  1265  		got := "<missing>"
  1266  		for e, tv := range info.Types {
  1267  			//println(name, ExprString(e))
  1268  			if ExprString(e) == test.expr {
  1269  				got = predString(tv)
  1270  				break
  1271  			}
  1272  		}
  1273  
  1274  		if got != test.pred {
  1275  			t.Errorf("package %s: got %s; want %s", name, got, test.pred)
  1276  		}
  1277  	}
  1278  }
  1279  
  1280  func TestScopesInfo(t *testing.T) {
  1281  	testenv.MustHaveGoBuild(t)
  1282  
  1283  	var tests = []struct {
  1284  		src    string
  1285  		scopes []string // list of scope descriptors of the form kind:varlist
  1286  	}{
  1287  		{`package p0`, []string{
  1288  			"file:",
  1289  		}},
  1290  		{`package p1; import ( "fmt"; m "math"; _ "os" ); var ( _ = fmt.Println; _ = m.Pi )`, []string{
  1291  			"file:fmt m",
  1292  		}},
  1293  		{`package p2; func _() {}`, []string{
  1294  			"file:", "func:",
  1295  		}},
  1296  		{`package p3; func _(x, y int) {}`, []string{
  1297  			"file:", "func:x y",
  1298  		}},
  1299  		{`package p4; func _(x, y int) { x, z := 1, 2; _ = z }`, []string{
  1300  			"file:", "func:x y z", // redeclaration of x
  1301  		}},
  1302  		{`package p5; func _(x, y int) (u, _ int) { return }`, []string{
  1303  			"file:", "func:u x y",
  1304  		}},
  1305  		{`package p6; func _() { { var x int; _ = x } }`, []string{
  1306  			"file:", "func:", "block:x",
  1307  		}},
  1308  		{`package p7; func _() { if true {} }`, []string{
  1309  			"file:", "func:", "if:", "block:",
  1310  		}},
  1311  		{`package p8; func _() { if x := 0; x < 0 { y := x; _ = y } }`, []string{
  1312  			"file:", "func:", "if:x", "block:y",
  1313  		}},
  1314  		{`package p9; func _() { switch x := 0; x {} }`, []string{
  1315  			"file:", "func:", "switch:x",
  1316  		}},
  1317  		{`package p10; func _() { switch x := 0; x { case 1: y := x; _ = y; default: }}`, []string{
  1318  			"file:", "func:", "switch:x", "case:y", "case:",
  1319  		}},
  1320  		{`package p11; func _(t interface{}) { switch t.(type) {} }`, []string{
  1321  			"file:", "func:t", "type switch:",
  1322  		}},
  1323  		{`package p12; func _(t interface{}) { switch t := t; t.(type) {} }`, []string{
  1324  			"file:", "func:t", "type switch:t",
  1325  		}},
  1326  		{`package p13; func _(t interface{}) { switch x := t.(type) { case int: _ = x } }`, []string{
  1327  			"file:", "func:t", "type switch:", "case:x", // x implicitly declared
  1328  		}},
  1329  		{`package p14; func _() { select{} }`, []string{
  1330  			"file:", "func:",
  1331  		}},
  1332  		{`package p15; func _(c chan int) { select{ case <-c: } }`, []string{
  1333  			"file:", "func:c", "comm:",
  1334  		}},
  1335  		{`package p16; func _(c chan int) { select{ case i := <-c: x := i; _ = x} }`, []string{
  1336  			"file:", "func:c", "comm:i x",
  1337  		}},
  1338  		{`package p17; func _() { for{} }`, []string{
  1339  			"file:", "func:", "for:", "block:",
  1340  		}},
  1341  		{`package p18; func _(n int) { for i := 0; i < n; i++ { _ = i } }`, []string{
  1342  			"file:", "func:n", "for:i", "block:",
  1343  		}},
  1344  		{`package p19; func _(a []int) { for i := range a { _ = i} }`, []string{
  1345  			"file:", "func:a", "range:i", "block:",
  1346  		}},
  1347  		{`package p20; var s int; func _(a []int) { for i, x := range a { s += x; _ = i } }`, []string{
  1348  			"file:", "func:a", "range:i x", "block:",
  1349  		}},
  1350  	}
  1351  
  1352  	for _, test := range tests {
  1353  		info := Info{Scopes: make(map[ast.Node]*Scope)}
  1354  		name := mustTypecheck(test.src, nil, &info).Name()
  1355  
  1356  		// number of scopes must match
  1357  		if len(info.Scopes) != len(test.scopes) {
  1358  			t.Errorf("package %s: got %d scopes; want %d", name, len(info.Scopes), len(test.scopes))
  1359  		}
  1360  
  1361  		// scope descriptions must match
  1362  		for node, scope := range info.Scopes {
  1363  			kind := "<unknown node kind>"
  1364  			switch node.(type) {
  1365  			case *ast.File:
  1366  				kind = "file"
  1367  			case *ast.FuncType:
  1368  				kind = "func"
  1369  			case *ast.BlockStmt:
  1370  				kind = "block"
  1371  			case *ast.IfStmt:
  1372  				kind = "if"
  1373  			case *ast.SwitchStmt:
  1374  				kind = "switch"
  1375  			case *ast.TypeSwitchStmt:
  1376  				kind = "type switch"
  1377  			case *ast.CaseClause:
  1378  				kind = "case"
  1379  			case *ast.CommClause:
  1380  				kind = "comm"
  1381  			case *ast.ForStmt:
  1382  				kind = "for"
  1383  			case *ast.RangeStmt:
  1384  				kind = "range"
  1385  			}
  1386  
  1387  			// look for matching scope description
  1388  			desc := kind + ":" + strings.Join(scope.Names(), " ")
  1389  			if !slices.Contains(test.scopes, desc) {
  1390  				t.Errorf("package %s: no matching scope found for %s", name, desc)
  1391  			}
  1392  		}
  1393  	}
  1394  }
  1395  
  1396  func TestInitOrderInfo(t *testing.T) {
  1397  	var tests = []struct {
  1398  		src   string
  1399  		inits []string
  1400  	}{
  1401  		{`package p0; var (x = 1; y = x)`, []string{
  1402  			"x = 1", "y = x",
  1403  		}},
  1404  		{`package p1; var (a = 1; b = 2; c = 3)`, []string{
  1405  			"a = 1", "b = 2", "c = 3",
  1406  		}},
  1407  		{`package p2; var (a, b, c = 1, 2, 3)`, []string{
  1408  			"a = 1", "b = 2", "c = 3",
  1409  		}},
  1410  		{`package p3; var _ = f(); func f() int { return 1 }`, []string{
  1411  			"_ = f()", // blank var
  1412  		}},
  1413  		{`package p4; var (a = 0; x = y; y = z; z = 0)`, []string{
  1414  			"a = 0", "z = 0", "y = z", "x = y",
  1415  		}},
  1416  		{`package p5; var (a, _ = m[0]; m map[int]string)`, []string{
  1417  			"a, _ = m[0]", // blank var
  1418  		}},
  1419  		{`package p6; var a, b = f(); func f() (_, _ int) { return z, z }; var z = 0`, []string{
  1420  			"z = 0", "a, b = f()",
  1421  		}},
  1422  		{`package p7; var (a = func() int { return b }(); b = 1)`, []string{
  1423  			"b = 1", "a = (func() int literal)()",
  1424  		}},
  1425  		{`package p8; var (a, b = func() (_, _ int) { return c, c }(); c = 1)`, []string{
  1426  			"c = 1", "a, b = (func() (_, _ int) literal)()",
  1427  		}},
  1428  		{`package p9; type T struct{}; func (T) m() int { _ = y; return 0 }; var x, y = T.m, 1`, []string{
  1429  			"y = 1", "x = T.m",
  1430  		}},
  1431  		{`package p10; var (d = c + b; a = 0; b = 0; c = 0)`, []string{
  1432  			"a = 0", "b = 0", "c = 0", "d = c + b",
  1433  		}},
  1434  		{`package p11; var (a = e + c; b = d + c; c = 0; d = 0; e = 0)`, []string{
  1435  			"c = 0", "d = 0", "b = d + c", "e = 0", "a = e + c",
  1436  		}},
  1437  		// emit an initializer for n:1 initializations only once (not for each node
  1438  		// on the lhs which may appear in different order in the dependency graph)
  1439  		{`package p12; var (a = x; b = 0; x, y = m[0]; m map[int]int)`, []string{
  1440  			"b = 0", "x, y = m[0]", "a = x",
  1441  		}},
  1442  		// test case from spec section on package initialization
  1443  		{`package p12
  1444  
  1445  		var (
  1446  			a = c + b
  1447  			b = f()
  1448  			c = f()
  1449  			d = 3
  1450  		)
  1451  
  1452  		func f() int {
  1453  			d++
  1454  			return d
  1455  		}`, []string{
  1456  			"d = 3", "b = f()", "c = f()", "a = c + b",
  1457  		}},
  1458  		// test case for go.dev/issue/7131
  1459  		{`package main
  1460  
  1461  		var counter int
  1462  		func next() int { counter++; return counter }
  1463  
  1464  		var _ = makeOrder()
  1465  		func makeOrder() []int { return []int{f, b, d, e, c, a} }
  1466  
  1467  		var a       = next()
  1468  		var b, c    = next(), next()
  1469  		var d, e, f = next(), next(), next()
  1470  		`, []string{
  1471  			"a = next()", "b = next()", "c = next()", "d = next()", "e = next()", "f = next()", "_ = makeOrder()",
  1472  		}},
  1473  		// test case for go.dev/issue/10709
  1474  		{`package p13
  1475  
  1476  		var (
  1477  		    v = t.m()
  1478  		    t = makeT(0)
  1479  		)
  1480  
  1481  		type T struct{}
  1482  
  1483  		func (T) m() int { return 0 }
  1484  
  1485  		func makeT(n int) T {
  1486  		    if n > 0 {
  1487  		        return makeT(n-1)
  1488  		    }
  1489  		    return T{}
  1490  		}`, []string{
  1491  			"t = makeT(0)", "v = t.m()",
  1492  		}},
  1493  		// test case for go.dev/issue/10709: same as test before, but variable decls swapped
  1494  		{`package p14
  1495  
  1496  		var (
  1497  		    t = makeT(0)
  1498  		    v = t.m()
  1499  		)
  1500  
  1501  		type T struct{}
  1502  
  1503  		func (T) m() int { return 0 }
  1504  
  1505  		func makeT(n int) T {
  1506  		    if n > 0 {
  1507  		        return makeT(n-1)
  1508  		    }
  1509  		    return T{}
  1510  		}`, []string{
  1511  			"t = makeT(0)", "v = t.m()",
  1512  		}},
  1513  		// another candidate possibly causing problems with go.dev/issue/10709
  1514  		{`package p15
  1515  
  1516  		var y1 = f1()
  1517  
  1518  		func f1() int { return g1() }
  1519  		func g1() int { f1(); return x1 }
  1520  
  1521  		var x1 = 0
  1522  
  1523  		var y2 = f2()
  1524  
  1525  		func f2() int { return g2() }
  1526  		func g2() int { return x2 }
  1527  
  1528  		var x2 = 0`, []string{
  1529  			"x1 = 0", "y1 = f1()", "x2 = 0", "y2 = f2()",
  1530  		}},
  1531  	}
  1532  
  1533  	for _, test := range tests {
  1534  		info := Info{}
  1535  		name := mustTypecheck(test.src, nil, &info).Name()
  1536  
  1537  		// number of initializers must match
  1538  		if len(info.InitOrder) != len(test.inits) {
  1539  			t.Errorf("package %s: got %d initializers; want %d", name, len(info.InitOrder), len(test.inits))
  1540  			continue
  1541  		}
  1542  
  1543  		// initializers must match
  1544  		for i, want := range test.inits {
  1545  			got := info.InitOrder[i].String()
  1546  			if got != want {
  1547  				t.Errorf("package %s, init %d: got %s; want %s", name, i, got, want)
  1548  				continue
  1549  			}
  1550  		}
  1551  	}
  1552  }
  1553  
  1554  func TestMultiFileInitOrder(t *testing.T) {
  1555  	fset := token.NewFileSet()
  1556  	fileA := mustParse(fset, `package main; var a = 1`)
  1557  	fileB := mustParse(fset, `package main; var b = 2`)
  1558  
  1559  	// The initialization order must not depend on the parse
  1560  	// order of the files, only on the presentation order to
  1561  	// the type-checker.
  1562  	for _, test := range []struct {
  1563  		files []*ast.File
  1564  		want  string
  1565  	}{
  1566  		{[]*ast.File{fileA, fileB}, "[a = 1 b = 2]"},
  1567  		{[]*ast.File{fileB, fileA}, "[b = 2 a = 1]"},
  1568  	} {
  1569  		var info Info
  1570  		if _, err := new(Config).Check("main", fset, test.files, &info); err != nil {
  1571  			t.Fatal(err)
  1572  		}
  1573  		if got := fmt.Sprint(info.InitOrder); got != test.want {
  1574  			t.Fatalf("got %s; want %s", got, test.want)
  1575  		}
  1576  	}
  1577  }
  1578  
  1579  func TestFiles(t *testing.T) {
  1580  	var sources = []string{
  1581  		"package p; type T struct{}; func (T) m1() {}",
  1582  		"package p; func (T) m2() {}; var x interface{ m1(); m2() } = T{}",
  1583  		"package p; func (T) m3() {}; var y interface{ m1(); m2(); m3() } = T{}",
  1584  		"package p",
  1585  	}
  1586  
  1587  	var conf Config
  1588  	fset := token.NewFileSet()
  1589  	pkg := NewPackage("p", "p")
  1590  	var info Info
  1591  	check := NewChecker(&conf, fset, pkg, &info)
  1592  
  1593  	for _, src := range sources {
  1594  		if err := check.Files([]*ast.File{mustParse(fset, src)}); err != nil {
  1595  			t.Error(err)
  1596  		}
  1597  	}
  1598  
  1599  	// check InitOrder is [x y]
  1600  	var vars []string
  1601  	for _, init := range info.InitOrder {
  1602  		for _, v := range init.Lhs {
  1603  			vars = append(vars, v.Name())
  1604  		}
  1605  	}
  1606  	if got, want := fmt.Sprint(vars), "[x y]"; got != want {
  1607  		t.Errorf("InitOrder == %s, want %s", got, want)
  1608  	}
  1609  }
  1610  
  1611  type testImporter map[string]*Package
  1612  
  1613  func (m testImporter) Import(path string) (*Package, error) {
  1614  	if pkg := m[path]; pkg != nil {
  1615  		return pkg, nil
  1616  	}
  1617  	return nil, fmt.Errorf("package %q not found", path)
  1618  }
  1619  
  1620  func TestSelection(t *testing.T) {
  1621  	selections := make(map[*ast.SelectorExpr]*Selection)
  1622  
  1623  	// We need a specific fileset in this test below for positions.
  1624  	// Cannot use typecheck helper.
  1625  	fset := token.NewFileSet()
  1626  	imports := make(testImporter)
  1627  	conf := Config{Importer: imports}
  1628  	makePkg := func(path, src string) {
  1629  		pkg, err := conf.Check(path, fset, []*ast.File{mustParse(fset, src)}, &Info{Selections: selections})
  1630  		if err != nil {
  1631  			t.Fatal(err)
  1632  		}
  1633  		imports[path] = pkg
  1634  	}
  1635  
  1636  	const libSrc = `
  1637  package lib
  1638  type T float64
  1639  const C T = 3
  1640  var V T
  1641  func F() {}
  1642  func (T) M() {}
  1643  `
  1644  	const mainSrc = `
  1645  package main
  1646  import "lib"
  1647  
  1648  type A struct {
  1649  	*B
  1650  	C
  1651  }
  1652  
  1653  type B struct {
  1654  	b int
  1655  }
  1656  
  1657  func (B) f(int)
  1658  
  1659  type C struct {
  1660  	c int
  1661  }
  1662  
  1663  type G[P any] struct {
  1664  	p P
  1665  }
  1666  
  1667  func (G[P]) m(P) {}
  1668  
  1669  var Inst G[int]
  1670  
  1671  func (C) g()
  1672  func (*C) h()
  1673  
  1674  func main() {
  1675  	// qualified identifiers
  1676  	var _ lib.T
  1677  	_ = lib.C
  1678  	_ = lib.F
  1679  	_ = lib.V
  1680  	_ = lib.T.M
  1681  
  1682  	// fields
  1683  	_ = A{}.B
  1684  	_ = new(A).B
  1685  
  1686  	_ = A{}.C
  1687  	_ = new(A).C
  1688  
  1689  	_ = A{}.b
  1690  	_ = new(A).b
  1691  
  1692  	_ = A{}.c
  1693  	_ = new(A).c
  1694  
  1695  	_ = Inst.p
  1696  	_ = G[string]{}.p
  1697  
  1698  	// methods
  1699  	_ = A{}.f
  1700  	_ = new(A).f
  1701  	_ = A{}.g
  1702  	_ = new(A).g
  1703  	_ = new(A).h
  1704  
  1705  	_ = B{}.f
  1706  	_ = new(B).f
  1707  
  1708  	_ = C{}.g
  1709  	_ = new(C).g
  1710  	_ = new(C).h
  1711  	_ = Inst.m
  1712  
  1713  	// method expressions
  1714  	_ = A.f
  1715  	_ = (*A).f
  1716  	_ = B.f
  1717  	_ = (*B).f
  1718  	_ = G[string].m
  1719  }`
  1720  
  1721  	wantOut := map[string][2]string{
  1722  		"lib.T.M": {"method expr (lib.T) M(lib.T)", ".[0]"},
  1723  
  1724  		"A{}.B":    {"field (main.A) B *main.B", ".[0]"},
  1725  		"new(A).B": {"field (*main.A) B *main.B", "->[0]"},
  1726  		"A{}.C":    {"field (main.A) C main.C", ".[1]"},
  1727  		"new(A).C": {"field (*main.A) C main.C", "->[1]"},
  1728  		"A{}.b":    {"field (main.A) b int", "->[0 0]"},
  1729  		"new(A).b": {"field (*main.A) b int", "->[0 0]"},
  1730  		"A{}.c":    {"field (main.A) c int", ".[1 0]"},
  1731  		"new(A).c": {"field (*main.A) c int", "->[1 0]"},
  1732  		"Inst.p":   {"field (main.G[int]) p int", ".[0]"},
  1733  
  1734  		"A{}.f":    {"method (main.A) f(int)", "->[0 0]"},
  1735  		"new(A).f": {"method (*main.A) f(int)", "->[0 0]"},
  1736  		"A{}.g":    {"method (main.A) g()", ".[1 0]"},
  1737  		"new(A).g": {"method (*main.A) g()", "->[1 0]"},
  1738  		"new(A).h": {"method (*main.A) h()", "->[1 1]"}, // TODO(gri) should this report .[1 1] ?
  1739  		"B{}.f":    {"method (main.B) f(int)", ".[0]"},
  1740  		"new(B).f": {"method (*main.B) f(int)", "->[0]"},
  1741  		"C{}.g":    {"method (main.C) g()", ".[0]"},
  1742  		"new(C).g": {"method (*main.C) g()", "->[0]"},
  1743  		"new(C).h": {"method (*main.C) h()", "->[1]"}, // TODO(gri) should this report .[1] ?
  1744  		"Inst.m":   {"method (main.G[int]) m(int)", ".[0]"},
  1745  
  1746  		"A.f":           {"method expr (main.A) f(main.A, int)", "->[0 0]"},
  1747  		"(*A).f":        {"method expr (*main.A) f(*main.A, int)", "->[0 0]"},
  1748  		"B.f":           {"method expr (main.B) f(main.B, int)", ".[0]"},
  1749  		"(*B).f":        {"method expr (*main.B) f(*main.B, int)", "->[0]"},
  1750  		"G[string].m":   {"method expr (main.G[string]) m(main.G[string], string)", ".[0]"},
  1751  		"G[string]{}.p": {"field (main.G[string]) p string", ".[0]"},
  1752  	}
  1753  
  1754  	makePkg("lib", libSrc)
  1755  	makePkg("main", mainSrc)
  1756  
  1757  	for e, sel := range selections {
  1758  		_ = sel.String() // assertion: must not panic
  1759  
  1760  		start := fset.Position(e.Pos()).Offset
  1761  		end := fset.Position(e.End()).Offset
  1762  		syntax := mainSrc[start:end] // (all SelectorExprs are in main, not lib)
  1763  
  1764  		direct := "."
  1765  		if sel.Indirect() {
  1766  			direct = "->"
  1767  		}
  1768  		got := [2]string{
  1769  			sel.String(),
  1770  			fmt.Sprintf("%s%v", direct, sel.Index()),
  1771  		}
  1772  		want := wantOut[syntax]
  1773  		if want != got {
  1774  			t.Errorf("%s: got %q; want %q", syntax, got, want)
  1775  		}
  1776  		delete(wantOut, syntax)
  1777  
  1778  		// We must explicitly assert properties of the
  1779  		// Signature's receiver since it doesn't participate
  1780  		// in Identical() or String().
  1781  		sig, _ := sel.Type().(*Signature)
  1782  		if sel.Kind() == MethodVal {
  1783  			got := sig.Recv().Type()
  1784  			want := sel.Recv()
  1785  			if !Identical(got, want) {
  1786  				t.Errorf("%s: Recv() = %s, want %s", syntax, got, want)
  1787  			}
  1788  		} else if sig != nil && sig.Recv() != nil {
  1789  			t.Errorf("%s: signature has receiver %s", sig, sig.Recv().Type())
  1790  		}
  1791  	}
  1792  	// Assert that all wantOut entries were used exactly once.
  1793  	for syntax := range wantOut {
  1794  		t.Errorf("no ast.Selection found with syntax %q", syntax)
  1795  	}
  1796  }
  1797  
  1798  func TestIssue8518(t *testing.T) {
  1799  	fset := token.NewFileSet()
  1800  	imports := make(testImporter)
  1801  	conf := Config{
  1802  		Error:    func(err error) { t.Log(err) }, // don't exit after first error
  1803  		Importer: imports,
  1804  	}
  1805  	makePkg := func(path, src string) {
  1806  		imports[path], _ = conf.Check(path, fset, []*ast.File{mustParse(fset, src)}, nil) // errors logged via conf.Error
  1807  	}
  1808  
  1809  	const libSrc = `
  1810  package a
  1811  import "missing"
  1812  const C1 = foo
  1813  const C2 = missing.C
  1814  `
  1815  
  1816  	const mainSrc = `
  1817  package main
  1818  import "a"
  1819  var _ = a.C1
  1820  var _ = a.C2
  1821  `
  1822  
  1823  	makePkg("a", libSrc)
  1824  	makePkg("main", mainSrc) // don't crash when type-checking this package
  1825  }
  1826  
  1827  func TestIssue59603(t *testing.T) {
  1828  	fset := token.NewFileSet()
  1829  	imports := make(testImporter)
  1830  	conf := Config{
  1831  		Error:    func(err error) { t.Log(err) }, // don't exit after first error
  1832  		Importer: imports,
  1833  	}
  1834  	makePkg := func(path, src string) {
  1835  		imports[path], _ = conf.Check(path, fset, []*ast.File{mustParse(fset, src)}, nil) // errors logged via conf.Error
  1836  	}
  1837  
  1838  	const libSrc = `
  1839  package a
  1840  const C = foo
  1841  `
  1842  
  1843  	const mainSrc = `
  1844  package main
  1845  import "a"
  1846  const _ = a.C
  1847  `
  1848  
  1849  	makePkg("a", libSrc)
  1850  	makePkg("main", mainSrc) // don't crash when type-checking this package
  1851  }
  1852  
  1853  func TestLookupFieldOrMethodOnNil(t *testing.T) {
  1854  	// LookupFieldOrMethod on a nil type is expected to produce a run-time panic.
  1855  	defer func() {
  1856  		const want = "LookupFieldOrMethod on nil type"
  1857  		p := recover()
  1858  		if s, ok := p.(string); !ok || s != want {
  1859  			t.Fatalf("got %v, want %s", p, want)
  1860  		}
  1861  	}()
  1862  	LookupFieldOrMethod(nil, false, nil, "")
  1863  }
  1864  
  1865  func TestLookupFieldOrMethod(t *testing.T) {
  1866  	// Test cases assume a lookup of the form a.f or x.f, where a stands for an
  1867  	// addressable value, and x for a non-addressable value (even though a variable
  1868  	// for ease of test case writing).
  1869  	//
  1870  	// Should be kept in sync with TestMethodSet.
  1871  	var tests = []struct {
  1872  		src      string
  1873  		found    bool
  1874  		index    []int
  1875  		indirect bool
  1876  	}{
  1877  		// field lookups
  1878  		{"var x T; type T struct{}", false, nil, false},
  1879  		{"var x T; type T struct{ f int }", true, []int{0}, false},
  1880  		{"var x T; type T struct{ a, b, f, c int }", true, []int{2}, false},
  1881  
  1882  		// field lookups on a generic type
  1883  		{"var x T[int]; type T[P any] struct{}", false, nil, false},
  1884  		{"var x T[int]; type T[P any] struct{ f P }", true, []int{0}, false},
  1885  		{"var x T[int]; type T[P any] struct{ a, b, f, c P }", true, []int{2}, false},
  1886  
  1887  		// method lookups
  1888  		{"var a T; type T struct{}; func (T) f() {}", true, []int{0}, false},
  1889  		{"var a *T; type T struct{}; func (T) f() {}", true, []int{0}, true},
  1890  		{"var a T; type T struct{}; func (*T) f() {}", true, []int{0}, false},
  1891  		{"var a *T; type T struct{}; func (*T) f() {}", true, []int{0}, true}, // TODO(gri) should this report indirect = false?
  1892  
  1893  		// method lookups on a generic type
  1894  		{"var a T[int]; type T[P any] struct{}; func (T[P]) f() {}", true, []int{0}, false},
  1895  		{"var a *T[int]; type T[P any] struct{}; func (T[P]) f() {}", true, []int{0}, true},
  1896  		{"var a T[int]; type T[P any] struct{}; func (*T[P]) f() {}", true, []int{0}, false},
  1897  		{"var a *T[int]; type T[P any] struct{}; func (*T[P]) f() {}", true, []int{0}, true}, // TODO(gri) should this report indirect = false?
  1898  
  1899  		// collisions
  1900  		{"type ( E1 struct{ f int }; E2 struct{ f int }; x struct{ E1; *E2 })", false, []int{1, 0}, false},
  1901  		{"type ( E1 struct{ f int }; E2 struct{}; x struct{ E1; *E2 }); func (E2) f() {}", false, []int{1, 0}, false},
  1902  
  1903  		// collisions on a generic type
  1904  		{"type ( E1[P any] struct{ f P }; E2[P any] struct{ f P }; x struct{ E1[int]; *E2[int] })", false, []int{1, 0}, false},
  1905  		{"type ( E1[P any] struct{ f P }; E2[P any] struct{}; x struct{ E1[int]; *E2[int] }); func (E2[P]) f() {}", false, []int{1, 0}, false},
  1906  
  1907  		// outside methodset
  1908  		// (*T).f method exists, but value of type T is not addressable
  1909  		{"var x T; type T struct{}; func (*T) f() {}", false, nil, true},
  1910  
  1911  		// outside method set of a generic type
  1912  		{"var x T[int]; type T[P any] struct{}; func (*T[P]) f() {}", false, nil, true},
  1913  
  1914  		// recursive generic types; see go.dev/issue/52715
  1915  		{"var a T[int]; type ( T[P any] struct { *N[P] }; N[P any] struct { *T[P] } ); func (N[P]) f() {}", true, []int{0, 0}, true},
  1916  		{"var a T[int]; type ( T[P any] struct { *N[P] }; N[P any] struct { *T[P] } ); func (T[P]) f() {}", true, []int{0}, false},
  1917  	}
  1918  
  1919  	for _, test := range tests {
  1920  		pkg := mustTypecheck("package p;"+test.src, nil, nil)
  1921  
  1922  		obj := pkg.Scope().Lookup("a")
  1923  		if obj == nil {
  1924  			if obj = pkg.Scope().Lookup("x"); obj == nil {
  1925  				t.Errorf("%s: incorrect test case - no object a or x", test.src)
  1926  				continue
  1927  			}
  1928  		}
  1929  
  1930  		f, index, indirect := LookupFieldOrMethod(obj.Type(), obj.Name() == "a", pkg, "f")
  1931  		if (f != nil) != test.found {
  1932  			if f == nil {
  1933  				t.Errorf("%s: got no object; want one", test.src)
  1934  			} else {
  1935  				t.Errorf("%s: got object = %v; want none", test.src, f)
  1936  			}
  1937  		}
  1938  		if !slices.Equal(index, test.index) {
  1939  			t.Errorf("%s: got index = %v; want %v", test.src, index, test.index)
  1940  		}
  1941  		if indirect != test.indirect {
  1942  			t.Errorf("%s: got indirect = %v; want %v", test.src, indirect, test.indirect)
  1943  		}
  1944  	}
  1945  }
  1946  
  1947  // Test for go.dev/issue/52715
  1948  func TestLookupFieldOrMethod_RecursiveGeneric(t *testing.T) {
  1949  	const src = `
  1950  package pkg
  1951  
  1952  type Tree[T any] struct {
  1953  	*Node[T]
  1954  }
  1955  
  1956  func (*Tree[R]) N(r R) R { return r }
  1957  
  1958  type Node[T any] struct {
  1959  	*Tree[T]
  1960  }
  1961  
  1962  type Instance = *Tree[int]
  1963  `
  1964  
  1965  	fset := token.NewFileSet()
  1966  	f := mustParse(fset, src)
  1967  	pkg := NewPackage("pkg", f.Name.Name)
  1968  	if err := NewChecker(nil, fset, pkg, nil).Files([]*ast.File{f}); err != nil {
  1969  		panic(err)
  1970  	}
  1971  
  1972  	T := pkg.Scope().Lookup("Instance").Type()
  1973  	_, _, _ = LookupFieldOrMethod(T, false, pkg, "M") // verify that LookupFieldOrMethod terminates
  1974  }
  1975  
  1976  // newDefined creates a new defined type named T with the given underlying type.
  1977  // Helper function for use with TestIncompleteInterfaces only.
  1978  func newDefined(underlying Type) *Named {
  1979  	tname := NewTypeName(nopos, nil, "T", nil)
  1980  	return NewNamed(tname, underlying, nil)
  1981  }
  1982  
  1983  func TestConvertibleTo(t *testing.T) {
  1984  	for _, test := range []struct {
  1985  		v, t Type
  1986  		want bool
  1987  	}{
  1988  		{Typ[Int], Typ[Int], true},
  1989  		{Typ[Int], Typ[Float32], true},
  1990  		{Typ[Int], Typ[String], true},
  1991  		{newDefined(Typ[Int]), Typ[Int], true},
  1992  		{newDefined(new(Struct)), new(Struct), true},
  1993  		{newDefined(Typ[Int]), new(Struct), false},
  1994  		{Typ[UntypedInt], Typ[Int], true},
  1995  		{NewSlice(Typ[Int]), NewArray(Typ[Int], 10), true},
  1996  		{NewSlice(Typ[Int]), NewArray(Typ[Uint], 10), false},
  1997  		{NewSlice(Typ[Int]), NewPointer(NewArray(Typ[Int], 10)), true},
  1998  		{NewSlice(Typ[Int]), NewPointer(NewArray(Typ[Uint], 10)), false},
  1999  		// Untyped string values are not permitted by the spec, so the behavior below is undefined.
  2000  		{Typ[UntypedString], Typ[String], true},
  2001  	} {
  2002  		if got := ConvertibleTo(test.v, test.t); got != test.want {
  2003  			t.Errorf("ConvertibleTo(%v, %v) = %t, want %t", test.v, test.t, got, test.want)
  2004  		}
  2005  	}
  2006  }
  2007  
  2008  func TestAssignableTo(t *testing.T) {
  2009  	for _, test := range []struct {
  2010  		v, t Type
  2011  		want bool
  2012  	}{
  2013  		{Typ[Int], Typ[Int], true},
  2014  		{Typ[Int], Typ[Float32], false},
  2015  		{newDefined(Typ[Int]), Typ[Int], false},
  2016  		{newDefined(new(Struct)), new(Struct), true},
  2017  		{Typ[UntypedBool], Typ[Bool], true},
  2018  		{Typ[UntypedString], Typ[Bool], false},
  2019  		// Neither untyped string nor untyped numeric assignments arise during
  2020  		// normal type checking, so the below behavior is technically undefined by
  2021  		// the spec.
  2022  		{Typ[UntypedString], Typ[String], true},
  2023  		{Typ[UntypedInt], Typ[Int], true},
  2024  	} {
  2025  		if got := AssignableTo(test.v, test.t); got != test.want {
  2026  			t.Errorf("AssignableTo(%v, %v) = %t, want %t", test.v, test.t, got, test.want)
  2027  		}
  2028  	}
  2029  }
  2030  
  2031  func TestIdentical(t *testing.T) {
  2032  	// For each test, we compare the types of objects X and Y in the source.
  2033  	tests := []struct {
  2034  		src  string
  2035  		want bool
  2036  	}{
  2037  		// Basic types.
  2038  		{"var X int; var Y int", true},
  2039  		{"var X int; var Y string", false},
  2040  
  2041  		// TODO: add more tests for complex types.
  2042  
  2043  		// Named types.
  2044  		{"type X int; type Y int", false},
  2045  
  2046  		// Aliases.
  2047  		{"type X = int; type Y = int", true},
  2048  
  2049  		// Functions.
  2050  		{`func X(int) string { return "" }; func Y(int) string { return "" }`, true},
  2051  		{`func X() string { return "" }; func Y(int) string { return "" }`, false},
  2052  		{`func X(int) string { return "" }; func Y(int) {}`, false},
  2053  
  2054  		// Generic functions. Type parameters should be considered identical modulo
  2055  		// renaming. See also go.dev/issue/49722.
  2056  		{`func X[P ~int](){}; func Y[Q ~int]() {}`, true},
  2057  		{`func X[P1 any, P2 ~*P1](){}; func Y[Q1 any, Q2 ~*Q1]() {}`, true},
  2058  		{`func X[P1 any, P2 ~[]P1](){}; func Y[Q1 any, Q2 ~*Q1]() {}`, false},
  2059  		{`func X[P ~int](P){}; func Y[Q ~int](Q) {}`, true},
  2060  		{`func X[P ~string](P){}; func Y[Q ~int](Q) {}`, false},
  2061  		{`func X[P ~int]([]P){}; func Y[Q ~int]([]Q) {}`, true},
  2062  	}
  2063  
  2064  	for _, test := range tests {
  2065  		pkg := mustTypecheck("package p;"+test.src, nil, nil)
  2066  		X := pkg.Scope().Lookup("X")
  2067  		Y := pkg.Scope().Lookup("Y")
  2068  		if X == nil || Y == nil {
  2069  			t.Fatal("test must declare both X and Y")
  2070  		}
  2071  		if got := Identical(X.Type(), Y.Type()); got != test.want {
  2072  			t.Errorf("Identical(%s, %s) = %t, want %t", X.Type(), Y.Type(), got, test.want)
  2073  		}
  2074  	}
  2075  }
  2076  
  2077  func TestIdentical_issue15173(t *testing.T) {
  2078  	// Identical should allow nil arguments and be symmetric.
  2079  	for _, test := range []struct {
  2080  		x, y Type
  2081  		want bool
  2082  	}{
  2083  		{Typ[Int], Typ[Int], true},
  2084  		{Typ[Int], nil, false},
  2085  		{nil, Typ[Int], false},
  2086  		{nil, nil, true},
  2087  	} {
  2088  		if got := Identical(test.x, test.y); got != test.want {
  2089  			t.Errorf("Identical(%v, %v) = %t", test.x, test.y, got)
  2090  		}
  2091  	}
  2092  }
  2093  
  2094  func TestIdenticalUnions(t *testing.T) {
  2095  	tname := NewTypeName(nopos, nil, "myInt", nil)
  2096  	myInt := NewNamed(tname, Typ[Int], nil)
  2097  	tmap := map[string]*Term{
  2098  		"int":     NewTerm(false, Typ[Int]),
  2099  		"~int":    NewTerm(true, Typ[Int]),
  2100  		"string":  NewTerm(false, Typ[String]),
  2101  		"~string": NewTerm(true, Typ[String]),
  2102  		"myInt":   NewTerm(false, myInt),
  2103  	}
  2104  	makeUnion := func(s string) *Union {
  2105  		parts := strings.Split(s, "|")
  2106  		var terms []*Term
  2107  		for _, p := range parts {
  2108  			term := tmap[p]
  2109  			if term == nil {
  2110  				t.Fatalf("missing term %q", p)
  2111  			}
  2112  			terms = append(terms, term)
  2113  		}
  2114  		return NewUnion(terms)
  2115  	}
  2116  	for _, test := range []struct {
  2117  		x, y string
  2118  		want bool
  2119  	}{
  2120  		// These tests are just sanity checks. The tests for type sets and
  2121  		// interfaces provide much more test coverage.
  2122  		{"int|~int", "~int", true},
  2123  		{"myInt|~int", "~int", true},
  2124  		{"int|string", "string|int", true},
  2125  		{"int|int|string", "string|int", true},
  2126  		{"myInt|string", "int|string", false},
  2127  	} {
  2128  		x := makeUnion(test.x)
  2129  		y := makeUnion(test.y)
  2130  		if got := Identical(x, y); got != test.want {
  2131  			t.Errorf("Identical(%v, %v) = %t", test.x, test.y, got)
  2132  		}
  2133  	}
  2134  }
  2135  
  2136  func TestIssue61737(t *testing.T) {
  2137  	// This test verifies that it is possible to construct invalid interfaces
  2138  	// containing duplicate methods using the go/types API.
  2139  	//
  2140  	// It must be possible for importers to construct such invalid interfaces.
  2141  	// Previously, this panicked.
  2142  
  2143  	sig1 := NewSignatureType(nil, nil, nil, NewTuple(NewParam(nopos, nil, "", Typ[Int])), nil, false)
  2144  	sig2 := NewSignatureType(nil, nil, nil, NewTuple(NewParam(nopos, nil, "", Typ[String])), nil, false)
  2145  
  2146  	methods := []*Func{
  2147  		NewFunc(nopos, nil, "M", sig1),
  2148  		NewFunc(nopos, nil, "M", sig2),
  2149  	}
  2150  
  2151  	embeddedMethods := []*Func{
  2152  		NewFunc(nopos, nil, "M", sig2),
  2153  	}
  2154  	embedded := NewInterfaceType(embeddedMethods, nil)
  2155  	iface := NewInterfaceType(methods, []Type{embedded})
  2156  	iface.Complete()
  2157  }
  2158  
  2159  func TestNewAlias_Issue65455(t *testing.T) {
  2160  	obj := NewTypeName(nopos, nil, "A", nil)
  2161  	alias := NewAlias(obj, Typ[Int])
  2162  	alias.Underlying() // must not panic
  2163  }
  2164  
  2165  func TestIssue15305(t *testing.T) {
  2166  	const src = "package p; func f() int16; var _ = f(undef)"
  2167  	fset := token.NewFileSet()
  2168  	f := mustParse(fset, src)
  2169  	conf := Config{
  2170  		Error: func(err error) {}, // allow errors
  2171  	}
  2172  	info := &Info{
  2173  		Types: make(map[ast.Expr]TypeAndValue),
  2174  	}
  2175  	conf.Check("p", fset, []*ast.File{f}, info) // ignore result
  2176  	for e, tv := range info.Types {
  2177  		if _, ok := e.(*ast.CallExpr); ok {
  2178  			if tv.Type != Typ[Int16] {
  2179  				t.Errorf("CallExpr has type %v, want int16", tv.Type)
  2180  			}
  2181  			return
  2182  		}
  2183  	}
  2184  	t.Errorf("CallExpr has no type")
  2185  }
  2186  
  2187  // TestCompositeLitTypes verifies that Info.Types registers the correct
  2188  // types for composite literal expressions and composite literal type
  2189  // expressions.
  2190  func TestCompositeLitTypes(t *testing.T) {
  2191  	for i, test := range []struct {
  2192  		lit, typ string
  2193  	}{
  2194  		{`[16]byte{}`, `[16]byte`},
  2195  		{`[...]byte{}`, `[0]byte`},                // test for go.dev/issue/14092
  2196  		{`[...]int{1, 2, 3}`, `[3]int`},           // test for go.dev/issue/14092
  2197  		{`[...]int{90: 0, 98: 1, 2}`, `[100]int`}, // test for go.dev/issue/14092
  2198  		{`[]int{}`, `[]int`},
  2199  		{`map[string]bool{"foo": true}`, `map[string]bool`},
  2200  		{`struct{}{}`, `struct{}`},
  2201  		{`struct{x, y int; z complex128}{}`, `struct{x int; y int; z complex128}`},
  2202  	} {
  2203  		fset := token.NewFileSet()
  2204  		f := mustParse(fset, fmt.Sprintf("package p%d; var _ = %s", i, test.lit))
  2205  		types := make(map[ast.Expr]TypeAndValue)
  2206  		if _, err := new(Config).Check("p", fset, []*ast.File{f}, &Info{Types: types}); err != nil {
  2207  			t.Fatalf("%s: %v", test.lit, err)
  2208  		}
  2209  
  2210  		cmptype := func(x ast.Expr, want string) {
  2211  			tv, ok := types[x]
  2212  			if !ok {
  2213  				t.Errorf("%s: no Types entry found", test.lit)
  2214  				return
  2215  			}
  2216  			if tv.Type == nil {
  2217  				t.Errorf("%s: type is nil", test.lit)
  2218  				return
  2219  			}
  2220  			if got := tv.Type.String(); got != want {
  2221  				t.Errorf("%s: got %v, want %s", test.lit, got, want)
  2222  			}
  2223  		}
  2224  
  2225  		// test type of composite literal expression
  2226  		rhs := f.Decls[0].(*ast.GenDecl).Specs[0].(*ast.ValueSpec).Values[0]
  2227  		cmptype(rhs, test.typ)
  2228  
  2229  		// test type of composite literal type expression
  2230  		cmptype(rhs.(*ast.CompositeLit).Type, test.typ)
  2231  	}
  2232  }
  2233  
  2234  // TestObjectParents verifies that objects have parent scopes or not
  2235  // as specified by the Object interface.
  2236  func TestObjectParents(t *testing.T) {
  2237  	const src = `
  2238  package p
  2239  
  2240  const C = 0
  2241  
  2242  type T1 struct {
  2243  	a, b int
  2244  	T2
  2245  }
  2246  
  2247  type T2 interface {
  2248  	im1()
  2249  	im2()
  2250  }
  2251  
  2252  func (T1) m1() {}
  2253  func (*T1) m2() {}
  2254  
  2255  func f(x int) { y := x; print(y) }
  2256  `
  2257  
  2258  	fset := token.NewFileSet()
  2259  	f := mustParse(fset, src)
  2260  
  2261  	info := &Info{
  2262  		Defs: make(map[*ast.Ident]Object),
  2263  	}
  2264  	if _, err := new(Config).Check("p", fset, []*ast.File{f}, info); err != nil {
  2265  		t.Fatal(err)
  2266  	}
  2267  
  2268  	for ident, obj := range info.Defs {
  2269  		if obj == nil {
  2270  			// only package names and implicit vars have a nil object
  2271  			// (in this test we only need to handle the package name)
  2272  			if ident.Name != "p" {
  2273  				t.Errorf("%v has nil object", ident)
  2274  			}
  2275  			continue
  2276  		}
  2277  
  2278  		// struct fields, type-associated and interface methods
  2279  		// have no parent scope
  2280  		wantParent := true
  2281  		switch obj := obj.(type) {
  2282  		case *Var:
  2283  			if obj.IsField() {
  2284  				wantParent = false
  2285  			}
  2286  		case *Func:
  2287  			if obj.Signature().Recv() != nil { // method
  2288  				wantParent = false
  2289  			}
  2290  		}
  2291  
  2292  		gotParent := obj.Parent() != nil
  2293  		switch {
  2294  		case gotParent && !wantParent:
  2295  			t.Errorf("%v: want no parent, got %s", ident, obj.Parent())
  2296  		case !gotParent && wantParent:
  2297  			t.Errorf("%v: no parent found", ident)
  2298  		}
  2299  	}
  2300  }
  2301  
  2302  // TestFailedImport tests that we don't get follow-on errors
  2303  // elsewhere in a package due to failing to import a package.
  2304  func TestFailedImport(t *testing.T) {
  2305  	testenv.MustHaveGoBuild(t)
  2306  
  2307  	const src = `
  2308  package p
  2309  
  2310  import foo "go/types/thisdirectorymustnotexistotherwisethistestmayfail/foo" // should only see an error here
  2311  
  2312  const c = foo.C
  2313  type T = foo.T
  2314  var v T = c
  2315  func f(x T) T { return foo.F(x) }
  2316  `
  2317  	fset := token.NewFileSet()
  2318  	f := mustParse(fset, src)
  2319  	files := []*ast.File{f}
  2320  
  2321  	// type-check using all possible importers
  2322  	for _, compiler := range []string{"gc", "gccgo", "source"} {
  2323  		errcount := 0
  2324  		conf := Config{
  2325  			Error: func(err error) {
  2326  				// we should only see the import error
  2327  				if errcount > 0 || !strings.Contains(err.Error(), "could not import") {
  2328  					t.Errorf("for %s importer, got unexpected error: %v", compiler, err)
  2329  				}
  2330  				errcount++
  2331  			},
  2332  			Importer: importer.For(compiler, nil),
  2333  		}
  2334  
  2335  		info := &Info{
  2336  			Uses: make(map[*ast.Ident]Object),
  2337  		}
  2338  		pkg, _ := conf.Check("p", fset, files, info)
  2339  		if pkg == nil {
  2340  			t.Errorf("for %s importer, type-checking failed to return a package", compiler)
  2341  			continue
  2342  		}
  2343  
  2344  		imports := pkg.Imports()
  2345  		if len(imports) != 1 {
  2346  			t.Errorf("for %s importer, got %d imports, want 1", compiler, len(imports))
  2347  			continue
  2348  		}
  2349  		imp := imports[0]
  2350  		if imp.Name() != "foo" {
  2351  			t.Errorf(`for %s importer, got %q, want "foo"`, compiler, imp.Name())
  2352  			continue
  2353  		}
  2354  
  2355  		// verify that all uses of foo refer to the imported package foo (imp)
  2356  		for ident, obj := range info.Uses {
  2357  			if ident.Name == "foo" {
  2358  				if obj, ok := obj.(*PkgName); ok {
  2359  					if obj.Imported() != imp {
  2360  						t.Errorf("%s resolved to %v; want %v", ident, obj.Imported(), imp)
  2361  					}
  2362  				} else {
  2363  					t.Errorf("%s resolved to %v; want package name", ident, obj)
  2364  				}
  2365  			}
  2366  		}
  2367  	}
  2368  }
  2369  
  2370  func TestInstantiate(t *testing.T) {
  2371  	// eventually we like more tests but this is a start
  2372  	const src = "package p; type T[P any] *T[P]"
  2373  	pkg := mustTypecheck(src, nil, nil)
  2374  
  2375  	// type T should have one type parameter
  2376  	T := pkg.Scope().Lookup("T").Type().(*Named)
  2377  	if n := T.TypeParams().Len(); n != 1 {
  2378  		t.Fatalf("expected 1 type parameter; found %d", n)
  2379  	}
  2380  
  2381  	// instantiation should succeed (no endless recursion)
  2382  	// even with a nil *Checker
  2383  	res, err := Instantiate(nil, T, []Type{Typ[Int]}, false)
  2384  	if err != nil {
  2385  		t.Fatal(err)
  2386  	}
  2387  
  2388  	// instantiated type should point to itself
  2389  	if p := res.Underlying().(*Pointer).Elem(); p != res {
  2390  		t.Fatalf("unexpected result type: %s points to %s", res, p)
  2391  	}
  2392  }
  2393  
  2394  func TestInstantiateConcurrent(t *testing.T) {
  2395  	const src = `package p
  2396  
  2397  type I[P any] interface {
  2398  	m(P)
  2399  	n() P
  2400  }
  2401  
  2402  type J = I[int]
  2403  
  2404  type Nested[P any] *interface{b(P)}
  2405  
  2406  type K = Nested[string]
  2407  `
  2408  	pkg := mustTypecheck(src, nil, nil)
  2409  
  2410  	insts := []*Interface{
  2411  		pkg.Scope().Lookup("J").Type().Underlying().(*Interface),
  2412  		pkg.Scope().Lookup("K").Type().Underlying().(*Pointer).Elem().(*Interface),
  2413  	}
  2414  
  2415  	// Use the interface instances concurrently.
  2416  	for _, inst := range insts {
  2417  		var (
  2418  			counts  [2]int      // method counts
  2419  			methods [2][]string // method strings
  2420  		)
  2421  		var wg sync.WaitGroup
  2422  		for i := 0; i < 2; i++ {
  2423  			i := i
  2424  			wg.Add(1)
  2425  			go func() {
  2426  				defer wg.Done()
  2427  
  2428  				counts[i] = inst.NumMethods()
  2429  				for mi := 0; mi < counts[i]; mi++ {
  2430  					methods[i] = append(methods[i], inst.Method(mi).String())
  2431  				}
  2432  			}()
  2433  		}
  2434  		wg.Wait()
  2435  
  2436  		if counts[0] != counts[1] {
  2437  			t.Errorf("mismatching method counts for %s: %d vs %d", inst, counts[0], counts[1])
  2438  			continue
  2439  		}
  2440  		for i := 0; i < counts[0]; i++ {
  2441  			if m0, m1 := methods[0][i], methods[1][i]; m0 != m1 {
  2442  				t.Errorf("mismatching methods for %s: %s vs %s", inst, m0, m1)
  2443  			}
  2444  		}
  2445  	}
  2446  }
  2447  
  2448  func TestInstantiateErrors(t *testing.T) {
  2449  	tests := []struct {
  2450  		src    string // by convention, T must be the type being instantiated
  2451  		targs  []Type
  2452  		wantAt int // -1 indicates no error
  2453  	}{
  2454  		{"type T[P interface{~string}] int", []Type{Typ[Int]}, 0},
  2455  		{"type T[P1 interface{int}, P2 interface{~string}] int", []Type{Typ[Int], Typ[Int]}, 1},
  2456  		{"type T[P1 any, P2 interface{~[]P1}] int", []Type{Typ[Int], NewSlice(Typ[String])}, 1},
  2457  		{"type T[P1 interface{~[]P2}, P2 any] int", []Type{NewSlice(Typ[String]), Typ[Int]}, 0},
  2458  	}
  2459  
  2460  	for _, test := range tests {
  2461  		src := "package p; " + test.src
  2462  		pkg := mustTypecheck(src, nil, nil)
  2463  
  2464  		T := pkg.Scope().Lookup("T").Type().(*Named)
  2465  
  2466  		_, err := Instantiate(nil, T, test.targs, true)
  2467  		if err == nil {
  2468  			t.Fatalf("Instantiate(%v, %v) returned nil error, want non-nil", T, test.targs)
  2469  		}
  2470  
  2471  		var argErr *ArgumentError
  2472  		if !errors.As(err, &argErr) {
  2473  			t.Fatalf("Instantiate(%v, %v): error is not an *ArgumentError", T, test.targs)
  2474  		}
  2475  
  2476  		if argErr.Index != test.wantAt {
  2477  			t.Errorf("Instantiate(%v, %v): error at index %d, want index %d", T, test.targs, argErr.Index, test.wantAt)
  2478  		}
  2479  	}
  2480  }
  2481  
  2482  func TestArgumentErrorUnwrapping(t *testing.T) {
  2483  	var err error = &ArgumentError{
  2484  		Index: 1,
  2485  		Err:   Error{Msg: "test"},
  2486  	}
  2487  	var e Error
  2488  	if !errors.As(err, &e) {
  2489  		t.Fatalf("error %v does not wrap types.Error", err)
  2490  	}
  2491  	if e.Msg != "test" {
  2492  		t.Errorf("e.Msg = %q, want %q", e.Msg, "test")
  2493  	}
  2494  }
  2495  
  2496  func TestInstanceIdentity(t *testing.T) {
  2497  	imports := make(testImporter)
  2498  	conf := Config{Importer: imports}
  2499  	makePkg := func(src string) {
  2500  		fset := token.NewFileSet()
  2501  		f := mustParse(fset, src)
  2502  		name := f.Name.Name
  2503  		pkg, err := conf.Check(name, fset, []*ast.File{f}, nil)
  2504  		if err != nil {
  2505  			t.Fatal(err)
  2506  		}
  2507  		imports[name] = pkg
  2508  	}
  2509  	makePkg(`package lib; type T[P any] struct{}`)
  2510  	makePkg(`package a; import "lib"; var A lib.T[int]`)
  2511  	makePkg(`package b; import "lib"; var B lib.T[int]`)
  2512  	a := imports["a"].Scope().Lookup("A")
  2513  	b := imports["b"].Scope().Lookup("B")
  2514  	if !Identical(a.Type(), b.Type()) {
  2515  		t.Errorf("mismatching types: a.A: %s, b.B: %s", a.Type(), b.Type())
  2516  	}
  2517  }
  2518  
  2519  // TestInstantiatedObjects verifies properties of instantiated objects.
  2520  func TestInstantiatedObjects(t *testing.T) {
  2521  	const src = `
  2522  package p
  2523  
  2524  type T[P any] struct {
  2525  	field P
  2526  }
  2527  
  2528  func (recv *T[Q]) concreteMethod(mParam Q) (mResult Q) { return }
  2529  
  2530  type FT[P any] func(ftParam P) (ftResult P)
  2531  
  2532  func F[P any](fParam P) (fResult P){ return }
  2533  
  2534  type I[P any] interface {
  2535  	interfaceMethod(P)
  2536  }
  2537  
  2538  type R[P any] T[P]
  2539  
  2540  func (R[P]) m() {} // having a method triggers expansion of R
  2541  
  2542  var (
  2543  	t T[int]
  2544  	ft FT[int]
  2545  	f = F[int]
  2546  	i I[int]
  2547  )
  2548  
  2549  func fn() {
  2550  	var r R[int]
  2551  	_ = r
  2552  }
  2553  `
  2554  	info := &Info{
  2555  		Defs: make(map[*ast.Ident]Object),
  2556  	}
  2557  	fset := token.NewFileSet()
  2558  	f := mustParse(fset, src)
  2559  	conf := Config{}
  2560  	pkg, err := conf.Check(f.Name.Name, fset, []*ast.File{f}, info)
  2561  	if err != nil {
  2562  		t.Fatal(err)
  2563  	}
  2564  
  2565  	lookup := func(name string) Type { return pkg.Scope().Lookup(name).Type() }
  2566  	fnScope := pkg.Scope().Lookup("fn").(*Func).Scope()
  2567  
  2568  	tests := []struct {
  2569  		name string
  2570  		obj  Object
  2571  	}{
  2572  		// Struct fields
  2573  		{"field", lookup("t").Underlying().(*Struct).Field(0)},
  2574  		{"field", fnScope.Lookup("r").Type().Underlying().(*Struct).Field(0)},
  2575  
  2576  		// Methods and method fields
  2577  		{"concreteMethod", lookup("t").(*Named).Method(0)},
  2578  		{"recv", lookup("t").(*Named).Method(0).Signature().Recv()},
  2579  		{"mParam", lookup("t").(*Named).Method(0).Signature().Params().At(0)},
  2580  		{"mResult", lookup("t").(*Named).Method(0).Signature().Results().At(0)},
  2581  
  2582  		// Interface methods
  2583  		{"interfaceMethod", lookup("i").Underlying().(*Interface).Method(0)},
  2584  
  2585  		// Function type fields
  2586  		{"ftParam", lookup("ft").Underlying().(*Signature).Params().At(0)},
  2587  		{"ftResult", lookup("ft").Underlying().(*Signature).Results().At(0)},
  2588  
  2589  		// Function fields
  2590  		{"fParam", lookup("f").(*Signature).Params().At(0)},
  2591  		{"fResult", lookup("f").(*Signature).Results().At(0)},
  2592  	}
  2593  
  2594  	// Collect all identifiers by name.
  2595  	idents := make(map[string][]*ast.Ident)
  2596  	ast.Inspect(f, func(n ast.Node) bool {
  2597  		if id, ok := n.(*ast.Ident); ok {
  2598  			idents[id.Name] = append(idents[id.Name], id)
  2599  		}
  2600  		return true
  2601  	})
  2602  
  2603  	for _, test := range tests {
  2604  		test := test
  2605  		t.Run(test.name, func(t *testing.T) {
  2606  			if got := len(idents[test.name]); got != 1 {
  2607  				t.Fatalf("found %d identifiers named %s, want 1", got, test.name)
  2608  			}
  2609  			ident := idents[test.name][0]
  2610  			def := info.Defs[ident]
  2611  			if def == test.obj {
  2612  				t.Fatalf("info.Defs[%s] contains the test object", test.name)
  2613  			}
  2614  			if orig := originObject(test.obj); def != orig {
  2615  				t.Errorf("info.Defs[%s] does not match obj.Origin()", test.name)
  2616  			}
  2617  			if def.Pkg() != test.obj.Pkg() {
  2618  				t.Errorf("Pkg() = %v, want %v", def.Pkg(), test.obj.Pkg())
  2619  			}
  2620  			if def.Name() != test.obj.Name() {
  2621  				t.Errorf("Name() = %v, want %v", def.Name(), test.obj.Name())
  2622  			}
  2623  			if def.Pos() != test.obj.Pos() {
  2624  				t.Errorf("Pos() = %v, want %v", def.Pos(), test.obj.Pos())
  2625  			}
  2626  			if def.Parent() != test.obj.Parent() {
  2627  				t.Fatalf("Parent() = %v, want %v", def.Parent(), test.obj.Parent())
  2628  			}
  2629  			if def.Exported() != test.obj.Exported() {
  2630  				t.Fatalf("Exported() = %v, want %v", def.Exported(), test.obj.Exported())
  2631  			}
  2632  			if def.Id() != test.obj.Id() {
  2633  				t.Fatalf("Id() = %v, want %v", def.Id(), test.obj.Id())
  2634  			}
  2635  			// String and Type are expected to differ.
  2636  		})
  2637  	}
  2638  }
  2639  
  2640  func originObject(obj Object) Object {
  2641  	switch obj := obj.(type) {
  2642  	case *Var:
  2643  		return obj.Origin()
  2644  	case *Func:
  2645  		return obj.Origin()
  2646  	}
  2647  	return obj
  2648  }
  2649  
  2650  func TestImplements(t *testing.T) {
  2651  	const src = `
  2652  package p
  2653  
  2654  type EmptyIface interface{}
  2655  
  2656  type I interface {
  2657  	m()
  2658  }
  2659  
  2660  type C interface {
  2661  	m()
  2662  	~int
  2663  }
  2664  
  2665  type Integer interface{
  2666  	int8 | int16 | int32 | int64
  2667  }
  2668  
  2669  type EmptyTypeSet interface{
  2670  	Integer
  2671  	~string
  2672  }
  2673  
  2674  type N1 int
  2675  func (N1) m() {}
  2676  
  2677  type N2 int
  2678  func (*N2) m() {}
  2679  
  2680  type N3 int
  2681  func (N3) m(int) {}
  2682  
  2683  type N4 string
  2684  func (N4) m()
  2685  
  2686  type Bad Bad // invalid type
  2687  `
  2688  
  2689  	fset := token.NewFileSet()
  2690  	f := mustParse(fset, src)
  2691  	conf := Config{Error: func(error) {}}
  2692  	pkg, _ := conf.Check(f.Name.Name, fset, []*ast.File{f}, nil)
  2693  
  2694  	lookup := func(tname string) Type { return pkg.Scope().Lookup(tname).Type() }
  2695  	var (
  2696  		EmptyIface   = lookup("EmptyIface").Underlying().(*Interface)
  2697  		I            = lookup("I").(*Named)
  2698  		II           = I.Underlying().(*Interface)
  2699  		C            = lookup("C").(*Named)
  2700  		CI           = C.Underlying().(*Interface)
  2701  		Integer      = lookup("Integer").Underlying().(*Interface)
  2702  		EmptyTypeSet = lookup("EmptyTypeSet").Underlying().(*Interface)
  2703  		N1           = lookup("N1")
  2704  		N1p          = NewPointer(N1)
  2705  		N2           = lookup("N2")
  2706  		N2p          = NewPointer(N2)
  2707  		N3           = lookup("N3")
  2708  		N4           = lookup("N4")
  2709  		Bad          = lookup("Bad")
  2710  	)
  2711  
  2712  	tests := []struct {
  2713  		V    Type
  2714  		T    *Interface
  2715  		want bool
  2716  	}{
  2717  		{I, II, true},
  2718  		{I, CI, false},
  2719  		{C, II, true},
  2720  		{C, CI, true},
  2721  		{Typ[Int8], Integer, true},
  2722  		{Typ[Int64], Integer, true},
  2723  		{Typ[String], Integer, false},
  2724  		{EmptyTypeSet, II, true},
  2725  		{EmptyTypeSet, EmptyTypeSet, true},
  2726  		{Typ[Int], EmptyTypeSet, false},
  2727  		{N1, II, true},
  2728  		{N1, CI, true},
  2729  		{N1p, II, true},
  2730  		{N1p, CI, false},
  2731  		{N2, II, false},
  2732  		{N2, CI, false},
  2733  		{N2p, II, true},
  2734  		{N2p, CI, false},
  2735  		{N3, II, false},
  2736  		{N3, CI, false},
  2737  		{N4, II, true},
  2738  		{N4, CI, false},
  2739  		{Bad, II, false},
  2740  		{Bad, CI, false},
  2741  		{Bad, EmptyIface, true},
  2742  	}
  2743  
  2744  	for _, test := range tests {
  2745  		if got := Implements(test.V, test.T); got != test.want {
  2746  			t.Errorf("Implements(%s, %s) = %t, want %t", test.V, test.T, got, test.want)
  2747  		}
  2748  
  2749  		// The type assertion x.(T) is valid if T is an interface or if T implements the type of x.
  2750  		// The assertion is never valid if T is a bad type.
  2751  		V := test.T
  2752  		T := test.V
  2753  		want := false
  2754  		if _, ok := T.Underlying().(*Interface); (ok || Implements(T, V)) && T != Bad {
  2755  			want = true
  2756  		}
  2757  		if got := AssertableTo(V, T); got != want {
  2758  			t.Errorf("AssertableTo(%s, %s) = %t, want %t", V, T, got, want)
  2759  		}
  2760  	}
  2761  }
  2762  
  2763  func TestMissingMethodAlternative(t *testing.T) {
  2764  	const src = `
  2765  package p
  2766  type T interface {
  2767  	m()
  2768  }
  2769  
  2770  type V0 struct{}
  2771  func (V0) m() {}
  2772  
  2773  type V1 struct{}
  2774  
  2775  type V2 struct{}
  2776  func (V2) m() int
  2777  
  2778  type V3 struct{}
  2779  func (*V3) m()
  2780  
  2781  type V4 struct{}
  2782  func (V4) M()
  2783  `
  2784  
  2785  	pkg := mustTypecheck(src, nil, nil)
  2786  
  2787  	T := pkg.Scope().Lookup("T").Type().Underlying().(*Interface)
  2788  	lookup := func(name string) (*Func, bool) {
  2789  		return MissingMethod(pkg.Scope().Lookup(name).Type(), T, true)
  2790  	}
  2791  
  2792  	// V0 has method m with correct signature. Should not report wrongType.
  2793  	method, wrongType := lookup("V0")
  2794  	if method != nil || wrongType {
  2795  		t.Fatalf("V0: got method = %v, wrongType = %v", method, wrongType)
  2796  	}
  2797  
  2798  	checkMissingMethod := func(tname string, reportWrongType bool) {
  2799  		method, wrongType := lookup(tname)
  2800  		if method == nil || method.Name() != "m" || wrongType != reportWrongType {
  2801  			t.Fatalf("%s: got method = %v, wrongType = %v", tname, method, wrongType)
  2802  		}
  2803  	}
  2804  
  2805  	// V1 has no method m. Should not report wrongType.
  2806  	checkMissingMethod("V1", false)
  2807  
  2808  	// V2 has method m with wrong signature type (ignoring receiver). Should report wrongType.
  2809  	checkMissingMethod("V2", true)
  2810  
  2811  	// V3 has no method m but it exists on *V3. Should report wrongType.
  2812  	checkMissingMethod("V3", true)
  2813  
  2814  	// V4 has no method m but has M. Should not report wrongType.
  2815  	checkMissingMethod("V4", false)
  2816  }
  2817  
  2818  func TestErrorURL(t *testing.T) {
  2819  	var conf Config
  2820  	*stringFieldAddr(&conf, "_ErrorURL") = " [go.dev/e/%s]"
  2821  
  2822  	// test case for a one-line error
  2823  	const src1 = `
  2824  package p
  2825  var _ T
  2826  `
  2827  	_, err := typecheck(src1, &conf, nil)
  2828  	if err == nil || !strings.HasSuffix(err.Error(), " [go.dev/e/UndeclaredName]") {
  2829  		t.Errorf("src1: unexpected error: got %v", err)
  2830  	}
  2831  
  2832  	// test case for a multi-line error
  2833  	const src2 = `
  2834  package p
  2835  func f() int { return 0 }
  2836  var _ = f(1, 2)
  2837  `
  2838  	_, err = typecheck(src2, &conf, nil)
  2839  	if err == nil || !strings.Contains(err.Error(), " [go.dev/e/WrongArgCount]\n") {
  2840  		t.Errorf("src1: unexpected error: got %v", err)
  2841  	}
  2842  }
  2843  
  2844  func TestModuleVersion(t *testing.T) {
  2845  	// version go1.dd must be able to typecheck go1.dd.0, go1.dd.1, etc.
  2846  	goversion := fmt.Sprintf("go1.%d", goversion.Version)
  2847  	for _, v := range []string{
  2848  		goversion,
  2849  		goversion + ".0",
  2850  		goversion + ".1",
  2851  		goversion + ".rc",
  2852  	} {
  2853  		conf := Config{GoVersion: v}
  2854  		pkg := mustTypecheck("package p", &conf, nil)
  2855  		if pkg.GoVersion() != conf.GoVersion {
  2856  			t.Errorf("got %s; want %s", pkg.GoVersion(), conf.GoVersion)
  2857  		}
  2858  	}
  2859  }
  2860  
  2861  func TestFileVersions(t *testing.T) {
  2862  	for _, test := range []struct {
  2863  		goVersion   string
  2864  		fileVersion string
  2865  		wantVersion string
  2866  	}{
  2867  		{"", "", ""},                    // no versions specified
  2868  		{"go1.19", "", "go1.19"},        // module version specified
  2869  		{"", "go1.20", "go1.21"},        // file version specified below minimum of 1.21
  2870  		{"go1", "", "go1"},              // no file version specified
  2871  		{"go1", "goo1.22", "go1"},       // invalid file version specified
  2872  		{"go1", "go1.19", "go1.21"},     // file version specified below minimum of 1.21
  2873  		{"go1", "go1.20", "go1.21"},     // file version specified below minimum of 1.21
  2874  		{"go1", "go1.21", "go1.21"},     // file version specified at 1.21
  2875  		{"go1", "go1.22", "go1.22"},     // file version specified above 1.21
  2876  		{"go1.19", "", "go1.19"},        // no file version specified
  2877  		{"go1.19", "goo1.22", "go1.19"}, // invalid file version specified
  2878  		{"go1.19", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2879  		{"go1.19", "go1.21", "go1.21"},  // file version specified at 1.21
  2880  		{"go1.19", "go1.22", "go1.22"},  // file version specified above 1.21
  2881  		{"go1.20", "", "go1.20"},        // no file version specified
  2882  		{"go1.20", "goo1.22", "go1.20"}, // invalid file version specified
  2883  		{"go1.20", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
  2884  		{"go1.20", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2885  		{"go1.20", "go1.21", "go1.21"},  // file version specified at 1.21
  2886  		{"go1.20", "go1.22", "go1.22"},  // file version specified above 1.21
  2887  		{"go1.21", "", "go1.21"},        // no file version specified
  2888  		{"go1.21", "goo1.22", "go1.21"}, // invalid file version specified
  2889  		{"go1.21", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
  2890  		{"go1.21", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2891  		{"go1.21", "go1.21", "go1.21"},  // file version specified at 1.21
  2892  		{"go1.21", "go1.22", "go1.22"},  // file version specified above 1.21
  2893  		{"go1.22", "", "go1.22"},        // no file version specified
  2894  		{"go1.22", "goo1.22", "go1.22"}, // invalid file version specified
  2895  		{"go1.22", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
  2896  		{"go1.22", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2897  		{"go1.22", "go1.21", "go1.21"},  // file version specified at 1.21
  2898  		{"go1.22", "go1.22", "go1.22"},  // file version specified above 1.21
  2899  
  2900  		// versions containing release numbers
  2901  		// (file versions containing release numbers are considered invalid)
  2902  		{"go1.19.0", "", "go1.19.0"},         // no file version specified
  2903  		{"go1.20.1", "go1.19.1", "go1.20.1"}, // invalid file version
  2904  		{"go1.20.1", "go1.21.1", "go1.20.1"}, // invalid file version
  2905  		{"go1.21.1", "go1.19.1", "go1.21.1"}, // invalid file version
  2906  		{"go1.21.1", "go1.21.1", "go1.21.1"}, // invalid file version
  2907  		{"go1.22.1", "go1.19.1", "go1.22.1"}, // invalid file version
  2908  		{"go1.22.1", "go1.21.1", "go1.22.1"}, // invalid file version
  2909  	} {
  2910  		var src string
  2911  		if test.fileVersion != "" {
  2912  			src = "//go:build " + test.fileVersion + "\n"
  2913  		}
  2914  		src += "package p"
  2915  
  2916  		conf := Config{GoVersion: test.goVersion}
  2917  		versions := make(map[*ast.File]string)
  2918  		var info Info
  2919  		info.FileVersions = versions
  2920  		mustTypecheck(src, &conf, &info)
  2921  
  2922  		n := 0
  2923  		for _, v := range versions {
  2924  			want := test.wantVersion
  2925  			if v != want {
  2926  				t.Errorf("%q: unexpected file version: got %q, want %q", src, v, want)
  2927  			}
  2928  			n++
  2929  		}
  2930  		if n != 1 {
  2931  			t.Errorf("%q: incorrect number of map entries: got %d", src, n)
  2932  		}
  2933  	}
  2934  }
  2935  
  2936  // TestTooNew ensures that "too new" errors are emitted when the file
  2937  // or module is tagged with a newer version of Go than this go/types.
  2938  func TestTooNew(t *testing.T) {
  2939  	for _, test := range []struct {
  2940  		goVersion   string // package's Go version (as if derived from go.mod file)
  2941  		fileVersion string // file's Go version (becomes a build tag)
  2942  		wantErr     string // expected substring of concatenation of all errors
  2943  	}{
  2944  		{"go1.98", "", "package requires newer Go version go1.98"},
  2945  		{"", "go1.99", "p:2:9: file requires newer Go version go1.99"},
  2946  		{"go1.98", "go1.99", "package requires newer Go version go1.98"}, // (two
  2947  		{"go1.98", "go1.99", "file requires newer Go version go1.99"},    // errors)
  2948  	} {
  2949  		var src string
  2950  		if test.fileVersion != "" {
  2951  			src = "//go:build " + test.fileVersion + "\n"
  2952  		}
  2953  		src += "package p; func f()"
  2954  
  2955  		var errs []error
  2956  		conf := Config{
  2957  			GoVersion: test.goVersion,
  2958  			Error:     func(err error) { errs = append(errs, err) },
  2959  		}
  2960  		info := &Info{Defs: make(map[*ast.Ident]Object)}
  2961  		typecheck(src, &conf, info)
  2962  		got := fmt.Sprint(errs)
  2963  		if !strings.Contains(got, test.wantErr) {
  2964  			t.Errorf("%q: unexpected error: got %q, want substring %q",
  2965  				src, got, test.wantErr)
  2966  		}
  2967  
  2968  		// Assert that declarations were type checked nonetheless.
  2969  		var gotObjs []string
  2970  		for id, obj := range info.Defs {
  2971  			if obj != nil {
  2972  				objStr := strings.ReplaceAll(fmt.Sprintf("%s:%T", id.Name, obj), "types2", "types")
  2973  				gotObjs = append(gotObjs, objStr)
  2974  			}
  2975  		}
  2976  		wantObjs := "f:*types.Func"
  2977  		if !strings.Contains(fmt.Sprint(gotObjs), wantObjs) {
  2978  			t.Errorf("%q: got %s, want substring %q",
  2979  				src, gotObjs, wantObjs)
  2980  		}
  2981  	}
  2982  }
  2983  
  2984  // This is a regression test for #66704.
  2985  func TestUnaliasTooSoonInCycle(t *testing.T) {
  2986  	setGotypesalias(t, true)
  2987  	const src = `package a
  2988  
  2989  var x T[B] // this appears to cause Unalias to be called on B while still Invalid
  2990  
  2991  type T[_ any] struct{}
  2992  type A T[B]
  2993  type B = T[A]
  2994  `
  2995  	pkg := mustTypecheck(src, nil, nil)
  2996  	B := pkg.Scope().Lookup("B")
  2997  
  2998  	got, want := Unalias(B.Type()).String(), "a.T[a.A]"
  2999  	if got != want {
  3000  		t.Errorf("Unalias(type B = T[A]) = %q, want %q", got, want)
  3001  	}
  3002  }
  3003  
  3004  func TestAlias_Rhs(t *testing.T) {
  3005  	setGotypesalias(t, true)
  3006  	const src = `package p
  3007  
  3008  type A = B
  3009  type B = C
  3010  type C = int
  3011  `
  3012  
  3013  	pkg := mustTypecheck(src, nil, nil)
  3014  	A := pkg.Scope().Lookup("A")
  3015  
  3016  	got, want := A.Type().(*Alias).Rhs().String(), "p.B"
  3017  	if got != want {
  3018  		t.Errorf("A.Rhs = %s, want %s", got, want)
  3019  	}
  3020  }
  3021  
  3022  // Test the hijacking described of "any" described in golang/go#66921, for type
  3023  // checking.
  3024  func TestAnyHijacking_Check(t *testing.T) {
  3025  	for _, enableAlias := range []bool{false, true} {
  3026  		t.Run(fmt.Sprintf("EnableAlias=%t", enableAlias), func(t *testing.T) {
  3027  			setGotypesalias(t, enableAlias)
  3028  			var wg sync.WaitGroup
  3029  			for i := 0; i < 10; i++ {
  3030  				wg.Add(1)
  3031  				go func() {
  3032  					defer wg.Done()
  3033  					pkg := mustTypecheck("package p; var x any", nil, nil)
  3034  					x := pkg.Scope().Lookup("x")
  3035  					if _, gotAlias := x.Type().(*Alias); gotAlias != enableAlias {
  3036  						t.Errorf(`Lookup("x").Type() is %T: got Alias: %t, want %t`, x.Type(), gotAlias, enableAlias)
  3037  					}
  3038  				}()
  3039  			}
  3040  			wg.Wait()
  3041  		})
  3042  	}
  3043  }
  3044  
  3045  // Test the hijacking described of "any" described in golang/go#66921, for
  3046  // Scope.Lookup outside of type checking.
  3047  func TestAnyHijacking_Lookup(t *testing.T) {
  3048  	for _, enableAlias := range []bool{false, true} {
  3049  		t.Run(fmt.Sprintf("EnableAlias=%t", enableAlias), func(t *testing.T) {
  3050  			setGotypesalias(t, enableAlias)
  3051  			a := Universe.Lookup("any")
  3052  			if _, gotAlias := a.Type().(*Alias); gotAlias != enableAlias {
  3053  				t.Errorf(`Lookup("x").Type() is %T: got Alias: %t, want %t`, a.Type(), gotAlias, enableAlias)
  3054  			}
  3055  		})
  3056  	}
  3057  }
  3058  
  3059  func setGotypesalias(t *testing.T, enable bool) {
  3060  	if enable {
  3061  		t.Setenv("GODEBUG", "gotypesalias=1")
  3062  	} else {
  3063  		t.Setenv("GODEBUG", "gotypesalias=0")
  3064  	}
  3065  }
  3066  
  3067  // TestVersionIssue69477 is a regression test for issue #69477,
  3068  // in which the type checker would panic while attempting
  3069  // to compute which file it is "in" based on syntax position.
  3070  func TestVersionIssue69477(t *testing.T) {
  3071  	fset := token.NewFileSet()
  3072  	f, _ := parser.ParseFile(fset, "a.go", "package p; const k = 123", 0)
  3073  
  3074  	// Set an invalid Pos on the BasicLit.
  3075  	ast.Inspect(f, func(n ast.Node) bool {
  3076  		if lit, ok := n.(*ast.BasicLit); ok {
  3077  			lit.ValuePos = 99999
  3078  		}
  3079  		return true
  3080  	})
  3081  
  3082  	// Type check. The checker will consult the effective
  3083  	// version for the BasicLit 123. This used to panic.
  3084  	pkg := NewPackage("p", "p")
  3085  	check := NewChecker(&Config{}, fset, pkg, nil)
  3086  	if err := check.Files([]*ast.File{f}); err != nil {
  3087  		t.Fatal(err)
  3088  	}
  3089  }
  3090  
  3091  // TestVersionWithoutPos is a regression test for issue #69477,
  3092  // in which the type checker would use position information
  3093  // to compute which file it is "in" based on syntax position.
  3094  //
  3095  // As a rule the type checker should not depend on position
  3096  // information for correctness, only for error messages and
  3097  // Object.Pos. (Scope.LookupParent was a mistake.)
  3098  //
  3099  // The Checker now holds the effective version in a state variable.
  3100  func TestVersionWithoutPos(t *testing.T) {
  3101  	fset := token.NewFileSet()
  3102  	f, _ := parser.ParseFile(fset, "a.go", "//go:build go1.22\n\npackage p; var _ int", 0)
  3103  
  3104  	// Splice in a decl from another file. Its pos will be wrong.
  3105  	f2, _ := parser.ParseFile(fset, "a.go", "package q; func _(s func(func() bool)) { for range s {} }", 0)
  3106  	f.Decls[0] = f2.Decls[0]
  3107  
  3108  	// Type check. The checker will consult the effective
  3109  	// version (1.22) for the for-range stmt to know whether
  3110  	// range-over-func are permitted: they are not.
  3111  	// (Previously, no error was reported.)
  3112  	pkg := NewPackage("p", "p")
  3113  	check := NewChecker(&Config{}, fset, pkg, nil)
  3114  	err := check.Files([]*ast.File{f})
  3115  	got := fmt.Sprint(err)
  3116  	want := "range over s (variable of type func(func() bool)): requires go1.23"
  3117  	if !strings.Contains(got, want) {
  3118  		t.Errorf("check error was %q, want substring %q", got, want)
  3119  	}
  3120  }
  3121  

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