operand.go

     1  // Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
     2  // Source: ../../cmd/compile/internal/types2/operand.go
     3  
     4  // Copyright 2012 The Go Authors. All rights reserved.
     5  // Use of this source code is governed by a BSD-style
     6  // license that can be found in the LICENSE file.
     7  
     8  // This file defines operands and associated operations.
     9  
    10  package types
    11  
    12  import (
    13  	"bytes"
    14  	"fmt"
    15  	"go/ast"
    16  	"go/constant"
    17  	"go/token"
    18  	. "internal/types/errors"
    19  )
    20  
    21  // An operandMode specifies the (addressing) mode of an operand.
    22  type operandMode byte
    23  
    24  const (
    25  	invalid   operandMode = iota // operand is invalid
    26  	novalue                      // operand represents no value (result of a function call w/o result)
    27  	builtin                      // operand is a built-in function
    28  	typexpr                      // operand is a type
    29  	constant_                    // operand is a constant; the operand's typ is a Basic type
    30  	variable                     // operand is an addressable variable
    31  	mapindex                     // operand is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment)
    32  	value                        // operand is a computed value
    33  	nilvalue                     // operand is the nil value - only used by types2
    34  	commaok                      // like value, but operand may be used in a comma,ok expression
    35  	commaerr                     // like commaok, but second value is error, not boolean
    36  	cgofunc                      // operand is a cgo function
    37  )
    38  
    39  var operandModeString = [...]string{
    40  	invalid:   "invalid operand",
    41  	novalue:   "no value",
    42  	builtin:   "built-in",
    43  	typexpr:   "type",
    44  	constant_: "constant",
    45  	variable:  "variable",
    46  	mapindex:  "map index expression",
    47  	value:     "value",
    48  	nilvalue:  "nil", // only used by types2
    49  	commaok:   "comma, ok expression",
    50  	commaerr:  "comma, error expression",
    51  	cgofunc:   "cgo function",
    52  }
    53  
    54  // An operand represents an intermediate value during type checking.
    55  // Operands have an (addressing) mode, the expression evaluating to
    56  // the operand, the operand's type, a value for constants, and an id
    57  // for built-in functions.
    58  // The zero value of operand is a ready to use invalid operand.
    59  type operand struct {
    60  	mode operandMode
    61  	expr ast.Expr
    62  	typ  Type
    63  	val  constant.Value
    64  	id   builtinId
    65  }
    66  
    67  // Pos returns the position of the expression corresponding to x.
    68  // If x is invalid the position is nopos.
    69  func (x *operand) Pos() token.Pos {
    70  	// x.expr may not be set if x is invalid
    71  	if x.expr == nil {
    72  		return nopos
    73  	}
    74  	return x.expr.Pos()
    75  }
    76  
    77  // Operand string formats
    78  // (not all "untyped" cases can appear due to the type system,
    79  // but they fall out naturally here)
    80  //
    81  // mode       format
    82  //
    83  // invalid    <expr> (               <mode>                    )
    84  // novalue    <expr> (               <mode>                    )
    85  // builtin    <expr> (               <mode>                    )
    86  // typexpr    <expr> (               <mode>                    )
    87  //
    88  // constant   <expr> (<untyped kind> <mode>                    )
    89  // constant   <expr> (               <mode>       of type <typ>)
    90  // constant   <expr> (<untyped kind> <mode> <val>              )
    91  // constant   <expr> (               <mode> <val> of type <typ>)
    92  //
    93  // variable   <expr> (<untyped kind> <mode>                    )
    94  // variable   <expr> (               <mode>       of type <typ>)
    95  //
    96  // mapindex   <expr> (<untyped kind> <mode>                    )
    97  // mapindex   <expr> (               <mode>       of type <typ>)
    98  //
    99  // value      <expr> (<untyped kind> <mode>                    )
   100  // value      <expr> (               <mode>       of type <typ>)
   101  //
   102  // nilvalue   untyped nil
   103  // nilvalue   nil    (                            of type <typ>)
   104  //
   105  // commaok    <expr> (<untyped kind> <mode>                    )
   106  // commaok    <expr> (               <mode>       of type <typ>)
   107  //
   108  // commaerr   <expr> (<untyped kind> <mode>                    )
   109  // commaerr   <expr> (               <mode>       of type <typ>)
   110  //
   111  // cgofunc    <expr> (<untyped kind> <mode>                    )
   112  // cgofunc    <expr> (               <mode>       of type <typ>)
   113  func operandString(x *operand, qf Qualifier) string {
   114  	// special-case nil
   115  	if isTypes2 {
   116  		if x.mode == nilvalue {
   117  			switch x.typ {
   118  			case nil, Typ[Invalid]:
   119  				return "nil (with invalid type)"
   120  			case Typ[UntypedNil]:
   121  				return "nil"
   122  			default:
   123  				return fmt.Sprintf("nil (of type %s)", TypeString(x.typ, qf))
   124  			}
   125  		}
   126  	} else { // go/types
   127  		if x.mode == value && x.typ == Typ[UntypedNil] {
   128  			return "nil"
   129  		}
   130  	}
   131  
   132  	var buf bytes.Buffer
   133  
   134  	var expr string
   135  	if x.expr != nil {
   136  		expr = ExprString(x.expr)
   137  	} else {
   138  		switch x.mode {
   139  		case builtin:
   140  			expr = predeclaredFuncs[x.id].name
   141  		case typexpr:
   142  			expr = TypeString(x.typ, qf)
   143  		case constant_:
   144  			expr = x.val.String()
   145  		}
   146  	}
   147  
   148  	// <expr> (
   149  	if expr != "" {
   150  		buf.WriteString(expr)
   151  		buf.WriteString(" (")
   152  	}
   153  
   154  	// <untyped kind>
   155  	hasType := false
   156  	switch x.mode {
   157  	case invalid, novalue, builtin, typexpr:
   158  		// no type
   159  	default:
   160  		// should have a type, but be cautious (don't crash during printing)
   161  		if x.typ != nil {
   162  			if isUntyped(x.typ) {
   163  				buf.WriteString(x.typ.(*Basic).name)
   164  				buf.WriteByte(' ')
   165  				break
   166  			}
   167  			hasType = true
   168  		}
   169  	}
   170  
   171  	// <mode>
   172  	buf.WriteString(operandModeString[x.mode])
   173  
   174  	// <val>
   175  	if x.mode == constant_ {
   176  		if s := x.val.String(); s != expr {
   177  			buf.WriteByte(' ')
   178  			buf.WriteString(s)
   179  		}
   180  	}
   181  
   182  	// <typ>
   183  	if hasType {
   184  		if isValid(x.typ) {
   185  			var desc string
   186  			if isGeneric(x.typ) {
   187  				desc = "generic "
   188  			}
   189  
   190  			// Describe the type structure if it is an *Alias or *Named type.
   191  			// If the type is a renamed basic type, describe the basic type,
   192  			// as in "int32 type MyInt" for a *Named type MyInt.
   193  			// If it is a type parameter, describe the constraint instead.
   194  			tpar, _ := Unalias(x.typ).(*TypeParam)
   195  			if tpar == nil {
   196  				switch x.typ.(type) {
   197  				case *Alias, *Named:
   198  					what := compositeKind(x.typ)
   199  					if what == "" {
   200  						// x.typ must be basic type
   201  						what = under(x.typ).(*Basic).name
   202  					}
   203  					desc += what + " "
   204  				}
   205  			}
   206  			// desc is "" or has a trailing space at the end
   207  
   208  			buf.WriteString(" of " + desc + "type ")
   209  			WriteType(&buf, x.typ, qf)
   210  
   211  			if tpar != nil {
   212  				buf.WriteString(" constrained by ")
   213  				WriteType(&buf, tpar.bound, qf) // do not compute interface type sets here
   214  				// If we have the type set and it's empty, say so for better error messages.
   215  				if hasEmptyTypeset(tpar) {
   216  					buf.WriteString(" with empty type set")
   217  				}
   218  			}
   219  		} else {
   220  			buf.WriteString(" with invalid type")
   221  		}
   222  	}
   223  
   224  	// )
   225  	if expr != "" {
   226  		buf.WriteByte(')')
   227  	}
   228  
   229  	return buf.String()
   230  }
   231  
   232  // compositeKind returns the kind of the given composite type
   233  // ("array", "slice", etc.) or the empty string if typ is not
   234  // composite but a basic type.
   235  func compositeKind(typ Type) string {
   236  	switch under(typ).(type) {
   237  	case *Basic:
   238  		return ""
   239  	case *Array:
   240  		return "array"
   241  	case *Slice:
   242  		return "slice"
   243  	case *Struct:
   244  		return "struct"
   245  	case *Pointer:
   246  		return "pointer"
   247  	case *Signature:
   248  		return "func"
   249  	case *Interface:
   250  		return "interface"
   251  	case *Map:
   252  		return "map"
   253  	case *Chan:
   254  		return "chan"
   255  	case *Tuple:
   256  		return "tuple"
   257  	case *Union:
   258  		return "union"
   259  	default:
   260  		panic("unreachable")
   261  	}
   262  }
   263  
   264  func (x *operand) String() string {
   265  	return operandString(x, nil)
   266  }
   267  
   268  // setConst sets x to the untyped constant for literal lit.
   269  func (x *operand) setConst(k token.Token, lit string) {
   270  	var kind BasicKind
   271  	switch k {
   272  	case token.INT:
   273  		kind = UntypedInt
   274  	case token.FLOAT:
   275  		kind = UntypedFloat
   276  	case token.IMAG:
   277  		kind = UntypedComplex
   278  	case token.CHAR:
   279  		kind = UntypedRune
   280  	case token.STRING:
   281  		kind = UntypedString
   282  	default:
   283  		panic("unreachable")
   284  	}
   285  
   286  	val := makeFromLiteral(lit, k)
   287  	if val.Kind() == constant.Unknown {
   288  		x.mode = invalid
   289  		x.typ = Typ[Invalid]
   290  		return
   291  	}
   292  	x.mode = constant_
   293  	x.typ = Typ[kind]
   294  	x.val = val
   295  }
   296  
   297  // isNil reports whether x is the (untyped) nil value.
   298  func (x *operand) isNil() bool {
   299  	if isTypes2 {
   300  		return x.mode == nilvalue
   301  	} else { // go/types
   302  		return x.mode == value && x.typ == Typ[UntypedNil]
   303  	}
   304  }
   305  
   306  // assignableTo reports whether x is assignable to a variable of type T. If the
   307  // result is false and a non-nil cause is provided, it may be set to a more
   308  // detailed explanation of the failure (result != ""). The returned error code
   309  // is only valid if the (first) result is false. The check parameter may be nil
   310  // if assignableTo is invoked through an exported API call, i.e., when all
   311  // methods have been type-checked.
   312  func (x *operand) assignableTo(check *Checker, T Type, cause *string) (bool, Code) {
   313  	if x.mode == invalid || !isValid(T) {
   314  		return true, 0 // avoid spurious errors
   315  	}
   316  
   317  	origT := T
   318  	V := Unalias(x.typ)
   319  	T = Unalias(T)
   320  
   321  	// x's type is identical to T
   322  	if Identical(V, T) {
   323  		return true, 0
   324  	}
   325  
   326  	Vu := under(V)
   327  	Tu := under(T)
   328  	Vp, _ := V.(*TypeParam)
   329  	Tp, _ := T.(*TypeParam)
   330  
   331  	// x is an untyped value representable by a value of type T.
   332  	if isUntyped(Vu) {
   333  		assert(Vp == nil)
   334  		if Tp != nil {
   335  			// T is a type parameter: x is assignable to T if it is
   336  			// representable by each specific type in the type set of T.
   337  			return Tp.is(func(t *term) bool {
   338  				if t == nil {
   339  					return false
   340  				}
   341  				// A term may be a tilde term but the underlying
   342  				// type of an untyped value doesn't change so we
   343  				// don't need to do anything special.
   344  				newType, _, _ := check.implicitTypeAndValue(x, t.typ)
   345  				return newType != nil
   346  			}), IncompatibleAssign
   347  		}
   348  		newType, _, _ := check.implicitTypeAndValue(x, T)
   349  		return newType != nil, IncompatibleAssign
   350  	}
   351  	// Vu is typed
   352  
   353  	// x's type V and T have identical underlying types
   354  	// and at least one of V or T is not a named type
   355  	// and neither V nor T is a type parameter.
   356  	if Identical(Vu, Tu) && (!hasName(V) || !hasName(T)) && Vp == nil && Tp == nil {
   357  		return true, 0
   358  	}
   359  
   360  	// T is an interface type, but not a type parameter, and V implements T.
   361  	// Also handle the case where T is a pointer to an interface so that we get
   362  	// the Checker.implements error cause.
   363  	if _, ok := Tu.(*Interface); ok && Tp == nil || isInterfacePtr(Tu) {
   364  		if check.implements(V, T, false, cause) {
   365  			return true, 0
   366  		}
   367  		// V doesn't implement T but V may still be assignable to T if V
   368  		// is a type parameter; do not report an error in that case yet.
   369  		if Vp == nil {
   370  			return false, InvalidIfaceAssign
   371  		}
   372  		if cause != nil {
   373  			*cause = ""
   374  		}
   375  	}
   376  
   377  	// If V is an interface, check if a missing type assertion is the problem.
   378  	if Vi, _ := Vu.(*Interface); Vi != nil && Vp == nil {
   379  		if check.implements(T, V, false, nil) {
   380  			// T implements V, so give hint about type assertion.
   381  			if cause != nil {
   382  				*cause = "need type assertion"
   383  			}
   384  			return false, IncompatibleAssign
   385  		}
   386  	}
   387  
   388  	// x is a bidirectional channel value, T is a channel
   389  	// type, x's type V and T have identical element types,
   390  	// and at least one of V or T is not a named type.
   391  	if Vc, ok := Vu.(*Chan); ok && Vc.dir == SendRecv {
   392  		if Tc, ok := Tu.(*Chan); ok && Identical(Vc.elem, Tc.elem) {
   393  			return !hasName(V) || !hasName(T), InvalidChanAssign
   394  		}
   395  	}
   396  
   397  	// optimization: if we don't have type parameters, we're done
   398  	if Vp == nil && Tp == nil {
   399  		return false, IncompatibleAssign
   400  	}
   401  
   402  	errorf := func(format string, args ...any) {
   403  		if check != nil && cause != nil {
   404  			msg := check.sprintf(format, args...)
   405  			if *cause != "" {
   406  				msg += "\n\t" + *cause
   407  			}
   408  			*cause = msg
   409  		}
   410  	}
   411  
   412  	// x's type V is not a named type and T is a type parameter, and
   413  	// x is assignable to each specific type in T's type set.
   414  	if !hasName(V) && Tp != nil {
   415  		ok := false
   416  		code := IncompatibleAssign
   417  		Tp.is(func(T *term) bool {
   418  			if T == nil {
   419  				return false // no specific types
   420  			}
   421  			ok, code = x.assignableTo(check, T.typ, cause)
   422  			if !ok {
   423  				errorf("cannot assign %s to %s (in %s)", x.typ, T.typ, Tp)
   424  				return false
   425  			}
   426  			return true
   427  		})
   428  		return ok, code
   429  	}
   430  
   431  	// x's type V is a type parameter and T is not a named type,
   432  	// and values x' of each specific type in V's type set are
   433  	// assignable to T.
   434  	if Vp != nil && !hasName(T) {
   435  		x := *x // don't clobber outer x
   436  		ok := false
   437  		code := IncompatibleAssign
   438  		Vp.is(func(V *term) bool {
   439  			if V == nil {
   440  				return false // no specific types
   441  			}
   442  			x.typ = V.typ
   443  			ok, code = x.assignableTo(check, T, cause)
   444  			if !ok {
   445  				errorf("cannot assign %s (in %s) to %s", V.typ, Vp, origT)
   446  				return false
   447  			}
   448  			return true
   449  		})
   450  		return ok, code
   451  	}
   452  
   453  	return false, IncompatibleAssign
   454  }
   455
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