lookup.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  // This file implements various field and method lookup functions.
     6  
     7  package types2
     8  
     9  import "bytes"
    10  
    11  // Internal use of LookupFieldOrMethod: If the obj result is a method
    12  // associated with a concrete (non-interface) type, the method's signature
    13  // may not be fully set up. Call Checker.objDecl(obj, nil) before accessing
    14  // the method's type.
    15  
    16  // LookupFieldOrMethod looks up a field or method with given package and name
    17  // in T and returns the corresponding *Var or *Func, an index sequence, and a
    18  // bool indicating if there were any pointer indirections on the path to the
    19  // field or method. If addressable is set, T is the type of an addressable
    20  // variable (only matters for method lookups). T must not be nil.
    21  //
    22  // The last index entry is the field or method index in the (possibly embedded)
    23  // type where the entry was found, either:
    24  //
    25  //  1. the list of declared methods of a named type; or
    26  //  2. the list of all methods (method set) of an interface type; or
    27  //  3. the list of fields of a struct type.
    28  //
    29  // The earlier index entries are the indices of the embedded struct fields
    30  // traversed to get to the found entry, starting at depth 0.
    31  //
    32  // If no entry is found, a nil object is returned. In this case, the returned
    33  // index and indirect values have the following meaning:
    34  //
    35  //   - If index != nil, the index sequence points to an ambiguous entry
    36  //     (the same name appeared more than once at the same embedding level).
    37  //
    38  //   - If indirect is set, a method with a pointer receiver type was found
    39  //     but there was no pointer on the path from the actual receiver type to
    40  //     the method's formal receiver base type, nor was the receiver addressable.
    41  func LookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (obj Object, index []int, indirect bool) {
    42  	if T == nil {
    43  		panic("LookupFieldOrMethod on nil type")
    44  	}
    45  	return lookupFieldOrMethod(T, addressable, pkg, name, false)
    46  }
    47  
    48  // lookupFieldOrMethod is like LookupFieldOrMethod but with the additional foldCase parameter
    49  // (see Object.sameId for the meaning of foldCase).
    50  func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
    51  	// Methods cannot be associated to a named pointer type.
    52  	// (spec: "The type denoted by T is called the receiver base type;
    53  	// it must not be a pointer or interface type and it must be declared
    54  	// in the same package as the method.").
    55  	// Thus, if we have a named pointer type, proceed with the underlying
    56  	// pointer type but discard the result if it is a method since we would
    57  	// not have found it for T (see also go.dev/issue/8590).
    58  	if t := asNamed(T); t != nil {
    59  		if p, _ := t.Underlying().(*Pointer); p != nil {
    60  			obj, index, indirect = lookupFieldOrMethodImpl(p, false, pkg, name, foldCase)
    61  			if _, ok := obj.(*Func); ok {
    62  				return nil, nil, false
    63  			}
    64  			return
    65  		}
    66  	}
    67  
    68  	obj, index, indirect = lookupFieldOrMethodImpl(T, addressable, pkg, name, foldCase)
    69  
    70  	// If we didn't find anything and if we have a type parameter with a core type,
    71  	// see if there is a matching field (but not a method, those need to be declared
    72  	// explicitly in the constraint). If the constraint is a named pointer type (see
    73  	// above), we are ok here because only fields are accepted as results.
    74  	const enableTParamFieldLookup = false // see go.dev/issue/51576
    75  	if enableTParamFieldLookup && obj == nil && isTypeParam(T) {
    76  		if t := coreType(T); t != nil {
    77  			obj, index, indirect = lookupFieldOrMethodImpl(t, addressable, pkg, name, foldCase)
    78  			if _, ok := obj.(*Var); !ok {
    79  				obj, index, indirect = nil, nil, false // accept fields (variables) only
    80  			}
    81  		}
    82  	}
    83  	return
    84  }
    85  
    86  // lookupFieldOrMethodImpl is the implementation of lookupFieldOrMethod.
    87  // Notably, in contrast to lookupFieldOrMethod, it won't find struct fields
    88  // in base types of defined (*Named) pointer types T. For instance, given
    89  // the declaration:
    90  //
    91  //	type T *struct{f int}
    92  //
    93  // lookupFieldOrMethodImpl won't find the field f in the defined (*Named) type T
    94  // (methods on T are not permitted in the first place).
    95  //
    96  // Thus, lookupFieldOrMethodImpl should only be called by lookupFieldOrMethod
    97  // and missingMethod (the latter doesn't care about struct fields).
    98  //
    99  // The resulting object may not be fully type-checked.
   100  func lookupFieldOrMethodImpl(T Type, addressable bool, pkg *Package, name string, foldCase bool) (obj Object, index []int, indirect bool) {
   101  	// WARNING: The code in this function is extremely subtle - do not modify casually!
   102  
   103  	if name == "_" {
   104  		return // blank fields/methods are never found
   105  	}
   106  
   107  	// Importantly, we must not call under before the call to deref below (nor
   108  	// does deref call under), as doing so could incorrectly result in finding
   109  	// methods of the pointer base type when T is a (*Named) pointer type.
   110  	typ, isPtr := deref(T)
   111  
   112  	// *typ where typ is an interface (incl. a type parameter) has no methods.
   113  	if isPtr {
   114  		if _, ok := under(typ).(*Interface); ok {
   115  			return
   116  		}
   117  	}
   118  
   119  	// Start with typ as single entry at shallowest depth.
   120  	current := []embeddedType{{typ, nil, isPtr, false}}
   121  
   122  	// seen tracks named types that we have seen already, allocated lazily.
   123  	// Used to avoid endless searches in case of recursive types.
   124  	//
   125  	// We must use a lookup on identity rather than a simple map[*Named]bool as
   126  	// instantiated types may be identical but not equal.
   127  	var seen instanceLookup
   128  
   129  	// search current depth
   130  	for len(current) > 0 {
   131  		var next []embeddedType // embedded types found at current depth
   132  
   133  		// look for (pkg, name) in all types at current depth
   134  		for _, e := range current {
   135  			typ := e.typ
   136  
   137  			// If we have a named type, we may have associated methods.
   138  			// Look for those first.
   139  			if named := asNamed(typ); named != nil {
   140  				if alt := seen.lookup(named); alt != nil {
   141  					// We have seen this type before, at a more shallow depth
   142  					// (note that multiples of this type at the current depth
   143  					// were consolidated before). The type at that depth shadows
   144  					// this same type at the current depth, so we can ignore
   145  					// this one.
   146  					continue
   147  				}
   148  				seen.add(named)
   149  
   150  				// look for a matching attached method
   151  				if i, m := named.lookupMethod(pkg, name, foldCase); m != nil {
   152  					// potential match
   153  					// caution: method may not have a proper signature yet
   154  					index = concat(e.index, i)
   155  					if obj != nil || e.multiples {
   156  						return nil, index, false // collision
   157  					}
   158  					obj = m
   159  					indirect = e.indirect
   160  					continue // we can't have a matching field or interface method
   161  				}
   162  			}
   163  
   164  			switch t := under(typ).(type) {
   165  			case *Struct:
   166  				// look for a matching field and collect embedded types
   167  				for i, f := range t.fields {
   168  					if f.sameId(pkg, name, foldCase) {
   169  						assert(f.typ != nil)
   170  						index = concat(e.index, i)
   171  						if obj != nil || e.multiples {
   172  							return nil, index, false // collision
   173  						}
   174  						obj = f
   175  						indirect = e.indirect
   176  						continue // we can't have a matching interface method
   177  					}
   178  					// Collect embedded struct fields for searching the next
   179  					// lower depth, but only if we have not seen a match yet
   180  					// (if we have a match it is either the desired field or
   181  					// we have a name collision on the same depth; in either
   182  					// case we don't need to look further).
   183  					// Embedded fields are always of the form T or *T where
   184  					// T is a type name. If e.typ appeared multiple times at
   185  					// this depth, f.typ appears multiple times at the next
   186  					// depth.
   187  					if obj == nil && f.embedded {
   188  						typ, isPtr := deref(f.typ)
   189  						// TODO(gri) optimization: ignore types that can't
   190  						// have fields or methods (only Named, Struct, and
   191  						// Interface types need to be considered).
   192  						next = append(next, embeddedType{typ, concat(e.index, i), e.indirect || isPtr, e.multiples})
   193  					}
   194  				}
   195  
   196  			case *Interface:
   197  				// look for a matching method (interface may be a type parameter)
   198  				if i, m := t.typeSet().LookupMethod(pkg, name, foldCase); m != nil {
   199  					assert(m.typ != nil)
   200  					index = concat(e.index, i)
   201  					if obj != nil || e.multiples {
   202  						return nil, index, false // collision
   203  					}
   204  					obj = m
   205  					indirect = e.indirect
   206  				}
   207  			}
   208  		}
   209  
   210  		if obj != nil {
   211  			// found a potential match
   212  			// spec: "A method call x.m() is valid if the method set of (the type of) x
   213  			//        contains m and the argument list can be assigned to the parameter
   214  			//        list of m. If x is addressable and &x's method set contains m, x.m()
   215  			//        is shorthand for (&x).m()".
   216  			if f, _ := obj.(*Func); f != nil {
   217  				// determine if method has a pointer receiver
   218  				if f.hasPtrRecv() && !indirect && !addressable {
   219  					return nil, nil, true // pointer/addressable receiver required
   220  				}
   221  			}
   222  			return
   223  		}
   224  
   225  		current = consolidateMultiples(next)
   226  	}
   227  
   228  	return nil, nil, false // not found
   229  }
   230  
   231  // embeddedType represents an embedded type
   232  type embeddedType struct {
   233  	typ       Type
   234  	index     []int // embedded field indices, starting with index at depth 0
   235  	indirect  bool  // if set, there was a pointer indirection on the path to this field
   236  	multiples bool  // if set, typ appears multiple times at this depth
   237  }
   238  
   239  // consolidateMultiples collects multiple list entries with the same type
   240  // into a single entry marked as containing multiples. The result is the
   241  // consolidated list.
   242  func consolidateMultiples(list []embeddedType) []embeddedType {
   243  	if len(list) <= 1 {
   244  		return list // at most one entry - nothing to do
   245  	}
   246  
   247  	n := 0                     // number of entries w/ unique type
   248  	prev := make(map[Type]int) // index at which type was previously seen
   249  	for _, e := range list {
   250  		if i, found := lookupType(prev, e.typ); found {
   251  			list[i].multiples = true
   252  			// ignore this entry
   253  		} else {
   254  			prev[e.typ] = n
   255  			list[n] = e
   256  			n++
   257  		}
   258  	}
   259  	return list[:n]
   260  }
   261  
   262  func lookupType(m map[Type]int, typ Type) (int, bool) {
   263  	// fast path: maybe the types are equal
   264  	if i, found := m[typ]; found {
   265  		return i, true
   266  	}
   267  
   268  	for t, i := range m {
   269  		if Identical(t, typ) {
   270  			return i, true
   271  		}
   272  	}
   273  
   274  	return 0, false
   275  }
   276  
   277  type instanceLookup struct {
   278  	// buf is used to avoid allocating the map m in the common case of a small
   279  	// number of instances.
   280  	buf [3]*Named
   281  	m   map[*Named][]*Named
   282  }
   283  
   284  func (l *instanceLookup) lookup(inst *Named) *Named {
   285  	for _, t := range l.buf {
   286  		if t != nil && Identical(inst, t) {
   287  			return t
   288  		}
   289  	}
   290  	for _, t := range l.m[inst.Origin()] {
   291  		if Identical(inst, t) {
   292  			return t
   293  		}
   294  	}
   295  	return nil
   296  }
   297  
   298  func (l *instanceLookup) add(inst *Named) {
   299  	for i, t := range l.buf {
   300  		if t == nil {
   301  			l.buf[i] = inst
   302  			return
   303  		}
   304  	}
   305  	if l.m == nil {
   306  		l.m = make(map[*Named][]*Named)
   307  	}
   308  	insts := l.m[inst.Origin()]
   309  	l.m[inst.Origin()] = append(insts, inst)
   310  }
   311  
   312  // MissingMethod returns (nil, false) if V implements T, otherwise it
   313  // returns a missing method required by T and whether it is missing or
   314  // just has the wrong type: either a pointer receiver or wrong signature.
   315  //
   316  // For non-interface types V, or if static is set, V implements T if all
   317  // methods of T are present in V. Otherwise (V is an interface and static
   318  // is not set), MissingMethod only checks that methods of T which are also
   319  // present in V have matching types (e.g., for a type assertion x.(T) where
   320  // x is of interface type V).
   321  func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
   322  	return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
   323  }
   324  
   325  // missingMethod is like MissingMethod but accepts a *Checker as receiver,
   326  // a comparator equivalent for type comparison, and a *string for error causes.
   327  // The receiver may be nil if missingMethod is invoked through an exported
   328  // API call (such as MissingMethod), i.e., when all methods have been type-
   329  // checked.
   330  // The underlying type of T must be an interface; T (rather than its under-
   331  // lying type) is used for better error messages (reported through *cause).
   332  // The comparator is used to compare signatures.
   333  // If a method is missing and cause is not nil, *cause describes the error.
   334  func (check *Checker) missingMethod(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) (method *Func, wrongType bool) {
   335  	methods := under(T).(*Interface).typeSet().methods // T must be an interface
   336  	if len(methods) == 0 {
   337  		return nil, false
   338  	}
   339  
   340  	const (
   341  		ok = iota
   342  		notFound
   343  		wrongName
   344  		unexported
   345  		wrongSig
   346  		ambigSel
   347  		ptrRecv
   348  		field
   349  	)
   350  
   351  	state := ok
   352  	var m *Func // method on T we're trying to implement
   353  	var f *Func // method on V, if found (state is one of ok, wrongName, wrongSig)
   354  
   355  	if u, _ := under(V).(*Interface); u != nil {
   356  		tset := u.typeSet()
   357  		for _, m = range methods {
   358  			_, f = tset.LookupMethod(m.pkg, m.name, false)
   359  
   360  			if f == nil {
   361  				if !static {
   362  					continue
   363  				}
   364  				state = notFound
   365  				break
   366  			}
   367  
   368  			if !equivalent(f.typ, m.typ) {
   369  				state = wrongSig
   370  				break
   371  			}
   372  		}
   373  	} else {
   374  		for _, m = range methods {
   375  			obj, index, indirect := lookupFieldOrMethodImpl(V, false, m.pkg, m.name, false)
   376  
   377  			// check if m is ambiguous, on *V, or on V with case-folding
   378  			if obj == nil {
   379  				switch {
   380  				case index != nil:
   381  					state = ambigSel
   382  				case indirect:
   383  					state = ptrRecv
   384  				default:
   385  					state = notFound
   386  					obj, _, _ = lookupFieldOrMethodImpl(V, false, m.pkg, m.name, true /* fold case */)
   387  					f, _ = obj.(*Func)
   388  					if f != nil {
   389  						state = wrongName
   390  						if f.name == m.name {
   391  							// If the names are equal, f must be unexported
   392  							// (otherwise the package wouldn't matter).
   393  							state = unexported
   394  						}
   395  					}
   396  				}
   397  				break
   398  			}
   399  
   400  			// we must have a method (not a struct field)
   401  			f, _ = obj.(*Func)
   402  			if f == nil {
   403  				state = field
   404  				break
   405  			}
   406  
   407  			// methods may not have a fully set up signature yet
   408  			if check != nil {
   409  				check.objDecl(f, nil)
   410  			}
   411  
   412  			if !equivalent(f.typ, m.typ) {
   413  				state = wrongSig
   414  				break
   415  			}
   416  		}
   417  	}
   418  
   419  	if state == ok {
   420  		return nil, false
   421  	}
   422  
   423  	if cause != nil {
   424  		if f != nil {
   425  			// This method may be formatted in funcString below, so must have a fully
   426  			// set up signature.
   427  			if check != nil {
   428  				check.objDecl(f, nil)
   429  			}
   430  		}
   431  		switch state {
   432  		case notFound:
   433  			switch {
   434  			case isInterfacePtr(V):
   435  				*cause = "(" + check.interfacePtrError(V) + ")"
   436  			case isInterfacePtr(T):
   437  				*cause = "(" + check.interfacePtrError(T) + ")"
   438  			default:
   439  				*cause = check.sprintf("(missing method %s)", m.Name())
   440  			}
   441  		case wrongName:
   442  			fs, ms := check.funcString(f, false), check.funcString(m, false)
   443  			*cause = check.sprintf("(missing method %s)\n\t\thave %s\n\t\twant %s", m.Name(), fs, ms)
   444  		case unexported:
   445  			*cause = check.sprintf("(unexported method %s)", m.Name())
   446  		case wrongSig:
   447  			fs, ms := check.funcString(f, false), check.funcString(m, false)
   448  			if fs == ms {
   449  				// Don't report "want Foo, have Foo".
   450  				// Add package information to disambiguate (go.dev/issue/54258).
   451  				fs, ms = check.funcString(f, true), check.funcString(m, true)
   452  			}
   453  			if fs == ms {
   454  				// We still have "want Foo, have Foo".
   455  				// This is most likely due to different type parameters with
   456  				// the same name appearing in the instantiated signatures
   457  				// (go.dev/issue/61685).
   458  				// Rather than reporting this misleading error cause, for now
   459  				// just point out that the method signature is incorrect.
   460  				// TODO(gri) should find a good way to report the root cause
   461  				*cause = check.sprintf("(wrong type for method %s)", m.Name())
   462  				break
   463  			}
   464  			*cause = check.sprintf("(wrong type for method %s)\n\t\thave %s\n\t\twant %s", m.Name(), fs, ms)
   465  		case ambigSel:
   466  			*cause = check.sprintf("(ambiguous selector %s.%s)", V, m.Name())
   467  		case ptrRecv:
   468  			*cause = check.sprintf("(method %s has pointer receiver)", m.Name())
   469  		case field:
   470  			*cause = check.sprintf("(%s.%s is a field, not a method)", V, m.Name())
   471  		default:
   472  			panic("unreachable")
   473  		}
   474  	}
   475  
   476  	return m, state == wrongSig || state == ptrRecv
   477  }
   478  
   479  // hasAllMethods is similar to checkMissingMethod but instead reports whether all methods are present.
   480  // If V is not a valid type, or if it is a struct containing embedded fields with invalid types, the
   481  // result is true because it is not possible to say with certainty whether a method is missing or not
   482  // (an embedded field may have the method in question).
   483  // If the result is false and cause is not nil, *cause describes the error.
   484  // Use hasAllMethods to avoid follow-on errors due to incorrect types.
   485  func (check *Checker) hasAllMethods(V, T Type, static bool, equivalent func(x, y Type) bool, cause *string) bool {
   486  	if !isValid(V) {
   487  		return true // we don't know anything about V, assume it implements T
   488  	}
   489  	m, _ := check.missingMethod(V, T, static, equivalent, cause)
   490  	return m == nil || hasInvalidEmbeddedFields(V, nil)
   491  }
   492  
   493  // hasInvalidEmbeddedFields reports whether T is a struct (or a pointer to a struct) that contains
   494  // (directly or indirectly) embedded fields with invalid types.
   495  func hasInvalidEmbeddedFields(T Type, seen map[*Struct]bool) bool {
   496  	if S, _ := under(derefStructPtr(T)).(*Struct); S != nil && !seen[S] {
   497  		if seen == nil {
   498  			seen = make(map[*Struct]bool)
   499  		}
   500  		seen[S] = true
   501  		for _, f := range S.fields {
   502  			if f.embedded && (!isValid(f.typ) || hasInvalidEmbeddedFields(f.typ, seen)) {
   503  				return true
   504  			}
   505  		}
   506  	}
   507  	return false
   508  }
   509  
   510  func isInterfacePtr(T Type) bool {
   511  	p, _ := under(T).(*Pointer)
   512  	return p != nil && IsInterface(p.base)
   513  }
   514  
   515  // check may be nil.
   516  func (check *Checker) interfacePtrError(T Type) string {
   517  	assert(isInterfacePtr(T))
   518  	if p, _ := under(T).(*Pointer); isTypeParam(p.base) {
   519  		return check.sprintf("type %s is pointer to type parameter, not type parameter", T)
   520  	}
   521  	return check.sprintf("type %s is pointer to interface, not interface", T)
   522  }
   523  
   524  // funcString returns a string of the form name + signature for f.
   525  // check may be nil.
   526  func (check *Checker) funcString(f *Func, pkgInfo bool) string {
   527  	buf := bytes.NewBufferString(f.name)
   528  	var qf Qualifier
   529  	if check != nil && !pkgInfo {
   530  		qf = check.qualifier
   531  	}
   532  	w := newTypeWriter(buf, qf)
   533  	w.pkgInfo = pkgInfo
   534  	w.paramNames = false
   535  	w.signature(f.typ.(*Signature))
   536  	return buf.String()
   537  }
   538  
   539  // assertableTo reports whether a value of type V can be asserted to have type T.
   540  // The receiver may be nil if assertableTo is invoked through an exported API call
   541  // (such as AssertableTo), i.e., when all methods have been type-checked.
   542  // The underlying type of V must be an interface.
   543  // If the result is false and cause is not nil, *cause describes the error.
   544  // TODO(gri) replace calls to this function with calls to newAssertableTo.
   545  func (check *Checker) assertableTo(V, T Type, cause *string) bool {
   546  	// no static check is required if T is an interface
   547  	// spec: "If T is an interface type, x.(T) asserts that the
   548  	//        dynamic type of x implements the interface T."
   549  	if IsInterface(T) {
   550  		return true
   551  	}
   552  	// TODO(gri) fix this for generalized interfaces
   553  	return check.hasAllMethods(T, V, false, Identical, cause)
   554  }
   555  
   556  // newAssertableTo reports whether a value of type V can be asserted to have type T.
   557  // It also implements behavior for interfaces that currently are only permitted
   558  // in constraint position (we have not yet defined that behavior in the spec).
   559  // The underlying type of V must be an interface.
   560  // If the result is false and cause is not nil, *cause is set to the error cause.
   561  func (check *Checker) newAssertableTo(V, T Type, cause *string) bool {
   562  	// no static check is required if T is an interface
   563  	// spec: "If T is an interface type, x.(T) asserts that the
   564  	//        dynamic type of x implements the interface T."
   565  	if IsInterface(T) {
   566  		return true
   567  	}
   568  	return check.implements(T, V, false, cause)
   569  }
   570  
   571  // deref dereferences typ if it is a *Pointer (but not a *Named type
   572  // with an underlying pointer type!) and returns its base and true.
   573  // Otherwise it returns (typ, false).
   574  func deref(typ Type) (Type, bool) {
   575  	if p, _ := Unalias(typ).(*Pointer); p != nil {
   576  		// p.base should never be nil, but be conservative
   577  		if p.base == nil {
   578  			if debug {
   579  				panic("pointer with nil base type (possibly due to an invalid cyclic declaration)")
   580  			}
   581  			return Typ[Invalid], true
   582  		}
   583  		return p.base, true
   584  	}
   585  	return typ, false
   586  }
   587  
   588  // derefStructPtr dereferences typ if it is a (named or unnamed) pointer to a
   589  // (named or unnamed) struct and returns its base. Otherwise it returns typ.
   590  func derefStructPtr(typ Type) Type {
   591  	if p, _ := under(typ).(*Pointer); p != nil {
   592  		if _, ok := under(p.base).(*Struct); ok {
   593  			return p.base
   594  		}
   595  	}
   596  	return typ
   597  }
   598  
   599  // concat returns the result of concatenating list and i.
   600  // The result does not share its underlying array with list.
   601  func concat(list []int, i int) []int {
   602  	var t []int
   603  	t = append(t, list...)
   604  	return append(t, i)
   605  }
   606  
   607  // fieldIndex returns the index for the field with matching package and name, or a value < 0.
   608  // See Object.sameId for the meaning of foldCase.
   609  func fieldIndex(fields []*Var, pkg *Package, name string, foldCase bool) int {
   610  	if name != "_" {
   611  		for i, f := range fields {
   612  			if f.sameId(pkg, name, foldCase) {
   613  				return i
   614  			}
   615  		}
   616  	}
   617  	return -1
   618  }
   619  
   620  // methodIndex returns the index of and method with matching package and name, or (-1, nil).
   621  // See Object.sameId for the meaning of foldCase.
   622  func methodIndex(methods []*Func, pkg *Package, name string, foldCase bool) (int, *Func) {
   623  	if name != "_" {
   624  		for i, m := range methods {
   625  			if m.sameId(pkg, name, foldCase) {
   626  				return i, m
   627  			}
   628  		}
   629  	}
   630  	return -1, nil
   631  }
   632
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