diff options
Diffstat (limited to 'src/go/types/signature.go')
| -rw-r--r-- | src/go/types/signature.go | 352 |
1 files changed, 352 insertions, 0 deletions
diff --git a/src/go/types/signature.go b/src/go/types/signature.go new file mode 100644 index 0000000000..d6c12cf3d9 --- /dev/null +++ b/src/go/types/signature.go @@ -0,0 +1,352 @@ +// Copyright 2021 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package types + +import ( + "fmt" + "go/ast" + "go/internal/typeparams" + "go/token" +) + +// ---------------------------------------------------------------------------- +// API + +// A Signature represents a (non-builtin) function or method type. +// The receiver is ignored when comparing signatures for identity. +type Signature struct { + // We need to keep the scope in Signature (rather than passing it around + // and store it in the Func Object) because when type-checking a function + // literal we call the general type checker which returns a general Type. + // We then unpack the *Signature and use the scope for the literal body. + rparams *TParamList // receiver type parameters from left to right, or nil + tparams *TParamList // type parameters from left to right, or nil + scope *Scope // function scope, present for package-local signatures + recv *Var // nil if not a method + params *Tuple // (incoming) parameters from left to right; or nil + results *Tuple // (outgoing) results from left to right; or nil + variadic bool // true if the last parameter's type is of the form ...T (or string, for append built-in only) +} + +// NewSignature returns a new function type for the given receiver, parameters, +// and results, either of which may be nil. If variadic is set, the function +// is variadic, it must have at least one parameter, and the last parameter +// must be of unnamed slice type. +func NewSignature(recv *Var, params, results *Tuple, variadic bool) *Signature { + if variadic { + n := params.Len() + if n == 0 { + panic("variadic function must have at least one parameter") + } + if _, ok := params.At(n - 1).typ.(*Slice); !ok { + panic("variadic parameter must be of unnamed slice type") + } + } + return &Signature{recv: recv, params: params, results: results, variadic: variadic} +} + +// Recv returns the receiver of signature s (if a method), or nil if a +// function. It is ignored when comparing signatures for identity. +// +// For an abstract method, Recv returns the enclosing interface either +// as a *Named or an *Interface. Due to embedding, an interface may +// contain methods whose receiver type is a different interface. +func (s *Signature) Recv() *Var { return s.recv } + +// TParams returns the type parameters of signature s, or nil. +func (s *Signature) TParams() *TParamList { return s.tparams } + +// SetTParams sets the type parameters of signature s. +func (s *Signature) SetTParams(tparams []*TypeParam) { s.tparams = bindTParams(tparams) } + +// RParams returns the receiver type parameters of signature s, or nil. +func (s *Signature) RParams() *TParamList { return s.rparams } + +// SetRParams sets the receiver type params of signature s. +func (s *Signature) SetRParams(rparams []*TypeParam) { s.rparams = bindTParams(rparams) } + +// Params returns the parameters of signature s, or nil. +func (s *Signature) Params() *Tuple { return s.params } + +// Results returns the results of signature s, or nil. +func (s *Signature) Results() *Tuple { return s.results } + +// Variadic reports whether the signature s is variadic. +func (s *Signature) Variadic() bool { return s.variadic } + +func (t *Signature) Underlying() Type { return t } +func (t *Signature) String() string { return TypeString(t, nil) } + +// ---------------------------------------------------------------------------- +// Implementation + +// funcType type-checks a function or method type. +func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast.FuncType) { + check.openScope(ftyp, "function") + check.scope.isFunc = true + check.recordScope(ftyp, check.scope) + sig.scope = check.scope + defer check.closeScope() + + var recvTyp ast.Expr // rewritten receiver type; valid if != nil + if recvPar != nil && len(recvPar.List) > 0 { + // collect generic receiver type parameters, if any + // - a receiver type parameter is like any other type parameter, except that it is declared implicitly + // - the receiver specification acts as local declaration for its type parameters, which may be blank + _, rname, rparams := check.unpackRecv(recvPar.List[0].Type, true) + if len(rparams) > 0 { + // Blank identifiers don't get declared and regular type-checking of the instantiated + // parameterized receiver type expression fails in Checker.collectParams of receiver. + // Identify blank type parameters and substitute each with a unique new identifier named + // "n_" (where n is the parameter index) and which cannot conflict with any user-defined + // name. + var smap map[*ast.Ident]*ast.Ident // substitution map from "_" to "n_" identifiers + for i, p := range rparams { + if p.Name == "_" { + new := *p + new.Name = fmt.Sprintf("%d_", i) + rparams[i] = &new // use n_ identifier instead of _ so it can be looked up + if smap == nil { + smap = make(map[*ast.Ident]*ast.Ident) + } + smap[p] = &new + } + } + if smap != nil { + // blank identifiers were found => use rewritten receiver type + recvTyp = isubst(recvPar.List[0].Type, smap) + } + sig.rparams = bindTParams(check.declareTypeParams(nil, rparams)) + // determine receiver type to get its type parameters + // and the respective type parameter bounds + var recvTParams []*TypeParam + if rname != nil { + // recv should be a Named type (otherwise an error is reported elsewhere) + // Also: Don't report an error via genericType since it will be reported + // again when we type-check the signature. + // TODO(gri) maybe the receiver should be marked as invalid instead? + if recv := asNamed(check.genericType(rname, false)); recv != nil { + recvTParams = recv.TParams().list() + } + } + // provide type parameter bounds + // - only do this if we have the right number (otherwise an error is reported elsewhere) + if sig.RParams().Len() == len(recvTParams) { + // We have a list of *TypeNames but we need a list of Types. + list := make([]Type, sig.RParams().Len()) + for i, t := range sig.RParams().list() { + list[i] = t + } + smap := makeSubstMap(recvTParams, list) + for i, tpar := range sig.RParams().list() { + bound := recvTParams[i].bound + // bound is (possibly) parameterized in the context of the + // receiver type declaration. Substitute parameters for the + // current context. + // TODO(gri) should we assume now that bounds always exist? + // (no bound == empty interface) + if bound != nil { + bound = check.subst(tpar.obj.pos, bound, smap, nil) + tpar.bound = bound + } + } + } + } + } + + if tparams := typeparams.Get(ftyp); tparams != nil { + sig.tparams = check.collectTypeParams(tparams) + // Always type-check method type parameters but complain that they are not allowed. + // (A separate check is needed when type-checking interface method signatures because + // they don't have a receiver specification.) + if recvPar != nil { + check.errorf(tparams, _Todo, "methods cannot have type parameters") + } + } + + // Value (non-type) parameters' scope starts in the function body. Use a temporary scope for their + // declarations and then squash that scope into the parent scope (and report any redeclarations at + // that time). + scope := NewScope(check.scope, token.NoPos, token.NoPos, "function body (temp. scope)") + recvList, _ := check.collectParams(scope, recvPar, recvTyp, false) // use rewritten receiver type, if any + params, variadic := check.collectParams(scope, ftyp.Params, nil, true) + results, _ := check.collectParams(scope, ftyp.Results, nil, false) + scope.squash(func(obj, alt Object) { + check.errorf(obj, _DuplicateDecl, "%s redeclared in this block", obj.Name()) + check.reportAltDecl(alt) + }) + + if recvPar != nil { + // recv parameter list present (may be empty) + // spec: "The receiver is specified via an extra parameter section preceding the + // method name. That parameter section must declare a single parameter, the receiver." + var recv *Var + switch len(recvList) { + case 0: + // error reported by resolver + recv = NewParam(0, nil, "", Typ[Invalid]) // ignore recv below + default: + // more than one receiver + check.error(recvList[len(recvList)-1], _BadRecv, "method must have exactly one receiver") + fallthrough // continue with first receiver + case 1: + recv = recvList[0] + } + + // TODO(gri) We should delay rtyp expansion to when we actually need the + // receiver; thus all checks here should be delayed to later. + rtyp, _ := deref(recv.typ) + + // spec: "The receiver type must be of the form T or *T where T is a type name." + // (ignore invalid types - error was reported before) + if rtyp != Typ[Invalid] { + var err string + switch T := rtyp.(type) { + case *Named: + T.expand(nil) + // spec: "The type denoted by T is called the receiver base type; it must not + // be a pointer or interface type and it must be declared in the same package + // as the method." + if T.obj.pkg != check.pkg { + err = "type not defined in this package" + } else { + // The underlying type of a receiver base type can be a type parameter; + // e.g. for methods with a generic receiver T[P] with type T[P any] P. + underIs(T, func(u Type) bool { + switch u := u.(type) { + case *Basic: + // unsafe.Pointer is treated like a regular pointer + if u.kind == UnsafePointer { + err = "unsafe.Pointer" + return false + } + case *Pointer, *Interface: + err = "pointer or interface type" + return false + } + return true + }) + } + case *Basic: + err = "basic or unnamed type" + default: + check.errorf(recv, _InvalidRecv, "invalid receiver type %s", recv.typ) + } + if err != "" { + check.errorf(recv, _InvalidRecv, "invalid receiver type %s (%s)", recv.typ, err) + // ok to continue + } + } + sig.recv = recv + } + + sig.params = NewTuple(params...) + sig.results = NewTuple(results...) + sig.variadic = variadic +} + +// collectParams declares the parameters of list in scope and returns the corresponding +// variable list. If type0 != nil, it is used instead of the first type in list. +func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, type0 ast.Expr, variadicOk bool) (params []*Var, variadic bool) { + if list == nil { + return + } + + var named, anonymous bool + for i, field := range list.List { + ftype := field.Type + if i == 0 && type0 != nil { + ftype = type0 + } + if t, _ := ftype.(*ast.Ellipsis); t != nil { + ftype = t.Elt + if variadicOk && i == len(list.List)-1 && len(field.Names) <= 1 { + variadic = true + } else { + check.softErrorf(t, _MisplacedDotDotDot, "can only use ... with final parameter in list") + // ignore ... and continue + } + } + typ := check.varType(ftype) + // The parser ensures that f.Tag is nil and we don't + // care if a constructed AST contains a non-nil tag. + if len(field.Names) > 0 { + // named parameter + for _, name := range field.Names { + if name.Name == "" { + check.invalidAST(name, "anonymous parameter") + // ok to continue + } + par := NewParam(name.Pos(), check.pkg, name.Name, typ) + check.declare(scope, name, par, scope.pos) + params = append(params, par) + } + named = true + } else { + // anonymous parameter + par := NewParam(ftype.Pos(), check.pkg, "", typ) + check.recordImplicit(field, par) + params = append(params, par) + anonymous = true + } + } + + if named && anonymous { + check.invalidAST(list, "list contains both named and anonymous parameters") + // ok to continue + } + + // For a variadic function, change the last parameter's type from T to []T. + // Since we type-checked T rather than ...T, we also need to retro-actively + // record the type for ...T. + if variadic { + last := params[len(params)-1] + last.typ = &Slice{elem: last.typ} + check.recordTypeAndValue(list.List[len(list.List)-1].Type, typexpr, last.typ, nil) + } + + return +} + +// isubst returns an x with identifiers substituted per the substitution map smap. +// isubst only handles the case of (valid) method receiver type expressions correctly. +func isubst(x ast.Expr, smap map[*ast.Ident]*ast.Ident) ast.Expr { + switch n := x.(type) { + case *ast.Ident: + if alt := smap[n]; alt != nil { + return alt + } + case *ast.StarExpr: + X := isubst(n.X, smap) + if X != n.X { + new := *n + new.X = X + return &new + } + case *ast.IndexExpr, *ast.MultiIndexExpr: + ix := typeparams.UnpackIndexExpr(x) + var newIndexes []ast.Expr + for i, index := range ix.Indices { + new := isubst(index, smap) + if new != index { + if newIndexes == nil { + newIndexes = make([]ast.Expr, len(ix.Indices)) + copy(newIndexes, ix.Indices) + } + newIndexes[i] = new + } + } + if newIndexes != nil { + return typeparams.PackIndexExpr(ix.X, ix.Lbrack, newIndexes, ix.Rbrack) + } + case *ast.ParenExpr: + return isubst(n.X, smap) // no need to keep parentheses + default: + // Other receiver type expressions are invalid. + // It's fine to ignore those here as they will + // be checked elsewhere. + } + return x +} |