golang signature 代码
文件路径：/src/cmd/compile/internal/types2/signature.go
/ 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 types2
import "cmd/compile/internal/syntax"
/ ----------------------------------------------------------------------------
/ 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 *TypeParamList / receiver type parameters from left to right, or nil
tparams *TypeParamList / type parameters from left to right, or nil
scope *Scope / function scope for package-local and non-instantiated signatures; nil otherwise
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)
}
/ NewSignatureType creates a new function type for the given receiver,
/ receiver type parameters, type parameters, parameters, and results. If
/ variadic is set, params must hold at least one parameter and the last
/ parameter must be of unnamed slice type. If recv is non-nil, typeParams must
/ be empty. If recvTypeParams is non-empty, recv must be non-nil.
func NewSignatureType(recv *Var, recvTypeParams, typeParams []*TypeParam, 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")
}
}
sig := &Signature{recv: recv, params: params, results: results, variadic: variadic}
if len(recvTypeParams) != 0 {
if recv == nil {
panic("function with receiver type parameters must have a receiver")
}
sig.rparams = bindTParams(recvTypeParams)
}
if len(typeParams) != 0 {
if recv != nil {
panic("function with type parameters cannot have a receiver")
}
sig.tparams = bindTParams(typeParams)
}
return sig
}
/ 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 }
/ TypeParams returns the type parameters of signature s, or nil.
func (s *Signature) TypeParams() *TypeParamList { return s.tparams }
/ SetTypeParams sets the type parameters of signature s.
func (s *Signature) SetTypeParams(tparams []*TypeParam) { s.tparams = bindTParams(tparams) }
/ RecvTypeParams returns the receiver type parameters of signature s, or nil.
func (s *Signature) RecvTypeParams() *TypeParamList { return s.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 (s *Signature) Underlying() Type { return s }
func (s *Signature) String() string { return TypeString(s, nil) }
/ ----------------------------------------------------------------------------
/ Implementation
/ funcType type-checks a function or method type.
func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []*syntax.Field, ftyp *syntax.FuncType) {
check.openScope(ftyp, "function")
check.scope.isFunc = true
check.recordScope(ftyp, check.scope)
sig.scope = check.scope
defer check.closeScope()
if recvPar != nil {
/ 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.Type, true)
if len(rparams) > 0 {
tparams := make([]*TypeParam, len(rparams))
for i, rparam := range rparams {
tparams[i] = check.declareTypeParam(rparam)
}
sig.rparams = bindTParams(tparams)
/ Blank identifiers don't get declared, so naive type-checking of the
/ receiver type expression would fail in Checker.collectParams below,
/ when Checker.ident cannot resolve the _ to a type.
/
/ Checker.recvTParamMap maps these blank identifiers to their type parameter
/ types, so that they may be resolved in Checker.ident when they fail
/ lookup in the scope.
for i, p := range rparams {
if p.Value == "_" {
if check.recvTParamMap == nil {
check.recvTParamMap = make(map[*syntax.Name]*TypeParam)
}
check.recvTParamMap[p] = tparams[i]
}
}
/ 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, _ := check.genericType(rname, false).(*Named); recv != nil {
recvTParams = recv.TypeParams().list()
}
}
/ provide type parameter bounds
if len(tparams) == len(recvTParams) {
smap := makeRenameMap(recvTParams, tparams)
for i, tpar := range tparams {
recvTPar := recvTParams[i]
check.mono.recordCanon(tpar, recvTPar)
/ recvTPar.bound is (possibly) parameterized in the context of the
/ receiver type declaration. Substitute parameters for the current
/ context.
tpar.bound = check.subst(tpar.obj.pos, recvTPar.bound, smap, nil, check.context())
}
} else if len(tparams) < len(recvTParams) {
/ Reporting an error here is a stop-gap measure to avoid crashes in the
/ compiler when a type parameter/argument cannot be inferred later. It
/ may lead to follow-on errors (see issues #51339, #51343).
/ TODO(gri) find a better solution
got := measure(len(tparams), "type parameter")
check.errorf(recvPar, "got %s, but receiver base type declares %d", got, len(recvTParams))
}
}
}
if tparams != nil {
/ The parser will complain about invalid type parameters for methods.
check.collectTypeParams(&sig.tparams, tparams)
}
/ 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, nopos, nopos, "function body (temp. scope)")
var recvList []*Var / TODO(gri) remove the need for making a list here
if recvPar != nil {
recvList, _ = check.collectParams(scope, []*syntax.Field{recvPar}, false) / use rewritten receiver type, if any
}
params, variadic := check.collectParams(scope, ftyp.ParamList, true)
results, _ := check.collectParams(scope, ftyp.ResultList, false)
scope.Squash(func(obj, alt Object) {
var err error_
err.errorf(obj, "%s redeclared in this block", obj.Name())
err.recordAltDecl(alt)
check.report(&err)
})
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(nopos, nil, "", Typ[Invalid]) / ignore recv below
default:
/ more than one receiver
check.error(recvList[len(recvList)-1].Pos(), "method must have exactly one receiver")
fallthrough / continue with first receiver
case 1:
recv = recvList[0]
}
sig.recv = recv
/ Delay validation of receiver type as it may cause premature expansion
/ of types the receiver type is dependent on (see issues #51232, #51233).
check.later(func() {
/ spec: "The receiver type must be of the form T or *T where T is a type name."
rtyp, _ := deref(recv.typ)
if rtyp == Typ[Invalid] {
return / error was reported before
}
/ 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."
switch T := rtyp.(type) {
case *Named:
/ The receiver type may be an instantiated type referred to
/ by an alias (which cannot have receiver parameters for now).
if T.TypeArgs() != nil && sig.RecvTypeParams() == nil {
check.errorf(recv, "cannot define new methods on instantiated type %s", rtyp)
break
}
if T.obj.pkg != check.pkg {
check.errorf(recv, "cannot define new methods on non-local type %s", rtyp)
break
}
var cause string
switch u := T.under().(type) {
case *Basic:
/ unsafe.Pointer is treated like a regular pointer
if u.kind == UnsafePointer {
cause = "unsafe.Pointer"
}
case *Pointer, *Interface:
cause = "pointer or interface type"
case *TypeParam:
/ The underlying type of a receiver base type cannot be a
/ type parameter: "type T[P any] P" is not a valid declaration.
unreachable()
}
if cause != "" {
check.errorf(recv, "invalid receiver type %s (%s)", rtyp, cause)
}
case *Basic:
check.errorf(recv, "cannot define new methods on non-local type %s", rtyp)
default:
check.errorf(recv, "invalid receiver type %s", recv.typ)
}
}).describef(recv, "validate receiver %s", 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.
func (check *Checker) collectParams(scope *Scope, list []*syntax.Field, variadicOk bool) (params []*Var, variadic bool) {
if list == nil {
return
}
var named, anonymous bool
var typ Type
var prev syntax.Expr
for i, field := range list {
ftype := field.Type
/ type-check type of grouped fields only once
if ftype != prev {
prev = ftype
if t, _ := ftype.(*syntax.DotsType); t != nil {
ftype = t.Elem
if variadicOk && i == len(list)-1 {
variadic = true
} else {
check.softErrorf(t, "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 field.Name != nil {
/ named parameter
name := field.Name.Value
if name == "" {
check.error(field.Name, invalidAST+"anonymous parameter")
/ ok to continue
}
par := NewParam(field.Name.Pos(), check.pkg, name, typ)
check.declare(scope, field.Name, par, scope.pos)
params = append(params, par)
named = true
} else {
/ anonymous parameter
par := NewParam(field.Pos(), check.pkg, "", typ)
check.recordImplicit(field, par)
params = append(params, par)
anonymous = true
}
}
if named && anonymous {
check.error(list[0], invalidAST+"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[len(list)-1].Type, typexpr, last.typ, nil)
}
return
}