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[dev.typeparams] go/types: implement types.Instantiate
This is a straightforward port of CL 314773 to go/types. Change-Id: If9e2d6d99790d694615389acbe6ccb3c8c0bd1da Reviewed-on: https://go-review.googlesource.com/c/go/+/324729 Trust: Robert Findley <rfindley@google.com> Run-TryBot: Robert Findley <rfindley@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
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src/go/types/instantiate.go
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63
src/go/types/instantiate.go
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@ -0,0 +1,63 @@
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package types
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import (
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"fmt"
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"go/token"
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)
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// Instantiate instantiates the type typ with the given type arguments.
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// typ must be a *Named or a *Signature type, it must be generic, and
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// its number of type parameters must match the number of provided type
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// arguments. The result is a new, instantiated (not generic) type of
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// the same kind (either a *Named or a *Signature). The type arguments
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// are not checked against the constraints of the type parameters.
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// Any methods attached to a *Named are simply copied; they are not
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// instantiated.
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func Instantiate(pos token.Pos, typ Type, targs []Type) (res Type) {
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// TODO(gri) This code is basically identical to the prolog
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// in Checker.instantiate. Factor.
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var tparams []*TypeName
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switch t := typ.(type) {
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case *Named:
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tparams = t.tparams
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case *Signature:
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tparams = t.tparams
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defer func() {
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// If we had an unexpected failure somewhere don't panic below when
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// asserting res.(*Signature). Check for *Signature in case Typ[Invalid]
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// is returned.
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if _, ok := res.(*Signature); !ok {
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return
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}
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// If the signature doesn't use its type parameters, subst
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// will not make a copy. In that case, make a copy now (so
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// we can set tparams to nil w/o causing side-effects).
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if t == res {
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copy := *t
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res = ©
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}
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// After instantiating a generic signature, it is not generic
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// anymore; we need to set tparams to nil.
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res.(*Signature).tparams = nil
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}()
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default:
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panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
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}
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// the number of supplied types must match the number of type parameters
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if len(targs) != len(tparams) {
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panic(fmt.Sprintf("%v: got %d arguments but %d type parameters", pos, len(targs), len(tparams)))
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}
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if len(tparams) == 0 {
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return typ // nothing to do (minor optimization)
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}
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smap := makeSubstMap(tparams, targs)
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return (*Checker)(nil).subst(pos, typ, smap)
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}
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@ -311,6 +311,9 @@ func (subst *subster) typ(typ Type) Type {
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embeddeds, ecopied := subst.typeList(t.embeddeds)
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if mcopied || types != t.types || ecopied {
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iface := &Interface{methods: methods, types: types, embeddeds: embeddeds}
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if subst.check == nil {
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panic("internal error: cannot instantiate interfaces yet")
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}
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subst.check.posMap[iface] = subst.check.posMap[t] // satisfy completeInterface requirement
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subst.check.completeInterface(token.NoPos, iface)
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return iface
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@ -330,12 +333,14 @@ func (subst *subster) typ(typ Type) Type {
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}
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case *Named:
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subst.check.indent++
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defer func() {
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subst.check.indent--
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}()
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dump := func(format string, args ...interface{}) {
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if trace {
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// dump is for debugging
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dump := func(string, ...interface{}) {}
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if subst.check != nil && trace {
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subst.check.indent++
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defer func() {
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subst.check.indent--
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}()
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dump = func(format string, args ...interface{}) {
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subst.check.trace(subst.pos, format, args...)
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}
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}
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@ -381,10 +386,12 @@ func (subst *subster) typ(typ Type) Type {
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// before creating a new named type, check if we have this one already
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h := instantiatedHash(t, newTargs)
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dump(">>> new type hash: %s", h)
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if named, found := subst.check.typMap[h]; found {
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dump(">>> found %s", named)
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subst.cache[t] = named
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return named
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if subst.check != nil {
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if named, found := subst.check.typMap[h]; found {
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dump(">>> found %s", named)
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subst.cache[t] = named
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return named
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}
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}
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// create a new named type and populate caches to avoid endless recursion
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@ -392,7 +399,9 @@ func (subst *subster) typ(typ Type) Type {
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named := subst.check.newNamed(tname, t.underlying, t.methods) // method signatures are updated lazily
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named.tparams = t.tparams // new type is still parameterized
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named.targs = newTargs
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subst.check.typMap[h] = named
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if subst.check != nil {
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subst.check.typMap[h] = named
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}
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subst.cache[t] = named
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// do the substitution
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