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[dev.typeparams] cmd/compile: allow types with the same underlying type to have the same shape

First baby step to sharing the underlying implementation among several types.

Change-Id: I6a156176d2b7f0131a87285a03b881ce380c26ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/338610
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
This commit is contained in:
Keith Randall 2021-07-30 09:06:38 -07:00
parent fd0011dca5
commit 40e561d933
4 changed files with 44 additions and 15 deletions

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@ -1920,7 +1920,7 @@ func methodWrapper(rcvr *types.Type, method *types.Field, forItab bool) *obj.LSy
// Target method uses shaped names.
targs2 := make([]*types.Type, len(targs))
for i, t := range targs {
targs2[i] = typecheck.Shaped[t]
targs2[i] = typecheck.Shapify(t)
}
targs = targs2

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@ -1348,32 +1348,26 @@ func Shapify(t *types.Type) *types.Type {
if t.IsShape() {
return t // TODO: is this right?
}
if s := Shaped[t]; s != nil {
// Map all types with the same underlying type to the same shape.
u := t.Underlying()
if s := shaped[u]; s != nil {
return s //TODO: keep?
}
// For now, there is a 1-1 mapping between regular types and shape types.
sym := Lookup(fmt.Sprintf(".shape%d", snum))
snum++
name := ir.NewDeclNameAt(t.Pos(), ir.OTYPE, sym)
name := ir.NewDeclNameAt(u.Pos(), ir.OTYPE, sym)
s := types.NewNamed(name)
s.SetUnderlying(t.Underlying())
s.SetUnderlying(u)
s.SetIsShape(true)
name.SetType(s)
name.SetTypecheck(1)
// TODO: add methods to s that the bound has?
Shaped[t] = s
shaped[u] = s
return s
}
var snum int
var Shaped = map[*types.Type]*types.Type{}
func ShapifyList(targs []*types.Type) []*types.Type {
r := make([]*types.Type, len(targs))
for i, t := range targs {
r[i] = Shapify(t)
}
return r
}
var shaped = map[*types.Type]*types.Type{}

33
test/typeparam/shape1.go Normal file
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@ -0,0 +1,33 @@
// run -gcflags=-G=3
// 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 main
type I interface {
foo() int
}
// There should be a single instantiation of f in this program.
func f[T I](x T) int {
return x.foo()
}
type squarer int
func (x squarer) foo() int {
return int(x*x)
}
type doubler int
func (x doubler) foo() int {
return int(2*x)
}
func main() {
println(f(squarer(5)))
println(f(doubler(5)))
}

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@ -0,0 +1,2 @@
25
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