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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>
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@ -1920,7 +1920,7 @@ func methodWrapper(rcvr *types.Type, method *types.Field, forItab bool) *obj.LSy
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// Target method uses shaped names.
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targs2 := make([]*types.Type, len(targs))
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for i, t := range targs {
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targs2[i] = typecheck.Shaped[t]
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targs2[i] = typecheck.Shapify(t)
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}
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targs = targs2
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@ -1348,32 +1348,26 @@ func Shapify(t *types.Type) *types.Type {
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if t.IsShape() {
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return t // TODO: is this right?
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}
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if s := Shaped[t]; s != nil {
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// Map all types with the same underlying type to the same shape.
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u := t.Underlying()
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if s := shaped[u]; s != nil {
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return s //TODO: keep?
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}
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// For now, there is a 1-1 mapping between regular types and shape types.
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sym := Lookup(fmt.Sprintf(".shape%d", snum))
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snum++
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name := ir.NewDeclNameAt(t.Pos(), ir.OTYPE, sym)
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name := ir.NewDeclNameAt(u.Pos(), ir.OTYPE, sym)
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s := types.NewNamed(name)
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s.SetUnderlying(t.Underlying())
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s.SetUnderlying(u)
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s.SetIsShape(true)
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name.SetType(s)
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name.SetTypecheck(1)
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// TODO: add methods to s that the bound has?
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Shaped[t] = s
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shaped[u] = s
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return s
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}
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var snum int
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var Shaped = map[*types.Type]*types.Type{}
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func ShapifyList(targs []*types.Type) []*types.Type {
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r := make([]*types.Type, len(targs))
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for i, t := range targs {
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r[i] = Shapify(t)
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}
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return r
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}
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var shaped = map[*types.Type]*types.Type{}
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33
test/typeparam/shape1.go
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33
test/typeparam/shape1.go
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@ -0,0 +1,33 @@
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// run -gcflags=-G=3
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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 main
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type I interface {
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foo() int
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}
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// There should be a single instantiation of f in this program.
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func f[T I](x T) int {
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return x.foo()
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}
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type squarer int
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func (x squarer) foo() int {
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return int(x*x)
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}
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type doubler int
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func (x doubler) foo() int {
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return int(2*x)
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}
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func main() {
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println(f(squarer(5)))
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println(f(doubler(5)))
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}
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2
test/typeparam/shape1.out
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2
test/typeparam/shape1.out
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@ -0,0 +1,2 @@
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25
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10
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