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go/types: fix type inference

This is a 1:1 port of CL 311651 to go/types.

Change-Id: I9d91b45cc5fa7ce686d6a91d4dde274d9f80e0d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/314595
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>
This commit is contained in:
Rob Findley 2021-04-28 10:07:18 -04:00 committed by Robert Findley
parent c96fec9036
commit 414af503d7
4 changed files with 49 additions and 1 deletions

View File

@ -17,4 +17,3 @@ func main() {
_ = Reduce[int](s, 0, f2)
_ = Reduce(s, 0, f2)
}

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@ -0,0 +1,13 @@
// 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 p
func f[F interface{type *Q}, G interface{type *R}, Q, R any](q Q, r R) {}
func _() {
f[*float64, *int](1, 2)
f[*float64](1, 2)
f(1, 2)
}

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@ -446,6 +446,25 @@ func (check *Checker) inferB(tparams []*TypeName, targs []Type, report bool) (ty
dirty = dirty[:n]
}
// Once nothing changes anymore, we may still have type parameters left;
// e.g., a structural constraint *P may match a type parameter Q but we
// don't have any type arguments to fill in for *P or Q (issue #45548).
// Don't let such inferences escape, instead nil them out.
for i, typ := range types {
if typ != nil && isParameterized(tparams, typ) {
types[i] = nil
}
}
// update index
index = -1
for i, typ := range types {
if typ == nil {
index = i
break
}
}
return
}

View File

@ -7,6 +7,7 @@
package types
import (
"bytes"
"go/token"
"sort"
)
@ -74,6 +75,22 @@ type tparamsList struct {
indices []int // len(d.indices) == len(d.tparams)
}
// String returns a string representation for a tparamsList. For debugging.
func (d *tparamsList) String() string {
var buf bytes.Buffer
buf.WriteByte('[')
for i, tname := range d.tparams {
if i > 0 {
buf.WriteString(", ")
}
writeType(&buf, tname.typ, nil, nil)
buf.WriteString(": ")
writeType(&buf, d.at(i), nil, nil)
}
buf.WriteByte(']')
return buf.String()
}
// init initializes d with the given type parameters.
// The type parameters must be in the order in which they appear in their declaration
// (this ensures that the tparams indices match the respective type parameter index).