From: Robert Findley <rfindley@google.com>
Date: Tue, 12 Oct 2021 15:54:09 +0000 (-0400)
Subject: cmd/api: use placeholder names for type parameters
X-Git-Tag: go1.18beta1~926
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=78d01be00b68d1f5c3f5eb493f053ba97adc92df;p=gostls13.git

cmd/api: use placeholder names for type parameters

Changing type parameter names is not a breaking API change, so we should
not include these names in the output of cmd/api. Instead print a
placeholder '$<index>' wherever type parameters are referenced.

This is valid for cmd/api as there is at most one type parameter list in
scope for any exported declaration. If we ever support method type
parameters, we'll need to revisit this syntax.

Change-Id: I7e677b1dab6ffeb0b79afefdb8d2580bef93891c
Reviewed-on: https://go-review.googlesource.com/c/go/+/355389
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>
---

diff --git a/src/cmd/api/goapi.go b/src/cmd/api/goapi.go
index eca113a638..0c61b1b489 100644
--- a/src/cmd/api/goapi.go
+++ b/src/cmd/api/goapi.go
@@ -838,7 +838,8 @@ func (w *Walker) writeType(buf *bytes.Buffer, typ types.Type) {
 		buf.WriteString(typ.Obj().Name())
 
 	case *types.TypeParam:
-		buf.WriteString(typ.Obj().Name())
+		// Type parameter names may change, so use a placeholder instead.
+		fmt.Fprintf(buf, "$%d", typ.Index())
 
 	default:
 		panic(fmt.Sprintf("unknown type %T", typ))
@@ -870,7 +871,7 @@ func (w *Walker) writeTypeParams(buf *bytes.Buffer, tparams *types.TypeParamList
 			buf.WriteString(", ")
 		}
 		tp := tparams.At(i)
-		buf.WriteString(tp.Obj().Name())
+		w.writeType(buf, tp)
 		if withConstraints {
 			buf.WriteByte(' ')
 			w.writeType(buf, tp.Constraint())
diff --git a/src/cmd/api/testdata/src/pkg/p4/golden.txt b/src/cmd/api/testdata/src/pkg/p4/golden.txt
index d5f282be8e..7997ab4471 100644
--- a/src/cmd/api/testdata/src/pkg/p4/golden.txt
+++ b/src/cmd/api/testdata/src/pkg/p4/golden.txt
@@ -1,4 +1,5 @@
-pkg p4, func NewPair[T1 interface{ M }, T2 interface{ ~int }](T1, T2) Pair
-pkg p4, method (Pair[_, X2]) Second() X2
-pkg p4, method (Pair[X1, _]) First() X1
-pkg p4, type Pair[T1 interface{ M }, T2 interface{ ~int }] struct
+pkg p4, func NewPair[$0 interface{ M }, $1 interface{ ~int }]($0, $1) Pair
+pkg p4, method (Pair[$0, $1]) Second() $1
+pkg p4, method (Pair[$0, $1]) First() $0
+pkg p4, type Pair[$0 interface{ M }, $1 interface{ ~int }] struct
+pkg p4, func Clone[$0 interface{ ~[]$1 }, $1 interface{}]($0) $0
diff --git a/src/cmd/api/testdata/src/pkg/p4/p4.go b/src/cmd/api/testdata/src/pkg/p4/p4.go
index 187339b169..462a75be1a 100644
--- a/src/cmd/api/testdata/src/pkg/p4/p4.go
+++ b/src/cmd/api/testdata/src/pkg/p4/p4.go
@@ -20,3 +20,7 @@ func (p Pair[X1, _]) First() X1 {
 func (p Pair[_, X2]) Second() X2 {
 	return p.f2
 }
+
+func Clone[S ~[]T, T any](s S) S {
+	return append(S(nil), s...)
+}