From: Rob Findley <rfindley@google.com>
Date: Wed, 14 Apr 2021 13:34:28 +0000 (-0400)
Subject: go/ast: fix broken build with typeparams build constraint
X-Git-Tag: go1.17beta1~651
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=bcbde83c200a7abb2b23666b59992265f3cf3621;p=gostls13.git

go/ast: fix broken build with typeparams build constraint

My rebase of https://golang.org/cl/300649 before submitting broke the
build (and tests) when using the typeparams build constraint. In a
subsequent CL I add test coverage back to cmd/dist.

This time, I've tested by running:
 - go test -tags=typeparams go/...
 - go test -tags=typeparams cmd/gofmt

All tests pass except for the new TestResolution/typeparams.go2, which I
will fix in a follow-up CL.

For #44933

Change-Id: I439d387841604cf43a90e2ce41dbe6bbbdb0306d
Reviewed-on: https://go-review.googlesource.com/c/go/+/310070
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
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/go/ast/walk.go b/src/go/ast/walk.go
index 9224264e29..ac1395fafd 100644
--- a/src/go/ast/walk.go
+++ b/src/go/ast/walk.go
@@ -112,7 +112,11 @@ func Walk(v Visitor, node Node) {
 
 	case *IndexExpr:
 		Walk(v, n.X)
-		Walk(v, n.Index)
+		// n.Index may be nil for invalid type instantiation expressions, e.g.
+		// var x T[].
+		if n.Index != nil {
+			Walk(v, n.Index)
+		}
 
 	case *SliceExpr:
 		Walk(v, n.X)
diff --git a/src/go/ast/walk_typeparams.go b/src/go/ast/walk_typeparams.go
index 77267a5b8c..b6621335b8 100644
--- a/src/go/ast/walk_typeparams.go
+++ b/src/go/ast/walk_typeparams.go
@@ -7,6 +7,10 @@
 
 package ast
 
+import (
+	"fmt"
+)
+
 func walkFuncTypeParams(v Visitor, n *FuncType) {
 	if n.TParams != nil {
 		Walk(v, n.TParams)
@@ -20,9 +24,11 @@ func walkTypeSpecParams(v Visitor, n *TypeSpec) {
 }
 
 func walkOtherNodes(v Visitor, n Node) {
-	if e, ok := n.(*ast.ListExpr); ok {
+	if e, ok := n.(*ListExpr); ok {
 		if e != nil {
-			Walk(v, e)
+			for _, elem := range e.ElemList {
+				Walk(v, elem)
+			}
 		}
 	} else {
 		panic(fmt.Sprintf("ast.Walk: unexpected node type %T", n))