cmd/compile: fix compile failure for lazily resolved shadowed types

If expanding an inline function body required lazily expanding a
package-scoped type whose identifier was shadowed within the function
body, the lazy expansion would instead overwrite the local symbol
definition instead of the package-scoped symbol. This was due to
importsym using s.Def instead of s.PkgDef.

Unfortunately, this is yet another consequence of the current awkward
scope handling code.

Passes toolstash-check.

Fixes #25984.

Change-Id: Ia7033e1749a883e6e979c854d4b12b0b28083dd8
Reviewed-on: https://go-review.googlesource.com/120456
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/types/scope.go b/src/cmd/compile/internal/types/scope.go
index 156174746f..40d3d86ef1 100644
--- a/src/cmd/compile/internal/types/scope.go
+++ b/src/cmd/compile/internal/types/scope.go
@@ -80,15 +80,24 @@ func IsDclstackValid() bool {
 
 // PkgDef returns the definition associated with s at package scope.
 func (s *Sym) PkgDef() *Node {
+	return *s.pkgDefPtr()
+}
+
+// SetPkgDef sets the definition associated with s at package scope.
+func (s *Sym) SetPkgDef(n *Node) {
+	*s.pkgDefPtr() = n
+}
+
+func (s *Sym) pkgDefPtr() **Node {
 	// Look for outermost saved declaration, which must be the
 	// package scope definition, if present.
 	for _, d := range dclstack {
 		if s == d.sym {
-			return d.def
+			return &d.def
 		}
 	}
 
 	// Otherwise, the declaration hasn't been shadowed within a
 	// function scope.
-	return s.Def
+	return &s.Def
 }