cmd/compile: revert internal parameter rename (from ".anonX" to "") before export

In the old binary export format, parameter names for parameter lists
which contained only types where never written, so this problem didn't
come up.

Fixes #25101.

Change-Id: Ia8b817f7f467570b05f88d584e86b6ef4acdccc6
Reviewed-on: https://go-review.googlesource.com/116376
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

diff --git a/src/cmd/compile/internal/gc/dcl.go b/src/cmd/compile/internal/gc/dcl.go
index d88c5e5c5e5427b9b182da0704a87f92d25f38f3..736ea0a018380b7dd5180c0bd66dda9df39c734b 100644 (file)
--- a/src/cmd/compile/internal/gc/dcl.go
+++ b/src/cmd/compile/internal/gc/dcl.go
@@ -778,15 +778,26 @@ func functypefield0(t *types.Type, this *types.Field, in, out []*types.Field) {
 
 // origSym returns the original symbol written by the user.
 func origSym(s *types.Sym) *types.Sym {
-       if s != nil && s.Name[0] == '~' {
+       if s == nil {
+               return nil
+       }
+
+       if len(s.Name) > 1 && s.Name[0] == '~' {
                switch s.Name[1] {
                case 'r': // originally an unnamed result
-                       s = nil
+                       return nil
                case 'b': // originally the blank identifier _
                        // TODO(mdempsky): Does s.Pkg matter here?
-                       s = nblank.Sym
+                       return nblank.Sym
                }
+               return s
        }
+
+       if strings.HasPrefix(s.Name, ".anon") {
+               // originally an unnamed or _ name (see subr.go: structargs)
+               return nil
+       }
+
        return s
 }
 

diff --git a/test/fixedbugs/issue25101.go b/test/fixedbugs/issue25101.go
new file mode 100644 (file)
index 0000000..4fd6bed
--- /dev/null
+++ b/test/fixedbugs/issue25101.go
@@ -0,0 +1,16 @@
+// compile
+
+// Copyright 2018 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.
+
+// Indexed export format must not crash when writing
+// the anonymous parameter for m.
+
+package p
+
+var x interface {
+       m(int)
+}
+
+var M = x.m