cmd/compile: prevent Noalg from breaking user types

Use a separate symbol for reflect metadata for types with Noalg set.

Fixes #17752.

Change-Id: Icb6cade7e3004fc4108f67df61105dc4085cd7e2
Reviewed-on: https://go-review.googlesource.com/32679Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/reflect.go

@@ -928,7 +928,14 @@ func dcommontype(s *Sym, ot int, t *Type) int {
 }
 
 func typesym(t *Type) *Sym {
-	return Pkglookup(t.tconv(FmtLeft), typepkg)
+	name := t.tconv(FmtLeft)
+
+	// Use a separate symbol name for Noalg types for #17752.
+	if a, bad := algtype1(t); a == ANOEQ && bad.Noalg {
+		name = "noalg." + name
+	}
+
+	return Pkglookup(name, typepkg)
 }
 
 // tracksym returns the symbol for tracking use of field/method f, assumed

src/cmd/compile/internal/gc/walk.go

@@ -1785,7 +1785,6 @@ func mkdotargslice(lr0, nn []*Node, l *Field, fp int, init *Nodes, ddd *Node) []
 	}
 
 	tslice := typSlice(l.Type.Elem())
-	tslice.Noalg = true
 
 	var n *Node
 	if len(lr0) == 0 {

test/fixedbugs/issue17752.go

+// run
+
+// Copyright 2016 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 main
+
+func f(m map[string]int) int {
+	return m["a"]
+}
+
+func g(m map[[8]string]int) int {
+	return m[[8]string{"a", "a", "a", "a", "a", "a", "a", "a"}]
+}
+
+func main() {
+	m := map[[8]string]int{}
+	g(m)
+}