cmd/compile: improve compiler error on embedded structs

Fixes #23609

Change-Id: I751aae3d849de7fce1306324fcb1a4c3842d873e
Reviewed-on: https://go-review.googlesource.com/97076
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index a1653d0e7f22b817961817bad9ef418f5f5fecf9..47a8a4294420373dd89abc246a6ce814974b2f7c 100644 (file)
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -3114,7 +3114,18 @@ func typecheckcomplit(n *Node) *Node {
                                        if ci := lookdot1(nil, l.Sym, t, t.Fields(), 2); ci != nil { // Case-insensitive lookup.
                                                yyerror("unknown field '%v' in struct literal of type %v (but does have %v)", l.Sym, t, ci.Sym)
                                        } else {
-                                               yyerror("unknown field '%v' in struct literal of type %v", l.Sym, t)
+                                               p, _ := dotpath(l.Sym, t, nil, true)
+                                               if p == nil {
+                                                       yyerror("unknown field '%v' in struct literal of type %v", l.Sym, t)
+                                                       continue
+                                               }
+                                               // dotpath returns the parent embedded types in reverse order.
+                                               var ep []string
+                                               for ei := len(p) - 1; ei >= 0; ei-- {
+                                                       ep = append(ep, p[ei].field.Type.Sym.Name)
+                                               }
+                                               ep = append(ep, l.Sym.Name)
+                                               yyerror("cannot use promoted field %v in struct literal of type %v", strings.Join(ep, "."), t)
                                        }
                                        continue
                                }

diff --git a/test/fixedbugs/issue23609.go b/test/fixedbugs/issue23609.go
new file mode 100644 (file)
index 0000000..7c17a98
--- /dev/null
+++ b/test/fixedbugs/issue23609.go
@@ -0,0 +1,27 @@
+// errorcheck
+
+// 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.
+
+package main
+
+type t1 struct {
+       t1f1 int
+       t1f2 int
+}
+type t2 struct {
+       t2f1 int
+       t2f2 int
+       t1
+}
+type t3 struct {
+       t3f1 int
+       t2
+}
+
+var (
+       _ = t2{t1f1: 600} // ERROR "cannot use promoted field t1.t1f1 in struct literal of type t2"
+       _ = t3{t1f2: 800} // ERROR "cannot use promoted field t2.t1.t1f2 in struct literal of type t3"
+       _ = t3{t2f1: 900} // ERROR "cannot use promoted field t2.t2f1 in struct literal of type t3"
+)