cmd/compile: better errors for structs with conflicting fields and methods

If a field and method have the same name, mark the respective struct field
so that we don't report follow-on errors when the field/method is accessed.

Per suggestion of @mdempsky.

Fixes #28268.

Change-Id: Ia1ca4cdfe9bacd3739d1fd7ca5e014ca094245ee
Reviewed-on: https://go-review.googlesource.com/c/144259
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 516c33d0bbb4d2254ae7e132f3ede9f1b05961f3..22201e504460ded8ff2247edc31d89e51b004eaf 100644 (file)
--- a/src/cmd/compile/internal/gc/dcl.go
+++ b/src/cmd/compile/internal/gc/dcl.go
@@ -863,7 +863,7 @@ func methodSymSuffix(recv *types.Type, msym *types.Sym, suffix string) *types.Sy
 // Add a method, declared as a function.
 // - msym is the method symbol
 // - t is function type (with receiver)
-// Returns a pointer to the existing or added Field.
+// Returns a pointer to the existing or added Field; or nil if there's an error.
 func addmethod(msym *types.Sym, t *types.Type, local, nointerface bool) *types.Field {
        if msym == nil {
                Fatalf("no method symbol")
@@ -918,6 +918,7 @@ func addmethod(msym *types.Sym, t *types.Type, local, nointerface bool) *types.F
                for _, f := range mt.Fields().Slice() {
                        if f.Sym == msym {
                                yyerror("type %v has both field and method named %v", mt, msym)
+                               f.SetBroke(true)
                                return nil
                        }
                }
@@ -927,7 +928,7 @@ func addmethod(msym *types.Sym, t *types.Type, local, nointerface bool) *types.F
                if msym.Name != f.Sym.Name {
                        continue
                }
-               // eqtype only checks that incoming and result parameters match,
+               // types.Identical only checks that incoming and result parameters match,
                // so explicitly check that the receiver parameters match too.
                if !types.Identical(t, f.Type) || !types.Identical(t.Recv().Type, f.Type.Recv().Type) {
                        yyerror("method redeclared: %v.%v\n\t%v\n\t%v", mt, msym, f.Type, t)

diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index 0bbd89f05e4a1f3f44026aebc280aba61c2f89e8..38d9fe078fb27642ac3d6dbd090a8a1680bee2e0 100644 (file)
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -2443,7 +2443,7 @@ func lookdot(n *Node, t *types.Type, dostrcmp int) *types.Field {
        }
 
        if f1 != nil {
-               if dostrcmp > 1 {
+               if dostrcmp > 1 || f1.Broke() {
                        // Already in the process of diagnosing an error.
                        return f1
                }

diff --git a/test/fixedbugs/issue28268.go b/test/fixedbugs/issue28268.go
new file mode 100644 (file)
index 0000000..fdc6974
--- /dev/null
+++ b/test/fixedbugs/issue28268.go
@@ -0,0 +1,30 @@
+// 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.
+
+// Verify that follow-on errors due to conflicting
+// struct field and method names are suppressed.
+
+package p
+
+type T struct {
+       a, b, c int
+       E
+}
+
+type E struct{}
+
+func (T) b()  {} // ERROR "field and method named b"
+func (*T) E() {} // ERROR "field and method named E"
+
+func _() {
+       var x T
+       _ = x.a
+       _ = x.b // no follow-on error here
+       x.b()   // no follow-on error here
+       _ = x.c
+       _ = x.E // no follow-on error here
+       x.E()   // no follow-on error here
+}