go/doc: added test case

Don't show conflicting method embedded via
a visible and invisible anonymous field.

R=rsc
CC=golang-dev
https://golang.org/cl/5564064

src/pkg/go/doc/testdata/e.0.golden

-// 
+// The package e is a go/doc test for embedded methods. 
 PACKAGE e
 
 IMPORTPATH
@@ -8,7 +8,7 @@ FILENAMES
 	testdata/e.go
 
 TYPES
-	// T1 has no (top-level) M method due to conflict. 
+	// T1 has no embedded (level 1) M method due to conflict. 
 	type T1 struct {
 		// contains filtered or unexported fields
 	}
@@ -29,3 +29,9 @@ TYPES
 	// T3.M should appear as method of T3. 
 	func (T3) M()
 
+	// T1 has no embedded (level 1) M method due to conflict. 
+	type T4 struct {
+		T2
+		// contains filtered or unexported fields
+	}
+

src/pkg/go/doc/testdata/e.1.golden

-// 
+// The package e is a go/doc test for embedded methods. 
 PACKAGE e
 
 IMPORTPATH
@@ -8,7 +8,7 @@ FILENAMES
 	testdata/e.go
 
 TYPES
-	// T1 has no (top-level) M method due to conflict. 
+	// T1 has no embedded (level 1) M method due to conflict. 
 	type T1 struct {
 		t1
 		t2
@@ -31,6 +31,12 @@ TYPES
 	// T3.M should appear as method of T3. 
 	func (T3) M()
 
+	// T1 has no embedded (level 1) M method due to conflict. 
+	type T4 struct {
+		t2
+		T2
+	}
+
 	// 
 	type t1 struct{}
 

src/pkg/go/doc/testdata/e.go

@@ -2,9 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Embedding tests.
-// TODO(gri): This should be comprehensive.
-
+// The package e is a go/doc test for embedded methods.
 package e
 
 // ----------------------------------------------------------------------------
@@ -20,7 +18,7 @@ type t2 struct{}
 // t2.M should not appear as method in a Tx type.
 func (t2) M() {}
 
-// T1 has no (top-level) M method due to conflict.
+// T1 has no embedded (level 1) M method due to conflict.
 type T1 struct {
 	t1
 	t2
@@ -56,3 +54,13 @@ type T3 struct {
 
 // T3.M should appear as method of T3.
 func (T3) M() {}
+
+// ----------------------------------------------------------------------------
+// Don't show conflicting methods M embedded via an exported and non-exported
+// type.
+
+// T1 has no embedded (level 1) M method due to conflict.
+type T4 struct {
+	t2
+	T2
+}