cmd/doc: suppress the error message for *package.ident embedded in struct type

The current implementation prints a log, "invalid program: unexpected
type for embedded field", when the form *package.ident is embedded in
a struct declaration.

Note that since valid qualified identifiers must be exported, the result
for a valid program does not change.

Change-Id: If8b9d7056c56b6a6c5482eb749168a63c65ef685
Reviewed-on: https://go-review.googlesource.com/84436
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

3 files changed, 19 insertions, 16 deletions

diff --git a/src/cmd/doc/doc_test.go b/src/cmd/doc/doc_test.go
index ee7c430cbd..07e59a2d3e 100644
--- a/src/cmd/doc/doc_test.go
+++ b/src/cmd/doc/doc_test.go
@@ -292,6 +292,7 @@ var tests = []test{
 			`unexportedField.*int.*Comment on line with unexported field.`,
 			`ExportedEmbeddedType.*Comment on line with exported embedded field.`,
 			`\*ExportedEmbeddedType.*Comment on line with exported embedded \*field.`,
+			`\*qualified.ExportedEmbeddedType.*Comment on line with exported embedded \*selector.field.`,
 			`unexportedType.*Comment on line with unexported embedded field.`,
 			`\*unexportedType.*Comment on line with unexported embedded \*field.`,
 			`io.Reader.*Comment on line with embedded Reader.`,
diff --git a/src/cmd/doc/pkg.go b/src/cmd/doc/pkg.go
index 99a00c5632..11011de018 100644
--- a/src/cmd/doc/pkg.go
+++ b/src/cmd/doc/pkg.go
@@ -702,9 +702,16 @@ func trimUnexportedFields(fields *ast.FieldList, isInterface bool) *ast.FieldLis
 	for _, field := range fields.List {
 		names := field.Names
 		if len(names) == 0 {
-			// Embedded type. Use the name of the type. It must be of type ident or *ident.
+			// Embedded type. Use the name of the type. It must be of the form ident or
+			// pkg.ident (for structs and interfaces), or *ident or *pkg.ident (structs only).
 			// Nothing else is allowed.
-			switch ident := field.Type.(type) {
+			ty := field.Type
+			if se, ok := field.Type.(*ast.StarExpr); !isInterface && ok {
+				// The form *ident or *pkg.ident is only valid on
+				// embedded types in structs.
+				ty = se.X
+			}
+			switch ident := ty.(type) {
 			case *ast.Ident:
 				if isInterface && ident.Name == "error" && ident.Obj == nil {
 					// For documentation purposes, we consider the builtin error
@@ -714,12 +721,6 @@ func trimUnexportedFields(fields *ast.FieldList, isInterface bool) *ast.FieldLis
 					continue
 				}
 				names = []*ast.Ident{ident}
-			case *ast.StarExpr:
-				// Must have the form *identifier.
-				// This is only valid on embedded types in structs.
-				if ident, ok := ident.X.(*ast.Ident); ok && !isInterface {
-					names = []*ast.Ident{ident}
-				}
 			case *ast.SelectorExpr:
 				// An embedded type may refer to a type in another package.
 				names = []*ast.Ident{ident.Sel}
diff --git a/src/cmd/doc/testdata/pkg.go b/src/cmd/doc/testdata/pkg.go
index d0995bbf7d..bc069939f8 100644
--- a/src/cmd/doc/testdata/pkg.go
+++ b/src/cmd/doc/testdata/pkg.go
@@ -60,14 +60,15 @@ func internalFunc(a int) bool
 // Comment about exported type.
 type ExportedType struct {
 	// Comment before exported field.
-	ExportedField         int // Comment on line with exported field.
-	unexportedField       int // Comment on line with unexported field.
-	ExportedEmbeddedType      // Comment on line with exported embedded field.
-	*ExportedEmbeddedType     // Comment on line with exported embedded *field.
-	unexportedType            // Comment on line with unexported embedded field.
-	*unexportedType           // Comment on line with unexported embedded *field.
-	io.Reader                 // Comment on line with embedded Reader.
-	error                     // Comment on line with embedded error.
+	ExportedField                   int // Comment on line with exported field.
+	unexportedField                 int // Comment on line with unexported field.
+	ExportedEmbeddedType                // Comment on line with exported embedded field.
+	*ExportedEmbeddedType               // Comment on line with exported embedded *field.
+	*qualified.ExportedEmbeddedType     // Comment on line with exported embedded *selector.field.
+	unexportedType                      // Comment on line with unexported embedded field.
+	*unexportedType                     // Comment on line with unexported embedded *field.
+	io.Reader                           // Comment on line with embedded Reader.
+	error                               // Comment on line with embedded error.
 }
 
 // Comment about exported method.