reflect: check pkgPath for unexported methods in Implements

Fixes #20541.

Change-Id: Ifdfdf3616482b71761daf6d114b779a8ec532051
Reviewed-on: https://go-review.googlesource.com/44495
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/reflect/set_test.go

@@ -7,6 +7,7 @@ package reflect_test
 import (
 	"bytes"
 	"go/ast"
+	"go/token"
 	"io"
 	. "reflect"
 	"testing"
@@ -172,6 +173,23 @@ var implementsTests = []struct {
 	{new(bytes.Buffer), new(io.Reader), false},
 	{new(*bytes.Buffer), new(io.ReaderAt), false},
 	{new(*ast.Ident), new(ast.Expr), true},
+	{new(*notAnExpr), new(ast.Expr), false},
+	{new(*ast.Ident), new(notASTExpr), false},
+	{new(notASTExpr), new(ast.Expr), false},
+	{new(ast.Expr), new(notASTExpr), false},
+	{new(*notAnExpr), new(notASTExpr), true},
+}
+
+type notAnExpr struct{}
+
+func (notAnExpr) Pos() token.Pos { return token.NoPos }
+func (notAnExpr) End() token.Pos { return token.NoPos }
+func (notAnExpr) exprNode()      {}
+
+type notASTExpr interface {
+	Pos() token.Pos
+	End() token.Pos
+	exprNode()
 }
 
 func TestImplements(t *testing.T) {

src/reflect/type.go

@@ -1515,8 +1515,23 @@ func implements(T, V *rtype) bool {
 		i := 0
 		for j := 0; j < len(v.methods); j++ {
 			tm := &t.methods[i]
+			tmName := t.nameOff(tm.name)
 			vm := &v.methods[j]
-			if V.nameOff(vm.name).name() == t.nameOff(tm.name).name() && V.typeOff(vm.typ) == t.typeOff(tm.typ) {
+			vmName := V.nameOff(vm.name)
+			if vmName.name() == tmName.name() && V.typeOff(vm.typ) == t.typeOff(tm.typ) {
+				if !tmName.isExported() {
+					tmPkgPath := tmName.pkgPath()
+					if tmPkgPath == "" {
+						tmPkgPath = t.pkgPath.name()
+					}
+					vmPkgPath := vmName.pkgPath()
+					if vmPkgPath == "" {
+						vmPkgPath = v.pkgPath.name()
+					}
+					if tmPkgPath != vmPkgPath {
+						continue
+					}
+				}
 				if i++; i >= len(t.methods) {
 					return true
 				}
@@ -1533,8 +1548,23 @@ func implements(T, V *rtype) bool {
 	vmethods := v.methods()
 	for j := 0; j < int(v.mcount); j++ {
 		tm := &t.methods[i]
+		tmName := t.nameOff(tm.name)
 		vm := vmethods[j]
-		if V.nameOff(vm.name).name() == t.nameOff(tm.name).name() && V.typeOff(vm.mtyp) == t.typeOff(tm.typ) {
+		vmName := V.nameOff(vm.name)
+		if vmName.name() == tmName.name() && V.typeOff(vm.mtyp) == t.typeOff(tm.typ) {
+			if !tmName.isExported() {
+				tmPkgPath := tmName.pkgPath()
+				if tmPkgPath == "" {
+					tmPkgPath = t.pkgPath.name()
+				}
+				vmPkgPath := vmName.pkgPath()
+				if vmPkgPath == "" {
+					vmPkgPath = V.nameOff(v.pkgPath).name()
+				}
+				if tmPkgPath != vmPkgPath {
+					continue
+				}
+			}
 			if i++; i >= len(t.methods) {
 				return true
 			}