go.tools/go/types: report identifier for methods with blank names

R=adonovan
CC=golang-dev
https://golang.org/cl/12123045

go/types/resolver.go

@@ -294,9 +294,8 @@ func (check *checker) resolveFiles(files []*ast.File) {
 				} else {
 					// Associate method with receiver base type name, if possible.
 					// Ignore methods that have an invalid receiver, or a blank _
-					// receiver or method name. They will be type-checked later,
-					// with non-method functions.
-					if obj.name != "_" {
+					// receiver name. They will be type-checked later, with regular
+					// functions.
 					if list := d.Recv.List; len(list) > 0 {
 						typ := list[0].Type
 						if ptr, _ := typ.(*ast.StarExpr); ptr != nil {
@@ -307,7 +306,6 @@ func (check *checker) resolveFiles(files []*ast.File) {
 						}
 					}
 				}
-				}
 				objList = append(objList, obj)
 				objMap[obj] = declInfo{scope, nil, nil, d}
 
@@ -547,9 +545,13 @@ func (check *checker) typeDecl(obj *TypeName, typ ast.Expr, def *Named, cycleOk
 		// and collect it with the named base type.
 		if m != nil {
 			check.objDecl(m, nil, true)
+			// Methods with blank _ names cannot be found.
+			// Don't add them to the method list.
+			if m.name != "_" {
 				named.methods = append(named.methods, m)
 			}
 		}
+	}
 
 	delete(check.methods, obj.name) // we don't need them anymore
 }

go/types/resolver_test.go

@@ -43,6 +43,7 @@ var sources = []string{
 	type I interface{ m() }
 	var _ = T{a: 1, b: 2, c: 3}
 	func (_ T) m() {}
+	func (T) _() {}
 	var i I
 	var _ = i.m
 	func _(s []int) { for i, x := range s {} }