go/go2go: use types.RelativeTo rather than doing it by hand

Change-Id: I0891f034ef71311df007bb9aa527132d5b45c672
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go2-dev/+/771559
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/go/go2go/rewrite.go

@@ -581,6 +581,7 @@ func (t *translator) translateExpr(pe *ast.Expr) {
 		t.translateExpr(&e.Key)
 		t.translateExpr(&e.Value)
 	case *ast.ArrayType:
+		t.translateExpr(&e.Len)
 		t.translateExpr(&e.Elt)
 	case *ast.StructType:
 		t.translateFieldList(e.Fields)
@@ -931,7 +932,7 @@ func (t *translator) typeWithoutArgs(typ *types.Named) *types.Named {
 func (t *translator) typeListToASTList(typeList []types.Type) ([]types.Type, []ast.Expr) {
 	argList := make([]ast.Expr, 0, len(typeList))
 	for _, typ := range typeList {
-		arg := ast.NewIdent(typ.String())
+		arg := ast.NewIdent(types.TypeString(typ, types.RelativeTo(t.tpkg)))
 		if named, ok := typ.(*types.Named); ok {
 			if len(named.TArgs()) > 0 {
 				var narg *ast.Ident
@@ -943,12 +944,6 @@ func (t *translator) typeListToASTList(typeList []types.Type) ([]types.Type, []a
 					arg = ast.NewIdent(narg.Name)
 				}
 			}
-			if named.Obj().Pkg() == t.tpkg {
-				fields := strings.Split(arg.Name, ".")
-				if len(fields) > 1 {
-					arg = ast.NewIdent(fields[1])
-				}
-			}
 		}
 		argList = append(argList, arg)
 		t.setType(arg, typ)

test/gen/g017.go2

@@ -0,0 +1,24 @@
+// run
+
+// Copyright 2020 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.
+
+package main
+
+type Recv <-chan int
+
+type sliceOf(type E) interface {
+	type []E
+}
+
+func Append(type S sliceOf(T), T interface{})(s S, t ...T) S {
+	return append(s, t...)
+}
+
+func main() {
+	a := Append([]Recv{nil}, Recv(nil))
+	if len(a) != 2 || a[0] != nil || a[1] != nil {
+		panic(a)
+	}
+}