compiler: Fix generated code for type switch with *js.Object case. (#683)

myitcv · dmitshur · commit b40cd48c38f9 · 2017-09-06T14:39:36.000-04:00
This brings generated JS code for a type switch with a *js.Object case in line with the runtime $assertType function. For *js.Object type, we have to dereference via .$val.object. See https://github.com/gopherjs/gopherjs/blob/4b94c02883c52ae7f268e602db1dacf7bd0fbd78/compiler/prelude/types.go#L735-L740. Fixes #682.
diff --git a/compiler/statements.go b/compiler/statements.go
@@ -123,7 +123,9 @@ func (c *funcContext) translateStmt(stmt ast.Stmt, label *types.Label) {
 			var bodyPrefix []ast.Stmt
 			if implicit := c.p.Implicits[clause]; implicit != nil {
 				value := refVar
-				if _, isInterface := implicit.Type().Underlying().(*types.Interface); !isInterface {
+				if typesutil.IsJsObject(implicit.Type().Underlying()) {
+					value += ".$val.object"
+				} else if _, ok := implicit.Type().Underlying().(*types.Interface); !ok {
 					value += ".$val"
 				}
 				bodyPrefix = []ast.Stmt{&ast.AssignStmt{
diff --git a/js/js_test.go b/js/js_test.go
@@ -571,3 +571,29 @@ func TestUint8Array(t *testing.T) {
 		t.Errorf("Non-empty byte array is not externalized as a Uint8Array")
 	}
 }
+
+func TestTypeSwitchJSObject(t *testing.T) {
+	obj := js.Global.Get("Object").New()
+	obj.Set("foo", "bar")
+
+	want := "bar"
+
+	if got := obj.Get("foo").String(); got != want {
+		t.Errorf("Direct access to *js.Object field gave %q, want %q", got, want)
+	}
+
+	var x interface{} = obj
+
+	switch x := x.(type) {
+	case *js.Object:
+		if got := x.Get("foo").String(); got != want {
+			t.Errorf("Value passed through interface and type switch gave %q, want %q", got, want)
+		}
+	}
+
+	if y, ok := x.(*js.Object); ok {
+		if got := y.Get("foo").String(); got != want {
+			t.Errorf("Value passed through interface and type assert gave %q, want %q", got, want)
+		}
+	}
+}
