[WIP] Test out GopherJS struct val fix

.vendor.txt

@@ -3,7 +3,7 @@
     ./_vendor/src/golang.org/x/crypto                        3cb07270c9455e8ad27956a70891c962d121a228  https://go.googlesource.com/crypto
     ./_vendor/src/golang.org/x/tools                         620ecdb8d7943e20dc030b61bfe898d1b000bdea  https://go.googlesource.com/tools
     ./_vendor/src/github.com/jteeuwen/go-bindata             a0ff2567cfb70903282db057e799fd826784d41d  git@github.com:jteeuwen/go-bindata
-    ./_vendor/src/github.com/gopherjs/gopherjs               e14987c0ef06db387b90fec85e8d06dc05598e24  git@github.com:gopherjs/gopherjs
+    ./_vendor/src/github.com/gopherjs/gopherjs               91be9d3fa503472d6ccde719f7ec6923dfb18699  git@github.com:gopherjs/gopherjs
     ./_vendor/src/github.com/gopherjs/jsbuiltin              67703bfb044e3192fbcab025c3aeaeedafad1f2f  git@github.com:gopherjs/jsbuiltin
     ./_vendor/src/github.com/kisielk/gotool                  0de1eaf82fa3f583ce21fde859f1e7e0c5e9b220  git@github.com:kisielk/gotool
     ./_vendor/src/github.com/fsnotify/fsnotify               7d7316ed6e1ed2de075aab8dfc76de5d158d66e1  git@github.com:fsnotify/fsnotify

_vendor/src/github.com/gopherjs/gopherjs/compiler/expressions.go

@@ -812,6 +812,11 @@ func (c *funcContext) makeReceiver(e *ast.SelectorExpr) *expression {
 
 	_, isPointer := recvType.Underlying().(*types.Pointer)
 	methodsRecvType := sel.Obj().Type().(*types.Signature).Recv().Type()
+
+	if _, isInterface := methodsRecvType.Underlying().(*types.Interface); isInterface {
+		return c.formatExpr("$copyInterfaceVal(%e)", x)
+	}
+
 	_, pointerExpected := methodsRecvType.(*types.Pointer)
 	if !isPointer && pointerExpected {
 		recvType = types.NewPointer(recvType)
@@ -825,6 +830,7 @@ func (c *funcContext) makeReceiver(e *ast.SelectorExpr) *expression {
 	if isWrapped(recvType) {
 		recv = c.formatExpr("new %s(%s)", c.typeName(methodsRecvType), recv)
 	}
+
 	return recv
 }
 
@@ -1130,12 +1136,17 @@ func (c *funcContext) translateImplicitConversion(expr ast.Expr, desiredType typ
 			// wrap JS object into js.Object struct when converting to interface
 			return c.formatExpr("new $jsObjectPtr(%e)", expr)
 		}
+
+		switch exprType.Underlying().(type) {
+		case *types.Array:
+			return c.formatExpr("new %1s($clone(%e, %1s))", c.typeName(exprType), expr)
+		case *types.Struct:
+			return c.formatExpr("new %1e.constructor.elem($clone(%1e, %s))", expr, c.typeName(exprType))
+		}
+
 		if isWrapped(exprType) {
 			return c.formatExpr("new %s(%e)", c.typeName(exprType), expr)
 		}
-		if _, isStruct := exprType.Underlying().(*types.Struct); isStruct {
-			return c.formatExpr("new %1e.constructor.elem(%1e)", expr)
-		}
 	}
 
 	return c.translateExpr(expr)

_vendor/src/github.com/gopherjs/gopherjs/compiler/prelude/jsmapping.go

@@ -163,10 +163,10 @@ var $externalizeFunction = function(v, t, passThis) {
       case 0:
         return;
       case 1:
-        return $externalize(result, t.results[0]);
+        return $externalize($copyInterfaceVal(result), t.results[0]);
       default:
         for (var i = 0; i < t.results.length; i++) {
-          result[i] = $externalize(result[i], t.results[i]);
+          result[i] = $externalize($copyInterfaceVal(result[i]), t.results[i]);
         }
         return result;
       }

_vendor/src/github.com/gopherjs/gopherjs/tests/interface_test.go

@@ -0,0 +1,88 @@
+package tests
+
+import (
+	"fmt"
+	"testing"
+)
+
+type Struct struct {
+	Name string
+}
+
+func (s Struct) SetName(n string) {
+	s.Name = n
+}
+
+type SetName interface {
+	SetName(n string)
+}
+
+func TestAssignStructValInterface(t *testing.T) {
+	s := Struct{
+		Name: "Rob",
+	}
+
+	var i1 interface{} = s
+	var i2 interface{} = i1
+
+	s.Name = "Pike"
+
+	ss := fmt.Sprintf("%#v", s)
+	i1s := fmt.Sprintf("%#v", i1)
+	i2s := fmt.Sprintf("%#v", i2)
+
+	if exp := "tests.Struct{Name:\"Pike\"}"; ss != exp {
+		t.Fatalf("ss should have been %q; got %q", exp, ss)
+	}
+
+	iexp := "tests.Struct{Name:\"Rob\"}"
+
+	if i1s != iexp {
+		t.Fatalf("is should have been %q; got %q", iexp, i1s)
+	}
+
+	if i2s != iexp {
+		t.Fatalf("is should have been %q; got %q", iexp, i2s)
+	}
+}
+
+func TestStructValInterfaceMethodCall(t *testing.T) {
+	var i SetName = Struct{
+		Name: "Rob",
+	}
+
+	i.SetName("Pike")
+
+	is := fmt.Sprintf("%#v", i)
+
+	if exp := "tests.Struct{Name:\"Rob\"}"; is != exp {
+		t.Fatalf("is should have been %q; got %q", exp, is)
+	}
+}
+
+func TestAssignArrayInterface(t *testing.T) {
+	a := [2]int{1, 2}
+
+	var i1 interface{} = a
+	var i2 interface{} = i1
+
+	a[0] = 0
+
+	as := fmt.Sprintf("%#v", a)
+	i1s := fmt.Sprintf("%#v", i1)
+	i2s := fmt.Sprintf("%#v", i2)
+
+	if exp := "[2]int{0, 2}"; as != exp {
+		t.Fatalf("ss should have been %q; got %q", exp, as)
+	}
+
+	iexp := "[2]int{1, 2}"
+
+	if i1s != iexp {
+		t.Fatalf("is should have been %q; got %q", iexp, i1s)
+	}
+
+	if i2s != iexp {
+		t.Fatalf("is should have been %q; got %q", iexp, i2s)
+	}
+}