compiler/natives/src/reflect: Override Value.assignTo method, drop v.Kind() == Interface && v.IsNil().

dmitshur · dmitshur · commit 28e102cafab5 · 2018-02-16T18:12:25.000-05:00
This change adds a copy of Value.assignTo method to reflect package, identical to upstream, except with golang/go@eafa29b not applied. That commit adds a short-circuit check to that skips ifaceE2I, in order to avoid a panic that occurs in ifaceE2I under that condition in gc and gccgo compilers. GopherJS implements a custom version of ifaceE2I which needs to run and does not panic in that condition. So, there's no need skip it. Fixes: $ gopherjs test --short reflect html/template --- FAIL: TestCallConvert (0.01s) all_test.go:1639: expected [nil], got [<io.Reader Value>] FAIL FAIL reflect 3.084s --- FAIL: TestEscapingNilNonemptyInterfaces (0.01s) go/src/github.com/shurcooL/play/241/test.243863553:9608 if (!(($parseInt(methodSet.length) === 0)) || !!(typ.named)) { ^ TypeError: Cannot read property 'length' of undefined at reflectType (go/src/github.com/shurcooL/play/241/test.243863553:9608:31) at Object.TypeOf (go/src/github.com/shurcooL/play/241/reflect.go:312:3) at indirect (/html/template/content.go:119:6) at stringify (/html/template/content.go:153:4) at htmlEscaper (/html/template/html.go:43:3) at $call (go/src/github.com/shurcooL/play/241/test.243863553:30:50) at go/src/github.com/shurcooL/play/241/test.243863553:1948:22 at Object.$packages.reflect.Value.ptr.call (go/src/github.com/shurcooL/play/241/reflect.go:880:3) at Object.$packages.reflect.Value.ptr.Call (/reflect/value.go:308:3) at Object.$packages.text/template.state.ptr.evalCall (/text/template/exec.go:667:3) at Object.$packages.text/template.state.ptr.evalFunction (/text/template/exec.go:535:3) at Object.$packages.text/template.state.ptr.evalCommand (/text/template/exec.go:432:4) at Object.$packages.text/template.state.ptr.evalPipeline (/text/template/exec.go:405:4) at Object.$packages.text/template.state.ptr.walk (/text/template/exec.go:231:4) at Object.$packages.text/template.state.ptr.walk (/text/template/exec.go:239:5) at Object.$packages.text/template.Template.ptr.execute (/text/template/exec.go:194:3) at Object.$packages.text/template.Template.ptr.Execute (/text/template/exec.go:177:3) at Object.$packages.html/template.Template.ptr.Execute (/html/template/template.go:122:3) at Object.TestEscapingNilNonemptyInterfaces [as $blk] (/html/template/content_test.go:448:3) at Object.tRunner [as $blk] (/testing/testing.go:777:3) at fun (go/src/github.com/shurcooL/play/241/test.243863553:1479:37) at $goroutine (go/src/github.com/shurcooL/play/241/test.243863553:1477:19) at $runScheduled (go/src/github.com/shurcooL/play/241/test.243863553:1517:7) at $schedule (go/src/github.com/shurcooL/play/241/test.243863553:1533:5) at $go (go/src/github.com/shurcooL/play/241/test.243863553:1509:3) at Object.<anonymous> (go/src/github.com/shurcooL/play/241/test.243863553:55363:1) at Object.<anonymous> (go/src/github.com/shurcooL/play/241/test.243863553:55366:4) at Module._compile (module.js:660:30) at Object.Module._extensions..js (module.js:671:10) at Module.load (module.js:573:32) at tryModuleLoad (module.js:513:12) at Function.Module._load (module.js:505:3) at Function.Module.runMain (module.js:701:10) at startup (bootstrap_node.js:190:16) at bootstrap_node.js:662:3 FAIL html/template 1.079s
diff --git a/compiler/natives/src/reflect/reflect.go b/compiler/natives/src/reflect/reflect.go
@@ -792,6 +792,39 @@ func (v Value) object() *js.Object {
 	return js.InternalObject(v.ptr)
 }
 
+func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value {
+	if v.flag&flagMethod != 0 {
+		v = makeMethodValue(context, v)
+	}
+
+	switch {
+	case directlyAssignable(dst, v.typ):
+		// Overwrite type so that they match.
+		// Same memory layout, so no harm done.
+		fl := v.flag&(flagAddr|flagIndir) | v.flag.ro()
+		fl |= flag(dst.Kind())
+		return Value{dst, v.ptr, fl}
+
+	case implements(dst, v.typ):
+		if target == nil {
+			target = unsafe_New(dst)
+		}
+		// GopherJS: Skip the v.Kind() == Interface && v.IsNil() if statement
+		//           from upstream. ifaceE2I below does not panic, and it needs
+		//           to run, given its custom implementation.
+		x := valueInterface(v, false)
+		if dst.NumMethod() == 0 {
+			*(*interface{})(target) = x
+		} else {
+			ifaceE2I(dst, x, target)
+		}
+		return Value{dst, target, flagIndir | flag(Interface)}
+	}
+
+	// Failed.
+	panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String())
+}
+
 var callHelper = js.Global.Get("$call").Interface().(func(...interface{}) *js.Object)
 
 func (v Value) call(op string, in []Value) []Value {
