Reapply "Enable full type-checks in checked mode."

sdk/lib/_internal/compiler/implementation/lib/js_rti.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_rti.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_rti.dart b/sdk/lib/_internal/compiler/implementation/lib/js_rti.dart
index c6d5727c0044537c9e3251f3c7965cc8fb5db787..2085dc4a64bc31ed6d1642923ed095801bb39d5f 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_rti.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_rti.dart
@@ -119,13 +119,13 @@ substitute(var substitution, var arguments) {
  *   against.
  */
 bool checkSubtype(Object object, String isField, List checks, String asField) {
-  if (object == null) return false;
+  if (object == null) return true;
   var arguments = getRuntimeTypeInfo(object);
   // Interceptor is needed for JSArray and native classes.
   // TODO(sra): It could be a more specialized interceptor since [object] is not
   // `null` or a primitive.
   // TODO(9586): Move type info for static functions onto an interceptor.
-  var interceptor = isJsFunction(object) ? object : getInterceptor(object);
+  var interceptor = getInterceptor(object);
   bool isSubclass = getField(interceptor, isField);
   // When we read the field and it is not there, [isSubclass] will be [:null:].
   if (isSubclass == null || !isSubclass) return false;
@@ -134,6 +134,19 @@ bool checkSubtype(Object object, String isField, List checks, String asField) {
   return checkArguments(substitution, arguments, checks);
 }
 
+Object assertSubtype(Object object, String isField, List checks,
+                     String asField) {
+  if (!checkSubtype(object, isField, checks, asField)) {
+    // Shorten the field name to the class name and append the textual
+    // representation of the type arguments.
+    int prefixLength = JS_OPERATOR_IS_PREFIX().length;
+    String typeName = '${isField.substring(prefixLength, isField.length)}'
+                      '${joinArguments(checks, 0)}';
+    throw new TypeErrorImplementation(object, typeName);
+  }
+  return object;
+}
+
 /**
  * Check that the types in the list [arguments] are subtypes of the types in
  * list [checks] (at the respective positions), possibly applying [substitution]
@@ -174,7 +187,7 @@ getField(var object, var name) => JS('var', r'#[#]', object, name);
  * representation [t], which is a type representation as described in the
  * comment on [isSubtype].
  */
-bool objectIsSubtype(Object o, var t) {
+bool checkSubtypeOfRuntimeType(Object o, var t) {
   if (JS('bool', '# == null', o) || JS('bool', '# == null', t)) return true;
   // Get the runtime type information from the object here, because we may
   // overwrite o with the interceptor below.
@@ -199,6 +212,13 @@ bool objectIsSubtype(Object o, var t) {
   return isSubtype(type, t);
 }
 
+Object assertSubtypeOfRuntimeType(Object object, var type) {
+  if (!checkSubtypeOfRuntimeType(object, type)) {
+    throw new TypeErrorImplementation(object, runtimeTypeToString(type));
+  }
+  return object;
+}
+
 /**
  * Check whether the type represented by [s] is a subtype of the type
  * represented by [t].
@@ -224,6 +244,10 @@ bool isSubtype(var s, var t) {
   // constructed from the type of [t].
   var typeOfS = isJsArray(s) ? s[0] : s;
   var typeOfT = isJsArray(t) ? t[0] : t;
+  // TODO(johnniwinther): replace this with the real function subtype test.
+  if (JS('bool', '#.func', s) == true || JS('bool', '#.func', t) == true ) {
+    return true;
+  }
   // Check for a subtyping flag.
   var test = '${JS_OPERATOR_IS_PREFIX()}${runtimeTypeToString(typeOfT)}';
   if (getField(typeOfS, test) == null) return false;