fuse some null checks with type checks, introduce a special bool variant

tool/input_sdk/private/ddc_runtime/operations.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// This library defines runtime operations on objects used by the code
 /// generator.
 part of dart._runtime;
 
 _canonicalFieldName(obj, name, args, displayName) => JS('', '''(() => {
   $name = $canonicalMember($obj, $name);
@@ skipping 203 matching lines @@
     }
     return false;
   });
 })()''');
 
 /// Returns true if [obj] is an instance of [type]
 /// Returns false if [obj] is not an instance of [type] in both spec
 ///  and strong mode
 /// Returns null if [obj] is not an instance of [type] in strong mode
 ///  but might be in spec mode
-strongInstanceOf(obj, type, ignoreFromWhiteList) => JS('', '''(() => {
+bool strongInstanceOf(obj, type, ignoreFromWhiteList) => JS('', '''(() => {
   let actual = $getReifiedType($obj);
   let result = $isSubtype(actual, $type);
   if (result || actual == $jsobject ||
       actual == $int && type == $double) return true;
   if (result === false) return false;
   if ($ignoreFromWhiteList == void 0) return result;
   if ($_ignoreTypeFailure(actual, $type)) return true;
   return result;
 })()''');
 
@@ skipping 10 matching lines @@
 instanceOf(obj, type) => JS('', '''(() => {
   let result = $strongInstanceOf($obj, $type);
   if (result !== null) return result;
   let actual = $getReifiedType($obj);
   $throwStrongModeError('Strong mode is check failure: ' +
     $typeName(actual) + ' does not soundly subtype ' +
     $typeName($type));
 })()''');
 
 @JSExportName('as')
-cast(obj, type) => JS('', '''(() => {
-  if ($obj == null) return $obj;
+cast(obj, type) {
+  if (obj == null) return obj;
 
-  let result = $strongInstanceOf($obj, $type, true);
-  if (result) return $obj;
+  bool result = strongInstanceOf(obj, type, true);
+  if (JS('bool', '#', result)) return obj;
+  _throwCastError(obj, type, result);
+}
 
-  let actual = $getReifiedType($obj);
+bool test(obj) {
+  if (JS('bool', 'typeof # == "boolean"', obj)) return JS('bool', '#', obj);
+  throwCastError(getReifiedType(obj), JS('', '#', bool));
+}
 
-  if (result === false) $throwCastError(actual, $type);
+void _throwCastError(obj, type, bool result) {
+  var actual = getReifiedType(obj);
+  if (result == false) throwCastError(actual, type);
 
-  $throwStrongModeError('Strong mode cast failure from ' +
-    $typeName(actual) + ' to ' + $typeName($type));
-})()''');
+  throwStrongModeError('Strong mode cast failure from ' +
+      typeName(actual) + ' to ' + typeName(type));
+}
 
-asInt(obj) => JS('', '''(() => {
-  if ($obj == null) {
-    return null;
+asInt(obj) {
+  if (obj == null) return null;
+
+  if (JS('bool', 'Math.floor(#) != #', obj, obj)) {
+    throwCastError(getReifiedType(obj), int);
   }
-  if (Math.floor($obj) != $obj) {
-    // Note: null will also be caught by this check
-    $throwCastError($getReifiedType($obj), $int);
-  }
-  return $obj;
-})()''');
-
-arity(f) => JS('', '''(() => {
-  // TODO(jmesserly): need to parse optional params.
-  // In ES6, length is the number of required arguments.
-  return { min: $f.length, max: $f.length };
-})()''');
+  return obj;
+}
 
 equals(x, y) => JS('', '''(() => {
   if ($x == null || $y == null) return $x == $y;
   let eq = $x['=='];
   return eq ? eq.call($x, $y) : $x === $y;
 })()''');
 
 /// Checks that `x` is not null or undefined. */
 notNull(x) {
   if (x == null) throwNullValueError();
@@ skipping 210 matching lines @@
     constructor(dartIterator) {
       this.dartIterator = dartIterator;
     }
     next() {
       let i = this.dartIterator;
       let done = !i.moveNext();
       return { done: done, value: done ? void 0 : i.current };
     }
   }
 ''');