Redo "dart2js: Redo known-type analysis after load-elimination"

pkg/compiler/lib/src/ssa/codegen.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:math' as math;
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
@@ skipping 2831 matching lines @@
       // input is !string
       checkString(input, '!==', input.sourceInformation);
       return pop();
     }
     reporter.internalError(input, 'Unexpected check: $checkedType.');
     return null;
   }
 
   void visitTypeConversion(HTypeConversion node) {
     if (node.isArgumentTypeCheck || node.isReceiverTypeCheck) {
-      // An int check if the input is not int or null, is not
-      // sufficient for doing an argument or receiver check.

[sra1, 2017/02/01 00:59:15]

I think this is incorrect. The check is Math.floor(x) !== x, which will not
accidentally accept numeric strings.

[Siggi Cherem (dart-lang), 2017/02/01 01:31:48]

Could we end up hitting the Math.floor case when the input is `null`? which will
say true instead of false? for example if input.isPrimitiveOrNull? 

I'm not as familiar with this as you are, so feel free to ignore and I'll ask
you in person later in the week.

[sra1, 2017/02/01 02:15:46]

It works as intended:

  Math.floor(null) --> 0,           0 !== null
  Math.floor(undefined) --> NaN,  NaN !== undefined

These cases might be a slow path, but only when the program is going to throw an
exception.
`x is int` sometimes generates an additional `typeof x === "number"` to avoid
this potential slowness.

-      assert(compiler.options.trustTypeAnnotations ||
-          !node.checkedType.containsOnlyInt(closedWorld) ||
-          node.checkedInput.isIntegerOrNull(closedWorld));
       js.Expression test = generateReceiverOrArgumentTypeTest(
           node.checkedInput, node.checkedType);
       js.Block oldContainer = currentContainer;
       js.Statement body = new js.Block.empty();
       currentContainer = body;
       if (node.isArgumentTypeCheck) {
         generateThrowWithHelper(
             helpers.throwIllegalArgumentException, node.checkedInput,
             sourceInformation: node.sourceInformation);
       } else if (node.isReceiverTypeCheck) {
@@ skipping 253 matching lines @@
     registry.registerStaticUse(new StaticUse.staticInvoke(
         helper, new CallStructure.unnamed(argumentCount)));
     return backend.emitter.staticFunctionAccess(helper);
   }
 
   @override
   void visitRef(HRef node) {
     visit(node.value);
   }
 }