Support creating elements from IR nodes in JsKernelToElementMap

pkg/compiler/lib/src/common_elements.dart

Index: pkg/compiler/lib/src/common_elements.dart
diff --git a/pkg/compiler/lib/src/common_elements.dart b/pkg/compiler/lib/src/common_elements.dart
index 760f5d16c2dc7a90abdfcf26d468bf97fe1a9512..379e9c8ba2922db9ee8ba59b4a985287c5009780 100644
--- a/pkg/compiler/lib/src/common_elements.dart
+++ b/pkg/compiler/lib/src/common_elements.dart
@@ -942,15 +942,32 @@ class CommonElements {
   FunctionEntity get throwConcurrentModificationError =>
       _findHelperFunction('throwConcurrentModificationError');
 
-  FunctionEntity _checkInt;
-  FunctionEntity get checkInt => _checkInt ??= _findHelperFunction('checkInt');
+  /// Return `true` if [member] is the 'checkInt' function defined in
+  /// dart:_js_helpers.
+  bool isCheckInt(MemberEntity member) {
+    return member.isFunction &&
+        member.name == 'checkInt' &&

[Siggi Cherem (dart-lang), 2017/07/05 20:13:37]

nit: let's move this one last, since I expect it's the most expensive check
(same below)

[Johnni Winther, 2017/07/06 13:30:40]

Done.

+        member.isTopLevel &&
+        member.library == jsHelperLibrary;
+  }
 
-  FunctionEntity _checkNum;
-  FunctionEntity get checkNum => _checkNum ??= _findHelperFunction('checkNum');
+  /// Return `true` if [member] is the 'checkNum' function defined in
+  /// dart:_js_helpers.
+  bool isCheckNum(MemberEntity member) {
+    return member.isFunction &&
+        member.name == 'checkNum' &&
+        member.isTopLevel &&
+        member.library == jsHelperLibrary;
+  }
 
-  FunctionEntity _checkString;
-  FunctionEntity get checkString =>
-      _checkString ??= _findHelperFunction('checkString');
+  /// Return `true` if [member] is the 'checkString' function defined in
+  /// dart:_js_helpers.
+  bool isCheckString(MemberEntity member) {
+    return member.isFunction &&
+        member.name == 'checkString' &&
+        member.isTopLevel &&
+        member.library == jsHelperLibrary;
+  }
 
   FunctionEntity get stringInterpolationHelper => _findHelperFunction('S');