Start implementing checked mode and tools support for using it.

lib/compiler/implementation/apiimpl.dart

Index: lib/compiler/implementation/apiimpl.dart
===================================================================
--- lib/compiler/implementation/apiimpl.dart	(revision 7269)
+++ lib/compiler/implementation/apiimpl.dart	(working copy)
@@ -21,9 +21,12 @@
   Uri packageRoot;
   List<String> options;
   bool mockableLibraryUsed = false;
+  bool checkedMode = false;

[ahe, 2012/05/07 11:59:57]

Developer mode, please.

[ngeoffray, 2012/05/07 13:15:42]

Renamed to enableTypeAssertions.

 
   Compiler(this.provider, this.handler, this.libraryRoot, this.options)
-    : super(tracer: new ssa.HTracer());
+    : super(tracer: new ssa.HTracer()) {
+    checkedMode = options.indexOf('--enable-checked-mode') !== -1;

[ahe, 2012/05/07 11:59:57]

I don't like this flag name. I think it should be something like:

--developer-mode

I'm fine having aliases for compatibility with the VM. But I think we need to
*think* about flag names, instead of just doing something. This is the most
fundamental interface to the compiler, and it should be "designed".

[ngeoffray, 2012/05/07 13:15:42]

As discussed, keeping enable-checked-mode only for now.

+  }
 
   elements.LibraryElement scanBuiltinLibrary(String path) {
     Uri uri = libraryRoot.resolve(DART2JS_LIBRARY_MAP[path]);
@@ -95,4 +98,8 @@
     return mockableLibraryUsed
       && (options.indexOf('--allow-mock-compilation') !== -1);
   }
+
+  bool get isCheckedModeEnabled() {

[ahe, 2012/05/07 11:59:57]

Developer mode, please.

[ngeoffray, 2012/05/07 13:15:42]

I removed the getter.

+    return checkedMode;
+  }
 }