Improve location information for some warnings/errors.

compiler/java/com/google/dart/compiler/resolver/CoreTypeProviderImplementation.java

Index: compiler/java/com/google/dart/compiler/resolver/CoreTypeProviderImplementation.java
===================================================================
--- compiler/java/com/google/dart/compiler/resolver/CoreTypeProviderImplementation.java	(revision 512)
+++ compiler/java/com/google/dart/compiler/resolver/CoreTypeProviderImplementation.java	(working copy)
@@ -60,7 +60,8 @@
     if (element == null) {
       Location location = null;
       DartCompilationError error =
-          new DartCompilationError(location, DartCompilerErrorCode.CANNOT_BE_RESOLVED, name);
+          new DartCompilationError(null, Location.NONE,

[Brian Wilkerson, 2011/10/18 21:01:39]

It's unfortunate that we don't have any context at this point, but I guess our
fallback approach (of associating the error with the library being compiled)
will be as good as we can get.

Do you know, off hand, whether we get another error generated if one of these
types is referenced in user code? I'm actually wondering whether it is
appropriate to create a compilation error here at all...

[John Lenz, 2011/10/18 21:07:13]

I believe this should only occur if there is some internal issue (the core lib
are not included, etc).  If so, I don't see it as user correctable.  I haven't
been paying much attention to the error policy, so I don't know if this is
"appropriate" or not.

+              DartCompilerErrorCode.CANNOT_BE_RESOLVED, name);
       listener.compilationError(error);
       return Types.newDynamicType();
     }