Wrong detection of "Duplicate definition"

[sgjesse]

The change in http://code.google.com/p/dart/source/detail?r=593 broke the the chat sample and tests. The issue is easy to reproduce. Having either

  typedef void callbackType(List<int> x);
  void main() { print("Hello, world!"); }

or

  interface X {
    void set handler(void callback(List<int> x));
  }
  void main() { print("Hello, world!"); }

in test.dart will produce the error:

out/Release_ia32/dart_bin test.dart
Duplicate definition : '(List<int>) => void' is defined in './dart:builtin-lib' and 'test.dart'

when running

$ out/Release_ia32/dart_bin test.dart

[a-siva]

Currently we are defining these implicit signature classes in the current library where they are found.
There was a change done to skip signature classes when looking for duplicate definitions but that is incorrect as we will miss cases where we are supposed to detect duplicates when the uses defines typedefs
e.g:
#library("library1.dart");
typdef void callbackType(int x, int y);

#library("library2.dart");
typedef int callbackType();

and an app with
#import("library1.dart");
#import("library2.dart");
This should produce a duplicate definition error for callbackType.

Regis and I discussed this and we think the implicit signature classes should not be defined in the current library that is being parsed but instead in the corelib so that

1. They will be shared across all code
2. Will not result in duplicate definitions

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cc @crelier.

[crelier]

Set owner to @crelier.

[crelier]

Duplicate import of a function type alias must be detected, but duplicate
import of a compiler generated canonical function type is necessary for proper
class resolution and is permitted.

The discussed solution above (storing all signature classes in the core library) is therefore not correct, because unresolved class names appearing in the function signature would not be resolved properly if the signature class was not part of the parsed library.

It is also important not to lookup and share a signature class in imported libraries, since class resolution would not work properly.
 
The solution implemented in r658 limits lookup and sharing of canonical signature classes to the current library.

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Added Fixed label.