[antlr-interest] Duplicate members when generating code with 2 import levels in Java with ANTLR-3.1.1

[Gavin Lambert]

At 12:04 28/10/2008, Loring Craymer wrote:
 >Just my 2 cents, but shouldn't duplicate imports be supported at 

 >the language level, as is true for Java, C#, and even C/C++ with 

 >the usual #ifdef wrapping?  It seems to me that leaving 
dependency
 >management to the user limits the convenience of composition.

If you think of grammar imports as class inheritance (which is 
what they behave most like), then I think you'll find that those 
other languages don't really support it all that well either :)

In C#, multiple inheritance of interfaces is supported cleanly, 
but interfaces carry no implementation.  Since the 
implementation-inheritance model is single-inheritance, there's no 
possibility of a serious clash.  I'm not sure about Java exactly, 
but I believe it's similar.

In C++, if you try to make class C inherit from both B1 and B2 
(where B2 inherits from B1), then it will indeed include an extra 
copy of B1 (in what's known as a "deadly diamond"), unless B1 is a 
virtual base class.  This seems like the same behaviour as what 
ANTLR exhibits, except that (currently at least) ANTLR provides no 
means to make it a virtual base :)