[RFC] Tightening up the type system

[Nathan Sidwell]

Andrew Haley wrote:
> Diego Novillo writes:
>  > 
>  > 
>  > My question to the FE folks is: what are the right semantics for
>  > checking MODIFY_EXPR?  Is compatible_types_p too strict?  Should we have
>  > had a cast operation in the above assignment?
>  > 
>  > Not having the right types is increasingly getting in the way of the
>  > optimizers because we use compatible_types_p quite often to validate
>  > propagation opportunities.
> 
> It's an interesting view.  I'm pretty sure that we violate this is the
> Java FE in a few places, but perhaps we shouldn't.  The trouble is
> that the GENERIC type system has never been so well-defined.
> 
> I'm sure that enforcing this would break things and it would take some
> time to find and fix them all. 

It'd force us to treat an lvalue packed field as incompatible to an
unpacked one, at last.

nathan

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