[Issue 7542] inout parameter contravariant should be allowed

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7542



--- Comment #3 from Kenji Hara <k.hara.pg at gmail.com> 2012-02-19 06:11:25 PST ---
(In reply to comment #2)
> This pull breaks the type system:
> 
> void main(){
>     // conversion from void function(int*) to void function(inout(int)*):
>     void function(inout(int)*) wfp = function(int*)(*p = 1;}
>     immutable int x = 0;
>     wfp(&x); // mutates x
> }
> 
> The title of the bug report is correct though, contravariance is safe.
> 
> Those are the safe conversions:
> mfp = wfp; // match inout as mutable
> wfp = cfp; // inout is a subtype of const
> cfp = wfp; // match inout as const
> ifp = wfp; // match inout as immutable

You are right, and this fix doesn't block 7543.

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