[Issue 6912] const(T[])/immutable(T[]) can be implicitly cast to inout(const(T)[])/inout(immutable(T)[])

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6912


timon.gehr at gmx.ch changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|non-transitivity of inout   |const(T[])/immutable(T[])
                   |breaks const system         |can be implicitly cast to
                   |                            |inout(const(T)[])/inout(imm
                   |                            |utable(T)[])


--- Comment #2 from timon.gehr at gmx.ch 2011-11-09 08:58:10 PST ---
(In reply to comment #1)
> inout a = q;
> 
> This line should fail to compile.  const does not implicitly cast to inout.
> 

Yes, but the issue here is that it casts to inout(const(int)[]). (dmd rejects
casting const(int[]) to inout(int[]) for exampe)

> Note that:
> 
> immutable a = q;
> 
> doesn't work.  inout should follow the same restrictions.
> 
> I don't think this has to do with transitivity (and indeed, inout cannot
> override const or immutable).  It's just a simple case of inout cannot be
> implicitly cast from something else.
> 
> Remember, inout can get implicitly cast back to immutable or mutable upon
> function return.  I don't think inout should override *any* qualifiers without
> casts.

You are right, it is not a transitivity/overriding issue.

Currently inout(const(T)) == inout(immutable(T)) == inout(T). That is bad, for
example, how to represent the element type of inout(const(char)[]) ? (DMD
treats it as const(char), which is obviously wrong, it should be
inout(const(char)).)

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