Error message for Integer type mismatch

[zilinc]

Now it says something like:

Mismatch between
   U16
and
   U32
   from constraint U16 :< U32
   when checking that the expression at ("fail_large-code.cogent" (line 244, column 80))
      const_ext2Magic
   has type
      U32

Can be better.

[liamoc]

How can it be improved specifically?

[zilinc]

Suggest using upcast maybe? The constraint U16 :< U32 is actually satisfiable.

[liamoc]

Ah, if you use upcast, right. OK, I can add that.

[zilinc]

Oh btw, we still have functions like u16_to_u32 etc...in ext2 and bilbyfs; should use upcast instead...

[zilinc]

Ummm. let a : U32 = 1 doesn't upcast.

[liamoc]

It shouldn't... it should infer that 1 : U32.

[zilinc]

interestingly if I put 0 to a U32 field in a record, it seems ok

[liamoc]

The type of a numeric literal is inferred from context.. so of course that would work??

[zilinc]

Ah, I might have misunderstood you. Should let a : U32 = 1 typecheck?

[liamoc]

Yes.

[zilinc]

I see. upcast is only for variables (and constants).

[liamoc]

Yes, the literals are no longer given the smallest integer type possible. They are now given whatever integer type is inferred from context (so long as it's big enough to fit the literal).