[m-rev.] for review: structured types in error messages

[Zoltan Somogyi]

2022-02-21 15:34 GMT+11:00 "Peter Wang" <novalazy at gmail.com>:
> I don't understand the relevance of function declarations here.
> The type of max_one_line_type_length would have to be written
> in a Mercury source file as:
> 
>     (func) = int
> 
> e.g.
> 
>     :- func max_one_line_type_length `with_type` ((func) = int).

Agreed, but that is what I meant by ((func) = int) being
inside another type, which in this case is the whole line.

> I think error messages should (as far as possible) print types
> in the same way they would be written in Mercury code.

Agreed; the question is: the same way they would be written
in Mercury code *where*? Inside another type, or at the top level?
You are arguing for the former, I am for the latter (for when the type
is actually at the top level).

> However, I do see that the current compiler behaves as in your change:
> 
>     t.m:027:   Argument 1 (X) has type `func = int',
>     t.m:027:   expected type was `int'.

Which is what my diff was based on.

Zoltan.