Confusion with name resolution

[Ingo60]

Given this:

module my.fine.Decimal where
    data Decimal = .... where
        max :: Decimal -> Decimal -> Decimal
    main = print (Decimal.max 5 3)

Here, the expectation is that this gives type errors, for example because 5 is not Decimal and Decimal is not an instance of Show. (This is, incidentally, exactly what happens when max is replaced with some different identifier like add.)

Istead, the code compiles without complaints and the output is 5.

The reson is that the (implicit) Prelude import created a link max → Prelude.max in the module namespace Decimal, hence the main function is equivalent to:

main = print (max 5 3)

While this is correct, it is quite confusing if the following applies on name resolution of M.x:

• the module name M is the same as some type name that is in scope
• the type M also has a binding for x
• the module M has no original binding for x because x was imported.

There should at least be a warning, saying something like:

M.x is resolved as I.x
Use I.x or X.M.x for unambiguous  name resolution.

where X is the module namespace where he type M was defined.