[MustardTiger]

>The second error message, on the other hand, proves that the first one is a lucky accident.

No, the second error message just shows that there's more options there so the error message is vague and not very helpful. The first one is not an accident, it is the standard type mismatch error.

[HelloNurse]

My point is that 1 2 should give the same type of error message as "foo" "bar", because it is the same kind of error (1 isn't a function with one or more arguments).

The compiler exposes that when numbers are involved it attempts (and fails) some fancy and unexpected reasoning involving forall, while with plain type constructors like [Char] it attempts (and fails) straightforward and intelligible pattern matching.

Figuring out the type of 1 and 2 might be more difficult than figuring out the type of "foo" and "bar", but the special rules should be hidden: a compiler that cares about practical usage would provide unified and clear error messages, possibly listing sets of alternative types it was unable to choose from.

[MustardTiger]

>My point is that 1 2 should give the same type of error message as "foo" "bar", because it is the same kind of error

And my point is that no it should not. "1 2" is more ambiguous, it could be more things, hence there is a more ambiguous error message.