Conflicting type variable bindings leads to contradictory error message

[avh4]

In 0.16: In the following,

type alias T a b c =
  { a : a, b : b, c : c }

f : T a b a -> ()
f _ = ()

x : T Int Float String -> ()
x = f

The error message is confusing and contradicts itself:

TYPE MISMATCH
The type annotation for `x` does not match its definition.

9| x : T Int Float String -> ()
The type annotation is saying:

    T Int Float Int -> ()

But I am inferring that the definition has this type:

    T Int Float Int -> ()

It shows the source code with the type annotation T Int Float String -> (), and then states that the type annotation says T Int Float Int -> ().

Instead, the error message should state "The type annotation is saying: T Int Float String -> ()"

[jvoigtlaender]

This "the compiler says two types are different, but shows the exact same two types" thing comes up so often. See elm/compiler#1192 and all the issues showing up as references there. We really need a process to avoid people opening duplicates after duplicates of issues. I think elm/compiler#1342 is a good start.

[jvoigtlaender]

This is supposed to be fixed now. See elm/compiler#1192 (comment).

[jvoigtlaender]

Actually it's not fixed. See elm/compiler#1371.

[rtfeldman]

Closing this since there is a compiler issue tracking it.