type errors can be wrong-kinded #5440
Description
Describe and demonstrate the bug
If an expression returns a value that doesn't have the same number of type parameters as the expected type, then the type error message is confusing and shows types with kind errors.
Instead of:
I found a value of type: Either Text
where I expected to find: Optional
I would expect:
I found a value of type: Either Text a
where I expected to find: Optional Nat
or something like that...I'm not quite sure what it should infer for the right side of the Either.
Input:
```ucm
fresh/main> builtins.merge
```
```unison
foo : Optional Nat
foo = Left "error"
```Output:
``` ucm
fresh/main> builtins.merge
Done.
```
``` unison
foo : Optional Nat
foo = Left "error"
```
``` ucm
Loading changes detected in scratch.u.
I found a value of type: Either Text
where I expected to find: Optional
1 | foo : Optional Nat
2 | foo = Left "error"
```
🛑
The transcript failed due to an error in the stanza above. The error is:
I found a value of type: Either Text
where I expected to find: Optional
1 | foo : Optional Nat
2 | foo = Left "error"Screenshots
If applicable, add screenshots to help explain your problem.
Environment (please complete the following information):
ucm --versionc8f4126