Improve compiler error messages for when pattern matching on functions

[jeffnm]

If one of the types is a function and the other is a value, print a message saying "did you forget to call that function?"

That might still be confusing, since it looks to a novice like they've called it and are operating on a result. Since not all languages require an argument to all functions, I think an additional comment about that might be helpful if the type is {} => ...

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