Compiler bug in applying an uncurried function when the function has a signature

[jfrolich]

This causes a compile error that the interface doesn't match the signature even though the types are exactly the same in the error. Without the signature it compiles just fine.

Some pointers:

• Adding the type annotation to the function in the implementation suddenly makes it compile
• Wrapping the function also fixes the issue
• Using core's Array function also makes it compile

So it seems to be a bug in using externals in uncurried mode because the issue is not present when the map function is not an external