Forcing the type to be IO {} instead of IO() causes a "panic! The impossible has happened" output.

Below is the source code in which the bug occurs. It is easily reproduce-able, by having the type be IO{} instead of IO().

When ran, this code will produce the "panic! The impossible has happened" output. Which told me to report the bug here.

By changing IO() to IO{} (which I did by accident), no exception is thrown, it simply tells the user to panic!

    main :: IO {}
    main = do
            e1 <- getLine
            e2 <- getLine
            print ((read e1) + (read e2))

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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