No warnings produced, yet the pattern matching fails at runtime.

The code below should produce a warning about a non-exhaustive pattern in the failure, yet it compiles alright. `style="font-size: 80%" {{{#!haskell # OPTIONS_GHC -Wall -Werror #

action :: (Monad m)=>t->m (Maybe a) action _=return Nothing

failure :: (Monad m)=>Int->(m Int) failure x=do Just y<-action x return y

main :: IO() main=do y<-failure 1 putStrLn $ (show y) ` }}}

The same should be the case if we replace the definition of failure with

style="font-size: 80%" {{{#!haskell failure :: (Monad m)=>Int->(m Int) failure x=(action x)>>=(\(Just y)->return y) }}}

yet once again no warnings are produced.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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