id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5957	signatures are too permissive	maeder		"ghc should reject the following (accidentally mistyped) signature, unless `-XFlexibleContexts` is used.

{{{
flex :: Int -> Show a => a -> String
flex i a = show a ++ show i
}}}

hugs and ghc version below 7 rejected this correctly:

{{{
    All of the type variables in the constraint `Show a'
    are already in scope (at least one must be universally quantified here)
        (Use -XFlexibleContexts to lift this restriction)
    In the type signature for `flex':
      flex :: Int -> (Show a) => a -> String
}}}

It is not Haskell98 nor Haskell2010 (I believe).
"	bug	new	low	_|_	Compiler (Type checker)	7.4.1				Unknown/Multiple	Unknown/Multiple	None/Unknown	Unknown	typecheck/should_fail/T5957