#7402: Warn about possible missing -XScopedTypeVariables on errors.
-----------------------------+----------------------------------------------
Reporter: Aninhumer | Owner:
Type: feature request | Status: new
Priority: normal | Component: Compiler
Version: 7.6.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Blockedby:
Blocking: | Related:
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Suggest that the user they may wish to add -XScopedTypeVariables, if an
error results from a free type variable which would be bound in its scope
with the flag enabled. (i.e. if its name exists as a variable in the type
declaration).
I ran into this problem on code similar to this:
{{{
instance (Sized a n, Nat n) => Rep a where
emptyRep = replicate (toInt (undefined :: n)) 0
}}}
and it took me some time to solve, and only by having vague knowledge that
such a flag existed.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7402>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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