#1316: add warning for local type signatures that use the same type variable
names
as outer type signatures
------------------------------+---------------------------------------------
Reporter: Isaac Dupree | Owner:
Type: feature request | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.6.1
Severity: normal | Keywords:
Difficulty: Unknown | Os: Unknown
Testcase: | Architecture: Unknown
------------------------------+---------------------------------------------
for a (poor) example,
{{{
f :: a -> a
f x = x
where
g :: a --this is (forall x. x) not the 'a' from f's type signature
-- So, warn about this signature.
g = undefined
}}}
Because it is likely to be confusing, as well as interfering with any
possibility of the type variables being considered scoped by default. In
fact, this may be a helpful/explanatory message in cases where there will
also be a type error due to the type variables not actually being scoped.
(although, detecting those cases particularly and giving a recommended
solution for how to give such a type signature, would be a more difficult
endeavor (what to recommend?))
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1316>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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