Incorrect type inferred with -fwarn-missing-signatures and a type class
The inferred type using -fwarn-missing-signatures and a type class is too general for top-level values.
Here is a simplified example:
{-# OPTIONS -Wall #-}
class C a where c :: a
instance C Int where c = 37
def = c
use :: Int
use = def
The inferred type reported by GHCi when -fwarn-missing-signatures is enabled is:
Ex.hs:7:0:
Warning: Definition but no type signature for `def'
Inferred type: def :: a
The most general possible type here is C a => a
. When asking GHCi for the type of def
, it reports Int
.
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | leather@cs.uu.nl |
Operating system | |
Architecture |