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