Duplicate type error messages with implicit parameters

The following ill-typed program generates two identical type errors at the same source location:

{-# LANGUAGE ImplicitParams #-}

foo :: (?x :: Int) => a
foo = undefined

bar =
    let ?x = "hello"
    in foo

The error messages are:

Test.hs:8:8:
    Couldn't match type `Int' with `[Char]'
    In the expression: foo
    In the expression: let ?x = "hello" in foo
    In an equation for `bar': bar = let ?x = "hello" in foo

Test.hs:8:8:
    Couldn't match type `Int' with `[Char]'
    In the expression: foo
    In the expression: let ?x = "hello" in foo
    In an equation for `bar': bar = let ?x = "hello" in foo

Obviously, it should only print this error once. I encountered this in a larger program where it meant I got eight identical type errors at the same source position!

Trac metadata

Trac field	Value
Version	7.0.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture