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  • #15471

Closed
Open
Opened Aug 03, 2018 by Matthew Pickering@mpickeringDeveloper

Polymorphism, typed splices and type inference don't mix

Trying to quote and splice a polymorphic function doesn't work unless you have a type signature.

{-# LANGUAGE TemplateHaskell #-}
module A where

foo1 x = x

test_foo = [|| foo1 ||]
{-# LANGUAGE TemplateHaskell #-}
module B where

import A

qux = $$(test_foo)

The type of qux is Any -> Any! Which is clearly wrong.

Adding a type signature to qux fixes the problem.

qux :: a -> a
qux = $$(test_foo)

Either there should be a better error or this should just work.

It seems that this has always been broken. Ryan tested on GHC 7.8.4 for me.

Trac metadata
Trac field Value
Version 8.4.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
Assignee
Assign to
8.8.1
Milestone
8.8.1 (Past due)
Assign milestone
Time tracking
None
Due date
None
Reference: ghc/ghc#15471