Template Haskell record splices are not renamer-resolved correctly.
While working on ticket #8761 (closed), I noticed that splicing in record selectors with Template Haskell seems to cause renamer issues in GHC HEAD.
Consider the following TH splice:
{- Test splicing in a data type with records -}
[d|
data D a = MkD { unD :: a }
someD = MkD "Hello"
getD = unD someD -- unD should resolve to the record selector above!
|]
getD' = unD someD -- dito here outside of the splice!
While GHC 7.10.3 accepts this splice and renames it correctly, GHC HEAD fails with the following error message (with -ddump-splices
enabled):
[1 of 1] Compiling Error ( Error.hs, Error.o )
Error.hs:(6,1)-(11,3): Splicing declarations
[d| someD_apF = MkD_apD "Hello"
getD_apG = unD someD_apF
data D_apC a_apH = MkD_apD {unD :: a_apH} |]
======>
data D_a4SA a_a4SD = MkD_a4SB {unD_a4SC :: a_a4SD}
someD_a4Sy = MkD_a4SB "Hello"
getD_a4Sz = unD_a4SC someD_a4Sy
Error.hs:6:1: error:
The exact Name ‘unD_a4SC’ is not in scope
Probable cause: you used a unique Template Haskell name (NameU),
perhaps via newName, but did not bind it
If that's it, then -ddump-splices might be useful
I'm not sure as to what introduced this bug, but investigating it I found that the notes
-
NOTE [Binders in Template Haskell] in Convert.hs
, and NOTE [Looking up Exact RdrNames] in RnEnv.hs
are not respected by function newRecordSelector
in rename/RnNames.hs
. I've fixed this function accordingly in D1940 for #8761 (closed), but since that patch is not going to be part of 8.0.1, Richard suggested to fix it separately in this ticket.
I'm submitting a patch in due course.
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Template Haskell |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |