Repository : ssh://git@git.haskell.org/ghc
On branch : master
Link : http://ghc.haskell.org/trac/ghc/changeset/322b48b92b93e1250b360d21873fa9f31c142403/ghc
>---------------------------------------------------------------
commit 322b48b92b93e1250b360d21873fa9f31c142403
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date: Thu Jan 9 16:55:31 2014 +0000
Further improve the "same-occurrence" error messages (Trac #8278)
Sometimes we actually have a good SrcSpan for the type constructor
and reporting that is better than just reporting which module it
was defined on
>---------------------------------------------------------------
322b48b92b93e1250b360d21873fa9f31c142403
compiler/typecheck/TcErrors.lhs | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/compiler/typecheck/TcErrors.lhs b/compiler/typecheck/TcErrors.lhs
index a28a9f5..f105cdd 100644
--- a/compiler/typecheck/TcErrors.lhs
+++ b/compiler/typecheck/TcErrors.lhs
@@ -858,7 +858,8 @@ misMatchMsg oriented ty1 ty2
, sameOccExtra ty2 ty1 ]
| otherwise
= sep [ ptext (sLit "Couldn't match") <+> what <+> quotes (ppr ty1)
- , nest 14 $ ptext (sLit "with") <+> quotes (ppr ty2) ]
+ , nest 14 $ ptext (sLit "with") <+> quotes (ppr ty2)
+ , sameOccExtra ty1 ty2 ]
where
what | isKind ty1 = ptext (sLit "kind")
| otherwise = ptext (sLit "type")
@@ -876,6 +877,7 @@ mkExpectedActualMsg ty1 ty2 (TypeEqOrigin { uo_actual = act, uo_expected = exp }
mkExpectedActualMsg _ _ _ = panic "mkExprectedAcutalMsg"
sameOccExtra :: TcType -> TcType -> SDoc
+-- See Note [Disambiguating (X ~ X) errors]
sameOccExtra ty1 ty2
| Just (tc1, _) <- tcSplitTyConApp_maybe ty1
, Just (tc2, _) <- tcSplitTyConApp_maybe ty2
@@ -890,6 +892,10 @@ sameOccExtra ty1 ty2
= empty
where
ppr_from same_pkg nm
+ | isGoodSrcSpan loc
+ = hang (quotes (ppr nm) <+> ptext (sLit "is defined at"))
+ 2 (ppr loc)
+ | otherwise -- Imported things have an UnhelpfulSrcSpan
= hang (quotes (ppr nm))
2 (sep [ ptext (sLit "is defined in") <+> quotes (ppr (moduleName mod))
, ppUnless (same_pkg || pkg == mainPackageId) $
@@ -897,8 +903,13 @@ sameOccExtra ty1 ty2
where
pkg = modulePackageId mod
mod = nameModule nm
+ loc = nameSrcSpan nm
\end{code}
+Note [Disambiguating (X ~ X) errors]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+See Trac #8278
+
Note [Reporting occurs-check errors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given (a ~ [a]), if 'a' is a rigid type variable bound by a user-supplied