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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2021-03-25 16:27:53 +0000 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-04-12 13:50:49 -0400 |
| commit | 792d9289434cb7418a559cd4157ee3bfaef54c99 (patch) | |
| tree | 252759700c5d633f5ac558723117a70add531d8c /compiler/GHC/Tc/TyCl/Class.hs | |
| parent | 6974c9e478120f6c4eeb53ebfa935c30cafcdf8e (diff) | |
| download | haskell-792d9289434cb7418a559cd4157ee3bfaef54c99.tar.gz | |
More accurate SrcSpan when reporting redundant constraints
We want an accurate SrcSpan for redundant constraints:
• Redundant constraint: Eq a
• In the type signature for:
f :: forall a. Eq a => a -> ()
|
5 | f :: Eq a => a -> ()
| ^^^^
This patch adds some plumbing to achieve this
* New data type GHC.Tc.Types.Origin.ReportRedundantConstraints (RRC)
* This RRC value is kept inside
- FunSigCtxt
- ExprSigCtxt
* Then, when reporting the error in GHC.Tc.Errors, use this SrcSpan
to control the error message: GHC.Tc.Errors.warnRedundantConstraints
Quite a lot of files are touched in a boring way.
Diffstat (limited to 'compiler/GHC/Tc/TyCl/Class.hs')
| -rw-r--r-- | compiler/GHC/Tc/TyCl/Class.hs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/compiler/GHC/Tc/TyCl/Class.hs b/compiler/GHC/Tc/TyCl/Class.hs index 491e657811..72de8f0652 100644 --- a/compiler/GHC/Tc/TyCl/Class.hs +++ b/compiler/GHC/Tc/TyCl/Class.hs @@ -282,8 +282,8 @@ tcDefMeth clas tyvars this_dict binds_in hs_sig_fn prag_fn -- NB: the binding is always a FunBind warn_redundant = case dm_spec of - GenericDM {} -> True - VanillaDM -> False + GenericDM {} -> lhsSigTypeContextSpan hs_ty + VanillaDM -> NoRRC -- For GenericDM, warn if the user specifies a signature -- with redundant constraints; but not for VanillaDM, where -- the default method may well be 'error' or something |