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| author | Iavor S. Diatchki <iavor.diatchki@gmail.com> | 2014-06-29 17:22:16 -0700 |
|---|---|---|
| committer | Iavor S. Diatchki <iavor.diatchki@gmail.com> | 2014-06-29 17:22:16 -0700 |
| commit | 6290eeadf61a40f2eb08d0fd7ef1f3b7f9804178 (patch) | |
| tree | a8b94173a7585cd1e7c543e2f76b32e7b6f31db1 /compiler/rename | |
| parent | 9982715002edfd789926fd4ccd42bea284a67939 (diff) | |
| download | haskell-6290eeadf61a40f2eb08d0fd7ef1f3b7f9804178.tar.gz | |
Overlapable pragmas for individual instances (#9242)
Programmers may provide a pragma immediately after the `instance` keyword
to control the overlap/incoherence behavior for individual instances.
For example:
instance {-# OVERLAP #-} C a where ...
I chose this notation, rather than the other two outlined in the ticket
for these reasons:
1. Having the pragma after the type looks odd, I think.
2. Having the pragma after there `where` does not work for
stand-alone derived instances
I have implemented 3 pragams:
1. NO_OVERLAP
2. OVERLAP
3. INCOHERENT
These correspond directly to the internal modes currently supported by
GHC. If a pragma is specified, it will be used no matter what flags are
turned on. For example, putting `NO_OVERLAP` on an instance will mark
it as non-overlapping, even if `OVERLAPPIN_INSTANCES` is turned on for the
module.
Diffstat (limited to 'compiler/rename')
| -rw-r--r-- | compiler/rename/RnSource.lhs | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/compiler/rename/RnSource.lhs b/compiler/rename/RnSource.lhs index 2618792e82..c6646ad563 100644 --- a/compiler/rename/RnSource.lhs +++ b/compiler/rename/RnSource.lhs @@ -445,12 +445,14 @@ rnSrcInstDecl (ClsInstD { cid_inst = cid }) rnClsInstDecl :: ClsInstDecl RdrName -> RnM (ClsInstDecl Name, FreeVars) rnClsInstDecl (ClsInstDecl { cid_poly_ty = inst_ty, cid_binds = mbinds , cid_sigs = uprags, cid_tyfam_insts = ats + , cid_overlap_mode = oflag , cid_datafam_insts = adts }) -- Used for both source and interface file decls = do { (inst_ty', inst_fvs) <- rnLHsInstType (text "In an instance declaration") inst_ty ; case splitLHsInstDeclTy_maybe inst_ty' of { Nothing -> return (ClsInstDecl { cid_poly_ty = inst_ty', cid_binds = emptyLHsBinds , cid_sigs = [], cid_tyfam_insts = [] + , cid_overlap_mode = oflag , cid_datafam_insts = [] } , inst_fvs) ; Just (inst_tyvars, _, L _ cls,_) -> @@ -493,6 +495,7 @@ rnClsInstDecl (ClsInstDecl { cid_poly_ty = inst_ty, cid_binds = mbinds `plusFV` inst_fvs ; return (ClsInstDecl { cid_poly_ty = inst_ty', cid_binds = mbinds' , cid_sigs = uprags', cid_tyfam_insts = ats' + , cid_overlap_mode = oflag , cid_datafam_insts = adts' }, all_fvs) } } } -- We return the renamed associated data type declarations so @@ -637,11 +640,11 @@ extendTyVarEnvForMethodBinds ktv_names thing_inside \begin{code} rnSrcDerivDecl :: DerivDecl RdrName -> RnM (DerivDecl Name, FreeVars) -rnSrcDerivDecl (DerivDecl ty) +rnSrcDerivDecl (DerivDecl ty overlap) = do { standalone_deriv_ok <- xoptM Opt_StandaloneDeriving ; unless standalone_deriv_ok (addErr standaloneDerivErr) ; (ty', fvs) <- rnLHsInstType (text "In a deriving declaration") ty - ; return (DerivDecl ty', fvs) } + ; return (DerivDecl ty' overlap, fvs) } standaloneDerivErr :: SDoc standaloneDerivErr |