[commit: ghc] wip/new-flatten-skolems-Oct14: White space only (d91da6a)
git at git.haskell.org
git at git.haskell.org
Thu Oct 30 12:54:10 UTC 2014
Repository : ssh://git@git.haskell.org/ghc
On branch : wip/new-flatten-skolems-Oct14
Link : http://ghc.haskell.org/trac/ghc/changeset/d91da6a7006c098bdbb6b676ae85d63d63bd1fd6/ghc
>---------------------------------------------------------------
commit d91da6a7006c098bdbb6b676ae85d63d63bd1fd6
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date: Wed Oct 29 16:27:50 2014 +0000
White space only
>---------------------------------------------------------------
d91da6a7006c098bdbb6b676ae85d63d63bd1fd6
compiler/main/PprTyThing.hs | 2 +-
compiler/typecheck/Inst.lhs | 96 +++++++++++++++++++++------------------
compiler/typecheck/TcDeriv.lhs | 6 +--
compiler/typecheck/TcGenDeriv.lhs | 2 +-
compiler/types/InstEnv.lhs | 4 +-
5 files changed, 59 insertions(+), 51 deletions(-)
diff --git a/compiler/main/PprTyThing.hs b/compiler/main/PprTyThing.hs
index eed4671..240e63b 100644
--- a/compiler/main/PprTyThing.hs
+++ b/compiler/main/PprTyThing.hs
@@ -128,7 +128,7 @@ pprTyThingInContextLoc tyThing
------------------------
ppr_ty_thing :: Bool -> [OccName] -> TyThing -> SDoc
-- We pretty-print 'TyThing' via 'IfaceDecl'
--- See Note [Pretty-pringint TyThings]
+-- See Note [Pretty-printing TyThings]
ppr_ty_thing hdr_only path ty_thing
= pprIfaceDecl ss (tyThingToIfaceDecl ty_thing)
where
diff --git a/compiler/typecheck/Inst.lhs b/compiler/typecheck/Inst.lhs
index 3405fd4..89955bf 100644
--- a/compiler/typecheck/Inst.lhs
+++ b/compiler/typecheck/Inst.lhs
@@ -473,52 +473,60 @@ addLocalInst (home_ie, my_insts) ispec
dupInstErr ispec (head dups)
; return (extendInstEnv home_ie' ispec, ispec:my_insts') }
+\end{code}
+
+Note [Signature files and type class instances]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Instances in signature files do not have an effect when compiling:
+when you compile a signature against an implementation, you will
+see the instances WHETHER OR NOT the instance is declared in
+the file (this is because the signatures go in the EPS and we
+can't filter them out easily.) This is also why we cannot
+place the instance in the hi file: it would show up as a duplicate,
+and we don't have instance reexports anyway.
+
+However, you might find them useful when typechecking against
+a signature: the instance is a way of indicating to GHC that
+some instance exists, in case downstream code uses it.
+
+Implementing this is a little tricky. Consider the following
+situation (sigof03):
+
+ module A where
+ instance C T where ...
+
+ module ASig where
+ instance C T
+
+When compiling ASig, A.hi is loaded, which brings its instances
+into the EPS. When we process the instance declaration in ASig,
+we should ignore it for the purpose of doing a duplicate check,
+since it's not actually a duplicate. But don't skip the check
+entirely, we still want this to fail (tcfail221):
+
+ module ASig where
+ instance C T
+ instance C T
--- Note [Signature files and type class instances]
--- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--- Instances in signature files do not have an effect when compiling:
--- when you compile a signature against an implementation, you will
--- see the instances WHETHER OR NOT the instance is declared in
--- the file (this is because the signatures go in the EPS and we
--- can't filter them out easily.) This is also why we cannot
--- place the instance in the hi file: it would show up as a duplicate,
--- and we don't have instance reexports anyway.
---
--- However, you might find them useful when typechecking against
--- a signature: the instance is a way of indicating to GHC that
--- some instance exists, in case downstream code uses it.
---
--- Implementing this is a little tricky. Consider the following
--- situation (sigof03):
---
--- module A where
--- instance C T where ...
---
--- module ASig where
--- instance C T
---
--- When compiling ASig, A.hi is loaded, which brings its instances
--- into the EPS. When we process the instance declaration in ASig,
--- we should ignore it for the purpose of doing a duplicate check,
--- since it's not actually a duplicate. But don't skip the check
--- entirely, we still want this to fail (tcfail221):
---
--- module ASig where
--- instance C T
--- instance C T
---
--- Note that in some situations, the interface containing the type
--- class instances may not have been loaded yet at all. The usual
--- situation when A imports another module which provides the
--- instances (sigof02m):
---
--- module A(module B) where
--- import B
---
--- See also Note [Signature lazy interface loading]. We can't
--- rely on this, however, since sometimes we'll have spurious
--- type class instances in the EPS, see #9422 (sigof02dm)
+Note that in some situations, the interface containing the type
+class instances may not have been loaded yet at all. The usual
+situation when A imports another module which provides the
+instances (sigof02m):
+ module A(module B) where
+ import B
+
+See also Note [Signature lazy interface loading]. We can't
+rely on this, however, since sometimes we'll have spurious
+type class instances in the EPS, see #9422 (sigof02dm)
+
+%************************************************************************
+%* *
+ Errors and tracing
+%* *
+%************************************************************************
+
+\begin{code}
traceDFuns :: [ClsInst] -> TcRn ()
traceDFuns ispecs
= traceTc "Adding instances:" (vcat (map pp ispecs))
diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index 1ef3ab4..b39739d 100644
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -402,8 +402,8 @@ tcDeriving tycl_decls inst_decls deriv_decls
; return (addTcgDUs gbl_env all_dus, inst_info, rn_binds) }
where
ddump_deriving :: Bag (InstInfo Name) -> HsValBinds Name
- -> Bag TyCon -- ^ Empty data constructors
- -> Bag (FamInst) -- ^ Rep type family instances
+ -> Bag TyCon -- ^ Empty data constructors
+ -> Bag FamInst -- ^ Rep type family instances
-> SDoc
ddump_deriving inst_infos extra_binds repMetaTys repFamInsts
= hang (ptext (sLit "Derived instances:"))
@@ -2041,7 +2041,7 @@ genDerivStuff loc clas dfun_name tycon comaux_maybe
Just metaTyCons = comaux_maybe -- well-guarded by commonAuxiliaries and genInst
in do
(binds, faminst) <- gen_Generic_binds gk tycon metaTyCons (nameModule dfun_name)
- return (binds, DerivFamInst faminst `consBag` emptyBag)
+ return (binds, unitBag (DerivFamInst faminst))
| otherwise -- Non-monadic generators
= do dflags <- getDynFlags
diff --git a/compiler/typecheck/TcGenDeriv.lhs b/compiler/typecheck/TcGenDeriv.lhs
index e416aaf..31e31ed 100644
--- a/compiler/typecheck/TcGenDeriv.lhs
+++ b/compiler/typecheck/TcGenDeriv.lhs
@@ -85,7 +85,7 @@ data DerivStuff -- Please add this auxiliary stuff
-- Generics
| DerivTyCon TyCon -- New data types
- | DerivFamInst (FamInst) -- New type family instances
+ | DerivFamInst FamInst -- New type family instances
-- New top-level auxiliary bindings
| DerivHsBind (LHsBind RdrName, LSig RdrName) -- Also used for SYB
diff --git a/compiler/types/InstEnv.lhs b/compiler/types/InstEnv.lhs
index 1e7e023..6d03fbe 100644
--- a/compiler/types/InstEnv.lhs
+++ b/compiler/types/InstEnv.lhs
@@ -161,8 +161,8 @@ pprInstance :: ClsInst -> SDoc
-- Prints the ClsInst as an instance declaration
pprInstance ispec
= hang (pprInstanceHdr ispec)
- 2 (vcat [ ptext (sLit "--") <+> pprDefinedAt (getName ispec)
- , ifPprDebug (ppr (is_dfun ispec)) ])
+ 2 (vcat [ ptext (sLit "--") <+> pprDefinedAt (getName ispec)
+ , ifPprDebug (ppr (is_dfun ispec)) ])
-- * pprInstanceHdr is used in VStudio to populate the ClassView tree
pprInstanceHdr :: ClsInst -> SDoc
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