Commit b0ca9904 authored by Ian Lynagh's avatar Ian Lynagh
Browse files

Fix whitespace in TcTyDecls

parent 8604da01
......@@ -17,8 +17,8 @@ files for imported data types.
-- for details
module TcTyDecls(
calcRecFlags,
calcClassCycles, calcSynCycles
calcRecFlags,
calcClassCycles, calcSynCycles
) where
#include "HsVersions.h"
......@@ -42,47 +42,47 @@ import Outputable
%************************************************************************
%* *
Cycles in class and type synonym declarations
%* *
%* *
Cycles in class and type synonym declarations
%* *
%************************************************************************
Checking for class-decl loops is easy, because we don't allow class decls
in interface files.
We allow type synonyms in hi-boot files, but we *trust* hi-boot files,
We allow type synonyms in hi-boot files, but we *trust* hi-boot files,
so we don't check for loops that involve them. So we only look for synonym
loops in the module being compiled.
We check for type synonym and class cycles on the *source* code.
Main reasons:
Main reasons:
a) Otherwise we'd need a special function to extract type-synonym tycons
from a type, whereas we have extractHsTyNames already
from a type, whereas we have extractHsTyNames already
b) If we checked for type synonym loops after building the TyCon, we
can't do a hoistForAllTys on the type synonym rhs, (else we fall into
a black hole) which seems unclean. Apart from anything else, it'd mean
that a type-synonym rhs could have for-alls to the right of an arrow,
which means adding new cases to the validity checker
can't do a hoistForAllTys on the type synonym rhs, (else we fall into
a black hole) which seems unclean. Apart from anything else, it'd mean
that a type-synonym rhs could have for-alls to the right of an arrow,
which means adding new cases to the validity checker
Indeed, in general, checking for cycles beforehand means we need to
be less careful about black holes through synonym cycles.
Indeed, in general, checking for cycles beforehand means we need to
be less careful about black holes through synonym cycles.
The main disadvantage is that a cycle that goes via a type synonym in an
The main disadvantage is that a cycle that goes via a type synonym in an
.hi-boot file can lead the compiler into a loop, because it assumes that cycles
only occur entirely within the source code of the module being compiled.
But hi-boot files are trusted anyway, so this isn't much worse than (say)
only occur entirely within the source code of the module being compiled.
But hi-boot files are trusted anyway, so this isn't much worse than (say)
a kind error.
[ NOTE ----------------------------------------------
If we reverse this decision, this comment came from tcTyDecl1, and should
go back there
-- dsHsType, not tcHsKindedType, to avoid a loop. tcHsKindedType does hoisting,
-- which requires looking through synonyms... and therefore goes into a loop
-- on (erroneously) recursive synonyms.
-- Solution: do not hoist synonyms, because they'll be hoisted soon enough
-- when they are substituted
-- dsHsType, not tcHsKindedType, to avoid a loop. tcHsKindedType does hoisting,
-- which requires looking through synonyms... and therefore goes into a loop
-- on (erroneously) recursive synonyms.
-- Solution: do not hoist synonyms, because they'll be hoisted soon enough
-- when they are substituted
We'd also need to add back in this definition
......@@ -93,16 +93,16 @@ synTyConsOfType ty
= nameEnvElts (go ty)
where
go :: Type -> NameEnv TyCon -- The NameEnv does duplicate elim
go (TyVarTy v) = emptyNameEnv
go (TyConApp tc tys) = go_tc tc tys
go (AppTy a b) = go a `plusNameEnv` go b
go (FunTy a b) = go a `plusNameEnv` go b
go (PredTy (IParam _ ty)) = go ty
go (PredTy (ClassP cls tys)) = go_s tys -- Ignore class
go (ForAllTy _ ty) = go ty
go (TyVarTy v) = emptyNameEnv
go (TyConApp tc tys) = go_tc tc tys
go (AppTy a b) = go a `plusNameEnv` go b
go (FunTy a b) = go a `plusNameEnv` go b
go (PredTy (IParam _ ty)) = go ty
go (PredTy (ClassP cls tys)) = go_s tys -- Ignore class
go (ForAllTy _ ty) = go ty
go_tc tc tys | isSynTyCon tc = extendNameEnv (go_s tys) (tyConName tc) tc
| otherwise = go_s tys
| otherwise = go_s tys
go_s tys = foldr (plusNameEnv . go) emptyNameEnv tys
---------------------------------------- END NOTE ]
......@@ -111,30 +111,30 @@ calcSynCycles :: [LTyClDecl Name] -> [SCC (LTyClDecl Name)]
calcSynCycles decls
= stronglyConnComp syn_edges
where
syn_edges = [ (ldecl, unLoc (tcdLName decl),
mk_syn_edges (tcdSynRhs decl))
| ldecl@(L _ decl) <- decls ]
syn_edges = [ (ldecl, unLoc (tcdLName decl),
mk_syn_edges (tcdSynRhs decl))
| ldecl@(L _ decl) <- decls ]
mk_syn_edges rhs = [ tc | tc <- nameSetToList (extractHsTyNames rhs),
not (isTyVarName tc) ]
mk_syn_edges rhs = [ tc | tc <- nameSetToList (extractHsTyNames rhs),
not (isTyVarName tc) ]
calcClassCycles :: [LTyClDecl Name] -> [[LTyClDecl Name]]
calcClassCycles decls
= [decls | CyclicSCC decls <- stronglyConnComp cls_edges]
where
cls_edges = [ (ldecl, unLoc (tcdLName decl),
mk_cls_edges (unLoc (tcdCtxt decl)))
| ldecl@(L _ decl) <- decls, isClassDecl decl ]
cls_edges = [ (ldecl, unLoc (tcdLName decl),
mk_cls_edges (unLoc (tcdCtxt decl)))
| ldecl@(L _ decl) <- decls, isClassDecl decl ]
mk_cls_edges ctxt = [ cls | L _ (HsClassP cls _) <- ctxt ]
\end{code}
%************************************************************************
%* *
Deciding which type constructors are recursive
%* *
%* *
Deciding which type constructors are recursive
%* *
%************************************************************************
For newtypes, we label some as "recursive" such that
......@@ -146,17 +146,17 @@ a "loop breaker". Labelling more than necessary as recursive is OK,
provided the invariant is maintained.
A newtype M.T is defined to be "recursive" iff
(a) it is declared in an hi-boot file (see RdrHsSyn.hsIfaceDecl)
(b) it is declared in a source file, but that source file has a
companion hi-boot file which declares the type
or (c) one can get from T's rhs to T via type
synonyms, or non-recursive newtypes *in M*
e.g. newtype T = MkT (T -> Int)
(a) is conservative; declarations in hi-boot files are always
made loop breakers. That's why in (b) we can restrict attention
to tycons in M, because any loops through newtypes outside M
will be broken by those newtypes
(a) it is declared in an hi-boot file (see RdrHsSyn.hsIfaceDecl)
(b) it is declared in a source file, but that source file has a
companion hi-boot file which declares the type
or (c) one can get from T's rhs to T via type
synonyms, or non-recursive newtypes *in M*
e.g. newtype T = MkT (T -> Int)
(a) is conservative; declarations in hi-boot files are always
made loop breakers. That's why in (b) we can restrict attention
to tycons in M, because any loops through newtypes outside M
will be broken by those newtypes
(b) ensures that a newtype is not treated as a loop breaker in one place
and later as a non-loop-breaker. This matters in GHCi particularly, when
a newtype T might be embedded in many types in the environment, and then
......@@ -166,13 +166,13 @@ The "recursive" flag for algebraic data types is irrelevant (never consulted)
for types with more than one constructor.
An algebraic data type M.T is "recursive" iff
it has just one constructor, and
(a) it is declared in an hi-boot file (see RdrHsSyn.hsIfaceDecl)
(b) it is declared in a source file, but that source file has a
companion hi-boot file which declares the type
or (c) one can get from its arg types to T via type synonyms,
or by non-recursive newtypes or non-recursive product types in M
e.g. data T = MkT (T -> Int) Bool
it has just one constructor, and
(a) it is declared in an hi-boot file (see RdrHsSyn.hsIfaceDecl)
(b) it is declared in a source file, but that source file has a
companion hi-boot file which declares the type
or (c) one can get from its arg types to T via type synonyms,
or by non-recursive newtypes or non-recursive product types in M
e.g. data T = MkT (T -> Int) Bool
Just like newtype in fact
A type synonym is recursive if one can get from its
......@@ -188,21 +188,21 @@ A data type read from an hi-boot file will have an AbstractTyCon as its AlgTyCon
and will respond True to isHiBootTyCon. The idea is that we treat these as if one
could get from these types to anywhere. So when we see
module Baz where
import {-# SOURCE #-} Foo( T )
newtype S = MkS T
module Baz where
import {-# SOURCE #-} Foo( T )
newtype S = MkS T
then we mark S as recursive, just in case. What that means is that if we see
import Baz( S )
newtype R = MkR S
import Baz( S )
newtype R = MkR S
then we don't need to look inside S to compute R's recursiveness. Since S is imported
(not from an hi-boot file), one cannot get from R back to S except via an hi-boot file,
and that means that some data type will be marked recursive along the way. So R is
unconditionly non-recursive (i.e. there'll be a loop breaker elsewhere if necessary)
This in turn means that we grovel through fewer interface files when computing
This in turn means that we grovel through fewer interface files when computing
recursiveness, because we need only look at the type decls in the module being
compiled, plus the outer structure of directly-mentioned types.
......@@ -214,73 +214,73 @@ calcRecFlags boot_details tyclss
= is_rec
where
is_rec n | n `elemNameSet` rec_names = Recursive
| otherwise = NonRecursive
| otherwise = NonRecursive
boot_name_set = availsToNameSet (md_exports boot_details)
rec_names = boot_name_set `unionNameSets`
nt_loop_breakers `unionNameSets`
prod_loop_breakers
rec_names = boot_name_set `unionNameSets`
nt_loop_breakers `unionNameSets`
prod_loop_breakers
all_tycons = [ tc | tycls <- tyclss,
-- Recursion of newtypes/data types can happen via
-- the class TyCon, so tyclss includes the class tycons
let tc = getTyCon tycls,
not (tyConName tc `elemNameSet` boot_name_set) ]
-- Remove the boot_name_set because they are going
-- to be loop breakers regardless.
-------------------------------------------------
-- NOTE
-- These edge-construction loops rely on
-- every loop going via tyclss, the types and classes
-- in the module being compiled. Stuff in interface
-- files should be correctly marked. If not (e.g. a
-- type synonym in a hi-boot file) we can get an infinite
-- loop. We could program round this, but it'd make the code
-- rather less nice, so I'm not going to do that yet.
--------------- Newtypes ----------------------
-- Recursion of newtypes/data types can happen via
-- the class TyCon, so tyclss includes the class tycons
let tc = getTyCon tycls,
not (tyConName tc `elemNameSet` boot_name_set) ]
-- Remove the boot_name_set because they are going
-- to be loop breakers regardless.
-------------------------------------------------
-- NOTE
-- These edge-construction loops rely on
-- every loop going via tyclss, the types and classes
-- in the module being compiled. Stuff in interface
-- files should be correctly marked. If not (e.g. a
-- type synonym in a hi-boot file) we can get an infinite
-- loop. We could program round this, but it'd make the code
-- rather less nice, so I'm not going to do that yet.
--------------- Newtypes ----------------------
new_tycons = filter isNewTyConAndNotOpen all_tycons
isNewTyConAndNotOpen tycon = isNewTyCon tycon && not (isOpenTyCon tycon)
nt_loop_breakers = mkNameSet (findLoopBreakers nt_edges)
is_rec_nt tc = tyConName tc `elemNameSet` nt_loop_breakers
-- is_rec_nt is a locally-used helper function
-- is_rec_nt is a locally-used helper function
nt_edges = [(t, mk_nt_edges t) | t <- new_tycons]
mk_nt_edges nt -- Invariant: nt is a newtype
= concatMap (mk_nt_edges1 nt) (tcTyConsOfType (new_tc_rhs nt))
-- tyConsOfType looks through synonyms
mk_nt_edges nt -- Invariant: nt is a newtype
= concatMap (mk_nt_edges1 nt) (tcTyConsOfType (new_tc_rhs nt))
-- tyConsOfType looks through synonyms
mk_nt_edges1 nt tc
| tc `elem` new_tycons = [tc] -- Loop
-- At this point we know that either it's a local *data* type,
-- or it's imported. Either way, it can't form part of a newtype cycle
| otherwise = []
mk_nt_edges1 nt tc
| tc `elem` new_tycons = [tc] -- Loop
-- At this point we know that either it's a local *data* type,
-- or it's imported. Either way, it can't form part of a newtype cycle
| otherwise = []
--------------- Product types ----------------------
-- The "prod_tycons" are the non-newtype products
prod_tycons = [tc | tc <- all_tycons,
not (isNewTyCon tc), isProductTyCon tc]
--------------- Product types ----------------------
-- The "prod_tycons" are the non-newtype products
prod_tycons = [tc | tc <- all_tycons,
not (isNewTyCon tc), isProductTyCon tc]
prod_loop_breakers = mkNameSet (findLoopBreakers prod_edges)
prod_edges = [(tc, mk_prod_edges tc) | tc <- prod_tycons]
mk_prod_edges tc -- Invariant: tc is a product tycon
= concatMap (mk_prod_edges1 tc) (dataConOrigArgTys (head (tyConDataCons tc)))
mk_prod_edges tc -- Invariant: tc is a product tycon
= concatMap (mk_prod_edges1 tc) (dataConOrigArgTys (head (tyConDataCons tc)))
mk_prod_edges1 ptc ty = concatMap (mk_prod_edges2 ptc) (tcTyConsOfType ty)
mk_prod_edges2 ptc tc
| tc `elem` prod_tycons = [tc] -- Local product
| tc `elem` new_tycons = if is_rec_nt tc -- Local newtype
then []
else mk_prod_edges1 ptc (new_tc_rhs tc)
-- At this point we know that either it's a local non-product data type,
-- or it's imported. Either way, it can't form part of a cycle
| otherwise = []
new_tc_rhs tc = snd (newTyConRhs tc) -- Ignore the type variables
mk_prod_edges2 ptc tc
| tc `elem` prod_tycons = [tc] -- Local product
| tc `elem` new_tycons = if is_rec_nt tc -- Local newtype
then []
else mk_prod_edges1 ptc (new_tc_rhs tc)
-- At this point we know that either it's a local non-product data type,
-- or it's imported. Either way, it can't form part of a cycle
| otherwise = []
new_tc_rhs tc = snd (newTyConRhs tc) -- Ignore the type variables
getTyCon (ATyCon tc) = tc
getTyCon (AClass cl) = classTyCon cl
......@@ -292,32 +292,32 @@ findLoopBreakers deps
= go [(tc,tc,ds) | (tc,ds) <- deps]
where
go edges = [ name
| CyclicSCC ((tc,_,_) : edges') <- stronglyConnCompR edges,
name <- tyConName tc : go edges']
| CyclicSCC ((tc,_,_) : edges') <- stronglyConnCompR edges,
name <- tyConName tc : go edges']
\end{code}
These two functions know about type representations, so they could be
in Type or TcType -- but they are very specialised to this module, so
in Type or TcType -- but they are very specialised to this module, so
I've chosen to put them here.
\begin{code}
tcTyConsOfType :: Type -> [TyCon]
-- tcTyConsOfType looks through all synonyms, but not through any newtypes.
-- tcTyConsOfType looks through all synonyms, but not through any newtypes.
-- When it finds a Class, it returns the class TyCon. The reaons it's here
-- (not in Type.lhs) is because it is newtype-aware.
tcTyConsOfType ty
tcTyConsOfType ty
= nameEnvElts (go ty)
where
go :: Type -> NameEnv TyCon -- The NameEnv does duplicate elim
go ty | Just ty' <- tcView ty = go ty'
go (TyVarTy v) = emptyNameEnv
go (TyConApp tc tys) = go_tc tc tys
go (AppTy a b) = go a `plusNameEnv` go b
go (FunTy a b) = go a `plusNameEnv` go b
go (TyVarTy v) = emptyNameEnv
go (TyConApp tc tys) = go_tc tc tys
go (AppTy a b) = go a `plusNameEnv` go b
go (FunTy a b) = go a `plusNameEnv` go b
go (PredTy (IParam _ ty)) = go ty
go (PredTy (ClassP cls tys)) = go_tc (classTyCon cls) tys
go (ForAllTy _ ty) = go ty
go other = panic "tcTyConsOfType"
go (ForAllTy _ ty) = go ty
go other = panic "tcTyConsOfType"
go_tc tc tys = extendNameEnv (go_s tys) (tyConName tc) tc
go_s tys = foldr (plusNameEnv . go) emptyNameEnv tys
......
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment