Commit 1b471823 authored by simonpj's avatar simonpj
Browse files

[project @ 2000-12-20 11:02:17 by simonpj]

Add comments and tidy
parent 1ecd776e
......@@ -241,11 +241,8 @@ data Sig name
| ClassOpSig name -- Selector name
(DefMeth name) -- (Just dm_name) for source-file class signatures
-- The name may not be used, if there isn't a
-- generic default method, but it's there if we
-- need it
-- Gives DefMeth info for interface files sigs
(DefMeth name) -- Default-method info
-- See "THE NAMING STORY" in HsDecls
(HsType name)
......@@ -116,10 +116,15 @@ instance (NamedThing name, Outputable name, Outputable pat)
%* *
Type and class declarations carry 'implicit names'. In particular:
Type A.
Here is the story about the implicit names that go with type, class, and instance
decls. It's a bit tricky, so pay attention!
"Implicit" (or "system") binders
Each data type decl defines
a worker name for each constructor
to-T and from-T convertors
......@@ -138,25 +143,108 @@ relevant type or class decl.
Plan of attack:
- Make up their occurrence names immediately
This is done in RdrHsSyn.mkClassDecl, mkTyDecl, mkConDecl
- Ensure they "point to" the parent data/class decl
when loading that decl from an interface file
(See RnHiFiles.getTyClDeclSysNames)
- When renaming the decl look them up in the name cache,
ensure correct module and provenance is set
Type B: Default methods and dictionary functions
Have their own binding in an interface file.
Default methods : occurrence name is derived uniquely from the class decl.
Dict functions : occurrence name is derived from the instance decl, plus a unique number.
Default methods
- Occurrence name is derived uniquely from the method name
E.g. $dmmax
- If there is a default method name at all, it's recorded in
the ClassOpSig (in HsBinds), in the DefMeth field.
(DefMeth is defined in Class.lhs)
Source-code class decls and interface-code class decls are treated subtly
differently, which has given me a great deal of confusion over the years.
Here's the deal. (We distinguish the two cases because source-code decls
have (Just binds) in the tcdMeths field, whereas interface decls have Nothing.
In *source-code* class declarations:
- When parsing, every ClassOpSig gets a DefMeth with a suitable RdrName
This is done by RdrHsSyn.mkClassOpSigDM
- The renamer renames it to a Name
- During typechecking, we generate a binding for each $dm for
which there's a programmer-supplied default method:
class Foo a where
op1 :: <type>
op2 :: <type>
op1 = ...
We generate a binding for $dmop1 but not for $dmop2.
The Class for Foo has a NoDefMeth for op2 and a DefMeth for op1.
The Name for $dmop2 is simply discarded.
In *interface-file* class declarations:
- When parsing, we see if there's an explicit programmer-supplied default method
because there's an '=' sign to indicate it:
class Foo a where
op1 = :: <type> -- NB the '='
op2 :: <type>
We use this info to generate a DefMeth with a suitable RdrName for op1,
and a NoDefMeth for op2
- The interface file has a separate definition for $dmop1, with unfolding etc.
- The renamer renames it to a Name.
- The renamer treats $dmop1 as a free variable of the declaration, so that
the binding for $dmop1 will be sucked in. (See RnHsSyn.tyClDeclFVs)
This doesn't happen for source code class decls, because they *bind* the default method.
Dictionary functions
Each instance declaration gives rise to one dictionary function binding.
The type checker makes up new source-code instance declarations
(e.g. from 'deriving' or generic default methods --- see
TcInstDcls.tcInstDecls1). So we can't generate the names for
dictionary functions in advance (we don't know how many we need).
On the other hand for interface-file instance declarations, the decl
specifies the name of the dictionary function, and it has a binding elsewhere
in the interface file:
instance {Eq Int} = dEqInt
dEqInt :: {Eq Int} <pragma info>
So again we treat source code and interface file code slightly differently.
Source code:
- Source code instance decls have a Nothing in the (Maybe name) field
(see data InstDecl below)
- The typechecker makes up a Local name for the dict fun for any source-code
instance decl, whether it comes from a source-code instance decl, or whether
the instance decl is derived from some other construct (e.g. 'deriving').
- The occurrence name it chooses is derived from the instance decl (just for
documentation really) --- e.g. dNumInt. Two dict funs may share a common
occurrence name, but will have different uniques. E.g.
instance Foo [Int] where ...
instance Foo [Bool] where ...
These might both be dFooList
- The CoreTidy phase globalises the name, and ensures the occurrence name is
unique (this isn't special to dict funs). So we'd get dFooList and dFooList1.
- We can take this relaxed approach (changing the occurrence name later)
because dict fun Ids are not captured in a TyCon or Class (unlike default
methods, say). Instead, they are kept separately in the InstEnv. This
makes it easy to adjust them after compiling a module. (Once we've finished
compiling that module, they don't change any more.)
Interface file code:
- The instance decl gives the dict fun name, so the InstDecl has a (Just name)
in the (Maybe name) field.
- RnHsSyn.instDeclFVs treats the dict fun name as free in the decl, so that we
suck in the dfun binding
Plan of attack:
- Do *not* make them point to the parent class decl
- Interface-file decls: treat just like Type A
- Source-file decls: the names aren't in the decl at all;
instead the typechecker makes them up
data TyClDecl name pat
......@@ -208,6 +208,8 @@ name of the class itself. This saves recording the names in the interface
file (which would be equally good).
Similarly for mkConDecl, mkClassOpSig and default-method names.
*** See "THE NAMING STORY" in HsDecls ****
mkClassDecl cxt cname tyvars fds sigs mbinds loc
......@@ -432,6 +432,9 @@ It's used for both source code (from @availsFromDecl@) and interface files
It doesn't deal with source-code specific things: @ValD@, @DefD@. They
are handled by the sourc-code specific stuff in @RnNames@.
*** See "THE NAMING STORY" in HsDecls ****
:: Module
......@@ -117,6 +117,8 @@ In all cases this is set up for interface-file declarations:
- for instance decls likewise, plus the pragmas
- for rule decls, we ignore HsRules
*** See "THE NAMING STORY" in HsDecls ****
tyClDeclFVs :: RenamedTyClDecl -> NameSet
tyClDeclFVs (IfaceSig {tcdType = ty, tcdIdInfo = id_infos})
......@@ -48,6 +48,7 @@ import SrcLoc ( SrcLoc )
import CmdLineOpts ( DynFlag(..) )
-- Warn of unused for-all'd tyvars
import Unique ( Uniquable(..) )
import Maybes ( maybeToBool )
import ErrUtils ( Message )
import CStrings ( isCLabelString )
import ListSetOps ( removeDupsEq )
......@@ -71,7 +72,7 @@ Checks the @(..)@ etc constraints in the export list.
%* *
\subsection{Value declarations}
\subsection{Source code declarations}
%* *
......@@ -90,17 +91,8 @@ rnSourceDecls gbl_env local_fixity_env decls
go fvs ds' (DeprecD _:ds) = go fvs ds' ds
go fvs ds' (d:ds) = rnSourceDecl d `thenRn` \(d', fvs') ->
go (fvs `plusFV` fvs') (d':ds') ds
%* *
\subsection{Value declarations}
%* *
-- rnSourceDecl does all the work
rnSourceDecl :: RdrNameHsDecl -> RnMS (RenamedHsDecl, FreeVars)
rnSourceDecl (ValD binds) = rnTopBinds binds `thenRn` \ (new_binds, fvs) ->
......@@ -164,6 +156,7 @@ rnSourceDecl (ForD (ForeignDecl name imp_exp ty ext_nm cconv src_loc))
rnInstDecl (InstDecl inst_ty mbinds uprags maybe_dfun_rdr_name src_loc)
-- Used for both source and interface file decls
= pushSrcLocRn src_loc $
rnHsSigType (text "an instance decl") inst_ty `thenRn` \ inst_ty' ->
......@@ -177,9 +170,11 @@ rnInstDecl (InstDecl inst_ty mbinds uprags maybe_dfun_rdr_name src_loc)
returnRn (InstDecl inst_ty' EmptyMonoBinds [] maybe_dfun_name src_loc)
-- Compare rnClassBinds
rnInstBinds (InstDecl _ mbinds uprags _ _ )
(InstDecl inst_ty _ _ maybe_dfun_rdr_name src_loc)
= let
rnInstBinds (InstDecl _ mbinds uprags _ _ )
(InstDecl inst_ty _ _ maybe_dfun_name src_loc)
-- Used for both source decls only
= ASSERT( not (maybeToBool maybe_dfun_name) ) -- Source decl!
meth_doc = text "the bindings in an instance declaration"
meth_names = collectLocatedMonoBinders mbinds
inst_tyvars = case inst_ty of
......@@ -210,7 +205,7 @@ rnInstBinds (InstDecl _ mbinds uprags _ _ )
renameSigsFVs (okInstDclSig binder_set) uprags
) `thenRn` \ (uprags', prag_fvs) ->
returnRn (InstDecl inst_ty mbinds' uprags' maybe_dfun_rdr_name src_loc,
returnRn (InstDecl inst_ty mbinds' uprags' maybe_dfun_name src_loc,
meth_fvs `plusFV` prag_fvs)
......@@ -326,6 +321,7 @@ rnTyClDecl (TySynonym {tcdName = name, tcdTyVars = tyvars, tcdSynRhs = ty, tcdLo
rnTyClDecl (ClassDecl {tcdCtxt = context, tcdName = cname,
tcdTyVars = tyvars, tcdFDs = fds, tcdSigs = sigs,
tcdSysNames = names, tcdLoc = src_loc})
-- Used for both source and interface file decls
= pushSrcLocRn src_loc $
lookupTopBndrRn cname `thenRn` \ cname' ->
......@@ -395,6 +391,7 @@ rnClassOp clas clas_tyvars clas_fds sig@(ClassOpSig op dm_stuff ty locn)
returnRn (ClassOpSig op_name dm_stuff' new_ty locn)
rnClassBinds :: RdrNameTyClDecl -> RenamedTyClDecl -> RnMS (RenamedTyClDecl, FreeVars)
-- Used for source file decls only
rnClassBinds (ClassDecl {tcdMeths = Just mbinds}) -- Get mbinds from here
rn_cls_decl@(ClassDecl {tcdTyVars = tyvars, tcdLoc = src_loc}) -- Everything else is here
-- There are some default-method bindings (abeit possibly empty) so
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