data Env gbl lcl -- Changes as we move into an expression
= Env {
env_top :: HscEnv, -- Top-level stuff that never changes
- -- Includes all info about imported things
+ -- Includes all info about imported things
env_us :: TcRef UniqSupply, -- Unique supply for local varibles
env_gbl :: gbl, -- Info about things defined at the top level
- -- of the module being compiled
+ -- of the module being compiled
- env_lcl :: lcl -- Nested stuff -- changes as we go into
+ env_lcl :: lcl -- Nested stuff; changes as we go into
-- an expression
}
tcg_inst_env :: InstEnv, -- Instance envt for *home-package* modules
-- Includes the dfuns in tcg_insts
- tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
- -- Used to generate version dependencies
- -- This records usages, rather like tcg_dus, but it has to
- -- be a mutable variable so it can be augmented
- -- when we look up an instance. These uses of dfuns are
- -- rather like the free variables of the program, but
- -- are implicit instead of explicit.
-
- tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
- -- We need this so that we can generate a dependency on the
- -- Template Haskell package, becuase the desugarer is going to
- -- emit loads of references to TH symbols. It's rather like
- -- tcg_inst_uses; the reference is implicit rather than explicit,
- -- so we have to zap a mutable variable.
-
-- Now a bunch of things about this module that are simply
-- accumulated, but never consulted until the end.
-- Nevertheless, it's convenient to accumulate them along
-- things have not changed version stamp
-- (b) unused-import info
- tcg_keep :: NameSet, -- Set of names to keep alive, and to expose in the
- -- interface file (but not to export to the user).
- -- These are typically extra definitions generated from
- -- data type declarations which would otherwise be
- -- dropped as dead code.
+ tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
+ -- "Keep alive" means give them an Exported flag, so
+ -- that the simplifier does not discard them as dead
+ -- code, and so that they are exposed in the interface file
+ -- (but not to export to the user).
+ --
+ -- Some things, like dict-fun Ids and default-method Ids are
+ -- "born" with the Exported flag on, for exactly the above reason,
+ -- but some we only discover as we go. Specifically:
+ -- * The to/from functions for generic data types
+ -- * Top-level variables appearing free in the RHS of an orphan rule
+ -- * Top-level variables appearing free in a TH bracket
+
+ tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
+ -- Used to generate version dependencies
+ -- This records usages, rather like tcg_dus, but it has to
+ -- be a mutable variable so it can be augmented
+ -- when we look up an instance. These uses of dfuns are
+ -- rather like the free variables of the program, but
+ -- are implicit instead of explicit.
+
+ tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
+ -- We need this so that we can generate a dependency on the
+ -- Template Haskell package, becuase the desugarer is going to
+ -- emit loads of references to TH symbols. It's rather like
+ -- tcg_inst_uses; the reference is implicit rather than explicit,
+ -- so we have to zap a mutable variable.
-- The next fields accumulate the payload of the module
-- The binds, rules and foreign-decl fiels are collected
tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
-- defined in this module
- tcl_gadt :: GadtRefinement, -- The current type refinement for GADTs
-
tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
- -- Namely, the in-scope TyVars bound in tcl_lenv,
+ -- Namely, the in-scope TyVars bound in tcl_env,
-- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
-- Why mutable? see notes with tcGetGlobalTyVars
- tcl_lie :: TcRef LIE -- Place to accumulate type constraints
+ tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
+ tcl_gadt :: GadtRefinement -- The current type refinement for GADTs
+
+-----------------------------------------------------------
+-- Not yet; it's a new complication and I want to see whether it bites
+-- tcl_given :: [Inst] -- Insts available in the current context (see Note [Given Insts])
+-----------------------------------------------------------
}
type GadtRefinement = TvSubstEnv -- Binds rigid type variables to their refinements
+{- Note [Given Insts]
+ ~~~~~~~~~~~~~~~~~~
+Because of GADTs, we have to pass inwards the Insts provided by type signatures
+and existential contexts. Consider
+ data T a where { T1 :: b -> b -> T [b] }
+ f :: Eq a => T a -> Bool
+ f (T1 x y) = [x]==[y]
+
+The constructor T1 binds an existential variable 'b', and we need Eq [b].
+Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
+pass it inwards.
+
+-}
---------------------------
-- Template Haskell levels
---------------------------
-type ThLevel = Int -- Always >= 0
+type ThLevel = Int
+ -- Indicates how many levels of brackets we are inside
+ -- (always >= 0)
+ -- Incremented when going inside a bracket,
+ -- decremented when going inside a splice
+
+impLevel, topLevel :: ThLevel
+topLevel = 1 -- Things defined at top level of this module
+impLevel = 0 -- Imported things; they can be used inside a top level splice
+--
+-- For example:
+-- f = ...
+-- g1 = $(map ...) is OK
+-- g2 = $(f ...) is not OK; because we havn't compiled f yet
+
data ThStage
= Comp -- Ordinary compiling, at level topLevel
topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
-impLevel, topLevel :: ThLevel
-topLevel = 1 -- Things defined at top level of this module
-impLevel = 0 -- Imported things; they can be used inside a top level splice
---
--- For example:
--- f = ...
--- g1 = $(map ...) is OK
--- g2 = $(f ...) is not OK; because we havn't compiled f yet
-
-
---------------------------
-- Arrow-notation stages
---------------------------
\begin{code}
data Inst
= Dict
- Id
+ Name
TcPredType
InstLoc
-- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
| LitInst
- Id
+ Name
HsOverLit -- The literal from the occurrence site
-- INVARIANT: never a rebindable-syntax literal
-- Reason: tcSyntaxName does unification, and we
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