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
-- 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
---------------------------
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