{-# LANGUAGE CPP #-}{-# LANGUAGE RankNTypes #-}-- | The Name CachemoduleNameCache(lookupOrigNameCache ,extendOrigNameCache ,extendNameCache ,initNameCache ,NameCache (..),OrigNameCache )whereimportGhcPrelude importModule importName importUniqSupply importTysWiredIn importUtil importOutputable importPrelNames #include "HsVersions.h"
{-
Note [The Name Cache]
~~~~~~~~~~~~~~~~~~~~~
The Name Cache makes sure that, during any invocation of GHC, each
External Name "M.x" has one, and only one globally-agreed Unique.
* The first time we come across M.x we make up a Unique and record that
 association in the Name Cache.
* When we come across "M.x" again, we look it up in the Name Cache,
 and get a hit.
The functions newGlobalBinder, allocateGlobalBinder do the main work.
When you make an External name, you should probably be calling one
of them.
Note [Built-in syntax and the OrigNameCache]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Built-in syntax like tuples and unboxed sums are quite ubiquitous. To lower
their cost we use two tricks,
 a. We specially encode tuple and sum Names in interface files' symbol tables
 to avoid having to look up their names while loading interface files.
 Namely these names are encoded as by their Uniques. We know how to get from
 a Unique back to the Name which it represents via the mapping defined in
 the SumTupleUniques module. See Note [Symbol table representation of names]
 in BinIface and for details.
 b. We don't include them in the Orig name cache but instead parse their
 OccNames (in isBuiltInOcc_maybe) to avoid bloating the name cache with
 them.
Why is the second measure necessary? Good question; afterall, 1) the parser
emits built-in syntax directly as Exact RdrNames, and 2) built-in syntax never
needs to looked-up during interface loading due to (a). It turns out that there
are two reasons why we might look up an Orig RdrName for built-in syntax,
 * If you use setRdrNameSpace on an Exact RdrName it may be
 turned into an Orig RdrName.
 * Template Haskell turns a BuiltInSyntax Name into a TH.NameG
 (DsMeta.globalVar), and parses a NameG into an Orig RdrName
 (Convert.thRdrName). So, e.g. $(do { reify '(,); ... }) will
 go this route (Trac #8954).
-}-- | Per-module cache of original 'OccName's given 'Name'stypeOrigNameCache =ModuleEnv (OccEnv Name )lookupOrigNameCache::OrigNameCache ->Module ->OccName ->MaybeName lookupOrigNameCache nc mod occ |mod ==gHC_TYPES ||mod ==gHC_PRIM ||mod ==gHC_TUPLE ,Justname <-isBuiltInOcc_maybe occ =-- See Note [Known-key names], 3(c) in PrelNames-- Special case for tuples; there are too many-- of them to pre-populate the original-name cacheJustname |otherwise=caselookupModuleEnv nc mod ofNothing->NothingJustocc_env ->lookupOccEnv occ_env occ extendOrigNameCache::OrigNameCache ->Name ->OrigNameCache extendOrigNameCache nc name =ASSERT2(isExternalNamename ,ppr name)extendNameCache nc (nameModule name )(nameOccName name )name extendNameCache::OrigNameCache ->Module ->OccName ->Name ->OrigNameCache extendNameCache nc mod occ name =extendModuleEnvWith combine nc mod (unitOccEnv occ name )wherecombine _occ_env =extendOccEnv occ_env occ name -- | The NameCache makes sure that there is just one Unique assigned for-- each original name; i.e. (module-name, occ-name) pair and provides-- something of a lookup mechanism for those names.dataNameCache =NameCache {nsUniqs ::!UniqSupply ,-- ^ Supply of uniquesnsNames ::!OrigNameCache -- ^ Ensures that one original name gets one unique}-- | Return a function to atomically update the name cache.initNameCache::UniqSupply ->[Name ]->NameCache initNameCache us names =NameCache {nsUniqs=us ,nsNames=initOrigNames names }initOrigNames::[Name ]->OrigNameCache initOrigNames names =foldl'extendOrigNameCache emptyModuleEnv names