X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FbasicTypes%2FId.lhs;h=070526e2f75916d8c926644c98f9398f19f0cd2f;hb=08652e67c4d5d9a40687f93c286021a867c1bca0;hp=9145badbaf3b4331068086c26c322cafbd7f8844;hpb=27061b5b4008a831eba4784358b040bb1250dcef;p=ghc-hetmet.git

diff --git a/compiler/basicTypes/Id.lhs b/compiler/basicTypes/Id.lhs
index 9145bad..070526e 100644
--- a/compiler/basicTypes/Id.lhs
+++ b/compiler/basicTypes/Id.lhs
@@ -136,12 +136,24 @@ Absolutely all Ids are made by mkId.  It is just like Var.mkId,
 but in addition it pins free-tyvar-info onto the Id's type, 
 where it can easily be found.
 
+Note [Free type variables]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+At one time we cached the free type variables of the type of an Id
+at the root of the type in a TyNote.  The idea was to avoid repeating
+the free-type-variable calculation.  But it turned out to slow down
+the compiler overall. I don't quite know why; perhaps finding free
+type variables of an Id isn't all that common whereas applying a 
+substitution (which changes the free type variables) is more common.
+Anyway, we removed it in March 2008.
+
 \begin{code}
 mkLocalIdWithInfo :: Name -> Type -> IdInfo -> Id
 mkLocalIdWithInfo name ty info = Var.mkLocalId name ty info
+	-- Note [Free type variables]
 
 mkExportedLocalId :: Name -> Type -> Id
 mkExportedLocalId name ty = Var.mkExportedLocalId name ty vanillaIdInfo
+	-- Note [Free type variables]
 
 mkGlobalId :: GlobalIdDetails -> Name -> Type -> IdInfo -> Id
 mkGlobalId details name ty info = Var.mkGlobalId details name ty info
@@ -171,7 +183,7 @@ instantiated before use.
 \begin{code}
 -- "Wild Id" typically used when you need a binder that you don't expect to use
 mkWildId :: Type -> Id
-mkWildId ty = mkSysLocal FSLIT("wild") (mkBuiltinUnique 1) ty
+mkWildId ty = mkSysLocal (fsLit "wild") (mkBuiltinUnique 1) ty
 
 mkWorkerId :: Unique -> Id -> Type -> Id
 -- A worker gets a local name.  CoreTidy will externalise it if necessary.
@@ -189,7 +201,7 @@ mkTemplateLocalsNum :: Int -> [Type] -> [Id]
 mkTemplateLocalsNum n tys = zipWith mkTemplateLocal [n..] tys
 
 mkTemplateLocal :: Int -> Type -> Id
-mkTemplateLocal i ty = mkSysLocal FSLIT("tpl") (mkBuiltinUnique i) ty
+mkTemplateLocal i ty = mkSysLocal (fsLit "tpl") (mkBuiltinUnique i) ty
 \end{code}