[project @ 2000-10-12 11:47:25 by sewardj]

[ghc-hetmet.git] / ghc / compiler / basicTypes / Var.lhs

diff --git a/ghc/compiler/basicTypes/Var.lhs b/ghc/compiler/basicTypes/Var.lhs
index 6315261..72422f8 100644 (file)
--- a/ghc/compiler/basicTypes/Var.lhs
+++ b/ghc/compiler/basicTypes/Var.lhs
@@ -1,4 +1,4 @@
-s%
+%
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
 \section{@Vars@: Variables}
@@ -170,24 +170,23 @@ mkSysTyVar uniq kind = Var { varName    = name
                       name = mkSysLocalName uniq SLIT("t")
 
 newMutTyVar :: Name -> Kind -> IO TyVar
-newMutTyVar name kind = 
-  do loc <- newIORef Nothing
-     return (Var { varName    = name
-                , realUnique = getKey (nameUnique name)
-                , varType    = kind
-                , varDetails = MutTyVar loc False
-                , varInfo    = pprPanic "newMutTyVar" (ppr name)
-                })
+newMutTyVar name kind = newTyVar name kind False
 
 newSigTyVar :: Name -> Kind -> IO TyVar
-newSigTyVar name kind = 
-  do loc <- newIORef Nothing
-     return (Var { varName    = name 
-                , realUnique = getKey (nameUnique name)
-                , varType    = kind
-                , varDetails = MutTyVar loc True
-                , varInfo    = pprPanic "newSigTyVar" (ppr name)
-                })
+-- Type variables from type signatures are still mutable, because
+-- they may get unified with type variables from other signatures
+-- But they do contain a flag to distinguish them, so we can tell if
+-- we unify them with a non-type-variable.
+newSigTyVar name kind = newTyVar name kind True
+
+newTyVar name kind is_sig
+ = do loc <- newIORef Nothing
+      return (Var { varName    = name
+                 , realUnique = getKey (nameUnique name)
+                 , varType    = kind
+                 , varDetails = MutTyVar loc is_sig
+                 , varInfo    = pprPanic "newMutTyVar" (ppr name)
+                 })
 
 readMutTyVar :: TyVar -> IO (Maybe Type)
 readMutTyVar (Var {varDetails = MutTyVar loc _}) = readIORef loc