Commit 9aab4f4c authored by Simon Peyton Jones's avatar Simon Peyton Jones

Improve exprIsConApp_maybe again

Now it handles value lambdas too; and I've dealt with
an out-of-scope error too.
parent 8c99deeb
......@@ -57,7 +57,7 @@ import BasicTypes ( Arity )
import Type
import Coercion
import PrelNames
import VarEnv ( mkInScopeSet )
import VarEnv
import Bag
import Util
import Pair
......@@ -1220,11 +1220,12 @@ data ConCont = CC [CoreExpr] Coercion
-- where are the *universally-qantified* type args of 'dc'
exprIsConApp_maybe :: IdUnfoldingFun -> CoreExpr -> Maybe (DataCon, [Type], [CoreExpr])
exprIsConApp_maybe id_unf expr
= go Nothing expr (CC [] (mkReflCo (exprType expr)))
= go (Left in_scope) expr (CC [] (mkReflCo (exprType expr)))
in_scope = mkInScopeSet (exprFreeVars expr)
go :: Maybe Subst -> CoreExpr -> ConCont
go :: Either InScopeSet Subst
-> CoreExpr -> ConCont
-> Maybe (DataCon, [Type], [CoreExpr])
go subst (Note note expr) cont
| notSccNote note = go subst expr cont
......@@ -1233,12 +1234,14 @@ exprIsConApp_maybe id_unf expr
go subst (App fun arg) (CC args co)
= go subst fun (CC (subst_arg subst arg : args) co)
go subst (Lam var body) (CC (arg:args) co)
| isTyCoArg arg -- Only beta-reduce types and coercions
= go (Just (extend subst var arg)) body (CC args co)
go (Just sub) (Var v) cont
= go Nothing (lookupIdSubst (text "exprIsConApp") sub v) cont
go Nothing (Var fun) cont@(CC args co)
| exprIsTrivial arg -- Don't duplicate stuff!
= go (extend subst var arg) body (CC args co)
go (Right sub) (Var v) cont
= go (Left (substInScope sub))
(lookupIdSubst (text "exprIsConApp" <+> ppr expr) sub v)
go (Left in_scope) (Var fun) cont@(CC args co)
| Just con <- isDataConWorkId_maybe fun
, count isValArg args == idArity fun
, let (univ_ty_args, rest_args) = splitAtList (dataConUnivTyVars con) args
......@@ -1256,23 +1259,28 @@ exprIsConApp_maybe id_unf expr
-- we are effectively duplicating the unfolding
| Just rhs <- expandUnfolding_maybe unfolding
= -- pprTrace "expanding" (ppr fun $$ ppr rhs) $
go Nothing rhs cont
let in_scope' = extendInScopeSetSet in_scope (exprFreeVars rhs)
res = go (Left in_scope') rhs cont
in WARN( unfoldingArity unfolding > 0 && isJust res,
text "Interesting! exprIsConApp_maybe:"
<+> ppr fun <+> ppr expr)
unfolding = id_unf fun
go _ _ _ = Nothing
-- Operations on the (Just CoreSubst)
-- The Nothing case is wildly dominant
subst_co Nothing co = co
subst_co (Just s) co = CoreSubst.substCo s co
-- Operations on the (Either InScopeSet CoreSubst)
-- The Left case is wildly dominant
subst_co (Left {}) co = co
subst_co (Right s) co = CoreSubst.substCo s co
subst_arg Nothing e = e
subst_arg (Just s) e = substExpr (text "exprIsConApp") s e
subst_arg (Left {}) e = e
subst_arg (Right s) e = substExpr (text "exprIsConApp") s e
extend Nothing v e = extendSubst (mkEmptySubst in_scope) v e
extend (Just s) v e = extendSubst s v e
extend (Left in_scope) v e = Right (extendSubst (mkEmptySubst in_scope) v e)
extend (Right s) v e = Right (extendSubst s v e)
dealWithCoercion :: Coercion
-> (DataCon, [Type], [CoreExpr])
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