Commit 371dd0d4 authored by twanvl's avatar twanvl
Browse files

Monadify deSugar/DsGRHSs: use do, return, applicative, standard monad functions

parent 794b8adb
......@@ -33,6 +33,8 @@ import PrelNames
import Name
import SrcLoc
import Control.Monad ((>=>))
\end{code}
@dsGuarded@ is used for both @case@ expressions and pattern bindings.
......@@ -49,9 +51,9 @@ necessary. The type argument gives the type of the @ei@.
\begin{code}
dsGuarded :: GRHSs Id -> Type -> DsM CoreExpr
dsGuarded grhss rhs_ty
= dsGRHSs PatBindRhs [] grhss rhs_ty `thenDs` \ match_result ->
mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID rhs_ty "" `thenDs` \ error_expr ->
dsGuarded grhss rhs_ty = do
match_result <- dsGRHSs PatBindRhs [] grhss rhs_ty
error_expr <- mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID rhs_ty ""
extractMatchResult match_result error_expr
\end{code}
......@@ -63,7 +65,7 @@ dsGRHSs :: HsMatchContext Name -> [Pat Id] -- These are to build a MatchContext
-> Type -- Type of RHS
-> DsM MatchResult
dsGRHSs hs_ctx pats grhssa@(GRHSs grhss binds) rhs_ty = do
match_results <- mappM (dsGRHS hs_ctx pats rhs_ty) grhss
match_results <- mapM (dsGRHS hs_ctx pats rhs_ty) grhss
let
match_result1 = foldr1 combineMatchResults match_results
match_result2 = adjustMatchResultDs
......@@ -71,7 +73,7 @@ dsGRHSs hs_ctx pats grhssa@(GRHSs grhss binds) rhs_ty = do
match_result1
-- NB: nested dsLet inside matchResult
--
returnDs match_result2
return match_result2
dsGRHS hs_ctx pats rhs_ty (L loc (GRHS guards rhs))
= matchGuards (map unLoc guards) hs_ctx rhs rhs_ty
......@@ -106,25 +108,25 @@ matchGuards [] ctx rhs rhs_ty
-- wrapping the 'otherwise' in empty HsTyApp or HsWrap constructors
-- If it does, you'll get bogus overlap warnings
matchGuards (ExprStmt e _ _ : stmts) ctx rhs rhs_ty
| Just addTicks <- isTrueLHsExpr e
= matchGuards stmts ctx rhs rhs_ty `thenDs` \ match_result ->
returnDs (adjustMatchResultDs addTicks match_result)
matchGuards (ExprStmt expr _ _ : stmts) ctx rhs rhs_ty
= matchGuards stmts ctx rhs rhs_ty `thenDs` \ match_result ->
dsLExpr expr `thenDs` \ pred_expr ->
returnDs (mkGuardedMatchResult pred_expr match_result)
matchGuards (LetStmt binds : stmts) ctx rhs rhs_ty
= matchGuards stmts ctx rhs rhs_ty `thenDs` \ match_result ->
returnDs (adjustMatchResultDs (dsLocalBinds binds) match_result)
| Just addTicks <- isTrueLHsExpr e = do
match_result <- matchGuards stmts ctx rhs rhs_ty
return (adjustMatchResultDs addTicks match_result)
matchGuards (ExprStmt expr _ _ : stmts) ctx rhs rhs_ty = do
match_result <- matchGuards stmts ctx rhs rhs_ty
pred_expr <- dsLExpr expr
return (mkGuardedMatchResult pred_expr match_result)
matchGuards (LetStmt binds : stmts) ctx rhs rhs_ty = do
match_result <- matchGuards stmts ctx rhs rhs_ty
return (adjustMatchResultDs (dsLocalBinds binds) match_result)
-- NB the dsLet occurs inside the match_result
-- Reason: dsLet takes the body expression as its argument
-- so we can't desugar the bindings without the
-- body expression in hand
matchGuards (BindStmt pat bind_rhs _ _ : stmts) ctx rhs rhs_ty
= matchGuards stmts ctx rhs rhs_ty `thenDs` \ match_result ->
dsLExpr bind_rhs `thenDs` \ core_rhs ->
matchGuards (BindStmt pat bind_rhs _ _ : stmts) ctx rhs rhs_ty = do
match_result <- matchGuards stmts ctx rhs rhs_ty
core_rhs <- dsLExpr bind_rhs
matchSinglePat core_rhs ctx pat rhs_ty match_result
isTrueLHsExpr :: LHsExpr Id -> Maybe (CoreExpr -> DsM CoreExpr)
......@@ -136,19 +138,15 @@ isTrueLHsExpr :: LHsExpr Id -> Maybe (CoreExpr -> DsM CoreExpr)
-- The arguments to Just are any HsTicks that we have found,
-- because we still want to tick then, even it they are aways evaluted.
isTrueLHsExpr (L _ (HsVar v)) | v `hasKey` otherwiseIdKey
|| v `hasKey` getUnique trueDataConId
= Just returnDs
|| v `hasKey` getUnique trueDataConId
= Just return
-- trueDataConId doesn't have the same unique as trueDataCon
isTrueLHsExpr (L loc (HsTick ix frees e))
| Just ticks <- isTrueLHsExpr e = Just (\ e1 ->
ticks e1 `thenDs` \ e2 ->
mkTickBox ix frees e2)
isTrueLHsExpr (L loc (HsTick ix frees e))
| Just ticks <- isTrueLHsExpr e = Just (ticks >=> mkTickBox ix frees)
-- This encodes that the result is constant True for Hpc tick purposes;
-- which is specifically what isTrueLHsExpr is trying to find out.
isTrueLHsExpr (L loc (HsBinTick ixT _ e))
| Just ticks <- isTrueLHsExpr e = Just (\ e1 ->
ticks e1 `thenDs` \ e2 ->
mkTickBox ixT [] e2)
| Just ticks <- isTrueLHsExpr e = Just (ticks >=> mkTickBox ixT [])
isTrueLHsExpr (L _ (HsPar e)) = isTrueLHsExpr e
isTrueLHsExpr other = Nothing
\end{code}
......
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