Matching guarded right-hand-sides (GRHSs)
\begin{code}
+{-# OPTIONS -fno-warn-incomplete-patterns #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
module DsGRHSs ( dsGuarded, dsGRHSs ) where
#include "HsVersions.h"
import {-# SOURCE #-} Match ( matchSinglePat )
import HsSyn
-import HsUtils
+import MkCore
import CoreSyn
import Var
import Type
import DsMonad
import DsUtils
-import Unique
-import PrelInfo
import TysWiredIn
import PrelNames
import Name
import SrcLoc
-
+import Outputable
\end{code}
@dsGuarded@ is used for both @case@ expressions and pattern bindings.
\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 empty
extractMatchResult match_result error_expr
\end{code}
-> GRHSs Id -- Guarded RHSs
-> Type -- Type of RHS
-> DsM MatchResult
-dsGRHSs hs_ctx pats grhssa@(GRHSs grhss binds) rhs_ty =
- bindLocalsDs binders $ do
- match_results <- mappM (dsGRHS hs_ctx pats rhs_ty) grhss
+dsGRHSs hs_ctx pats (GRHSs grhss binds) rhs_ty = do
+ match_results <- mapM (dsGRHS hs_ctx pats rhs_ty) grhss
let
match_result1 = foldr1 combineMatchResults match_results
match_result2 = adjustMatchResultDs
- (\e -> bindLocalsDs binders $
- dsLocalBinds binds e)
+ (\e -> dsLocalBinds binds e)
match_result1
-- NB: nested dsLet inside matchResult
--
- returnDs match_result2
- where bindsBinders = map unLoc (collectLocalBinders binds)
- patsBinders = collectPatsBinders (map (L undefined) pats)
- binders = bindsBinders ++ patsBinders
+ return match_result2
-dsGRHS hs_ctx pats rhs_ty (L loc (GRHS guards rhs))
+dsGRHS :: HsMatchContext Name -> [Pat Id] -> Type -> LGRHS Id -> DsM MatchResult
+dsGRHS hs_ctx _ rhs_ty (L _ (GRHS guards rhs))
= matchGuards (map unLoc guards) hs_ctx rhs rhs_ty
\end{code}
-- See comments with HsExpr.Stmt re what an ExprStmt means
-- Here we must be in a guard context (not do-expression, nor list-comp)
-matchGuards [] ctx rhs rhs_ty
+matchGuards [] _ rhs _
= do { core_rhs <- dsLExpr rhs
; return (cantFailMatchResult core_rhs) }
-- NB: The success of this clause depends on the typechecker not
-- wrapping the 'otherwise' in empty HsTyApp or HsWrap constructors
-- If it does, you'll get bogus overlap warnings
-matchGuards (ExprStmt (L _ (HsVar v)) _ _ : stmts) ctx rhs rhs_ty
- | v `hasKey` otherwiseIdKey
- || v `hasKey` getUnique trueDataConId
- -- trueDataConId doesn't have the same unique as trueDataCon
- = matchGuards stmts ctx rhs rhs_ty
-
-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
- = bindLocalsDs (map unLoc $ collectLocalBinders binds) $
- matchGuards stmts ctx rhs rhs_ty `thenDs` \ match_result ->
- returnDs (adjustMatchResultDs (dsLocalBinds binds) match_result)
+matchGuards (ExprStmt e _ _ : stmts) ctx rhs rhs_ty
+ | 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
- = bindLocalsDs (collectPatBinders pat) $
- 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)
+
+-- Returns Just {..} if we're sure that the expression is True
+-- I.e. * 'True' datacon
+-- * 'otherwise' Id
+-- * Trivial wappings of these
+-- 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 return
+ -- trueDataConId doesn't have the same unique as trueDataCon
+isTrueLHsExpr (L _ (HsTick ix frees e))
+ | Just ticks <- isTrueLHsExpr e = Just (\x -> ticks x >>= 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 _ (HsBinTick ixT _ e))
+ | Just ticks <- isTrueLHsExpr e = Just (\x -> ticks x >>= mkTickBox ixT [])
+isTrueLHsExpr (L _ (HsPar e)) = isTrueLHsExpr e
+isTrueLHsExpr _ = Nothing
\end{code}
Should {\em fail} if @e@ returns @D@
projects / ghc-hetmet.git / blobdiff