X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsGRHSs.lhs;h=be697fa323e4f09470195acbf0af318f82f067b7;hp=31d48b6eca2ec35d6eae174f96caf39d3e537e23;hb=7fc01c4671980ea3c66d549c0ece4d82fd3f5ade;hpb=cdce647711c0f46f5799b24de087622cb77e647f diff --git a/compiler/deSugar/DsGRHSs.lhs b/compiler/deSugar/DsGRHSs.lhs index 31d48b6..be697fa 100644 --- a/compiler/deSugar/DsGRHSs.lhs +++ b/compiler/deSugar/DsGRHSs.lhs @@ -6,6 +6,13 @@ 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" @@ -14,20 +21,18 @@ import {-# SOURCE #-} DsExpr ( dsLExpr, dsLocalBinds ) 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. @@ -44,9 +49,9 @@ 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 empty extractMatchResult match_result error_expr \end{code} @@ -57,21 +62,19 @@ dsGRHSs :: HsMatchContext Name -> [Pat Id] -- These are to build a MatchContext -> GRHSs Id -- Guarded RHSs -> Type -- Type of RHS -> DsM MatchResult -dsGRHSs hs_ctx pats (GRHSs grhss binds) rhs_ty = - bindLocalsDs (bindsBinders ++ patsBinders) $ - mappM (dsGRHS hs_ctx pats rhs_ty) grhss `thenDs` \ match_results -> +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 patsBinders $ dsLocalBinds binds e) + (\e -> dsLocalBinds binds e) match_result1 -- NB: nested dsLet inside matchResult - in - returnDs match_result2 - where bindsBinders = map unLoc (collectLocalBinders binds) - patsBinders = collectPatsBinders (map (L undefined) pats) + -- + 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} @@ -92,7 +95,7 @@ matchGuards :: [Stmt Id] -- Guard -- 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) } @@ -103,31 +106,48 @@ matchGuards [] ctx rhs rhs_ty -- 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@