Fix the build

[ghc-hetmet.git] / compiler / deSugar / DsGRHSs.lhs

diff --git a/compiler/deSugar/DsGRHSs.lhs b/compiler/deSugar/DsGRHSs.lhs
index e0bb5f2..70a3724 100644 (file)
--- a/compiler/deSugar/DsGRHSs.lhs
+++ b/compiler/deSugar/DsGRHSs.lhs
@@ -10,7 +10,7 @@ Matching guarded right-hand-sides (GRHSs)
 -- 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/CodingStyle#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module DsGRHSs ( dsGuarded, dsGRHSs ) where
@@ -49,9 +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 ""
     extractMatchResult match_result error_expr
 \end{code}
 
@@ -63,7 +63,7 @@ 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 +71,7 @@ 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
@@ -105,29 +105,48 @@ 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
-  = 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
-  = 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 loc (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 loc (HsBinTick ixT _ e))
+    | Just ticks <- isTrueLHsExpr e   = Just (\x -> ticks x >>= mkTickBox ixT [])
+isTrueLHsExpr (L _ (HsPar e))         = isTrueLHsExpr e
+isTrueLHsExpr other = Nothing
 \end{code}
 
 Should {\em fail} if @e@ returns @D@