Capturing and keeping track of local bindins in the desugarer

Used in the desugaring of the breakpoint primitive

compiler/deSugar/DsExpr.lhs

@@ -290,8 +290,11 @@ dsExpr (HsCase discrim matches)
     matchWrapper CaseAlt matches 	`thenDs` \ ([discrim_var], matching_code) ->
     returnDs (scrungleMatch discrim_var core_discrim matching_code)
 
+-- Pepe: The binds are in scope in the body but NOT in the binding group
+--       This is to avoid silliness in breakpoints
 dsExpr (HsLet binds body)
-  = dsAndThenMaybeInsertBreakpoint body `thenDs` \ body' ->
+  = (bindLocalsDs (map unLoc $ collectLocalBinders binds) $ 
+     dsAndThenMaybeInsertBreakpoint body) `thenDs` \ body' ->
     dsLocalBinds binds body'
 
 -- We need the `ListComp' form to use `deListComp' (rather than the "do" form)
@@ -602,11 +605,16 @@ dsDo stmts body result_ty
 	   ; returnDs (mkApps then_expr2 [rhs2, rest]) }
     
     go (LetStmt binds : stmts)
-      = do { rest <- go stmts
+      = do { rest <- bindLocalsDs (map unLoc$ collectLocalBinders binds) $ 
+                      go stmts
 	   ; dsLocalBinds binds rest }
-        
+
+    -- Notice how due to the placement of bindLocals, binders in this stmt
+    -- are available in posterior stmts but Not in this one rhs.
+    -- This is to avoid silliness in breakpoints
     go (BindStmt pat rhs bind_op fail_op : stmts)
-      = do { body  <- go stmts
+      = 
+       do { body  <- bindLocalsDs (collectPatBinders pat) $ go stmts
 	   ; var   <- selectSimpleMatchVarL pat
 	   ; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat
     				  result_ty (cantFailMatchResult body)
@@ -666,7 +674,7 @@ dsMDo tbl stmts body result_ty
 	   ; returnDs (mkApps (Var then_id) [Type rhs_ty, Type b_ty, rhs2, rest]) }
     
     go (BindStmt pat rhs _ _ : stmts)
-      = do { body  <- go stmts
+      = do { body  <- bindLocalsDs (collectPatBinders pat) $ go stmts
 	   ; var   <- selectSimpleMatchVarL pat
 	   ; match <- matchSinglePat (Var var) (StmtCtxt ctxt) pat
     				  result_ty (cantFailMatchResult body)

compiler/deSugar/DsGRHSs.lhs

@@ -14,6 +14,7 @@ import {-# SOURCE #-} DsExpr  ( dsLExpr, dsLocalBinds )
 import {-# SOURCE #-} Match   ( matchSinglePat )
 
 import HsSyn
+import HsUtils
 import CoreSyn
 import Var
 import Type
@@ -27,6 +28,7 @@ import TysWiredIn
 import PrelNames
 import Name
 import SrcLoc
+
 \end{code}
 
 @dsGuarded@ is used for both @case@ expressions and pattern bindings.
@@ -56,18 +58,23 @@ 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
-  = mappM (dsGRHS hs_ctx pats rhs_ty) grhss	`thenDs` \ match_results ->
+dsGRHSs hs_ctx pats (GRHSs grhss binds) rhs_ty =
+   bindLocalsDs (bindsBinders ++ patsBinders) $
+    mappM (dsGRHS hs_ctx pats rhs_ty) grhss	`thenDs` \ match_results ->
     let 
 	match_result1 = foldr1 combineMatchResults match_results
-	match_result2 = adjustMatchResultDs (dsLocalBinds binds) match_result1
+	match_result2 = adjustMatchResultDs 
+                                 (\e -> bindLocalsDs patsBinders $ 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) 
 
 dsGRHS hs_ctx pats rhs_ty (L loc (GRHS guards rhs))
-  = matchGuards (map unLoc guards) hs_ctx rhs rhs_ty
+  = do rhs' <- maybeInsertBreakpoint rhs rhs_ty
+       matchGuards (map unLoc guards) hs_ctx rhs' rhs_ty
 \end{code}
 
 
@@ -110,7 +117,8 @@ matchGuards (ExprStmt expr _ _ : stmts) ctx rhs rhs_ty
     returnDs (mkGuardedMatchResult pred_expr match_result)
 
 matchGuards (LetStmt binds : stmts) ctx rhs rhs_ty
-  = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
+  = bindLocalsDs (map unLoc $ collectLocalBinders binds) $
+    matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
     returnDs (adjustMatchResultDs (dsLocalBinds binds) match_result)
 	-- NB the dsLet occurs inside the match_result
 	-- Reason: dsLet takes the body expression as its argument
@@ -118,7 +126,8 @@ matchGuards (LetStmt binds : stmts) ctx rhs rhs_ty
 	--	   body expression in hand
 
 matchGuards (BindStmt pat bind_rhs _ _ : stmts) ctx rhs rhs_ty
-  = matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
+  = bindLocalsDs (collectPatBinders pat) $
+    matchGuards stmts ctx rhs rhs_ty	`thenDs` \ match_result ->
     dsLExpr bind_rhs			`thenDs` \ core_rhs ->
     matchSinglePat core_rhs ctx pat rhs_ty match_result
 \end{code}

compiler/deSugar/DsMonad.lhs

@@ -23,7 +23,7 @@ module DsMonad (
 
 	DsMetaEnv, DsMetaVal(..), dsLookupMetaEnv, dsExtendMetaEnv,
 
-        getBkptSitesDs,
+        bindLocalsDs, getLocalBindsDs, getBkptSitesDs,
 	-- Warnings
 	DsWarning, warnDs, failWithDs,
 
@@ -143,7 +143,8 @@ data DsGblEnv = DsGblEnv {
 
 data DsLclEnv = DsLclEnv {
 	ds_meta	   :: DsMetaEnv,	-- Template Haskell bindings
-	ds_loc	   :: SrcSpan		-- to put in pattern-matching error msgs
+	ds_loc	   :: SrcSpan,		-- to put in pattern-matching error msgs
+        ds_locals  :: OccEnv Id         -- For locals in breakpoints
      }
 
 -- Inside [| |] brackets, the desugarer looks 
@@ -166,7 +167,7 @@ initDs  :: HscEnv
 
 initDs hsc_env mod rdr_env type_env thing_inside
   = do 	{ msg_var <- newIORef (emptyBag, emptyBag)
-	; let (ds_gbl_env, ds_lcl_env) = mkDsEnvs mod rdr_env type_env msg_var
+        ; (ds_gbl_env, ds_lcl_env) <- mkDsEnvs mod rdr_env type_env msg_var
 
 	; either_res <- initTcRnIf 'd' hsc_env ds_gbl_env ds_lcl_env $
 		        tryM thing_inside	-- Catch exceptions (= errors during desugaring)
@@ -194,21 +195,26 @@ initDsTc thing_inside
 	; msg_var  <- getErrsVar
 	; let type_env = tcg_type_env tcg_env
 	      rdr_env  = tcg_rdr_env tcg_env
-	; setEnvs (mkDsEnvs this_mod rdr_env type_env msg_var) thing_inside }
+        ; ds_envs <- ioToIOEnv$ mkDsEnvs this_mod rdr_env type_env msg_var
+	; setEnvs ds_envs thing_inside }
 
-mkDsEnvs :: Module -> GlobalRdrEnv -> TypeEnv
-	 -> IORef Messages -> (DsGblEnv, DsLclEnv)
+mkDsEnvs :: Module -> GlobalRdrEnv -> TypeEnv -> IORef Messages -> IO (DsGblEnv, DsLclEnv)
 mkDsEnvs mod rdr_env type_env msg_var
-  = (gbl_env, lcl_env)
-  where
-    if_genv = IfGblEnv { if_rec_types = Just (mod, return type_env) }
-    if_lenv = mkIfLclEnv mod (ptext SLIT("GHC error in desugarer lookup in") <+> ppr mod)
-    gbl_env = DsGblEnv { ds_mod = mod, 
-    			 ds_if_env = (if_genv, if_lenv),
-    			 ds_unqual = mkPrintUnqualified rdr_env,
-    			 ds_msgs = msg_var }
-    lcl_env = DsLclEnv { ds_meta = emptyNameEnv, 
-			 ds_loc = noSrcSpan }
+  = do 
+       sites_var <- newIORef []
+       let     if_genv = IfGblEnv { if_rec_types = Just (mod, return type_env) }
+               if_lenv = mkIfLclEnv mod (ptext SLIT("GHC error in desugarer lookup in") <+> ppr mod)
+               gbl_env = DsGblEnv { ds_mod = mod, 
+    			            ds_if_env = (if_genv, if_lenv),
+    			            ds_unqual = mkPrintUnqualified rdr_env,
+    			            ds_msgs = msg_var,
+                                    ds_bkptSites = sites_var}
+               lcl_env = DsLclEnv { ds_meta = emptyNameEnv, 
+			            ds_loc = noSrcSpan,
+                                    ds_locals = emptyOccEnv }
+
+       return (gbl_env, lcl_env)
+
 \end{code}
 
 %************************************************************************
@@ -328,6 +334,14 @@ dsExtendMetaEnv menv thing_inside
 \end{code}
 
 \begin{code}
+getLocalBindsDs :: DsM [Id]
+getLocalBindsDs = do { env <- getLclEnv; return (occEnvElts$ ds_locals env) }
+
+bindLocalsDs :: [Id] -> DsM a -> DsM a
+bindLocalsDs new_ids enclosed_scope = 
+    updLclEnv (\env-> env {ds_locals = ds_locals env `extendOccEnvList` occnamed_ids})
+	      enclosed_scope
+  where occnamed_ids = [ (nameOccName (idName id),id) | id <- new_ids ] 
 
 getBkptSitesDs :: DsM (IORef SiteMap)
 getBkptSitesDs = do { env <- getGblEnv; return (ds_bkptSites env) }