diff options
Diffstat (limited to 'compiler/GHC/Rename/Expr.hs')
| -rw-r--r-- | compiler/GHC/Rename/Expr.hs | 51 |
1 files changed, 42 insertions, 9 deletions
diff --git a/compiler/GHC/Rename/Expr.hs b/compiler/GHC/Rename/Expr.hs index 1e1f7bdce1..fe8056f6c6 100644 --- a/compiler/GHC/Rename/Expr.hs +++ b/compiler/GHC/Rename/Expr.hs @@ -35,7 +35,7 @@ import GHC.Hs import GHC.Tc.Errors.Types import GHC.Tc.Utils.Env ( isBrackStage ) import GHC.Tc.Utils.Monad -import GHC.Unit.Module ( getModule ) +import GHC.Unit.Module ( getModule, isInteractiveModule ) import GHC.Rename.Env import GHC.Rename.Fixity import GHC.Rename.Utils ( HsDocContext(..), bindLocalNamesFV, checkDupNames @@ -1170,7 +1170,11 @@ rnStmt ctxt rnBody (L loc (RecStmt { recS_stmts = L _ rec_stmts })) thing_inside segs -- See Note [Deterministic ApplicativeDo and RecursiveDo desugaring] ; (thing, fvs_later) <- thing_inside bndrs - ; let (rec_stmts', fvs) = segmentRecStmts (locA loc) ctxt empty_rec_stmt segs fvs_later + -- In interactive mode, assume that all variables are used later + ; is_interactive <- isInteractiveModule . tcg_mod <$> getGblEnv + ; let + final_fvs_later = if is_interactive then Nothing else Just fvs_later + (rec_stmts', fvs) = segmentRecStmts (locA loc) ctxt empty_rec_stmt segs final_fvs_later -- We aren't going to try to group RecStmts with -- ApplicativeDo, so attaching empty FVs is fine. ; return ( ((zip rec_stmts' (repeat emptyNameSet)), thing) @@ -1522,15 +1526,17 @@ rn_rec_stmts ctxt rnBody bndrs stmts segmentRecStmts :: AnnoBody body => SrcSpan -> HsStmtContext GhcRn -> Stmt GhcRn (LocatedA (body GhcRn)) - -> [Segment (LStmt GhcRn (LocatedA (body GhcRn)))] -> FreeVars + -> [Segment (LStmt GhcRn (LocatedA (body GhcRn)))] + -> Maybe FreeVars -- Nothing when in interactive mode, everything can be used later + -- Note [What is "used later" in a rec stmt] -> ([LStmt GhcRn (LocatedA (body GhcRn))], FreeVars) -segmentRecStmts loc ctxt empty_rec_stmt segs fvs_later +segmentRecStmts loc ctxt empty_rec_stmt segs mfvs_later | null segs - = ([], fvs_later) + = ([], final_fv_uses) | HsDoStmt (MDoExpr _) <- ctxt - = segsToStmts empty_rec_stmt grouped_segs fvs_later + = segsToStmts empty_rec_stmt grouped_segs later_ids -- Step 4: Turn the segments into Stmts -- Use RecStmt when and only when there are fwd refs -- Also gather up the uses from the end towards the @@ -1540,14 +1546,20 @@ segmentRecStmts loc ctxt empty_rec_stmt segs fvs_later | otherwise = ([ L (noAnnSrcSpan loc) $ empty_rec_stmt { recS_stmts = noLocA ss - , recS_later_ids = nameSetElemsStable - (defs `intersectNameSet` fvs_later) + , recS_later_ids = nameSetElemsStable later_ids , recS_rec_ids = nameSetElemsStable (defs `intersectNameSet` uses) }] -- See Note [Deterministic ApplicativeDo and RecursiveDo desugaring] - , uses `plusFV` fvs_later) + , uses `plusFV` final_fv_uses) where + final_fv_uses = case mfvs_later of + Nothing -> defs + Just later -> uses `plusFV` later + later_ids = case mfvs_later of + Nothing -> defs + Just fvs_later -> defs `intersectNameSet` fvs_later + (defs_s, uses_s, _, ss) = unzip4 segs defs = plusFVs defs_s uses = plusFVs uses_s @@ -1622,6 +1634,27 @@ glom it together with the first two groups { rec { x <- ...y...; p <- z ; y <- ...x... ; q <- x ; z <- y } ; r <- x } + +Note [What is "used later" in a rec stmt] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We desugar a recursive Stmt to somethign like + + (a,_,c) <- mfix (\(a,b,_) -> do { ... ; return (a,b,c) }) + ...stuff after the rec... + +The knot-tied tuple must contain +* All the variables that are used before they are bound in the `rec` block +* All the variables that are used after the entire `rec` block + +In the case of GHCi, however, we don't know what variables will be used +after the `rec` (#20206). For example, we might have + ghci> rec { x <- e1; y <- e2 } + ghci> print x + ghci> print y + +So we have to assume that *all* the variables bound in the `rec` are used +afterwards. We use `Nothing` in the argument to segmentRecStmts to signal +that all the variables are used. -} glomSegments :: HsStmtContext GhcRn |