Commit cad5d0b6 authored by Simon Peyton Jones's avatar Simon Peyton Jones

Buglet in reporting out of scope errors in rules

Most out of scope errors get reported by the type checker these
days, but not all.  Example, the function on the LHS of a RULE.

Trace #15659 pointed out that this less-heavily-used code path
produce a "wacky" error message.  Indeed so.  Easily fixed.
parent 7e77f414
......@@ -179,8 +179,15 @@ is Less Cool because
typecheck do-notation with (>>=) :: m1 a -> (a -> m2 b) -> m2 b.)
-}
-- | An unbound variable; used for treating out-of-scope variables as
-- expression holes
-- | An unbound variable; used for treating
-- out-of-scope variables as expression holes
--
-- Either "x", "y" Plain OutOfScope
-- or "_", "_x" A TrueExprHole
--
-- Both forms indicate an out-of-scope variable, but the latter
-- indicates that the user /expects/ it to be out of scope, and
-- just wants GHC to report its type
data UnboundVar
= OutOfScope OccName GlobalRdrEnv -- ^ An (unqualified) out-of-scope
-- variable, together with the GlobalRdrEnv
......
......@@ -29,7 +29,7 @@ import RnUtils ( HsDocContext(..), mapFvRn, bindLocalNames
, checkDupRdrNames, inHsDocContext, bindLocalNamesFV
, checkShadowedRdrNames, warnUnusedTypePatterns
, extendTyVarEnvFVRn, newLocalBndrsRn )
import RnUnbound ( mkUnboundName )
import RnUnbound ( mkUnboundName, notInScopeErr )
import RnNames
import RnHsDoc ( rnHsDoc, rnMbLHsDoc )
import TcAnnotations ( annCtxt )
......@@ -1093,14 +1093,14 @@ badRuleVar name var
badRuleLhsErr :: FastString -> LHsExpr GhcRn -> HsExpr GhcRn -> SDoc
badRuleLhsErr name lhs bad_e
= sep [text "Rule" <+> pprRuleName name <> colon,
nest 4 (vcat [err,
nest 2 (vcat [err,
text "in left-hand side:" <+> ppr lhs])]
$$
text "LHS must be of form (f e1 .. en) where f is not forall'd"
where
err = case bad_e of
HsUnboundVar _ uv -> text "Not in scope:" <+> ppr uv
_ -> text "Illegal expression:" <+> ppr bad_e
HsUnboundVar _ uv -> notInScopeErr (mkRdrUnqual (unboundVarOcc uv))
_ -> text "Illegal expression:" <+> ppr bad_e
{- **************************************************************
* *
......
......@@ -12,7 +12,8 @@ module RnUnbound ( mkUnboundName
, WhereLooking(..)
, unboundName
, unboundNameX
, perhapsForallMsg ) where
, perhapsForallMsg
, notInScopeErr ) where
import GhcPrelude
......@@ -60,8 +61,7 @@ unboundNameX :: WhereLooking -> RdrName -> SDoc -> RnM Name
unboundNameX where_look rdr_name extra
= do { dflags <- getDynFlags
; let show_helpful_errors = gopt Opt_HelpfulErrors dflags
what = pprNonVarNameSpace (occNameSpace (rdrNameOcc rdr_name))
err = unknownNameErr what rdr_name $$ extra
err = notInScopeErr rdr_name $$ extra
; if not show_helpful_errors
then addErr err
else do { local_env <- getLocalRdrEnv
......@@ -72,12 +72,13 @@ unboundNameX where_look rdr_name extra
; addErr (err $$ suggestions) }
; return (mkUnboundNameRdr rdr_name) }
unknownNameErr :: SDoc -> RdrName -> SDoc
unknownNameErr what rdr_name
notInScopeErr :: RdrName -> SDoc
notInScopeErr rdr_name
= vcat [ hang (text "Not in scope:")
2 (what <+> quotes (ppr rdr_name))
, extra ]
where
what = pprNonVarNameSpace (occNameSpace (rdrNameOcc rdr_name))
extra | rdr_name == forall_tv_RDR = perhapsForallMsg
| otherwise = Outputable.empty
......
module T15659 where
{-# RULES "test" forall x. f x = x #-}
T15659.hs:3:11: error:
Rule "test":
Not in scope: ‘f’
in left-hand side: f x
LHS must be of form (f e1 .. en) where f is not forall'd
......@@ -134,4 +134,4 @@ test('T14591', normal, compile_fail, [''])
test('T15214', normal, compile_fail, [''])
test('T15539', normal, compile_fail, [''])
test('T15487', normal, multimod_compile_fail, ['T15487','-v0'])
test('T15659', normal, compile_fail, [''])
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