-- { x = 3, y = True }
-- Used for both expressions and patterns
= HsRecFields { rec_flds :: [HsRecField id arg],
- rec_dotdot :: Maybe Int }
- -- Nothing => the normal case
- -- Just n => the group uses ".." notation,
- -- and the first n elts of rec_flds
- -- were the user-written ones
- -- (In the latter case, the remaining elts of
- -- rec_flds are the non-user-written ones)
+ rec_dotdot :: Maybe Int } -- Note [DotDot fields]
+
+-- Note [DotDot fields]
+-- ~~~~~~~~~~~~~~~~~~~~
+-- The rec_dotdot field means this:
+-- Nothing => the normal case
+-- Just n => the group uses ".." notation,
+--
+-- In the latter case:
+--
+-- *before* renamer: rec_flds are exactly the n user-written fields
+--
+-- *after* renamer: rec_flds includes *all* fields, with
+-- the first 'n' being the user-written ones
+-- and the remainder being 'filled in' implicitly
data HsRecField id arg = HsRecField {
hsRecFieldId :: Located id,
-- If you write T { x, y = v+1 }, the HsRecFields will be
-- HsRecField x x True ...
-- HsRecField y (v+1) False ...
--- That is, for "punned" field x is immediately expanded to x=x
--- but with a punning flag so we can detect it later
+-- That is, for "punned" field x is expanded (in the renamer)
+-- to x=x; but with a punning flag so we can detect it later
-- (e.g. when pretty printing)
+--
+-- If the original field was qualified, we un-qualify it, thus
+-- T { A.x } means T { A.x = x }
hsRecFields :: HsRecFields id arg -> [id]
hsRecFields rbinds = map (unLoc . hsRecFieldId) (rec_flds rbinds)
fbind :: { HsRecField RdrName (LHsExpr RdrName) }
: qvar '=' exp { HsRecField $1 $3 False }
- | qvar { HsRecField $1 (L (getLoc $1) (HsVar (unLoc $1))) True }
+ | qvar { HsRecField $1 (L (getLoc $1) placeHolderPunRhs) True }
-- Here's where we say that plain 'x'
-- means exactly 'x = x'. The pun-flag boolean is
-- there so we can still print it right
cvBindsAndSigs,
cvTopDecls,
findSplice, checkDecBrGroup,
+ placeHolderPunRhs,
-- Stuff to do with Foreign declarations
mkImport,
HsType ty -> return (TypePat ty)
_ -> patFail loc
-plus_RDR, bang_RDR :: RdrName
+placeHolderPunRhs :: HsExpr RdrName
+-- The RHS of a punned record field will be filled in by the renamer
+-- It's better not to make it an error, in case we want to print it when debugging
+placeHolderPunRhs = HsVar pun_RDR
+
+plus_RDR, bang_RDR, pun_RDR :: RdrName
plus_RDR = mkUnqual varName (fsLit "+") -- Hack
bang_RDR = mkUnqual varName (fsLit "!") -- Hack
+pun_RDR = mkUnqual varName (fsLit "pun-right-hand-side")
checkPatField :: HsRecField RdrName (LHsExpr RdrName) -> P (HsRecField RdrName (LPat RdrName))
checkPatField fld = do { p <- checkLPat (hsRecFieldArg fld)