-- { 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)