I want to do some kind of book-keeping in sequence after ams does its, but I cannot grasp the error.

Parser.hs

qual  :: { LStmt GhcPs (LHsExpr GhcPs) }
    : bindpat '<-' exp maybeweight      {% (ams (sLL $1 $> $ mkBindStmt $1 $3)
                                               [mu AnnLarrow $2]) >>= aw $4 }
    -- ^ Would like to apply the returned value from ams (sLL $1 $> [...]) to aw (see below)
    -- Fails with error (see below)

    | exp maybeweight                   {% aw $2 (sL1 $1 $ mkBodyStmt $1) 
    -- ^ This is fine!
   
-- aw adds the found weight to the parser state, same style as ams
aw :: Maybe Weight -> Located a -> P (Located a)
aw Nothing a = return a
aw (Just w) a@(L l _)  = addWeightAt l w >> return a

-- ams implementations for reference:
ams :: Located a -> [AddAnn] -> P (Located a)
ams a@(L l _) bs = addAnnsAt l bs >> return a

-- Some types
sLL :: Located a -> Located b -> c -> Located
mkBindStmt :: LPat idL -> Located (bodyR idR) -> StmtLR idL idR (Located (bodyR idR)) 


{- row 2 of qual fails compilation with the following error:

compiler/stage1/build/Parser.hs:9908:33: error:
    • Couldn't match type ‘Maybe Weight’ with ‘GenLocated SrcSpan b0’
      Expected type: Located b0
        Actual type: Maybe Weight
    • In the second argument of ‘sLL’, namely ‘happy_var_4’
      In the expression: sLL happy_var_1 happy_var_4
      In the first argument of ‘ams’, namely
        ‘(sLL happy_var_1 happy_var_4
            $ mkBindStmt happy_var_1 happy_var_3)’
     |
9908 |         ( (ams (sLL happy_var_1 happy_var_4 $ mkBindStmt happy_var_1 happy_var_3)
     |                                 ^^^^^^^^^^^
-}