Implement missing clauses generates pattern variables for implicit parameters

[sxhya]

Suppose that you are defining a function with an implicit parameter which also happens to be a class.

\instance DecWordMonoid (S : DecSet) : DecSet
  | E => List (\Sigma S Bool)
  | decideEq x y => {?}
  | # => {?}
  | #-irreflexive => {?}
  | #-symmetric => {?}
  | #-comparison => {?}
  | tightness => {?}
  | nonEqualApart => {?} \where {
  \func word-dec (x y : List (\Sigma S Bool)) : Dec (x = y)
}

If you attempt to run the Generate missing clauses quick-fix on word-dec it produces the following result:

\func word-dec (x y : List (\Sigma S Bool)) : Dec (x = y)
    | {(E,#,#-irreflexive,#-symmetric,#-comparison,tightness,decideEq,nonEqualApart)}, nil, nil => {?}
    | {(E,#,#-irreflexive,#-symmetric,#-comparison,tightness,decideEq,nonEqualApart)}, nil, a :: y => {?}
    | {(E,#,#-irreflexive,#-symmetric,#-comparison,tightness,decideEq,nonEqualApart)}, a :: x, nil => {?}
    | {(E,#,#-irreflexive,#-symmetric,#-comparison,tightness,decideEq,nonEqualApart)}, a :: x, a1 :: y => {?}

The problem here is that no first implicit argument is expected for any of the clauses.