How about
```
dsExpr (HsStatic _) = panic "DsExpr.dsExpr: HsStatic: unhandled case." -- see Note [The argument of static form is a variable]

-- Note [The argument of static form is a variable]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- During type-checking the arguments of static forms which are not variables are
-- floated as top-level bindings with fresh names, and the fresh names are placed
-- as the arguments of the static forms. Thus, in the desugaring phase all static forms
-- should have variables as arguments.
```