- head_type_args_tyvars_msg = parens (
- text "All instance types must be of the form (T a1 ... an)" $$
- text "where a1 ... an are distinct type *variables*" $$
- text "Use -XFlexibleInstances if you want to disable this.")
+ head_type_args_tyvars_msg = parens (vcat [
+ text "All instance types must be of the form (T a1 ... an)",
+ text "where a1 ... an are type *variables*,",
+ text "and each type variable appears at most once in the instance head.",
+ text "Use -XFlexibleInstances if you want to disable this."])