Incorrect warning for active pattern signature with generic parameters

[nojaf]

The following signature leads to unnecessary warning (I think).

Repro steps

val (|Fst|)<'a ,'b> : a: 'a * 'b -> 'a

Expected behavior

The code should parse without warnings. (Again, I think)

Actual behavior

Warning: [FS1189] Remove spaces between the type name and type parameter, e.g. "type C<'T>", not type "C <'T>". Type parameters must be placed directly adjacent to the type name.