Missing parentheses when pretty-printing multiplicity
```
f = id :: a %(m n) -> a
```
gives
```
• Couldn't match type ‘'Many’ with ‘m1 n1’
Expected: a1 %m1 n1 -> a1
```
This should be `a %(m1 n1) -> a1`.
issue
Due to a large amount of spam we do not allow new users to create repositories, they are "external" users. If you are a new user and want to create a repository, for example for forking GHC, open a new issue on ghc/ghc using the "get-verified" issue template