Grouping match arms

[nrc]

If there are groups of patterns in a match arm, we should ensure there is either indentation or a blank line between groups. This is a bit tricky because for simple matches we don't want to insert a bunch of newlines.

e.g.,

            ExprKind::Index { .. } |
            ExprKind::SelfRef |
            ExprKind::VarRef { .. } |
            ExprKind::StaticRef { .. } => Some(Category::Lvalue),

            ExprKind::Index { .. } |
            ExprKind::SelfRef |
            ExprKind::VarRef { .. } |
            ExprKind::StaticRef { .. } => Some(Category::Lvalue),

but also

            ExprKind::Index { .. } => Some(Category::Lvalue),
            ExprKind::SelfRef => Some(Category::Lvalue),
            ExprKind::VarRef { .. } => Some(Category::Lvalue),
            ExprKind::StaticRef { .. } => Some(Category::Lvalue),

[calebcartwright]

Closing as this was implemented some time ago