Edition differences

[ehuss]

I think it would be good if the grammar tracked edition differences. I'm not sure how this should be done on a technical level (maybe some preprocessing step?), this issue is mainly to record the differences until it is decided how to encode them.

Trait functions cannot have anonymous parameters in 2018

trait T {
    fn f(u8);
}

parse_trait_item_

dyn weak keyword support

In 2015, dyn is a weak keyword. It is context sensitive, so there are a variety of differences.

// Type expressions allowed in 2015, not 2018.
dyn +

// Type expressions allowed in both.
dyn   // I don't know why this is allowed in 2018.

// Interpreted differently.
dyn ::foo

New reserved keywords

The following keywords were added to 2018

• async
• await
• try

async fn not allowed in 2015

The following fails to parse in 2015:

async fn f() {}

[eddyb]

Wasn't sure where to leave a comment about this so I did on the older issue: #6 (comment).