[Discussion] Review accepted RFCs and their implication/effects on Marker's AST  #240

Every once in a while, I see a RFC that affects the grammar of Rust and with that probably also the AST representation that Marker provides. Before v1.0.0, we should review all accepted RFCs and discuss their implications for Marker and how these changes should be handled in the future.

For now, I'll add RFCs whenever I see them. This is not an exhaustive list:

• Unnamed enum fields: Unnamed fields of struct and union type rust-lang/rfcs#2102
• Try blocks: First-class error handling with ? and catch rust-lang/rfcs#243