syntax_data: {"ast_node_type":"other","tokens":[{"end":66,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // will unify `$0` with `Vec<$1>` (for some fresh variable
context_before:         // unbound variable. When we evaluate this trait-reference, we
context_after:         // `$1`), on the condition that `$1 : Eq`. We will then wind