syntax_data: {"ast_node_type":"impl","tokens":[{"end":80,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // Ensure that the impl is constrained, otherwise projection may give us
context_before:     if let Some(assoc_item) = ancestors.leaf_def(tcx, assoc_def_id) {
context_after:         // bad unconstrained infer vars.