syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
context_before:         //
context_after:         //   has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,