syntax_data: {"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // (as it's created inside the body itself, not passed in from outside).
context_before:             // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
context_after:             let ty = if fn_decl.c_variadic && index == fn_decl.inputs.len() {