syntax_data: {"ast_node_type":"variable","tokens":[{"end":42,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let local_decls = IndexVec::from_iter(
context_before:     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
context_after:         [output].iter().chain(&inputs).map(|ty| LocalDecl::with_source_info(*ty, source_info)),