syntax_data: {"ast_node_type":"other","tokens":[{"end":48,"kind":"keyword","start":0,"text":"arm.pattern.span.shrink_to_hi(),"}]}
source_snippet:                 arm.pattern.span.shrink_to_hi(),
context_before:             err.span_suggestion_verbose(
context_after:                 "if you meant to introduce a binding, use a different name",