syntax_data: {"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:                     if !test.overlaps(pat, self.tcx, self.typing_env())? {
context_before:                     // the pattern can be matched only if this test fails.
context_after:                         Some(TestBranch::Failure)