syntax_data: {"ast_node_type":"variable","tokens":[{"end":61,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let fail = target_block(TestBranch::Failure);
context_before:                 let success = target_block(TestBranch::Success);
context_after:                 // Test `val` by computing `lo <= val && val <= hi`, using primitive comparisons.