{"item_id": "ker-stack_insert", "crate_dir": "../../bench/kernels/stack_insert/pre", "lib_name": "k_stack_insert_pre", "provenance": {"author": "claude-sonnet subagent, blind", "written_from": "signature + doc string only", "saw_source": false, "saw_diff": false, "saw_advisory": false},
 "properties": [
  {"id": "p1", "fn": "insert_shift_len", "args": [["len", "usize"], ["index", "usize"]], "pre": "true", "post": "index <= len || r.is_err()", "ret": "Result<usize, u8>", "basis": "Err if index > len"},
  {"id": "p2", "fn": "insert_shift_len", "args": [["len", "usize"], ["index", "usize"]], "pre": "true", "post": "index > len || r == Ok(len - index)", "ret": "Result<usize, u8>", "basis": "elements to shift when inserting at index are those at positions index..len, i.e. len - index"},
  {"id": "p3", "fn": "insert_shift_len", "args": [["len", "usize"], ["index", "usize"]], "pre": "true", "post": "index != len || r == Ok(0)", "ret": "Result<usize, u8>", "basis": "inserting at the end (index == len) shifts nothing and is not an error"}
 ]}