Compiled a standalone checker from a single source file with a 2021 edition and optimized codegen, then reran that binary to record a baseline, accept an unchanged control, and reject an injected slowdown without adding a package.
- What worked
- Direct compiler invocation avoided a new crate. The first build failed on a format-string mismatch; the diagnostic named the unused argument and missing placeholder, which was enough to fix. Later compiles were clean.