Compiler

Does this code compile? The cheapest and most certain sensor in the catalog.

A compiler doesn’t just check syntax — it resolves imports, validates module structure, and produces an artifact. If the compiler fails, no downstream sensor can run. This makes it the foundation of the confidence stack: every other sensor assumes compilation succeeded.

In practice

A compiler reading is the most direct verdict in the catalog: pass produces an artifact, fail produces a diagnostic pinned to a file, line, and column. There is no score to interpret and no threshold to set.

error[E0308]: mismatched types
  --> src/invoice.rs:42:12
   |
42 |     return total_with_tax;
   |            ^^^^^^^^^^^^^^ expected `u64`, found `f64`

error: could not compile `billing` (lib) due to 1 previous error

Two habits keep the reading honest. Fix diagnostics in the order they appear, because one bad signature can cascade into dozens of downstream errors, and clearing the first one is cheaper than triaging the avalanche. And treat warnings as debts due now: an unused result or an unreachable arm is the compiler downgrading a verdict it could have made hard, and a codebase that ignores warnings is training everyone to ignore errors too.

Response playbook

When the compiler fires, the response is mechanical:

1. Read the first error, not the last. Later diagnostics are often consequences of the first failure. Fix, recompile, re-read.
2. Trust the diagnostic over your memory of the code. The compiler read the file you actually wrote, not the one you intended.
3. If the message contradicts the source, rebuild clean. Stale incremental state is the usual cause; clear the build cache and compile from scratch before suspecting the toolchain.
4. Never silence the message to pass the build. A cast, an unsafe block, or a suppression attribute converts a maximum-oracle verdict into a deferred bug.

What it cannot detect

A compiler cannot detect logical errors — a function that compiles perfectly but returns the wrong answer. It also cannot detect architectural problems or runtime behavior.

Related sensors

References

Tooling

• GCCGNU Compiler Collection
• ClangLLVM C/C++/ObjC compiler
• rustcThe Rust compiler
• tscTypeScript compiler with type checking

Further reading

• Aho et al., 'Compilers: Principles, Techniques, and Tools'