confval turns a configuration file into runtime types in four phases: parse, validate, gate, and lower.
See The pipeline contract for the detail on each phase, including the rare lowering error that short-circuits.
confval
Span-first configuration parsing, validation, and lowering for Rust
Define a configuration as Rust types, parse a file into them, validate the values, and lower them into the types your program runs on. Errors report the line and column they came from.