Instruction file imported from ncosentino/needlr (
.github/instructions/genesis/parser-outcomes.instructions.md). Copyright stays with the author.
Parser Outcome and Speculative Probe Rules
Apply these rules when the matching file parses or speculatively probes structured input. An ordinary I/O reader that does not interpret input is outside this instruction's scope.
- Model expected outcomes explicitly, preserving distinctions such as success, no-match, incomplete input, invalid input, unsupported input, and budget exceeded whenever callers respond differently to them.
- Do not use a deliberately thrown exception as a parser branch, backtracking signal, or probe result.
- A speculative probe must either commit or restore every input position, buffered value, diagnostic, budget counter, and terminal disposition it was allowed to change.
- A failed probe must not consume input or leak provisional diagnostics unless that is part of its documented result contract.
- Prefer immutable/local probe state or an explicit snapshot-and-restore boundary over manually reversing individual mutations.
- Catch exception-based framework parsers only at the narrow conversion boundary and translate malformed input into the explicit parser outcome.