Module error_flag_lint 

Error Flag Detection (Phase 2b)

Abstract stack simulation that tracks Bool values produced by fallible operations. Warns when these “error flags” are dropped without being checked via if or cond.

This catches patterns that the TOML-based pattern linter misses:

• file.slurp swap nip (Bool moved by swap, then dropped by nip)
• i./ >aux ... aux> drop (Bool stashed on aux stack, dropped later)

Architecture

Modeled on resource_lint.rs:

1. Tag Bools from fallible ops with their origin
2. Simulate stack operations to track tag movement
3. When a tagged Bool is consumed by if/cond, mark checked
4. When consumed by drop/nip/other, emit warning

Conservative Design

• Only tracks Bools from known fallible builtins (not all Bools)
• If a tagged Bool flows into an unknown user word, assume checked (avoids false positives from cross-word analysis)
• Bools remaining on the stack at word end are assumed returned (escape analysis, same as resource_lint)

Structs

ErrorFlagAnalyzer

Analyzer for unchecked error flags