preprocess.rs:107: Language::Yaml/Toml/Json arm is dead code — wildcard _ already matches

[EffortlessSteven]

In crates/diffguard-domain/src/preprocess.rs:107, the match arm:

Language::Yaml | Language::Toml | Language::Json => StringSyntax::CStyle,
// All other languages (C, C++, Java, etc.) use C-style strings
_ => StringSyntax::CStyle,

The wildcard arm _ already covers Yaml, Toml, and Json — the explicit arm is identical dead code. The wildcard comment even says "All other languages" implying it was meant to exclude these.

Fix: Remove the | Language::Yaml | Language::Toml | Language::Json from line 107, leaving only the wildcard arm (or move it above the wildcard if ordering matters for clarity).

[EffortlessSteven]

doc-writer update (work-9811a5e3)

Added missing docstrings to preprocess.rs:

• Preprocessor::new — explains language defaults to Unknown and user should call with_language or set_language to configure
• Preprocessor::reset — clarifies it is for new files, not continuing same-file lines
• Preprocessor::set_language — explains why reset is called (fresh state for new file)
• PreprocessOptions::none/comments_only/strings_only/comments_and_strings — documented what each masks and that tracking still occurs

All public items now have docstrings. Tests pass (cargo test -p diffguard-domain: 12 tests passed).

Note: The redundant match arm at line 107 (Language::Yaml | Language::Toml | Language::Json => StringSyntax::CStyle) was NOT removed — that is the refactor agent responsibility. As doc-writer I documented the existing code as requested.

[EffortlessSteven]

PROVEN Gate: fuzz-agent

Issue: preprocess.rs:107: redundant match arm — Language::Yaml/Toml/Json caught by wildcard

What This Change Does

Removes the dead match arm from in . This arm is unreachable because the wildcard already handles these three variants with identical behavior. The comment above the wildcard is also updated to accurately reflect its coverage.

Fuzz Testing Applicability

Not applicable — This is a mechanical refactor with no input surface.

The method is a pure enum-to-value mapping (). The enum is a fixed set of ~20 variants — not external input that can vary. No file formats, network protocols, CLI arguments, or user-controlled data are processed. The compiler verifies exhaustiveness at compile time, and existing tests verify the mapping.

Files Changed

: Removed dead match arm | Fuzz surface: No — pure enum mapping, compiler-verified exhaustive match

Fuzz Targets

• Targets written: 0
• Input space covered: N/A
• Iterations: N/A

Crashes Found

No crashes found after 0 iterations. No panics, no unexpected errors.

Coverage Assessment

N/A — mechanical refactor. The compiler enforces exhaustiveness and existing tests verify return for YAML/TOML/JSON via the wildcard.

Recommendations

No recommendations — change has no input surface requiring fuzzing. Pure dead code removal with identical behavior guaranteed by the compiler.

[EffortlessSteven]

PROVEN Gate: fuzz-agent

Issue: preprocess.rs:107: redundant match arm — Language::Yaml/Toml/Json caught by wildcard

What This Change Does

Removes the dead Language::Yaml | Language::Toml | Language::Json => StringSyntax::CStyle match arm from string_syntax() in crates/diffguard-domain/src/preprocess.rs:107. This arm is unreachable because the wildcard _ => StringSyntax::CStyle already handles these three variants with identical behavior. The comment above the wildcard is also updated to accurately reflect its coverage.

Fuzz Testing Applicability

Not applicable — This is a mechanical refactor with no input surface.

The string_syntax() method is a pure enum-to-value mapping (Language → StringSyntax). The Language enum is a fixed set of ~20 variants — not external input that can vary. No file formats, network protocols, CLI arguments, or user-controlled data are processed. The compiler verifies exhaustiveness at compile time, and existing tests verify the mapping.

Files Changed

preprocess.rs: Removed dead match arm | Fuzz surface: No — pure enum mapping, compiler-verified exhaustive match

Fuzz Targets

• Targets written: 0
• Input space covered: N/A
• Iterations: N/A

Crashes Found

No crashes found after 0 iterations. No panics, no unexpected errors.

Coverage Assessment

N/A — mechanical refactor. The compiler enforces exhaustiveness and existing tests verify StringSyntax::CStyle return for YAML/TOML/JSON via the wildcard.

Recommendations

No recommendations — change has no input surface requiring fuzzing. Pure dead code removal with identical behavior guaranteed by the compiler.

Proceeding to HARDENING.

[EffortlessSteven]

HARDENED Gate: code-quality-agent

Issue: preprocess.rs:107: Language::Yaml/Toml/Json arm is dead code — wildcard _ already matches

What This Change Does

Removes the redundant explicit match arm from in . These three languages are now handled by the wildcard . The change simplifies the code without changing behavior — Yaml, Toml, and Json all use C-style strings.

Readability Improvements Made

• Fixed doc overindented list item in (lines 9-10). The continuation line had incorrect indentation (10 spaces) which violated clippy's doc_overindented_list_items rule. Fixed by using 2-space indentation for the continuation.

Code Smells Found and Fixed

None — the implementation was already clean. The redundant match arm removal was done correctly:

• The wildcard comment clearly states "All other languages use C-style strings"
• Comments explain the "why" for each language grouping
• Match arms are organized logically by language family

Remaining Issues

No remaining issues in work-9811a5e3 changes.

Note: Pre-existing CI failures in property_tests.rs (type errors, unused variable) and main.rs (dead_code for exit_code_from_i32) are unrelated to this work item — they exist on the broader branch due to work-83475ef5.

Clippy

• Before: 1 error in snapshot_tests_work_9811a5e3.rs (doc overindented list item)
• After: 0 warnings in diffguard-domain crate (cargo clippy -p diffguard-domain --lib --tests)

Format

cargo fmt — clean, no formatting issues in work-9811a5e3 files.

Tests

All 46 work-9811a5e3 tests pass:

• edge_tests_work_9811a5e3: 22 passed
• red_tests_work_9811a5e3: 8 passed
• snapshot_tests_work_9811a5e3: 16 passed

Files Modified

• crates/diffguard-domain/tests/snapshot_tests_work_9811a5e3.rs: Fixed doc overindented list item (2-space indentation for continuation line)

Code is cleaner without changing behavior. Proceeding to deep review.