fix: handle multi-line function signatures in contract extraction

[chubes4]

Summary

Fixes two extraction gaps that caused wrong test generation for functions with multi-line signatures (#818).

Problem

The contract extractor operated per-line:

• Params: grammar regex only captured the first line → functions with 3+ params across lines got called with wrong argument count
• Return type: detect_return_shape only read the fn line → return type on a continuation line was invisible (Unit instead of Result)

// This function's params and return type were lost:
pub fn complex_function(
    root: &Path,           // ← only this line was seen
    files: &[PathBuf],     // ← lost
    config: &Config,       // ← lost
) -> Result<(), Error> {   // ← return type lost too

Fix

• join_declaration_lines() — concatenates raw lines from fn through { into a single string
• extract_params_from_declaration() — re-parses the full param list with balanced-paren tracking (handles HashMap<String, Vec<u8>> correctly)
• detect_return_shape now receives the joined declaration, so return types on continuation lines are found
• is_async detection also uses the full declaration

Tests

9 unit tests covering:

• Single-line signatures (unchanged behavior)
• Multi-line params
• Return type on next line
• Nested generics in params
• No params
• Self receiver

[homeboy-ci]

Homeboy Results — homeboy

Audit

Failure Digest

Audit Failure Digest

• Alignment score: 0.921
• Severity counts: info: 1, unknown: 3, warning: 1
• Outliers in current run: 3
• Parsed outlier entries: 3
• Drift increased: yes
• New findings since baseline: 2
  1. structural — File has 16 top-level items (threshold: 15) (structural::src/core/engine/contract_extract.rs::HighItemCount)
  2. test_coverage — Method 'extract_contracts_from_grammar' has no corresponding test (expected 'test_extract_contracts_from_grammar') (test_coverage::src/core/engine/contract_extract.rs::MissingTestMethod)
• Top actionable findings:
  1. src/core/engine/contract_extract.rs — high_item_count — File has 16 top-level items (threshold: 15)
  2. src/core/engine/contract_extract.rs — missing_test_method — Method 'extract_contracts_from_grammar' has no corresponding test (expected 'test_extract_contracts_from_grammar')
  3. src/commands/docs.rs — outlier — (outlier)
  4. tests/commands/deploy_test.rs — outlier — (outlier)
  5. src/core/engine/undo/snapshot.rs — outlier — (outlier)

All parsed audit findings (5)

1. **src/core/engine/contract_extract.rs** — high_item_count — File has 16 top-level items (threshold: 15)
2. **src/core/engine/contract_extract.rs** — missing_test_method — Method 'extract_contracts_from_grammar' has no corresponding test (expected 'test_extract_contracts_from_grammar')
3. **src/commands/docs.rs** — outlier — (outlier)
4. **tests/commands/deploy_test.rs** — outlier — (outlier)
5. **src/core/engine/undo/snapshot.rs** — outlier — (outlier)

- Full audit log: https://github.com/Extra-Chill/homeboy/actions/runs/23418444285

Autofixability classification

• Overall: auto_fixable
• Autofix enabled: yes
• Autofix attempted this run: no
• Auto-fixable failed commands:
  • audit
• Failed commands with available automated fixes:
  • audit

Machine-readable artifacts

• homeboy-lint-summary.json
• homeboy-test-failures.json
• homeboy-audit-summary.json
• homeboy-autofixability.json

⚡ Scope: changed files only

❌ audit (changed files only)

Auto-refactor

ℹ️ Autofix enabled, but no fixable file changes were produced

Failure Digest

Autofixability classification

• Overall: human_needed
• Autofix enabled: yes
• Autofix attempted this run: no
• Human-needed failed commands:
  • refactor --from all

Machine-readable artifacts

• homeboy-lint-summary.json
• homeboy-test-failures.json
• homeboy-audit-summary.json
• homeboy-autofixability.json

⚡ Scope: changed files only

❌ refactor --from all

Tooling versions

• Homeboy CLI: homeboy 0.85.3+a28d0e8
• Extension: rust from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: unknown
• Action: Extra-Chill/homeboy-action@v2

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Homeboy Action v1