---

description: Fix Rust build errors, borrow checker issues, and dependency problems incrementally. Invokes the rust-build-resolver agent for minimal, surgical fixes.

Rust Build and Fix

This command invokes the rust-build-resolver agent to incrementally fix Rust build errors with minimal changes.

What This Command Does

1. Run Diagnostics: Execute cargo check, cargo clippy, cargo fmt --check
2. Parse Errors: Identify error codes and affected files
3. Fix Incrementally: One error at a time
4. Verify Each Fix: Re-run cargo check after each change
5. Report Summary: Show what was fixed and what remains

When to Use

Use /rust-build when:

• cargo build or cargo check fails with errors
• cargo clippy reports warnings
• Borrow checker or lifetime errors block compilation
• Cargo dependency resolution fails
• After pulling changes that break the build

Diagnostic Commands Run

# Primary build check
cargo check 2>&1

# Lints and suggestions
cargo clippy -- -D warnings 2>&1

# Formatting check
cargo fmt --check 2>&1

# Dependency issues
cargo tree --duplicates

# Security audit (if available)
if command -v cargo-audit >/dev/null; then cargo audit; else echo "cargo-audit not installed"; fi

Example Session

User: /rust-build

Agent:
# Rust Build Resolution

## Initial Diagnostics

```bash
$ cargo check
error[E0502]: cannot borrow `map` as mutable because it is also borrowed as immutable
  --> src/service/cache.rs:25:5
error[E0308]: mismatched types
  --> src/handler/api.rs:42:12
error[E0425]: cannot find value `db` in this scope
  --> src/handler/api.rs:58:9
```

Errors found: 3

## Fix 1: Borrow Checker Error

File: src/service/cache.rs:25
Error: E0502 — cannot borrow `map` as mutable because also borrowed as immutable
Cause: Immutable borrow still active during mutable insert

```rust
// Changed: restructured to end immutable borrow before mutable access
if !map.contains_key("key") {
    map.insert("key".into(), default);
}
```

```bash
$ cargo check
# 2 errors remaining
```

## Fix 2: Type Mismatch

File: src/handler/api.rs:42
Error: E0308 — mismatched types: expected `usize`, found `&str`

```rust
// Changed
let count = params.get("count");
// To
let count: usize = params.get("count")
    .and_then(|s| s.parse().ok())
    .unwrap_or(0);
```

```bash
$ cargo check
# 1 error remaining
```

## Fix 3: Unresolved Name

File: src/handler/api.rs:58
Error: E0425 — cannot find value `db` in this scope
Cause: Missing import

```rust
// Added
use crate::db;
```

```bash
$ cargo check
# Build successful!
```

## Final Verification

```bash
$ cargo clippy -- -D warnings
# No warnings

$ cargo test
running 6 tests
test service::cache::tests::test_insert ... ok
test service::cache::tests::test_get ... ok
test handler::api::tests::test_parse_count ... ok
test handler::api::tests::test_missing_count ... ok
test handler::api::tests::test_db_import ... ok
test handler::api::tests::test_response ... ok

test result: ok. 6 passed; 0 failed; 0 ignored
```

## Summary

| Metric | Count |
|--------|-------|
| Build errors fixed | 3 |
| Clippy warnings fixed | 0 |
| Files modified | 2 |
| Remaining issues | 0 |

Build Status: SUCCESS

Common Errors Fixed

Error	Typical Fix
cannot borrow as mutable	Restructure to end immutable borrow first; clone only if justified
does not live long enough	Use owned type or add lifetime annotation
cannot move out of	Restructure to take ownership; clone only as last resort
mismatched types	Add .into(), as, or explicit conversion
trait X not implemented	Add #[derive(Trait)] or implement manually
unresolved import	Add to Cargo.toml or fix use path
cannot find value	Add import or fix path

Fix Strategy

1. Build errors first - Code must compile
2. Clippy warnings second - Fix suspicious constructs
3. Formatting third - cargo fmt compliance
4. One fix at a time - Verify each change
5. Minimal changes - Don't refactor, just fix

Stop Conditions

The agent will stop and report if:

• Same error persists after 3 attempts
• Fix introduces more errors
• Requires architectural changes
• Borrow checker error requires redesigning data ownership

Related Commands

• /rust-test - Run tests after build succeeds
• /rust-review - Review code quality
• verification-loop skill - Full verification loop

Related

• Agent: agents/rust-build-resolver.md
• Skill: skills/rust-patterns/