rust-build

Command View source on GitHub

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

Run Diagnostics: Execute cargo check, cargo clippy, cargo fmt --check
Parse Errors: Identify error codes and affected files
Fix Incrementally: One error at a time
Verify Each Fix: Re-run cargo check after each change
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

Build errors first - Code must compile
Clippy warnings second - Fix suspicious constructs
Formatting third - cargo fmt compliance
One fix at a time - Verify each change
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

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

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

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