Rust cargo build compilation failure

What this failure means

The Rust compiler rejected the crate with one or more hard errors — type mismatches, borrow checker violations, unresolved imports, or missing trait implementations. The binary cannot be produced until all errors are resolved.

Symptoms

Faultline looks for one or more of these log fragments:

error[E
error: could not compile
aborting due to previous error
aborting due to
undefined reference to
multiple definition of

Diagnosis

rustc emits structured errors in the form error[EXXXX]: <description> followed by source locations. Every error is deterministic and must be resolved before the build can succeed.

Common error classes:

• E0308 — mismatched types: a value of one type is used where a different type is expected. Check function signatures and generic bounds.
• E0382 — borrow of moved value / E0502 — conflicting borrows: the borrow checker rejected unsafe aliasing or use-after-move. Review ownership and lifetime annotations.
• E0412 / E0433 — unresolved name or module: a type, function, or crate is referenced that is not in scope. Add the correct use statement or add the crate to Cargo.toml.
• E0277 — trait not implemented: a concrete type is used where a trait bound is required but the type does not implement the trait. Implement the trait or use a type adapter.
• E0599 — method not found: the method does not exist for this type, or a required feature flag is not enabled.

The compiler always names the exact file, line, and column. Start there.

Fix steps

1. Run cargo build locally to reproduce the exact error output:

   cargo build 2>&1 | head -60
   

2. Read the first error and its suggestion. rustc often suggests the exact fix (e.g., help: consider borrowing here: &val).

3. For E0308 type mismatch: check the types on both sides of the assignment or call and add an explicit conversion or change the type.

4. For E0382/E0502 borrow errors: restructure to avoid overlapping borrows, use .clone() where ownership transfer is undesirable, or annotate lifetimes explicitly.

5. For E0412/E0433 unresolved path: verify the crate is listed in Cargo.toml and the use path matches the module tree:

   cargo tree | grep <crate-name>
   

6. For E0277 trait not implemented: implement the missing trait for your type, or add a #[derive(...)] macro if the trait supports it.

7. Run cargo check after each fix for fast feedback without producing a binary:

   cargo check
   

Validation

• cargo build exits zero with no error[E lines in output.
• cargo check exits zero.
• Confirm the CI build step exits zero.

Why it matters

Rust compilation errors are fully deterministic and hard failures — rustc rejects the crate entirely, producing no binary. All downstream test and deploy steps are blocked. The compiler’s structured error codes and source-location hints make the fix unambiguous once the error is understood.

Prevention

• Run cargo check as a pre-push hook for fast local feedback.
• Enable rust-analyzer or another LSP in your editor so errors surface on save, not at CI time.
• Ensure rustfmt and clippy are run in CI before cargo build so style and lint issues don’t mask compile errors.
• Pin the Rust toolchain with rust-toolchain.toml to prevent version drift between local and CI environments.

Try it locally

cargo build
cargo check
cargo build

How Faultline detects it

Use faultline explain cargo-compile-error to see the full playbook.

faultline analyze build.log
faultline explain cargo-compile-error

Generated from playbooks/bundled/log/build/cargo-compile-error.yaml. Do not edit directly.