Error map
E0004: non-exhaustive patterns Rust: error[E0004]: non-exhaustive patterns: `None` not covered
Rust · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (10). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (10)
Rust: error[E0308]: mismatched types — expected `X`, found `Y`
A value’s type doesn’t match what the context expects — common with &str vs String, Option/Result vs plain values, and integer ty…
Rust: error[E0277]: the trait bound `Foo: Display` is not satisfied / `Rc<RefCell<T>>` cannot be sent between threads safely
A type doesn't implement a trait required by a function, macro or generic bound.
Rust: error[E0599]: no method named `push_str` found for struct `Vec<String>` in the current scope
The type doesn't have that method — wrong type, trait not in scope, or missing derive/feature.
Cargo: error: failed to parse manifest — feature `edition2024` is required / lock file version 4 requires `-Znext-lockfile-bump`
Your Cargo is older than the manifest or lockfile requires.
Cargo: Blocking waiting for file lock on package cache / on build directory
Another cargo process (or rust-analyzer/IDE) holds the lock, so this command waits.
Rust: error[E0381]: used binding `x` is possibly-uninitialized
A variable might be read before every code path assigned it.
Cargo: error: failed to select a version for the requirement `serde = "^2.0"` — candidate versions found which didn't match: 1.0.197
Cargo can't find a version of a dependency satisfying the constraints you (or other crates) set.
Cargo: warning: spurious network error (2 tries remaining): [35] SSL connect error / error: failed to download from `https://index.crates.io/...`
Cargo couldn't reach crates.io (network, proxy, TLS or DNS issues).
Cargo: error: package `home v0.5.9` cannot be built because it requires rustc 1.81 or newer, while the currently active rustc version is 1.78.0
A dependency's minimum supported Rust version (MSRV) is higher than your toolchain.
rustup: error: toolchain 'nightly-x86_64-unknown-linux-gnu' is not installed / error: no override and no default toolchain set
rustup can't find the toolchain requested by `rust-toolchain.toml`, an override, or no default is set.
Two steps away (24)
AttributeError: 'X' object has no attribute 'y'
You accessed an attribute or method that doesn’t exist on that object type.
java.lang.ClassCastException: class A cannot be cast to class B
An object was cast to a type it isn’t.
TS7016: Could not find a declaration file for module 'x'. 'x.js' implicitly has an 'any' type.
The JavaScript package has no TypeScript types bundled and no @types package installed.
Rust: error[E0061]: this function takes 2 arguments but 1 argument was supplied
A call has too few or too many arguments for the function signature.
Rust: error[E0282]: type annotations needed for `Vec<_>` / consider giving `x` an explicit type
The compiler can't infer a type from the available information.
Rust: error[E0038]: the trait `Shape` cannot be made into an object (not dyn compatible)
You used `dyn Trait` for a trait whose methods aren't object-safe (generic methods, `Self` returns, `Sized`).
Rust: error[E0425]: cannot find value `x` in this scope
The identifier (variable, function, constant) isn't defined where it's used.
Rust: error[E0432]: unresolved import `crate::utils` — maybe a missing crate `utils`?
A `use` path doesn't point to an existing module, crate or item.
Rust: error[E0369]: binary operation `+` cannot be applied to type `Foo` / cannot add `&str` to `&str`
An operator (`+`, `==`, `
Rust: error[E0507]: cannot move out of `self.name` which is behind a shared reference
You tried to take ownership of a value through a reference (or from a Vec/Option behind `&`).
Rust: error[E0373]: closure may outlive the current function, but it borrows `v`, which is owned by the current function
A closure borrowing a local is passed somewhere that may outlive it (thread::spawn, tokio::spawn, returned closures).
Rust: error[E0384]: cannot assign twice to immutable variable `x`
You reassigned a variable declared without `mut`.
Rust: error[E0499]: cannot borrow `v` as mutable more than once at a time
Two mutable references to the same value were alive at once, which Rust forbids.
Rust: error[E0505]: cannot move out of `s` because it is borrowed
You moved a value while a reference to it was still in use.
Rust: error[E0106]: missing lifetime specifier — this function's return type contains a borrowed value, but the signature does not say which one of `x`'s 2 lifetimes it is borrowed from
The compiler can't infer which input reference the returned/stored reference is tied to.
Unmet dependencies / E: Unable to correct problems, you have held broken packages
apt can’t find a set of package versions that satisfies all dependencies — usually mixed repositories or a package from another r…
Rust: error[E0433]: failed to resolve: use of undeclared type `HashMap`
A path starts with a name that isn't in scope (a type or module you didn't import).
Rust: error[E0015]: cannot call non-const function `String::from` in constants
A `const`/`static` initializer used something that can't run at compile time.
ssh: connect to host x port 22: Connection refused
The server answered, but nothing is listening on the SSH port — sshd isn’t running, it uses another port, or a firewall actively…
ssh: connect to host x port 22: Connection timed out
SSH packets get no reply — a firewall/security group drops them, the server is off, or the IP is wrong.
ping: google.com: Temporary failure in name resolution
The Linux host can’t resolve domain names — no working DNS server is configured or reachable.
Rust: error[E0658]: use of unstable library feature `let_chains` / `#![feature]` may not be used on the stable release channel
Your code uses a nightly-only feature on the stable toolchain.
Cargo: error: failed to run custom build command for `openssl-sys v0.9.99` — Could not find directory of OpenSSL installation / pkg-config not found
The `openssl-sys` crate can't find OpenSSL headers/libraries (or pkg-config) to link against.
Rust: error: linker `cc` not found — note: No such file or directory (os error 2)
Rust needs a C linker (gcc/clang) to produce executables, and none is installed.
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