Rust

'crate' misplaced in path: Reports incorrect use of the literal `crate` in a path.
`#[dbg]` usage: Reports usages of dbg! macro.
`#[derive]` not allowed: Reports `derive` attributes applied to items other than structs, enums, or unions.
`#[inline]` not allowed: Reports `inline` attributes applied to items other than functions or closures.
`#[repr(inttype)]` missing for enum: Reports enums that require a `#[repr(inttype)]` attribute.
`_` on the right-hand side of assignment: Reports invalid use of underscores (`_`) in expressions: they are only allowed on the left-hand side of an assignment.
`async` non-`move` closure with parameters (unsupported): Reports the use of `async` non-`move` closures with parameters for Rust 1.76 or earlier versions that do not support it.
`compile_error!` macro: Highlights `compile_error!()` macro invocation.
`continue`/`break` used outside `loop`/`while`: Reports the use of `break`/`continue` keywords outside `loop`/`while` blocks.
`Copy` type dropped: Reports calls to std::mem::drop with values that derive the Copy trait.
`crate` in paths: Reports `crate` used in paths.
`default` qualifier not allowed: Reports invalid `default` keyword placement.
`extern crate self` missing `as <name>`: Reports `extern crate self` that is not followed by `as <name>`.
`if` condition is constant: Reports if expressions that have true or false constant literal condition and can be simplified.
`impl Trait` not allowed: Reports incorrect use of `impl Trait`.
`impl` member order differs from trait: Checks if members in the impl have a same order as in the trait.
`main` function with generic parameters: Reports `main` functions defined with generic parameters.
`println!` macro can be simplified: Detects usages of println!("") which can be simplified to println!() since from Rust 1.14.0.
`return` can be lifted: Reports if and match statements that can be converted to expressions by lifting a return out.
`return` must have a value: Reports `return;` statements contained in functions whose return type is not `()`.
`self` function parameter not allowed: Reports the use of `self` as a function parameter in case it is not allowed.
`self` in static method: Reports the use of the `self` keyword in static methods.
`self` unavailable in context: Reports the use of `self` in contexts where it is not available.
`self`/`super` misplaced in path: Reports the use of `self` and `super` keywords not at the beginning of the path.
`Sized`/`Unsized` trait implemented explicitly: Reports explicit implementations of the `Sized` and `Unsized` traits.
`thread_rng().gen()` can be replaced with `random()`: Detects usage of thread_rng().gen() that can be replaced with random() from rand crate.
`ToString` should not be implemented directly: Detects implementations of ToString trait which, as its documentation states, shouldn't be implemented directly and Display trait should be implemented instead.
`try!` macro usage: Finds usages of the try! macro which can be replaced with ? operator starting from Rust 1.13.0.
`with` call can be replaced with thread local stable method: Detects usages of LocalKey::with() method that can be replaced with stable thread local methods.
A non-constant value was used in a constant expression: Reports a non-constant value or function call used in a constant expression.
Additional non-auto trait in trait object: Reports trait objects with additional non-auto traits.
Ambiguous method call (experimental): Reports ambiguous method calls (E0034).
Anonymous function parameters not allowed: Reports the use of anonymous parameters in functions that do not allow it.
Approximated constants: Reports hard coded numeric constants such as std::f64::consts::PI.
Attempt to call not a function: When calling somethings, checks that it is function or method.
Attribute error: Reports issues with attributes including misuse, redundancy, formatting errors, invalid entries, outdated syntax, and more.
Attribute without parentheses: Detects incomplete attributes that require parentheses.
Base expression required after `..`: Highlights .
Blocking `sleep` function cannot be used in `async` context: Detects usages of blocking thread::sleep() function in async contexts.
Boolean expression can be simplified: Detects boolean expressions that can be safely simplified like a || true.
Borrow checker errors: Reports basic borrow checker errors.
Both `Copy` and `Drop` implemented: Reports cases where the `Copy` trait is implemented along with `Drop`, which is considered unsafe and currently not allowed in the Rust language.
Char literal empty or too long: Reports char literals which are empty or too long.
Circular modules: Reports circular module declarations with the #path attribute.
Comma-separated trait bounds: Reports trait bounds for a single type that are separated with a comma instead of a `+` sign.
Compiler feature is unavailable: Reports code that uses unavailable compiler features.
Complex pattern in function: Reports incorrect use of patterns in functions.
Const generic argument expression without braces: Reports const generic argument expressions with missing braces.
Dangling `else`: Detects suspiciously looking else if-statements split by new lines.
Default parameter values (unsupported): Reports the use of default parameter values, which are not supported in Rust.
Default type parameters syntax: Report incorrect usage of default type parameters.
Defaults for const parameters not allowed: Reports invalid use of defaults for const parameters.
Deprecated `...` syntax: Reports the use of `...` deprecated syntax.
Derived trait not implemented: Reports members that do not implement the traits being derived.
Detached file: Detects files that are not attached to any Rust module.
Double negation: Detects expressions of the form --x which might be mistook for pre-decrements.
Duplicate definition: Reports duplicate items (such as field declarations, type parameters, etc.).
Duplicate hash key: Reports duplicate keys when creating hash maps.
Duplicate macro pattern: Checks duplicated patterns in macro definitions.
Duplicate trait method parameter name: Checks duplicated parameter names of abstract trait methods.
Dynamic environment capture in `fn`: Reports captures of a dynamic environment in a `fn` item.
Entry point is async: Checks if the entry point of the program was marked as async.
Equality assertion can be simplified: Detect assert!(a == b) (and assert!(a != b)) macro call that can be simplified into assert_eq!(a, b) (or assert_ne!(a, b)).
Experimental inspections: Some unstable experimental checks which are disabled by default.
Explicit call to `drop`: Reports explicit calls to `drop`.
External linter: This inspection runs external linter to check for rustc or clippy errors.
Failed line in test: Reports failed function calls or assertions in tests.
Foreign trait implementation: Reports implementations of foreign traits (traits defined outside the current crate) for arbitrary types.
Format macro error: Reports errors in the use of macros that support formatting.
Forward-declared identifier for parameter with default value: Reports generic parameters with default values that use forward-declared identifiers.
Function cannot be variadic: Reports functions that cannot be declared variadic.
Generic arguments must be specified before the first constraint: Reports generic arguments specified after the first constraint.
Immutable reassigned: Reports format! calls with missing format arguments.
Immutable variable reassigned: Detects immutable bindings reassignments.
Inclusive range without an end bound: Reports inclusive ranges without a specified end bound (`..=b` or `a..=b`).
Incorrect const syntax: Reports incorrect const syntax.
Incorrect function syntax: Reports incorrect function syntax.
Incorrect order of lifetime/type/const parameters: Reports incorrectly ordered lifetime, type, and const parameters.
Incorrect type alias syntax: Reports incorrect type alias syntax.
Incorrect visibility restriction: Reports incorrect visibility restrictions.
Index expression has a wrong type: Checks type of index expression.
Inherent `impl` block not allowed for item: Reports inherent `impl` blocks defined for items other than structs, enums, unions, or trait objects.
Inherent `impl` defined outside type's containing crate: Reports inherent type implementations defined outside the type's original crate.
Inherent `impl` for dyn auto trait: Reports inherent implementations for dynamic auto traits.
Invalid 'break' or 'continue': Reports invalid usages of break and continue in loops.
Invalid `?` usage: Reports incorrect usage of the ? operator.
Invalid `Copy` implementation: Reports invalid `Copy` implementations.
Invalid `Drop` implementation: Reports invalid `Drop` implementations.
Invalid `self` import: Reports invalid `self` imports.
Invalid access of private item: Reports invalid attempts to access private fields or methods.
Invalid crate name: Check if the crate name is valid, namely the crate name must not be empty, and must only contain Unicode alphanumeric or _ (U+005F) characters.
Invalid fields in struct: Reports incorrect field use in struct literals.
Invalid fields in struct or tuple struct pattern: Reports invalid fields in struct and tuple struct patterns.
Invalid label name: Reports labels with invalid names.
Invalid lifetime name: Reports lifetimes with invalid names.
Invalid literal suffix: Reports literals with invalid suffixes.
Invalid macro call: Reports errors when calling macros.
Invalid macro definition: Reports errors in `macro_rules!` definitions.
Invalid macro variable type: Reports invalid fragment specifier of a macro variable.
Invalid place expression: Reports invalid place expressions.
Item cannot be inside another item: Reports structs, enums, macro definitions and traits placed inside other structs, enums, macro definitions or traits.
Lifetime bounds in parentheses: Reports lifetime bounds in parentheses.
Literal out of range: Check if a numerical value is out of the range of the receiver.
Main function not found: Checks if the main function exists in the binary crates.
Manual implementation of `Fn`, `FnMut`, or `FnOnce`: Reports manual implementations of `Fn`, `FnMut`, and `FnOnce` traits.
Match expression can be replaced with a method call: Reports match expressions that can be replaced with a method call.
Misordered generic arguments: Generic arguments were not provided in the same order as the corresponding generic parameters are declared.
Misplaced `...` argument: Reports variadic functions where `...` is not positioned as the last argument.
Missing `dyn` in trait objects: Checks if trait objects are explicitly specified with dyn keyword.
Missing `else`: Detects suspiciously looking if-statements with potentially missing elses.
Missing features: Detects Cargo packages with missing cargo features in some of their dependency packages.
Missing parentheses for chained comparison: Reports chained comparison operators with missing parentheses.
Missing struct field type: Reports struct fields declared without a type.
Missing type for constant: Reports constant declarations with missing types.
Module declared outside mod.rs: Reports module declarations in files other than mod.rs.
Multiple lifetime bounds for trait object: Reports trait objects with multiple lifetime bounds.
Multiple relaxed default bounds for type parameter: Reports type parameters with multiple relaxed default bounds.
Nested `impl Trait` not allowed: Reports the use of nested `impl Trait`.
Nested lifetime quantification: Reports where clauses containing nested quantification over lifetimes, which is not supported.
No boxing for async recursion: Reports recursion used in async functions without boxing.
No file found for module: Reports module declarations with no corresponding file found.
Non-exhaustive match: Checks that match expression is exhaustive, i.e.
Non-existent field access: Reports attempts to access non-existent fields.
Non-inline module declaration missing path attribute: Reports non-inline modules declared inside a block and missing the path attribute.
Non-shorthand field initialization: Reports cases where field initialization shorthand (RFC 1682) can be used.
Non-string ABI literal: Reports non-string ABI literals.
Non-structural-match type used for const generic parameter: Reports the use of non-structural-match types for const generic parameters.
Object type with no traits: Reports trait objects declared without a single trait.
Parameter type with unknown size: Reports function parameters whose types are unknown at compile time.
Proc macro defined outside `proc-macro` crate: Reports the use of #[proc_macro], #[proc_macro_attribute], and #[proc_macro_derive] attributes in non-procedural macro crates.
Public item in proc-macro crate: Reports public items located in the root of a procedural macro crate and not marked with a #[proc_macro], #[proc_macro_attribute], or #[proc_macro_derive] attribute.
Re-export of a private item: Reports private items that were re-exported publicly.
Redundant `::`: Reports redundant ::.
Redundant `else`: Detects else-statements preceded by irrefutable patterns.
Reference dropped: Reports calls to std::mem::drop with a reference instead of an owned value.
Repeated discriminant value: Reports discriminant values that are present more than once in a single enum.
Repeated identifier in pattern: Reports identifiers bound more than once in the same pattern.
Reserved keyword used as an identifier: Reports the use of reserved keywords.
Reserved lifetime name: Reports the use of reserved lifetime names.
Rust 2018 edition violation: Reports the use of keywords reserved in Rust 2018 edition, as well as features unavailable in Rust 2018 edition.
Rust 2024 edition violation: Reports the use of keywords reserved in Rust 2024 edition, as well as features unavailable in Rust 2024 edition.
Struct inheritance (unsupported): Reports struct inheritance, which is not supported in Rust.
Supertrait is not implemented: Reports missing supertrait implementations.
Suspicious assignment: Detects use of the non-existent =*, =! and =- operators that are probably typos.
Trait expected: Reports non-trait items referenced as traits.
Trait implementation issue: Reports errors in trait implementation like "Missing members", "Unknown member", etc.
Trait safety mismatch: Reports mismatches between the safety of a trait's definition and its implementation.
Tuple-like union: Reports union declarations with tuple syntax.
Type checker: The Rust type checker.
Type checker (experimental): The Rust type checker (experimental).
Type does not implement trait: Reports the use of types that do not implement the necessary traits.
Type does not implement trait (experimental): Reports the use of types that do not implement the necessary traits.
Type mismatched the trait's associated type: A type mismatched an associated type of a trait.
Type placeholder used in item signature: Reports the use of type placeholders (_) in an item's signature.
Unclosed text literal: Reports unclosed text literals.
Undeclared label: Reports undeclared labels.
Undeclared lifetime name: Reports undeclared lifetimes.
Union expression fields count: Checks that union expr has exactly one field.
Unlabeled `continue`/`break` in `while` loop condition: Reports the use of `break`/`continue` keywords without labels in `while` loop conditions.
Unlabeled `continue`/`break` in labeled block: Reports the use of unlabeled `break`/`continue` statements inside labeled blocks.
Unnecessary visibility qualifier: Reports unnecessary visibility qualifiers.
Unreachable label: Reports unreachable labels.
Unresolved method: Reports unresolved method references.
Unresolved method (experimental): Reports unresolved method references.
Unresolved path: Reports unresolved path references.
Unresolved path (experimental): Reports unresolved path references.
Unsafe CString pointer: Detects unsafe usage of CString.
Unsafe inherent implementation: Reports inherent implementations marked as unsafe.
Unsafe item in safe context: Reports the use of unsafe items in a safe context.
Unsafe module: Reports modules declared as unsafe.
Unstable item: Reports the use of unstable items.
Unsupported `let` expression: Reports `let` expressions in places where they are unsupported.
Use of `dyn`/`impl Trait` in type parameter bounds: Reports the use of `dyn` and `impl Trait` in type parameter bounds.
Use of increment/decrement operator (unsupported): Reports the use of `++` and `--` operators, which are not supported in Rust.
Variadic parameters for non-C ABI function: Reports C-variadic functions that do not use a compatible calling convention.
Wrong associated type arguments: Checks if correct associated type arguments were used for a type or a trait reference.
Wrong number of arguments: Reports function calls with an incorrect number of arguments.
Wrong number of generic arguments: Checks if the right number of generic arguments was used for a type, trait, function call or method call.
Wrong number of lifetime parameters: Checks if the right number of lifetime parameters was used for a type or trait.
Wrong number of type or const parameters: Checks if an attempted implementation of a trait method or an associated type has the right number of type or const parameters.
Cargo.toml: Sub-group of 10 inspections that provide checks for Cargo.toml
Lints: Sub-group of 21 inspections that provide checks for Lints

Last modified: 18 September 2025