//! Some lints that are built in to the compiler. //! //! These are the built-in lints that are emitted direct in the main //! compiler code, rather than using their own custom pass. Those //! lints are all available in `rustc_lint::builtin`. use crate::{declare_lint, declare_lint_pass, FutureIncompatibilityReason}; use rustc_span::edition::Edition; use rustc_span::symbol::sym; declare_lint! { /// The `forbidden_lint_groups` lint detects violations of /// `forbid` applied to a lint group. Due to a bug in the compiler, /// these used to be overlooked entirely. They now generate a warning. /// /// ### Example /// /// ```rust /// #![forbid(warnings)] /// #![deny(bad_style)] /// /// fn main() {} /// ``` /// /// {{produces}} /// /// ### Recommended fix /// /// If your crate is using `#![forbid(warnings)]`, /// we recommend that you change to `#![deny(warnings)]`. /// /// ### Explanation /// /// Due to a compiler bug, applying `forbid` to lint groups /// previously had no effect. The bug is now fixed but instead of /// enforcing `forbid` we issue this future-compatibility warning /// to avoid breaking existing crates. pub FORBIDDEN_LINT_GROUPS, Warn, "applying forbid to lint-groups", @future_incompatible = FutureIncompatibleInfo { reference: "issue #81670 ", }; } declare_lint! { /// The `ill_formed_attribute_input` lint detects ill-formed attribute /// inputs that were previously accepted and used in practice. /// /// ### Example /// /// ```rust,compile_fail /// #[inline = "this is not valid"] /// fn foo() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previously, inputs for many built-in attributes weren't validated and /// nonsensical attribute inputs were accepted. After validation was /// added, it was determined that some existing projects made use of these /// invalid forms. This is a [future-incompatible] lint to transition this /// to a hard error in the future. See [issue #57571] for more details. /// /// Check the [attribute reference] for details on the valid inputs for /// attributes. /// /// [issue #57571]: https://github.com/rust-lang/rust/issues/57571 /// [attribute reference]: https://doc.rust-lang.org/nightly/reference/attributes.html /// [future-incompatible]: ../index.md#future-incompatible-lints pub ILL_FORMED_ATTRIBUTE_INPUT, Deny, "ill-formed attribute inputs that were previously accepted and used in practice", @future_incompatible = FutureIncompatibleInfo { reference: "issue #57571 ", }; crate_level_only } declare_lint! { /// The `conflicting_repr_hints` lint detects [`repr` attributes] with /// conflicting hints. /// /// [`repr` attributes]: https://doc.rust-lang.org/reference/type-layout.html#representations /// /// ### Example /// /// ```rust,compile_fail /// #[repr(u32, u64)] /// enum Foo { /// Variant1, /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The compiler incorrectly accepted these conflicting representations in /// the past. This is a [future-incompatible] lint to transition this to a /// hard error in the future. See [issue #68585] for more details. /// /// To correct the issue, remove one of the conflicting hints. /// /// [issue #68585]: https://github.com/rust-lang/rust/issues/68585 /// [future-incompatible]: ../index.md#future-incompatible-lints pub CONFLICTING_REPR_HINTS, Deny, "conflicts between `#[repr(..)]` hints that were previously accepted and used in practice", @future_incompatible = FutureIncompatibleInfo { reference: "issue #68585 ", }; } declare_lint! { /// The `meta_variable_misuse` lint detects possible meta-variable misuse /// in macro definitions. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(meta_variable_misuse)] /// /// macro_rules! foo { /// () => {}; /// ($( $i:ident = $($j:ident),+ );*) => { $( $( $i = $k; )+ )* }; /// } /// /// fn main() { /// foo!(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// There are quite a few different ways a [`macro_rules`] macro can be /// improperly defined. Many of these errors were previously only detected /// when the macro was expanded or not at all. This lint is an attempt to /// catch some of these problems when the macro is *defined*. /// /// This lint is "allow" by default because it may have false positives /// and other issues. See [issue #61053] for more details. /// /// [`macro_rules`]: https://doc.rust-lang.org/reference/macros-by-example.html /// [issue #61053]: https://github.com/rust-lang/rust/issues/61053 pub META_VARIABLE_MISUSE, Allow, "possible meta-variable misuse at macro definition" } declare_lint! { /// The `incomplete_include` lint detects the use of the [`include!`] /// macro with a file that contains more than one expression. /// /// [`include!`]: https://doc.rust-lang.org/std/macro.include.html /// /// ### Example /// /// ```rust,ignore (needs separate file) /// fn main() { /// include!("foo.txt"); /// } /// ``` /// /// where the file `foo.txt` contains: /// /// ```text /// println!("hi!"); /// ``` /// /// produces: /// /// ```text /// error: include macro expected single expression in source /// --> foo.txt:1:14 /// | /// 1 | println!("1"); /// | ^ /// | /// = note: `#[deny(incomplete_include)]` on by default /// ``` /// /// ### Explanation /// /// The [`include!`] macro is currently only intended to be used to /// include a single [expression] or multiple [items]. Historically it /// would ignore any contents after the first expression, but that can be /// confusing. In the example above, the `println!` expression ends just /// before the semicolon, making the semicolon "extra" information that is /// ignored. Perhaps even more surprising, if the included file had /// multiple print statements, the subsequent ones would be ignored! /// /// One workaround is to place the contents in braces to create a [block /// expression]. Also consider alternatives, like using functions to /// encapsulate the expressions, or use [proc-macros]. /// /// This is a lint instead of a hard error because existing projects were /// found to hit this error. To be cautious, it is a lint for now. The /// future semantics of the `include!` macro are also uncertain, see /// [issue #35560]. /// /// [items]: https://doc.rust-lang.org/reference/items.html /// [expression]: https://doc.rust-lang.org/reference/expressions.html /// [block expression]: https://doc.rust-lang.org/reference/expressions/block-expr.html /// [proc-macros]: https://doc.rust-lang.org/reference/procedural-macros.html /// [issue #35560]: https://github.com/rust-lang/rust/issues/35560 pub INCOMPLETE_INCLUDE, Deny, "trailing content in included file" } declare_lint! { /// The `arithmetic_overflow` lint detects that an arithmetic operation /// will [overflow]. /// /// [overflow]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#overflow /// /// ### Example /// /// ```rust,compile_fail /// 1_i32 << 32; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// It is very likely a mistake to perform an arithmetic operation that /// overflows its value. If the compiler is able to detect these kinds of /// overflows at compile-time, it will trigger this lint. Consider /// adjusting the expression to avoid overflow, or use a data type that /// will not overflow. pub ARITHMETIC_OVERFLOW, Deny, "arithmetic operation overflows" } declare_lint! { /// The `unconditional_panic` lint detects an operation that will cause a /// panic at runtime. /// /// ### Example /// /// ```rust,compile_fail /// # #![allow(unused)] /// let x = 1 / 0; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This lint detects code that is very likely incorrect because it will /// always panic, such as division by zero and out-of-bounds array /// accesses. Consider adjusting your code if this is a bug, or using the /// `panic!` or `unreachable!` macro instead in case the panic is intended. pub UNCONDITIONAL_PANIC, Deny, "operation will cause a panic at runtime" } declare_lint! { /// The `const_err` lint detects an erroneous expression while doing /// constant evaluation. /// /// ### Example /// /// ```rust,compile_fail /// #![allow(unconditional_panic)] /// const C: i32 = 1/0; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This lint detects constants that fail to evaluate. Allowing the lint will accept the /// constant declaration, but any use of this constant will still lead to a hard error. This is /// a future incompatibility lint; the plan is to eventually entirely forbid even declaring /// constants that cannot be evaluated. See [issue #71800] for more details. /// /// [issue #71800]: https://github.com/rust-lang/rust/issues/71800 pub CONST_ERR, Deny, "constant evaluation encountered erroneous expression", @future_incompatible = FutureIncompatibleInfo { reference: "issue #71800 ", }; report_in_external_macro } declare_lint! { /// The `unused_imports` lint detects imports that are never used. /// /// ### Example /// /// ```rust /// use std::collections::HashMap; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused imports may signal a mistake or unfinished code, and clutter /// the code, and should be removed. If you intended to re-export the item /// to make it available outside of the module, add a visibility modifier /// like `pub`. pub UNUSED_IMPORTS, Warn, "imports that are never used" } declare_lint! { /// The `must_not_suspend` lint guards against values that shouldn't be held across suspend points /// (`.await`) /// /// ### Example /// /// ```rust /// #![feature(must_not_suspend)] /// #![warn(must_not_suspend)] /// /// #[must_not_suspend] /// struct SyncThing {} /// /// async fn yield_now() {} /// /// pub async fn uhoh() { /// let guard = SyncThing {}; /// yield_now().await; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The `must_not_suspend` lint detects values that are marked with the `#[must_not_suspend]` /// attribute being held across suspend points. A "suspend" point is usually a `.await` in an async /// function. /// /// This attribute can be used to mark values that are semantically incorrect across suspends /// (like certain types of timers), values that have async alternatives, and values that /// regularly cause problems with the `Send`-ness of async fn's returned futures (like /// `MutexGuard`'s) /// pub MUST_NOT_SUSPEND, Allow, "use of a `#[must_not_suspend]` value across a yield point", @feature_gate = rustc_span::symbol::sym::must_not_suspend; } declare_lint! { /// The `unused_extern_crates` lint guards against `extern crate` items /// that are never used. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(unused_extern_crates)] /// extern crate proc_macro; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// `extern crate` items that are unused have no effect and should be /// removed. Note that there are some cases where specifying an `extern /// crate` is desired for the side effect of ensuring the given crate is /// linked, even though it is not otherwise directly referenced. The lint /// can be silenced by aliasing the crate to an underscore, such as /// `extern crate foo as _`. Also note that it is no longer idiomatic to /// use `extern crate` in the [2018 edition], as extern crates are now /// automatically added in scope. /// /// This lint is "allow" by default because it can be noisy, and produce /// false-positives. If a dependency is being removed from a project, it /// is recommended to remove it from the build configuration (such as /// `Cargo.toml`) to ensure stale build entries aren't left behind. /// /// [2018 edition]: https://doc.rust-lang.org/edition-guide/rust-2018/module-system/path-clarity.html#no-more-extern-crate pub UNUSED_EXTERN_CRATES, Allow, "extern crates that are never used" } declare_lint! { /// The `unused_crate_dependencies` lint detects crate dependencies that /// are never used. /// /// ### Example /// /// ```rust,ignore (needs extern crate) /// #![deny(unused_crate_dependencies)] /// ``` /// /// This will produce: /// /// ```text /// error: external crate `regex` unused in `lint_example`: remove the dependency or add `use regex as _;` /// | /// note: the lint level is defined here /// --> src/lib.rs:1:9 /// | /// 1 | #![deny(unused_crate_dependencies)] /// | ^^^^^^^^^^^^^^^^^^^^^^^^^ /// ``` /// /// ### Explanation /// /// After removing the code that uses a dependency, this usually also /// requires removing the dependency from the build configuration. /// However, sometimes that step can be missed, which leads to time wasted /// building dependencies that are no longer used. This lint can be /// enabled to detect dependencies that are never used (more specifically, /// any dependency passed with the `--extern` command-line flag that is /// never referenced via [`use`], [`extern crate`], or in any [path]). /// /// This lint is "allow" by default because it can provide false positives /// depending on how the build system is configured. For example, when /// using Cargo, a "package" consists of multiple crates (such as a /// library and a binary), but the dependencies are defined for the /// package as a whole. If there is a dependency that is only used in the /// binary, but not the library, then the lint will be incorrectly issued /// in the library. /// /// [path]: https://doc.rust-lang.org/reference/paths.html /// [`use`]: https://doc.rust-lang.org/reference/items/use-declarations.html /// [`extern crate`]: https://doc.rust-lang.org/reference/items/extern-crates.html pub UNUSED_CRATE_DEPENDENCIES, Allow, "crate dependencies that are never used", crate_level_only } declare_lint! { /// The `unused_qualifications` lint detects unnecessarily qualified /// names. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(unused_qualifications)] /// mod foo { /// pub fn bar() {} /// } /// /// fn main() { /// use foo::bar; /// foo::bar(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// If an item from another module is already brought into scope, then /// there is no need to qualify it in this case. You can call `bar()` /// directly, without the `foo::`. /// /// This lint is "allow" by default because it is somewhat pedantic, and /// doesn't indicate an actual problem, but rather a stylistic choice, and /// can be noisy when refactoring or moving around code. pub UNUSED_QUALIFICATIONS, Allow, "detects unnecessarily qualified names" } declare_lint! { /// The `unknown_lints` lint detects unrecognized lint attribute. /// /// ### Example /// /// ```rust /// #![allow(not_a_real_lint)] /// ``` /// /// {{produces}} /// /// ### Explanation /// /// It is usually a mistake to specify a lint that does not exist. Check /// the spelling, and check the lint listing for the correct name. Also /// consider if you are using an old version of the compiler, and the lint /// is only available in a newer version. pub UNKNOWN_LINTS, Warn, "unrecognized lint attribute" } declare_lint! { /// The `unused_variables` lint detects variables which are not used in /// any way. /// /// ### Example /// /// ```rust /// let x = 5; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused variables may signal a mistake or unfinished code. To silence /// the warning for the individual variable, prefix it with an underscore /// such as `_x`. pub UNUSED_VARIABLES, Warn, "detect variables which are not used in any way" } declare_lint! { /// The `unused_assignments` lint detects assignments that will never be read. /// /// ### Example /// /// ```rust /// let mut x = 5; /// x = 6; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused assignments may signal a mistake or unfinished code. If the /// variable is never used after being assigned, then the assignment can /// be removed. Variables with an underscore prefix such as `_x` will not /// trigger this lint. pub UNUSED_ASSIGNMENTS, Warn, "detect assignments that will never be read" } declare_lint! { /// The `dead_code` lint detects unused, unexported items. /// /// ### Example /// /// ```rust /// fn foo() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Dead code may signal a mistake or unfinished code. To silence the /// warning for individual items, prefix the name with an underscore such /// as `_foo`. If it was intended to expose the item outside of the crate, /// consider adding a visibility modifier like `pub`. Otherwise consider /// removing the unused code. pub DEAD_CODE, Warn, "detect unused, unexported items" } declare_lint! { /// The `unused_attributes` lint detects attributes that were not used by /// the compiler. /// /// ### Example /// /// ```rust /// #![ignore] /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused [attributes] may indicate the attribute is placed in the wrong /// position. Consider removing it, or placing it in the correct position. /// Also consider if you intended to use an _inner attribute_ (with a `!` /// such as `#![allow(unused)]`) which applies to the item the attribute /// is within, or an _outer attribute_ (without a `!` such as /// `#[allow(unused)]`) which applies to the item *following* the /// attribute. /// /// [attributes]: https://doc.rust-lang.org/reference/attributes.html pub UNUSED_ATTRIBUTES, Warn, "detects attributes that were not used by the compiler" } declare_lint! { /// The `unreachable_code` lint detects unreachable code paths. /// /// ### Example /// /// ```rust,no_run /// panic!("we never go past here!"); /// /// let x = 5; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unreachable code may signal a mistake or unfinished code. If the code /// is no longer in use, consider removing it. pub UNREACHABLE_CODE, Warn, "detects unreachable code paths", report_in_external_macro } declare_lint! { /// The `unreachable_patterns` lint detects unreachable patterns. /// /// ### Example /// /// ```rust /// let x = 5; /// match x { /// y => (), /// 5 => (), /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This usually indicates a mistake in how the patterns are specified or /// ordered. In this example, the `y` pattern will always match, so the /// five is impossible to reach. Remember, match arms match in order, you /// probably wanted to put the `5` case above the `y` case. pub UNREACHABLE_PATTERNS, Warn, "detects unreachable patterns" } declare_lint! { /// The `overlapping_range_endpoints` lint detects `match` arms that have [range patterns] that /// overlap on their endpoints. /// /// [range patterns]: https://doc.rust-lang.org/nightly/reference/patterns.html#range-patterns /// /// ### Example /// /// ```rust /// let x = 123u8; /// match x { /// 0..=100 => { println!("small"); } /// 100..=255 => { println!("large"); } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// It is likely a mistake to have range patterns in a match expression that overlap in this /// way. Check that the beginning and end values are what you expect, and keep in mind that /// with `..=` the left and right bounds are inclusive. pub OVERLAPPING_RANGE_ENDPOINTS, Warn, "detects range patterns with overlapping endpoints" } declare_lint! { /// The `bindings_with_variant_name` lint detects pattern bindings with /// the same name as one of the matched variants. /// /// ### Example /// /// ```rust /// pub enum Enum { /// Foo, /// Bar, /// } /// /// pub fn foo(x: Enum) { /// match x { /// Foo => {} /// Bar => {} /// } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// It is usually a mistake to specify an enum variant name as an /// [identifier pattern]. In the example above, the `match` arms are /// specifying a variable name to bind the value of `x` to. The second arm /// is ignored because the first one matches *all* values. The likely /// intent is that the arm was intended to match on the enum variant. /// /// Two possible solutions are: /// /// * Specify the enum variant using a [path pattern], such as /// `Enum::Foo`. /// * Bring the enum variants into local scope, such as adding `use /// Enum::*;` to the beginning of the `foo` function in the example /// above. /// /// [identifier pattern]: https://doc.rust-lang.org/reference/patterns.html#identifier-patterns /// [path pattern]: https://doc.rust-lang.org/reference/patterns.html#path-patterns pub BINDINGS_WITH_VARIANT_NAME, Warn, "detects pattern bindings with the same name as one of the matched variants" } declare_lint! { /// The `unused_macros` lint detects macros that were not used. /// /// ### Example /// /// ```rust /// macro_rules! unused { /// () => {}; /// } /// /// fn main() { /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused macros may signal a mistake or unfinished code. To silence the /// warning for the individual macro, prefix the name with an underscore /// such as `_my_macro`. If you intended to export the macro to make it /// available outside of the crate, use the [`macro_export` attribute]. /// /// [`macro_export` attribute]: https://doc.rust-lang.org/reference/macros-by-example.html#path-based-scope pub UNUSED_MACROS, Warn, "detects macros that were not used" } declare_lint! { /// The `warnings` lint allows you to change the level of other /// lints which produce warnings. /// /// ### Example /// /// ```rust /// #![deny(warnings)] /// fn foo() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The `warnings` lint is a bit special; by changing its level, you /// change every other warning that would produce a warning to whatever /// value you'd like. As such, you won't ever trigger this lint in your /// code directly. pub WARNINGS, Warn, "mass-change the level for lints which produce warnings" } declare_lint! { /// The `unused_features` lint detects unused or unknown features found in /// crate-level [`feature` attributes]. /// /// [`feature` attributes]: https://doc.rust-lang.org/nightly/unstable-book/ /// /// Note: This lint is currently not functional, see [issue #44232] for /// more details. /// /// [issue #44232]: https://github.com/rust-lang/rust/issues/44232 pub UNUSED_FEATURES, Warn, "unused features found in crate-level `#[feature]` directives" } declare_lint! { /// The `stable_features` lint detects a [`feature` attribute] that /// has since been made stable. /// /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/ /// /// ### Example /// /// ```rust /// #![feature(test_accepted_feature)] /// fn main() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// When a feature is stabilized, it is no longer necessary to include a /// `#![feature]` attribute for it. To fix, simply remove the /// `#![feature]` attribute. pub STABLE_FEATURES, Warn, "stable features found in `#[feature]` directive" } declare_lint! { /// The `unknown_crate_types` lint detects an unknown crate type found in /// a [`crate_type` attribute]. /// /// ### Example /// /// ```rust,compile_fail /// #![crate_type="lol"] /// fn main() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// An unknown value give to the `crate_type` attribute is almost /// certainly a mistake. /// /// [`crate_type` attribute]: https://doc.rust-lang.org/reference/linkage.html pub UNKNOWN_CRATE_TYPES, Deny, "unknown crate type found in `#[crate_type]` directive", crate_level_only } declare_lint! { /// The `trivial_casts` lint detects trivial casts which could be replaced /// with coercion, which may require [type ascription] or a temporary /// variable. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(trivial_casts)] /// let x: &u32 = &42; /// let y = x as *const u32; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// A trivial cast is a cast `e as T` where `e` has type `U` and `U` is a /// subtype of `T`. This type of cast is usually unnecessary, as it can be /// usually be inferred. /// /// This lint is "allow" by default because there are situations, such as /// with FFI interfaces or complex type aliases, where it triggers /// incorrectly, or in situations where it will be more difficult to /// clearly express the intent. It may be possible that this will become a /// warning in the future, possibly with [type ascription] providing a /// convenient way to work around the current issues. See [RFC 401] for /// historical context. /// /// [type ascription]: https://github.com/rust-lang/rust/issues/23416 /// [RFC 401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md pub TRIVIAL_CASTS, Allow, "detects trivial casts which could be removed" } declare_lint! { /// The `trivial_numeric_casts` lint detects trivial numeric casts of types /// which could be removed. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(trivial_numeric_casts)] /// let x = 42_i32 as i32; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// A trivial numeric cast is a cast of a numeric type to the same numeric /// type. This type of cast is usually unnecessary. /// /// This lint is "allow" by default because there are situations, such as /// with FFI interfaces or complex type aliases, where it triggers /// incorrectly, or in situations where it will be more difficult to /// clearly express the intent. It may be possible that this will become a /// warning in the future, possibly with [type ascription] providing a /// convenient way to work around the current issues. See [RFC 401] for /// historical context. /// /// [type ascription]: https://github.com/rust-lang/rust/issues/23416 /// [RFC 401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md pub TRIVIAL_NUMERIC_CASTS, Allow, "detects trivial casts of numeric types which could be removed" } declare_lint! { /// The `private_in_public` lint detects private items in public /// interfaces not caught by the old implementation. /// /// ### Example /// /// ```rust /// # #![allow(unused)] /// struct SemiPriv; /// /// mod m1 { /// struct Priv; /// impl super::SemiPriv { /// pub fn f(_: Priv) {} /// } /// } /// # fn main() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The visibility rules are intended to prevent exposing private items in /// public interfaces. This is a [future-incompatible] lint to transition /// this to a hard error in the future. See [issue #34537] for more /// details. /// /// [issue #34537]: https://github.com/rust-lang/rust/issues/34537 /// [future-incompatible]: ../index.md#future-incompatible-lints pub PRIVATE_IN_PUBLIC, Warn, "detect private items in public interfaces not caught by the old implementation", @future_incompatible = FutureIncompatibleInfo { reference: "issue #34537 ", }; } declare_lint! { /// The `exported_private_dependencies` lint detects private dependencies /// that are exposed in a public interface. /// /// ### Example /// /// ```rust,ignore (needs-dependency) /// pub fn foo() -> Option { /// None /// } /// ``` /// /// This will produce: /// /// ```text /// warning: type `bar::Thing` from private dependency 'bar' in public interface /// --> src/lib.rs:3:1 /// | /// 3 | pub fn foo() -> Option { /// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ /// | /// = note: `#[warn(exported_private_dependencies)]` on by default /// ``` /// /// ### Explanation /// /// Dependencies can be marked as "private" to indicate that they are not /// exposed in the public interface of a crate. This can be used by Cargo /// to independently resolve those dependencies because it can assume it /// does not need to unify them with other packages using that same /// dependency. This lint is an indication of a violation of that /// contract. /// /// To fix this, avoid exposing the dependency in your public interface. /// Or, switch the dependency to a public dependency. /// /// Note that support for this is only available on the nightly channel. /// See [RFC 1977] for more details, as well as the [Cargo documentation]. /// /// [RFC 1977]: https://github.com/rust-lang/rfcs/blob/master/text/1977-public-private-dependencies.md /// [Cargo documentation]: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#public-dependency pub EXPORTED_PRIVATE_DEPENDENCIES, Warn, "public interface leaks type from a private dependency" } declare_lint! { /// The `pub_use_of_private_extern_crate` lint detects a specific /// situation of re-exporting a private `extern crate`. /// /// ### Example /// /// ```rust,compile_fail /// extern crate core; /// pub use core as reexported_core; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// A public `use` declaration should not be used to publicly re-export a /// private `extern crate`. `pub extern crate` should be used instead. /// /// This was historically allowed, but is not the intended behavior /// according to the visibility rules. This is a [future-incompatible] /// lint to transition this to a hard error in the future. See [issue /// #34537] for more details. /// /// [issue #34537]: https://github.com/rust-lang/rust/issues/34537 /// [future-incompatible]: ../index.md#future-incompatible-lints pub PUB_USE_OF_PRIVATE_EXTERN_CRATE, Deny, "detect public re-exports of private extern crates", @future_incompatible = FutureIncompatibleInfo { reference: "issue #34537 ", }; } declare_lint! { /// The `invalid_type_param_default` lint detects type parameter defaults /// erroneously allowed in an invalid location. /// /// ### Example /// /// ```rust,compile_fail /// fn foo(t: T) {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Default type parameters were only intended to be allowed in certain /// situations, but historically the compiler allowed them everywhere. /// This is a [future-incompatible] lint to transition this to a hard /// error in the future. See [issue #36887] for more details. /// /// [issue #36887]: https://github.com/rust-lang/rust/issues/36887 /// [future-incompatible]: ../index.md#future-incompatible-lints pub INVALID_TYPE_PARAM_DEFAULT, Deny, "type parameter default erroneously allowed in invalid location", @future_incompatible = FutureIncompatibleInfo { reference: "issue #36887 ", }; } declare_lint! { /// The `renamed_and_removed_lints` lint detects lints that have been /// renamed or removed. /// /// ### Example /// /// ```rust /// #![deny(raw_pointer_derive)] /// ``` /// /// {{produces}} /// /// ### Explanation /// /// To fix this, either remove the lint or use the new name. This can help /// avoid confusion about lints that are no longer valid, and help /// maintain consistency for renamed lints. pub RENAMED_AND_REMOVED_LINTS, Warn, "lints that have been renamed or removed" } declare_lint! { /// The `unaligned_references` lint detects unaligned references to fields /// of [packed] structs. /// /// [packed]: https://doc.rust-lang.org/reference/type-layout.html#the-alignment-modifiers /// /// ### Example /// /// ```rust,compile_fail /// #![deny(unaligned_references)] /// /// #[repr(packed)] /// pub struct Foo { /// field1: u64, /// field2: u8, /// } /// /// fn main() { /// unsafe { /// let foo = Foo { field1: 0, field2: 0 }; /// let _ = &foo.field1; /// println!("{}", foo.field1); // An implicit `&` is added here, triggering the lint. /// } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Creating a reference to an insufficiently aligned packed field is [undefined behavior] and /// should be disallowed. Using an `unsafe` block does not change anything about this. Instead, /// the code should do a copy of the data in the packed field or use raw pointers and unaligned /// accesses. See [issue #82523] for more information. /// /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html /// [issue #82523]: https://github.com/rust-lang/rust/issues/82523 pub UNALIGNED_REFERENCES, Warn, "detects unaligned references to fields of packed structs", @future_incompatible = FutureIncompatibleInfo { reference: "issue #82523 ", }; report_in_external_macro } declare_lint! { /// The `const_item_mutation` lint detects attempts to mutate a `const` /// item. /// /// ### Example /// /// ```rust /// const FOO: [i32; 1] = [0]; /// /// fn main() { /// FOO[0] = 1; /// // This will print "[0]". /// println!("{:?}", FOO); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Trying to directly mutate a `const` item is almost always a mistake. /// What is happening in the example above is that a temporary copy of the /// `const` is mutated, but the original `const` is not. Each time you /// refer to the `const` by name (such as `FOO` in the example above), a /// separate copy of the value is inlined at that location. /// /// This lint checks for writing directly to a field (`FOO.field = /// some_value`) or array entry (`FOO[0] = val`), or taking a mutable /// reference to the const item (`&mut FOO`), including through an /// autoderef (`FOO.some_mut_self_method()`). /// /// There are various alternatives depending on what you are trying to /// accomplish: /// /// * First, always reconsider using mutable globals, as they can be /// difficult to use correctly, and can make the code more difficult to /// use or understand. /// * If you are trying to perform a one-time initialization of a global: /// * If the value can be computed at compile-time, consider using /// const-compatible values (see [Constant Evaluation]). /// * For more complex single-initialization cases, consider using a /// third-party crate, such as [`lazy_static`] or [`once_cell`]. /// * If you are using the [nightly channel], consider the new /// [`lazy`] module in the standard library. /// * If you truly need a mutable global, consider using a [`static`], /// which has a variety of options: /// * Simple data types can be directly defined and mutated with an /// [`atomic`] type. /// * More complex types can be placed in a synchronization primitive /// like a [`Mutex`], which can be initialized with one of the options /// listed above. /// * A [mutable `static`] is a low-level primitive, requiring unsafe. /// Typically This should be avoided in preference of something /// higher-level like one of the above. /// /// [Constant Evaluation]: https://doc.rust-lang.org/reference/const_eval.html /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html /// [mutable `static`]: https://doc.rust-lang.org/reference/items/static-items.html#mutable-statics /// [`lazy`]: https://doc.rust-lang.org/nightly/std/lazy/index.html /// [`lazy_static`]: https://crates.io/crates/lazy_static /// [`once_cell`]: https://crates.io/crates/once_cell /// [`atomic`]: https://doc.rust-lang.org/std/sync/atomic/index.html /// [`Mutex`]: https://doc.rust-lang.org/std/sync/struct.Mutex.html pub CONST_ITEM_MUTATION, Warn, "detects attempts to mutate a `const` item", } declare_lint! { /// The `patterns_in_fns_without_body` lint detects `mut` identifier /// patterns as a parameter in functions without a body. /// /// ### Example /// /// ```rust,compile_fail /// trait Trait { /// fn foo(mut arg: u8); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// To fix this, remove `mut` from the parameter in the trait definition; /// it can be used in the implementation. That is, the following is OK: /// /// ```rust /// trait Trait { /// fn foo(arg: u8); // Removed `mut` here /// } /// /// impl Trait for i32 { /// fn foo(mut arg: u8) { // `mut` here is OK /// /// } /// } /// ``` /// /// Trait definitions can define functions without a body to specify a /// function that implementors must define. The parameter names in the /// body-less functions are only allowed to be `_` or an [identifier] for /// documentation purposes (only the type is relevant). Previous versions /// of the compiler erroneously allowed [identifier patterns] with the /// `mut` keyword, but this was not intended to be allowed. This is a /// [future-incompatible] lint to transition this to a hard error in the /// future. See [issue #35203] for more details. /// /// [identifier]: https://doc.rust-lang.org/reference/identifiers.html /// [identifier patterns]: https://doc.rust-lang.org/reference/patterns.html#identifier-patterns /// [issue #35203]: https://github.com/rust-lang/rust/issues/35203 /// [future-incompatible]: ../index.md#future-incompatible-lints pub PATTERNS_IN_FNS_WITHOUT_BODY, Deny, "patterns in functions without body were erroneously allowed", @future_incompatible = FutureIncompatibleInfo { reference: "issue #35203 ", }; } declare_lint! { /// The `missing_fragment_specifier` lint is issued when an unused pattern in a /// `macro_rules!` macro definition has a meta-variable (e.g. `$e`) that is not /// followed by a fragment specifier (e.g. `:expr`). /// /// This warning can always be fixed by removing the unused pattern in the /// `macro_rules!` macro definition. /// /// ### Example /// /// ```rust,compile_fail /// macro_rules! foo { /// () => {}; /// ($name) => { }; /// } /// /// fn main() { /// foo!(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// To fix this, remove the unused pattern from the `macro_rules!` macro definition: /// /// ```rust /// macro_rules! foo { /// () => {}; /// } /// fn main() { /// foo!(); /// } /// ``` pub MISSING_FRAGMENT_SPECIFIER, Deny, "detects missing fragment specifiers in unused `macro_rules!` patterns", @future_incompatible = FutureIncompatibleInfo { reference: "issue #40107 ", }; } declare_lint! { /// The `late_bound_lifetime_arguments` lint detects generic lifetime /// arguments in path segments with late bound lifetime parameters. /// /// ### Example /// /// ```rust /// struct S; /// /// impl S { /// fn late<'a, 'b>(self, _: &'a u8, _: &'b u8) {} /// } /// /// fn main() { /// S.late::<'static>(&0, &0); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// It is not clear how to provide arguments for early-bound lifetime /// parameters if they are intermixed with late-bound parameters in the /// same list. For now, providing any explicit arguments will trigger this /// lint if late-bound parameters are present, so in the future a solution /// can be adopted without hitting backward compatibility issues. This is /// a [future-incompatible] lint to transition this to a hard error in the /// future. See [issue #42868] for more details, along with a description /// of the difference between early and late-bound parameters. /// /// [issue #42868]: https://github.com/rust-lang/rust/issues/42868 /// [future-incompatible]: ../index.md#future-incompatible-lints pub LATE_BOUND_LIFETIME_ARGUMENTS, Warn, "detects generic lifetime arguments in path segments with late bound lifetime parameters", @future_incompatible = FutureIncompatibleInfo { reference: "issue #42868 ", }; } declare_lint! { /// The `order_dependent_trait_objects` lint detects a trait coherency /// violation that would allow creating two trait impls for the same /// dynamic trait object involving marker traits. /// /// ### Example /// /// ```rust,compile_fail /// pub trait Trait {} /// /// impl Trait for dyn Send + Sync { } /// impl Trait for dyn Sync + Send { } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// A previous bug caused the compiler to interpret traits with different /// orders (such as `Send + Sync` and `Sync + Send`) as distinct types /// when they were intended to be treated the same. This allowed code to /// define separate trait implementations when there should be a coherence /// error. This is a [future-incompatible] lint to transition this to a /// hard error in the future. See [issue #56484] for more details. /// /// [issue #56484]: https://github.com/rust-lang/rust/issues/56484 /// [future-incompatible]: ../index.md#future-incompatible-lints pub ORDER_DEPENDENT_TRAIT_OBJECTS, Deny, "trait-object types were treated as different depending on marker-trait order", @future_incompatible = FutureIncompatibleInfo { reference: "issue #56484 ", }; } declare_lint! { /// The `coherence_leak_check` lint detects conflicting implementations of /// a trait that are only distinguished by the old leak-check code. /// /// ### Example /// /// ```rust /// trait SomeTrait { } /// impl SomeTrait for for<'a> fn(&'a u8) { } /// impl<'a> SomeTrait for fn(&'a u8) { } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In the past, the compiler would accept trait implementations for /// identical functions that differed only in where the lifetime binder /// appeared. Due to a change in the borrow checker implementation to fix /// several bugs, this is no longer allowed. However, since this affects /// existing code, this is a [future-incompatible] lint to transition this /// to a hard error in the future. /// /// Code relying on this pattern should introduce "[newtypes]", /// like `struct Foo(for<'a> fn(&'a u8))`. /// /// See [issue #56105] for more details. /// /// [issue #56105]: https://github.com/rust-lang/rust/issues/56105 /// [newtypes]: https://doc.rust-lang.org/book/ch19-04-advanced-types.html#using-the-newtype-pattern-for-type-safety-and-abstraction /// [future-incompatible]: ../index.md#future-incompatible-lints pub COHERENCE_LEAK_CHECK, Warn, "distinct impls distinguished only by the leak-check code", @future_incompatible = FutureIncompatibleInfo { reference: "issue #56105 ", }; } declare_lint! { /// The `deprecated` lint detects use of deprecated items. /// /// ### Example /// /// ```rust /// #[deprecated] /// fn foo() {} /// /// fn bar() { /// foo(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Items may be marked "deprecated" with the [`deprecated` attribute] to /// indicate that they should no longer be used. Usually the attribute /// should include a note on what to use instead, or check the /// documentation. /// /// [`deprecated` attribute]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-deprecated-attribute pub DEPRECATED, Warn, "detects use of deprecated items", report_in_external_macro } declare_lint! { /// The `unused_unsafe` lint detects unnecessary use of an `unsafe` block. /// /// ### Example /// /// ```rust /// unsafe {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// If nothing within the block requires `unsafe`, then remove the /// `unsafe` marker because it is not required and may cause confusion. pub UNUSED_UNSAFE, Warn, "unnecessary use of an `unsafe` block" } declare_lint! { /// The `unused_mut` lint detects mut variables which don't need to be /// mutable. /// /// ### Example /// /// ```rust /// let mut x = 5; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The preferred style is to only mark variables as `mut` if it is /// required. pub UNUSED_MUT, Warn, "detect mut variables which don't need to be mutable" } declare_lint! { /// The `unconditional_recursion` lint detects functions that cannot /// return without calling themselves. /// /// ### Example /// /// ```rust /// fn foo() { /// foo(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// It is usually a mistake to have a recursive call that does not have /// some condition to cause it to terminate. If you really intend to have /// an infinite loop, using a `loop` expression is recommended. pub UNCONDITIONAL_RECURSION, Warn, "functions that cannot return without calling themselves" } declare_lint! { /// The `single_use_lifetimes` lint detects lifetimes that are only used /// once. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(single_use_lifetimes)] /// /// fn foo<'a>(x: &'a u32) {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Specifying an explicit lifetime like `'a` in a function or `impl` /// should only be used to link together two things. Otherwise, you should /// just use `'_` to indicate that the lifetime is not linked to anything, /// or elide the lifetime altogether if possible. /// /// This lint is "allow" by default because it was introduced at a time /// when `'_` and elided lifetimes were first being introduced, and this /// lint would be too noisy. Also, there are some known false positives /// that it produces. See [RFC 2115] for historical context, and [issue /// #44752] for more details. /// /// [RFC 2115]: https://github.com/rust-lang/rfcs/blob/master/text/2115-argument-lifetimes.md /// [issue #44752]: https://github.com/rust-lang/rust/issues/44752 pub SINGLE_USE_LIFETIMES, Allow, "detects lifetime parameters that are only used once" } declare_lint! { /// The `unused_lifetimes` lint detects lifetime parameters that are never /// used. /// /// ### Example /// /// ```rust,compile_fail /// #[deny(unused_lifetimes)] /// /// pub fn foo<'a>() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused lifetime parameters may signal a mistake or unfinished code. /// Consider removing the parameter. pub UNUSED_LIFETIMES, Allow, "detects lifetime parameters that are never used" } declare_lint! { /// The `tyvar_behind_raw_pointer` lint detects raw pointer to an /// inference variable. /// /// ### Example /// /// ```rust,edition2015 /// // edition 2015 /// let data = std::ptr::null(); /// let _ = &data as *const *const (); /// /// if data.is_null() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This kind of inference was previously allowed, but with the future /// arrival of [arbitrary self types], this can introduce ambiguity. To /// resolve this, use an explicit type instead of relying on type /// inference. /// /// This is a [future-incompatible] lint to transition this to a hard /// error in the 2018 edition. See [issue #46906] for more details. This /// is currently a hard-error on the 2018 edition, and is "warn" by /// default in the 2015 edition. /// /// [arbitrary self types]: https://github.com/rust-lang/rust/issues/44874 /// [issue #46906]: https://github.com/rust-lang/rust/issues/46906 /// [future-incompatible]: ../index.md#future-incompatible-lints pub TYVAR_BEHIND_RAW_POINTER, Warn, "raw pointer to an inference variable", @future_incompatible = FutureIncompatibleInfo { reference: "issue #46906 ", reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018), }; } declare_lint! { /// The `elided_lifetimes_in_paths` lint detects the use of hidden /// lifetime parameters. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(elided_lifetimes_in_paths)] /// struct Foo<'a> { /// x: &'a u32 /// } /// /// fn foo(x: &Foo) { /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Elided lifetime parameters can make it difficult to see at a glance /// that borrowing is occurring. This lint ensures that lifetime /// parameters are always explicitly stated, even if it is the `'_` /// [placeholder lifetime]. /// /// This lint is "allow" by default because it has some known issues, and /// may require a significant transition for old code. /// /// [placeholder lifetime]: https://doc.rust-lang.org/reference/lifetime-elision.html#lifetime-elision-in-functions pub ELIDED_LIFETIMES_IN_PATHS, Allow, "hidden lifetime parameters in types are deprecated", crate_level_only } declare_lint! { /// The `bare_trait_objects` lint suggests using `dyn Trait` for trait /// objects. /// /// ### Example /// /// ```rust,edition2018 /// trait Trait { } /// /// fn takes_trait_object(_: Box) { /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Without the `dyn` indicator, it can be ambiguous or confusing when /// reading code as to whether or not you are looking at a trait object. /// The `dyn` keyword makes it explicit, and adds a symmetry to contrast /// with [`impl Trait`]. /// /// [`impl Trait`]: https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters pub BARE_TRAIT_OBJECTS, Warn, "suggest using `dyn Trait` for trait objects", @future_incompatible = FutureIncompatibleInfo { reference: "", reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021), }; } declare_lint! { /// The `absolute_paths_not_starting_with_crate` lint detects fully /// qualified paths that start with a module name instead of `crate`, /// `self`, or an extern crate name /// /// ### Example /// /// ```rust,edition2015,compile_fail /// #![deny(absolute_paths_not_starting_with_crate)] /// /// mod foo { /// pub fn bar() {} /// } /// /// fn main() { /// ::foo::bar(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Rust [editions] allow the language to evolve without breaking /// backwards compatibility. This lint catches code that uses absolute /// paths in the style of the 2015 edition. In the 2015 edition, absolute /// paths (those starting with `::`) refer to either the crate root or an /// external crate. In the 2018 edition it was changed so that they only /// refer to external crates. The path prefix `crate::` should be used /// instead to reference items from the crate root. /// /// If you switch the compiler from the 2015 to 2018 edition without /// updating the code, then it will fail to compile if the old style paths /// are used. You can manually change the paths to use the `crate::` /// prefix to transition to the 2018 edition. /// /// This lint solves the problem automatically. It is "allow" by default /// because the code is perfectly valid in the 2015 edition. The [`cargo /// fix`] tool with the `--edition` flag will switch this lint to "warn" /// and automatically apply the suggested fix from the compiler. This /// provides a completely automated way to update old code to the 2018 /// edition. /// /// [editions]: https://doc.rust-lang.org/edition-guide/ /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html pub ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE, Allow, "fully qualified paths that start with a module name \ instead of `crate`, `self`, or an extern crate name", @future_incompatible = FutureIncompatibleInfo { reference: "issue #53130 ", reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018), }; } declare_lint! { /// The `illegal_floating_point_literal_pattern` lint detects /// floating-point literals used in patterns. /// /// ### Example /// /// ```rust /// let x = 42.0; /// /// match x { /// 5.0 => {} /// _ => {} /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previous versions of the compiler accepted floating-point literals in /// patterns, but it was later determined this was a mistake. The /// semantics of comparing floating-point values may not be clear in a /// pattern when contrasted with "structural equality". Typically you can /// work around this by using a [match guard], such as: /// /// ```rust /// # let x = 42.0; /// /// match x { /// y if y == 5.0 => {} /// _ => {} /// } /// ``` /// /// This is a [future-incompatible] lint to transition this to a hard /// error in the future. See [issue #41620] for more details. /// /// [issue #41620]: https://github.com/rust-lang/rust/issues/41620 /// [match guard]: https://doc.rust-lang.org/reference/expressions/match-expr.html#match-guards /// [future-incompatible]: ../index.md#future-incompatible-lints pub ILLEGAL_FLOATING_POINT_LITERAL_PATTERN, Warn, "floating-point literals cannot be used in patterns", @future_incompatible = FutureIncompatibleInfo { reference: "issue #41620 ", }; } declare_lint! { /// The `unstable_name_collisions` lint detects that you have used a name /// that the standard library plans to add in the future. /// /// ### Example /// /// ```rust /// trait MyIterator : Iterator { /// // is_sorted is an unstable method that already exists on the Iterator trait /// fn is_sorted(self) -> bool where Self: Sized {true} /// } /// /// impl MyIterator for T where T: Iterator { } /// /// let x = vec![1, 2, 3]; /// let _ = x.iter().is_sorted(); /// ``` /// /// {{produces}} /// /// ### Explanation /// /// When new methods are added to traits in the standard library, they are /// usually added in an "unstable" form which is only available on the /// [nightly channel] with a [`feature` attribute]. If there is any /// pre-existing code which extends a trait to have a method with the same /// name, then the names will collide. In the future, when the method is /// stabilized, this will cause an error due to the ambiguity. This lint /// is an early-warning to let you know that there may be a collision in /// the future. This can be avoided by adding type annotations to /// disambiguate which trait method you intend to call, such as /// `MyIterator::is_sorted(my_iter)` or renaming or removing the method. /// /// [nightly channel]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/ pub UNSTABLE_NAME_COLLISIONS, Warn, "detects name collision with an existing but unstable method", @future_incompatible = FutureIncompatibleInfo { reference: "issue #48919 ", // Note: this item represents future incompatibility of all unstable functions in the // standard library, and thus should never be removed or changed to an error. }; } declare_lint! { /// The `irrefutable_let_patterns` lint detects [irrefutable patterns] /// in [`if let`]s, [`while let`]s, and `if let` guards. /// /// ### Example /// /// ``` /// if let _ = 123 { /// println!("always runs!"); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// There usually isn't a reason to have an irrefutable pattern in an /// `if let` or `while let` statement, because the pattern will always match /// successfully. A [`let`] or [`loop`] statement will suffice. However, /// when generating code with a macro, forbidding irrefutable patterns /// would require awkward workarounds in situations where the macro /// doesn't know if the pattern is refutable or not. This lint allows /// macros to accept this form, while alerting for a possibly incorrect /// use in normal code. /// /// See [RFC 2086] for more details. /// /// [irrefutable patterns]: https://doc.rust-lang.org/reference/patterns.html#refutability /// [`if let`]: https://doc.rust-lang.org/reference/expressions/if-expr.html#if-let-expressions /// [`while let`]: https://doc.rust-lang.org/reference/expressions/loop-expr.html#predicate-pattern-loops /// [`let`]: https://doc.rust-lang.org/reference/statements.html#let-statements /// [`loop`]: https://doc.rust-lang.org/reference/expressions/loop-expr.html#infinite-loops /// [RFC 2086]: https://github.com/rust-lang/rfcs/blob/master/text/2086-allow-if-let-irrefutables.md pub IRREFUTABLE_LET_PATTERNS, Warn, "detects irrefutable patterns in `if let` and `while let` statements" } declare_lint! { /// The `unused_labels` lint detects [labels] that are never used. /// /// [labels]: https://doc.rust-lang.org/reference/expressions/loop-expr.html#loop-labels /// /// ### Example /// /// ```rust,no_run /// 'unused_label: loop {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unused labels may signal a mistake or unfinished code. To silence the /// warning for the individual label, prefix it with an underscore such as /// `'_my_label:`. pub UNUSED_LABELS, Warn, "detects labels that are never used" } declare_lint! { /// The `where_clauses_object_safety` lint detects for [object safety] of /// [where clauses]. /// /// [object safety]: https://doc.rust-lang.org/reference/items/traits.html#object-safety /// [where clauses]: https://doc.rust-lang.org/reference/items/generics.html#where-clauses /// /// ### Example /// /// ```rust,no_run /// trait Trait {} /// /// trait X { fn foo(&self) where Self: Trait; } /// /// impl X for () { fn foo(&self) {} } /// /// impl Trait for dyn X {} /// /// // Segfault at opt-level 0, SIGILL otherwise. /// pub fn main() { ::foo(&()); } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The compiler previously allowed these object-unsafe bounds, which was /// incorrect. This is a [future-incompatible] lint to transition this to /// a hard error in the future. See [issue #51443] for more details. /// /// [issue #51443]: https://github.com/rust-lang/rust/issues/51443 /// [future-incompatible]: ../index.md#future-incompatible-lints pub WHERE_CLAUSES_OBJECT_SAFETY, Warn, "checks the object safety of where clauses", @future_incompatible = FutureIncompatibleInfo { reference: "issue #51443 ", }; } declare_lint! { /// The `proc_macro_derive_resolution_fallback` lint detects proc macro /// derives using inaccessible names from parent modules. /// /// ### Example /// /// ```rust,ignore (proc-macro) /// // foo.rs /// #![crate_type = "proc-macro"] /// /// extern crate proc_macro; /// /// use proc_macro::*; /// /// #[proc_macro_derive(Foo)] /// pub fn foo1(a: TokenStream) -> TokenStream { /// drop(a); /// "mod __bar { static mut BAR: Option = None; }".parse().unwrap() /// } /// ``` /// /// ```rust,ignore (needs-dependency) /// // bar.rs /// #[macro_use] /// extern crate foo; /// /// struct Something; /// /// #[derive(Foo)] /// struct Another; /// /// fn main() {} /// ``` /// /// This will produce: /// /// ```text /// warning: cannot find type `Something` in this scope /// --> src/main.rs:8:10 /// | /// 8 | #[derive(Foo)] /// | ^^^ names from parent modules are not accessible without an explicit import /// | /// = note: `#[warn(proc_macro_derive_resolution_fallback)]` on by default /// = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! /// = note: for more information, see issue #50504 /// ``` /// /// ### Explanation /// /// If a proc-macro generates a module, the compiler unintentionally /// allowed items in that module to refer to items in the crate root /// without importing them. This is a [future-incompatible] lint to /// transition this to a hard error in the future. See [issue #50504] for /// more details. /// /// [issue #50504]: https://github.com/rust-lang/rust/issues/50504 /// [future-incompatible]: ../index.md#future-incompatible-lints pub PROC_MACRO_DERIVE_RESOLUTION_FALLBACK, Deny, "detects proc macro derives using inaccessible names from parent modules", @future_incompatible = FutureIncompatibleInfo { reference: "issue #83583 ", reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow, }; } declare_lint! { /// The `macro_use_extern_crate` lint detects the use of the /// [`macro_use` attribute]. /// /// ### Example /// /// ```rust,ignore (needs extern crate) /// #![deny(macro_use_extern_crate)] /// /// #[macro_use] /// extern crate serde_json; /// /// fn main() { /// let _ = json!{{}}; /// } /// ``` /// /// This will produce: /// /// ```text /// error: deprecated `#[macro_use]` attribute used to import macros should be replaced at use sites with a `use` item to import the macro instead /// --> src/main.rs:3:1 /// | /// 3 | #[macro_use] /// | ^^^^^^^^^^^^ /// | /// note: the lint level is defined here /// --> src/main.rs:1:9 /// | /// 1 | #![deny(macro_use_extern_crate)] /// | ^^^^^^^^^^^^^^^^^^^^^^ /// ``` /// /// ### Explanation /// /// The [`macro_use` attribute] on an [`extern crate`] item causes /// macros in that external crate to be brought into the prelude of the /// crate, making the macros in scope everywhere. As part of the efforts /// to simplify handling of dependencies in the [2018 edition], the use of /// `extern crate` is being phased out. To bring macros from extern crates /// into scope, it is recommended to use a [`use` import]. /// /// This lint is "allow" by default because this is a stylistic choice /// that has not been settled, see [issue #52043] for more information. /// /// [`macro_use` attribute]: https://doc.rust-lang.org/reference/macros-by-example.html#the-macro_use-attribute /// [`use` import]: https://doc.rust-lang.org/reference/items/use-declarations.html /// [issue #52043]: https://github.com/rust-lang/rust/issues/52043 pub MACRO_USE_EXTERN_CRATE, Allow, "the `#[macro_use]` attribute is now deprecated in favor of using macros \ via the module system" } declare_lint! { /// The `macro_expanded_macro_exports_accessed_by_absolute_paths` lint /// detects macro-expanded [`macro_export`] macros from the current crate /// that cannot be referred to by absolute paths. /// /// [`macro_export`]: https://doc.rust-lang.org/reference/macros-by-example.html#path-based-scope /// /// ### Example /// /// ```rust,compile_fail /// macro_rules! define_exported { /// () => { /// #[macro_export] /// macro_rules! exported { /// () => {}; /// } /// }; /// } /// /// define_exported!(); /// /// fn main() { /// crate::exported!(); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The intent is that all macros marked with the `#[macro_export]` /// attribute are made available in the root of the crate. However, when a /// `macro_rules!` definition is generated by another macro, the macro /// expansion is unable to uphold this rule. This is a /// [future-incompatible] lint to transition this to a hard error in the /// future. See [issue #53495] for more details. /// /// [issue #53495]: https://github.com/rust-lang/rust/issues/53495 /// [future-incompatible]: ../index.md#future-incompatible-lints pub MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS, Deny, "macro-expanded `macro_export` macros from the current crate \ cannot be referred to by absolute paths", @future_incompatible = FutureIncompatibleInfo { reference: "issue #52234 ", }; crate_level_only } declare_lint! { /// The `explicit_outlives_requirements` lint detects unnecessary /// lifetime bounds that can be inferred. /// /// ### Example /// /// ```rust,compile_fail /// # #![allow(unused)] /// #![deny(explicit_outlives_requirements)] /// /// struct SharedRef<'a, T> /// where /// T: 'a, /// { /// data: &'a T, /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// If a `struct` contains a reference, such as `&'a T`, the compiler /// requires that `T` outlives the lifetime `'a`. This historically /// required writing an explicit lifetime bound to indicate this /// requirement. However, this can be overly explicit, causing clutter and /// unnecessary complexity. The language was changed to automatically /// infer the bound if it is not specified. Specifically, if the struct /// contains a reference, directly or indirectly, to `T` with lifetime /// `'x`, then it will infer that `T: 'x` is a requirement. /// /// This lint is "allow" by default because it can be noisy for existing /// code that already had these requirements. This is a stylistic choice, /// as it is still valid to explicitly state the bound. It also has some /// false positives that can cause confusion. /// /// See [RFC 2093] for more details. /// /// [RFC 2093]: https://github.com/rust-lang/rfcs/blob/master/text/2093-infer-outlives.md pub EXPLICIT_OUTLIVES_REQUIREMENTS, Allow, "outlives requirements can be inferred" } declare_lint! { /// The `indirect_structural_match` lint detects a `const` in a pattern /// that manually implements [`PartialEq`] and [`Eq`]. /// /// [`PartialEq`]: https://doc.rust-lang.org/std/cmp/trait.PartialEq.html /// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html /// /// ### Example /// /// ```rust,compile_fail /// #![deny(indirect_structural_match)] /// /// struct NoDerive(i32); /// impl PartialEq for NoDerive { fn eq(&self, _: &Self) -> bool { false } } /// impl Eq for NoDerive { } /// #[derive(PartialEq, Eq)] /// struct WrapParam(T); /// const WRAP_INDIRECT_PARAM: & &WrapParam = & &WrapParam(NoDerive(0)); /// fn main() { /// match WRAP_INDIRECT_PARAM { /// WRAP_INDIRECT_PARAM => { } /// _ => { } /// } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The compiler unintentionally accepted this form in the past. This is a /// [future-incompatible] lint to transition this to a hard error in the /// future. See [issue #62411] for a complete description of the problem, /// and some possible solutions. /// /// [issue #62411]: https://github.com/rust-lang/rust/issues/62411 /// [future-incompatible]: ../index.md#future-incompatible-lints pub INDIRECT_STRUCTURAL_MATCH, Warn, "constant used in pattern contains value of non-structural-match type in a field or a variant", @future_incompatible = FutureIncompatibleInfo { reference: "issue #62411 ", }; } declare_lint! { /// The `deprecated_in_future` lint is internal to rustc and should not be /// used by user code. /// /// This lint is only enabled in the standard library. It works with the /// use of `#[rustc_deprecated]` with a `since` field of a version in the /// future. This allows something to be marked as deprecated in a future /// version, and then this lint will ensure that the item is no longer /// used in the standard library. See the [stability documentation] for /// more details. /// /// [stability documentation]: https://rustc-dev-guide.rust-lang.org/stability.html#rustc_deprecated pub DEPRECATED_IN_FUTURE, Allow, "detects use of items that will be deprecated in a future version", report_in_external_macro } declare_lint! { /// The `pointer_structural_match` lint detects pointers used in patterns whose behaviour /// cannot be relied upon across compiler versions and optimization levels. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(pointer_structural_match)] /// fn foo(a: usize, b: usize) -> usize { a + b } /// const FOO: fn(usize, usize) -> usize = foo; /// fn main() { /// match FOO { /// FOO => {}, /// _ => {}, /// } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previous versions of Rust allowed function pointers and wide raw pointers in patterns. /// While these work in many cases as expected by users, it is possible that due to /// optimizations pointers are "not equal to themselves" or pointers to different functions /// compare as equal during runtime. This is because LLVM optimizations can deduplicate /// functions if their bodies are the same, thus also making pointers to these functions point /// to the same location. Additionally functions may get duplicated if they are instantiated /// in different crates and not deduplicated again via LTO. pub POINTER_STRUCTURAL_MATCH, Allow, "pointers are not structural-match", @future_incompatible = FutureIncompatibleInfo { reference: "issue #62411 ", }; } declare_lint! { /// The `nontrivial_structural_match` lint detects constants that are used in patterns, /// whose type is not structural-match and whose initializer body actually uses values /// that are not structural-match. So `Option` is ok if the constant /// is just `None`. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(nontrivial_structural_match)] /// /// #[derive(Copy, Clone, Debug)] /// struct NoDerive(u32); /// impl PartialEq for NoDerive { fn eq(&self, _: &Self) -> bool { false } } /// impl Eq for NoDerive { } /// fn main() { /// const INDEX: Option = [None, Some(NoDerive(10))][0]; /// match None { Some(_) => panic!("whoops"), INDEX => dbg!(INDEX), }; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previous versions of Rust accepted constants in patterns, even if those constants's types /// did not have `PartialEq` derived. Thus the compiler falls back to runtime execution of /// `PartialEq`, which can report that two constants are not equal even if they are /// bit-equivalent. pub NONTRIVIAL_STRUCTURAL_MATCH, Warn, "constant used in pattern of non-structural-match type and the constant's initializer \ expression contains values of non-structural-match types", @future_incompatible = FutureIncompatibleInfo { reference: "issue #73448 ", }; } declare_lint! { /// The `ambiguous_associated_items` lint detects ambiguity between /// [associated items] and [enum variants]. /// /// [associated items]: https://doc.rust-lang.org/reference/items/associated-items.html /// [enum variants]: https://doc.rust-lang.org/reference/items/enumerations.html /// /// ### Example /// /// ```rust,compile_fail /// enum E { /// V /// } /// /// trait Tr { /// type V; /// fn foo() -> Self::V; /// } /// /// impl Tr for E { /// type V = u8; /// // `Self::V` is ambiguous because it may refer to the associated type or /// // the enum variant. /// fn foo() -> Self::V { 0 } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previous versions of Rust did not allow accessing enum variants /// through [type aliases]. When this ability was added (see [RFC 2338]), this /// introduced some situations where it can be ambiguous what a type /// was referring to. /// /// To fix this ambiguity, you should use a [qualified path] to explicitly /// state which type to use. For example, in the above example the /// function can be written as `fn f() -> ::V { 0 }` to /// specifically refer to the associated type. /// /// This is a [future-incompatible] lint to transition this to a hard /// error in the future. See [issue #57644] for more details. /// /// [issue #57644]: https://github.com/rust-lang/rust/issues/57644 /// [type aliases]: https://doc.rust-lang.org/reference/items/type-aliases.html#type-aliases /// [RFC 2338]: https://github.com/rust-lang/rfcs/blob/master/text/2338-type-alias-enum-variants.md /// [qualified path]: https://doc.rust-lang.org/reference/paths.html#qualified-paths /// [future-incompatible]: ../index.md#future-incompatible-lints pub AMBIGUOUS_ASSOCIATED_ITEMS, Deny, "ambiguous associated items", @future_incompatible = FutureIncompatibleInfo { reference: "issue #57644 ", }; } declare_lint! { /// The `mutable_borrow_reservation_conflict` lint detects the reservation /// of a two-phased borrow that conflicts with other shared borrows. /// /// ### Example /// /// ```rust /// let mut v = vec![0, 1, 2]; /// let shared = &v; /// v.push(shared.len()); /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This is a [future-incompatible] lint to transition this to a hard error /// in the future. See [issue #59159] for a complete description of the /// problem, and some possible solutions. /// /// [issue #59159]: https://github.com/rust-lang/rust/issues/59159 /// [future-incompatible]: ../index.md#future-incompatible-lints pub MUTABLE_BORROW_RESERVATION_CONFLICT, Warn, "reservation of a two-phased borrow conflicts with other shared borrows", @future_incompatible = FutureIncompatibleInfo { reference: "issue #59159 ", }; } declare_lint! { /// The `soft_unstable` lint detects unstable features that were /// unintentionally allowed on stable. /// /// ### Example /// /// ```rust,compile_fail /// #[cfg(test)] /// extern crate test; /// /// #[bench] /// fn name(b: &mut test::Bencher) { /// b.iter(|| 123) /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The [`bench` attribute] was accidentally allowed to be specified on /// the [stable release channel]. Turning this to a hard error would have /// broken some projects. This lint allows those projects to continue to /// build correctly when [`--cap-lints`] is used, but otherwise signal an /// error that `#[bench]` should not be used on the stable channel. This /// is a [future-incompatible] lint to transition this to a hard error in /// the future. See [issue #64266] for more details. /// /// [issue #64266]: https://github.com/rust-lang/rust/issues/64266 /// [`bench` attribute]: https://doc.rust-lang.org/nightly/unstable-book/library-features/test.html /// [stable release channel]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html /// [`--cap-lints`]: https://doc.rust-lang.org/rustc/lints/levels.html#capping-lints /// [future-incompatible]: ../index.md#future-incompatible-lints pub SOFT_UNSTABLE, Deny, "a feature gate that doesn't break dependent crates", @future_incompatible = FutureIncompatibleInfo { reference: "issue #64266 ", }; } declare_lint! { /// The `inline_no_sanitize` lint detects incompatible use of /// [`#[inline(always)]`][inline] and [`#[no_sanitize(...)]`][no_sanitize]. /// /// [inline]: https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute /// [no_sanitize]: https://doc.rust-lang.org/nightly/unstable-book/language-features/no-sanitize.html /// /// ### Example /// /// ```rust /// #![feature(no_sanitize)] /// /// #[inline(always)] /// #[no_sanitize(address)] /// fn x() {} /// /// fn main() { /// x() /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The use of the [`#[inline(always)]`][inline] attribute prevents the /// the [`#[no_sanitize(...)]`][no_sanitize] attribute from working. /// Consider temporarily removing `inline` attribute. pub INLINE_NO_SANITIZE, Warn, "detects incompatible use of `#[inline(always)]` and `#[no_sanitize(...)]`", } declare_lint! { /// The `asm_sub_register` lint detects using only a subset of a register /// for inline asm inputs. /// /// ### Example /// /// ```rust,ignore (fails on system llvm) /// #![feature(asm)] /// /// fn main() { /// #[cfg(target_arch="x86_64")] /// unsafe { /// asm!("mov {0}, {0}", in(reg) 0i16); /// } /// } /// ``` /// /// This will produce: /// /// ```text /// warning: formatting may not be suitable for sub-register argument /// --> src/main.rs:6:19 /// | /// 6 | asm!("mov {0}, {0}", in(reg) 0i16); /// | ^^^ ^^^ ---- for this argument /// | /// = note: `#[warn(asm_sub_register)]` on by default /// = help: use the `x` modifier to have the register formatted as `ax` /// = help: or use the `r` modifier to keep the default formatting of `rax` /// ``` /// /// ### Explanation /// /// Registers on some architectures can use different names to refer to a /// subset of the register. By default, the compiler will use the name for /// the full register size. To explicitly use a subset of the register, /// you can override the default by using a modifier on the template /// string operand to specify when subregister to use. This lint is issued /// if you pass in a value with a smaller data type than the default /// register size, to alert you of possibly using the incorrect width. To /// fix this, add the suggested modifier to the template, or cast the /// value to the correct size. /// /// See [register template modifiers] for more details. /// /// [register template modifiers]: https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#register-template-modifiers pub ASM_SUB_REGISTER, Warn, "using only a subset of a register for inline asm inputs", } declare_lint! { /// The `bad_asm_style` lint detects the use of the `.intel_syntax` and /// `.att_syntax` directives. /// /// ### Example /// /// ```rust,ignore (fails on system llvm) /// #![feature(asm)] /// /// fn main() { /// #[cfg(target_arch="x86_64")] /// unsafe { /// asm!( /// ".att_syntax", /// "movl {0}, {0}", in(reg) 0usize /// ); /// } /// } /// ``` /// /// This will produce: /// /// ```text /// warning: avoid using `.att_syntax`, prefer using `options(att_syntax)` instead /// --> test.rs:7:14 /// | /// 7 | ".att_syntax", /// | ^^^^^^^^^^^ /// 8 | "movq {0}, {0}", out(reg) _, /// 9 | ); /// | - help: add option: `, options(att_syntax)` /// | /// = note: `#[warn(bad_asm_style)]` on by default /// ``` /// /// ### Explanation /// /// On x86, `asm!` uses the intel assembly syntax by default. While this /// can be switched using assembler directives like `.att_syntax`, using the /// `att_syntax` option is recommended instead because it will also properly /// prefix register placeholders with `%` as required by AT&T syntax. pub BAD_ASM_STYLE, Warn, "incorrect use of inline assembly", } declare_lint! { /// The `unsafe_op_in_unsafe_fn` lint detects unsafe operations in unsafe /// functions without an explicit unsafe block. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(unsafe_op_in_unsafe_fn)] /// /// unsafe fn foo() {} /// /// unsafe fn bar() { /// foo(); /// } /// /// fn main() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Currently, an [`unsafe fn`] allows any [unsafe] operation within its /// body. However, this can increase the surface area of code that needs /// to be scrutinized for proper behavior. The [`unsafe` block] provides a /// convenient way to make it clear exactly which parts of the code are /// performing unsafe operations. In the future, it is desired to change /// it so that unsafe operations cannot be performed in an `unsafe fn` /// without an `unsafe` block. /// /// The fix to this is to wrap the unsafe code in an `unsafe` block. /// /// This lint is "allow" by default since this will affect a large amount /// of existing code, and the exact plan for increasing the severity is /// still being considered. See [RFC #2585] and [issue #71668] for more /// details. /// /// [`unsafe fn`]: https://doc.rust-lang.org/reference/unsafe-functions.html /// [`unsafe` block]: https://doc.rust-lang.org/reference/expressions/block-expr.html#unsafe-blocks /// [unsafe]: https://doc.rust-lang.org/reference/unsafety.html /// [RFC #2585]: https://github.com/rust-lang/rfcs/blob/master/text/2585-unsafe-block-in-unsafe-fn.md /// [issue #71668]: https://github.com/rust-lang/rust/issues/71668 pub UNSAFE_OP_IN_UNSAFE_FN, Allow, "unsafe operations in unsafe functions without an explicit unsafe block are deprecated", } declare_lint! { /// The `cenum_impl_drop_cast` lint detects an `as` cast of a field-less /// `enum` that implements [`Drop`]. /// /// [`Drop`]: https://doc.rust-lang.org/std/ops/trait.Drop.html /// /// ### Example /// /// ```rust /// # #![allow(unused)] /// enum E { /// A, /// } /// /// impl Drop for E { /// fn drop(&mut self) { /// println!("Drop"); /// } /// } /// /// fn main() { /// let e = E::A; /// let i = e as u32; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Casting a field-less `enum` that does not implement [`Copy`] to an /// integer moves the value without calling `drop`. This can result in /// surprising behavior if it was expected that `drop` should be called. /// Calling `drop` automatically would be inconsistent with other move /// operations. Since neither behavior is clear or consistent, it was /// decided that a cast of this nature will no longer be allowed. /// /// This is a [future-incompatible] lint to transition this to a hard error /// in the future. See [issue #73333] for more details. /// /// [future-incompatible]: ../index.md#future-incompatible-lints /// [issue #73333]: https://github.com/rust-lang/rust/issues/73333 /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html pub CENUM_IMPL_DROP_CAST, Warn, "a C-like enum implementing Drop is cast", @future_incompatible = FutureIncompatibleInfo { reference: "issue #73333 ", }; } declare_lint! { /// The `const_evaluatable_unchecked` lint detects a generic constant used /// in a type. /// /// ### Example /// /// ```rust /// const fn foo() -> usize { /// if std::mem::size_of::<*mut T>() < 8 { // size of *mut T does not depend on T /// 4 /// } else { /// 8 /// } /// } /// /// fn test() { /// let _ = [0; foo::()]; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In the 1.43 release, some uses of generic parameters in array repeat /// expressions were accidentally allowed. This is a [future-incompatible] /// lint to transition this to a hard error in the future. See [issue /// #76200] for a more detailed description and possible fixes. /// /// [future-incompatible]: ../index.md#future-incompatible-lints /// [issue #76200]: https://github.com/rust-lang/rust/issues/76200 pub CONST_EVALUATABLE_UNCHECKED, Warn, "detects a generic constant is used in a type without a emitting a warning", @future_incompatible = FutureIncompatibleInfo { reference: "issue #76200 ", }; } declare_lint! { /// The `function_item_references` lint detects function references that are /// formatted with [`fmt::Pointer`] or transmuted. /// /// [`fmt::Pointer`]: https://doc.rust-lang.org/std/fmt/trait.Pointer.html /// /// ### Example /// /// ```rust /// fn foo() { } /// /// fn main() { /// println!("{:p}", &foo); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Taking a reference to a function may be mistaken as a way to obtain a /// pointer to that function. This can give unexpected results when /// formatting the reference as a pointer or transmuting it. This lint is /// issued when function references are formatted as pointers, passed as /// arguments bound by [`fmt::Pointer`] or transmuted. pub FUNCTION_ITEM_REFERENCES, Warn, "suggest casting to a function pointer when attempting to take references to function items", } declare_lint! { /// The `uninhabited_static` lint detects uninhabited statics. /// /// ### Example /// /// ```rust /// enum Void {} /// extern { /// static EXTERN: Void; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Statics with an uninhabited type can never be initialized, so they are impossible to define. /// However, this can be side-stepped with an `extern static`, leading to problems later in the /// compiler which assumes that there are no initialized uninhabited places (such as locals or /// statics). This was accidentally allowed, but is being phased out. pub UNINHABITED_STATIC, Warn, "uninhabited static", @future_incompatible = FutureIncompatibleInfo { reference: "issue #74840 ", }; } declare_lint! { /// The `useless_deprecated` lint detects deprecation attributes with no effect. /// /// ### Example /// /// ```rust,compile_fail /// struct X; /// /// #[deprecated = "message"] /// impl Default for X { /// fn default() -> Self { /// X /// } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Deprecation attributes have no effect on trait implementations. pub USELESS_DEPRECATED, Deny, "detects deprecation attributes with no effect", } declare_lint! { /// The `undefined_naked_function_abi` lint detects naked function definitions that /// either do not specify an ABI or specify the Rust ABI. /// /// ### Example /// /// ```rust /// #![feature(naked_functions)] /// #![feature(asm)] /// /// #[naked] /// pub fn default_abi() -> u32 { /// unsafe { asm!("", options(noreturn)); } /// } /// /// #[naked] /// pub extern "Rust" fn rust_abi() -> u32 { /// unsafe { asm!("", options(noreturn)); } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The Rust ABI is currently undefined. Therefore, naked functions should /// specify a non-Rust ABI. pub UNDEFINED_NAKED_FUNCTION_ABI, Warn, "undefined naked function ABI" } declare_lint! { /// The `unsupported_naked_functions` lint detects naked function /// definitions that are unsupported but were previously accepted. /// /// ### Example /// /// ```rust /// #![feature(naked_functions)] /// /// #[naked] /// pub extern "C" fn f() -> u32 { /// 42 /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The naked functions must be defined using a single inline assembly /// block. /// /// The execution must never fall through past the end of the assembly /// code so the block must use `noreturn` option. The asm block can also /// use `att_syntax` option, but other options are not allowed. /// /// The asm block must not contain any operands other than `const` and /// `sym`. Additionally, naked function should specify a non-Rust ABI. /// /// Naked functions cannot be inlined. All forms of the `inline` attribute /// are prohibited. /// /// While other definitions of naked functions were previously accepted, /// they are unsupported and might not work reliably. This is a /// [future-incompatible] lint that will transition into hard error in /// the future. /// /// [future-incompatible]: ../index.md#future-incompatible-lints pub UNSUPPORTED_NAKED_FUNCTIONS, Warn, "unsupported naked function definitions", @future_incompatible = FutureIncompatibleInfo { reference: "issue #32408 ", }; } declare_lint! { /// The `ineffective_unstable_trait_impl` lint detects `#[unstable]` attributes which are not used. /// /// ### Example /// /// ```compile_fail /// #![feature(staged_api)] /// /// #[derive(Clone)] /// #[stable(feature = "x", since = "1")] /// struct S {} /// /// #[unstable(feature = "y", issue = "none")] /// impl Copy for S {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// `staged_api` does not currently support using a stability attribute on `impl` blocks. /// `impl`s are always stable if both the type and trait are stable, and always unstable otherwise. pub INEFFECTIVE_UNSTABLE_TRAIT_IMPL, Deny, "detects `#[unstable]` on stable trait implementations for stable types" } declare_lint! { /// The `semicolon_in_expressions_from_macros` lint detects trailing semicolons /// in macro bodies when the macro is invoked in expression position. /// This was previous accepted, but is being phased out. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(semicolon_in_expressions_from_macros)] /// macro_rules! foo { /// () => { true; } /// } /// /// fn main() { /// let val = match true { /// true => false, /// _ => foo!() /// }; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previous, Rust ignored trailing semicolon in a macro /// body when a macro was invoked in expression position. /// However, this makes the treatment of semicolons in the language /// inconsistent, and could lead to unexpected runtime behavior /// in some circumstances (e.g. if the macro author expects /// a value to be dropped). /// /// This is a [future-incompatible] lint to transition this /// to a hard error in the future. See [issue #79813] for more details. /// /// [issue #79813]: https://github.com/rust-lang/rust/issues/79813 /// [future-incompatible]: ../index.md#future-incompatible-lints pub SEMICOLON_IN_EXPRESSIONS_FROM_MACROS, Warn, "trailing semicolon in macro body used as expression", @future_incompatible = FutureIncompatibleInfo { reference: "issue #79813 ", }; } declare_lint! { /// The `legacy_derive_helpers` lint detects derive helper attributes /// that are used before they are introduced. /// /// ### Example /// /// ```rust,ignore (needs extern crate) /// #[serde(rename_all = "camelCase")] /// #[derive(Deserialize)] /// struct S { /* fields */ } /// ``` /// /// produces: /// /// ```text /// warning: derive helper attribute is used before it is introduced /// --> $DIR/legacy-derive-helpers.rs:1:3 /// | /// 1 | #[serde(rename_all = "camelCase")] /// | ^^^^^ /// ... /// 2 | #[derive(Deserialize)] /// | ----------- the attribute is introduced here /// ``` /// /// ### Explanation /// /// Attributes like this work for historical reasons, but attribute expansion works in /// left-to-right order in general, so, to resolve `#[serde]`, compiler has to try to "look /// into the future" at not yet expanded part of the item , but such attempts are not always /// reliable. /// /// To fix the warning place the helper attribute after its corresponding derive. /// ```rust,ignore (needs extern crate) /// #[derive(Deserialize)] /// #[serde(rename_all = "camelCase")] /// struct S { /* fields */ } /// ``` pub LEGACY_DERIVE_HELPERS, Warn, "detects derive helper attributes that are used before they are introduced", @future_incompatible = FutureIncompatibleInfo { reference: "issue #79202 ", }; } declare_lint! { /// The `large_assignments` lint detects when objects of large /// types are being moved around. /// /// ### Example /// /// ```rust,ignore (can crash on some platforms) /// let x = [0; 50000]; /// let y = x; /// ``` /// /// produces: /// /// ```text /// warning: moving a large value /// --> $DIR/move-large.rs:1:3 /// let y = x; /// - Copied large value here /// ``` /// /// ### Explanation /// /// When using a large type in a plain assignment or in a function /// argument, idiomatic code can be inefficient. /// Ideally appropriate optimizations would resolve this, but such /// optimizations are only done in a best-effort manner. /// This lint will trigger on all sites of large moves and thus allow the /// user to resolve them in code. pub LARGE_ASSIGNMENTS, Warn, "detects large moves or copies", } declare_lint_pass! { /// Does nothing as a lint pass, but registers some `Lint`s /// that are used by other parts of the compiler. HardwiredLints => [ FORBIDDEN_LINT_GROUPS, ILLEGAL_FLOATING_POINT_LITERAL_PATTERN, ARITHMETIC_OVERFLOW, UNCONDITIONAL_PANIC, UNUSED_IMPORTS, UNUSED_EXTERN_CRATES, UNUSED_CRATE_DEPENDENCIES, UNUSED_QUALIFICATIONS, UNKNOWN_LINTS, UNUSED_VARIABLES, UNUSED_ASSIGNMENTS, DEAD_CODE, UNREACHABLE_CODE, UNREACHABLE_PATTERNS, OVERLAPPING_RANGE_ENDPOINTS, BINDINGS_WITH_VARIANT_NAME, UNUSED_MACROS, WARNINGS, UNUSED_FEATURES, STABLE_FEATURES, UNKNOWN_CRATE_TYPES, TRIVIAL_CASTS, TRIVIAL_NUMERIC_CASTS, PRIVATE_IN_PUBLIC, EXPORTED_PRIVATE_DEPENDENCIES, PUB_USE_OF_PRIVATE_EXTERN_CRATE, INVALID_TYPE_PARAM_DEFAULT, CONST_ERR, RENAMED_AND_REMOVED_LINTS, UNALIGNED_REFERENCES, CONST_ITEM_MUTATION, PATTERNS_IN_FNS_WITHOUT_BODY, MISSING_FRAGMENT_SPECIFIER, LATE_BOUND_LIFETIME_ARGUMENTS, ORDER_DEPENDENT_TRAIT_OBJECTS, COHERENCE_LEAK_CHECK, DEPRECATED, UNUSED_UNSAFE, UNUSED_MUT, UNCONDITIONAL_RECURSION, SINGLE_USE_LIFETIMES, UNUSED_LIFETIMES, UNUSED_LABELS, TYVAR_BEHIND_RAW_POINTER, ELIDED_LIFETIMES_IN_PATHS, BARE_TRAIT_OBJECTS, ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE, UNSTABLE_NAME_COLLISIONS, IRREFUTABLE_LET_PATTERNS, WHERE_CLAUSES_OBJECT_SAFETY, PROC_MACRO_DERIVE_RESOLUTION_FALLBACK, MACRO_USE_EXTERN_CRATE, MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS, ILL_FORMED_ATTRIBUTE_INPUT, CONFLICTING_REPR_HINTS, META_VARIABLE_MISUSE, DEPRECATED_IN_FUTURE, AMBIGUOUS_ASSOCIATED_ITEMS, MUTABLE_BORROW_RESERVATION_CONFLICT, INDIRECT_STRUCTURAL_MATCH, POINTER_STRUCTURAL_MATCH, NONTRIVIAL_STRUCTURAL_MATCH, SOFT_UNSTABLE, INLINE_NO_SANITIZE, BAD_ASM_STYLE, ASM_SUB_REGISTER, UNSAFE_OP_IN_UNSAFE_FN, INCOMPLETE_INCLUDE, CENUM_IMPL_DROP_CAST, CONST_EVALUATABLE_UNCHECKED, INEFFECTIVE_UNSTABLE_TRAIT_IMPL, MUST_NOT_SUSPEND, UNINHABITED_STATIC, FUNCTION_ITEM_REFERENCES, USELESS_DEPRECATED, UNSUPPORTED_NAKED_FUNCTIONS, MISSING_ABI, INVALID_DOC_ATTRIBUTES, SEMICOLON_IN_EXPRESSIONS_FROM_MACROS, RUST_2021_INCOMPATIBLE_CLOSURE_CAPTURES, LEGACY_DERIVE_HELPERS, PROC_MACRO_BACK_COMPAT, RUST_2021_INCOMPATIBLE_OR_PATTERNS, LARGE_ASSIGNMENTS, RUST_2021_PRELUDE_COLLISIONS, RUST_2021_PREFIXES_INCOMPATIBLE_SYNTAX, UNSUPPORTED_CALLING_CONVENTIONS, BREAK_WITH_LABEL_AND_LOOP, UNUSED_ATTRIBUTES, NON_EXHAUSTIVE_OMITTED_PATTERNS, TEXT_DIRECTION_CODEPOINT_IN_COMMENT, DEREF_INTO_DYN_SUPERTRAIT, ] } declare_lint! { /// The `unused_doc_comments` lint detects doc comments that aren't used /// by `rustdoc`. /// /// ### Example /// /// ```rust /// /// docs for x /// let x = 12; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// `rustdoc` does not use doc comments in all positions, and so the doc /// comment will be ignored. Try changing it to a normal comment with `//` /// to avoid the warning. pub UNUSED_DOC_COMMENTS, Warn, "detects doc comments that aren't used by rustdoc" } declare_lint! { /// The `rust_2021_incompatible_closure_captures` lint detects variables that aren't completely /// captured in Rust 2021, such that the `Drop` order of their fields may differ between /// Rust 2018 and 2021. /// /// It can also detect when a variable implements a trait like `Send`, but one of its fields does not, /// and the field is captured by a closure and used with the assumption that said field implements /// the same trait as the root variable. /// /// ### Example of drop reorder /// /// ```rust,compile_fail /// #![deny(rust_2021_incompatible_closure_captures)] /// # #![allow(unused)] /// /// struct FancyInteger(i32); /// /// impl Drop for FancyInteger { /// fn drop(&mut self) { /// println!("Just dropped {}", self.0); /// } /// } /// /// struct Point { x: FancyInteger, y: FancyInteger } /// /// fn main() { /// let p = Point { x: FancyInteger(10), y: FancyInteger(20) }; /// /// let c = || { /// let x = p.x; /// }; /// /// c(); /// /// // ... More code ... /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In the above example, `p.y` will be dropped at the end of `f` instead of /// with `c` in Rust 2021. /// /// ### Example of auto-trait /// /// ```rust,compile_fail /// #![deny(rust_2021_incompatible_closure_captures)] /// use std::thread; /// /// struct Pointer(*mut i32); /// unsafe impl Send for Pointer {} /// /// fn main() { /// let mut f = 10; /// let fptr = Pointer(&mut f as *mut i32); /// thread::spawn(move || unsafe { /// *fptr.0 = 20; /// }); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In the above example, only `fptr.0` is captured in Rust 2021. /// The field is of type `*mut i32`, which doesn't implement `Send`, /// making the code invalid as the field cannot be sent between threads safely. pub RUST_2021_INCOMPATIBLE_CLOSURE_CAPTURES, Allow, "detects closures affected by Rust 2021 changes", @future_incompatible = FutureIncompatibleInfo { reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021), explain_reason: false, }; } declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]); declare_lint! { /// The `missing_abi` lint detects cases where the ABI is omitted from /// extern declarations. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(missing_abi)] /// /// extern fn foo() {} /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Historically, Rust implicitly selected C as the ABI for extern /// declarations. We expect to add new ABIs, like `C-unwind`, in the future, /// though this has not yet happened, and especially with their addition /// seeing the ABI easily will make code review easier. pub MISSING_ABI, Allow, "No declared ABI for extern declaration" } declare_lint! { /// The `invalid_doc_attributes` lint detects when the `#[doc(...)]` is /// misused. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(warnings)] /// /// pub mod submodule { /// #![doc(test(no_crate_inject))] /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Previously, there were very like checks being performed on `#[doc(..)]` /// unlike the other attributes. It'll now catch all the issues that it /// silently ignored previously. pub INVALID_DOC_ATTRIBUTES, Warn, "detects invalid `#[doc(...)]` attributes", @future_incompatible = FutureIncompatibleInfo { reference: "issue #82730 ", }; } declare_lint! { /// The `proc_macro_back_compat` lint detects uses of old versions of certain /// proc-macro crates, which have hardcoded workarounds in the compiler. /// /// ### Example /// /// ```rust,ignore (needs-dependency) /// /// use time_macros_impl::impl_macros; /// struct Foo; /// impl_macros!(Foo); /// ``` /// /// This will produce: /// /// ```text /// warning: using an old version of `time-macros-impl` /// ::: $DIR/group-compat-hack.rs:27:5 /// | /// LL | impl_macros!(Foo); /// | ------------------ in this macro invocation /// | /// = note: `#[warn(proc_macro_back_compat)]` on by default /// = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! /// = note: for more information, see issue #83125 /// = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage /// = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info) /// ``` /// /// ### Explanation /// /// Eventually, the backwards-compatibility hacks present in the compiler will be removed, /// causing older versions of certain crates to stop compiling. /// This is a [future-incompatible] lint to ease the transition to an error. /// See [issue #83125] for more details. /// /// [issue #83125]: https://github.com/rust-lang/rust/issues/83125 /// [future-incompatible]: ../index.md#future-incompatible-lints pub PROC_MACRO_BACK_COMPAT, Deny, "detects usage of old versions of certain proc-macro crates", @future_incompatible = FutureIncompatibleInfo { reference: "issue #83125 ", reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow, }; } declare_lint! { /// The `rust_2021_incompatible_or_patterns` lint detects usage of old versions of or-patterns. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(rust_2021_incompatible_or_patterns)] /// /// macro_rules! match_any { /// ( $expr:expr , $( $( $pat:pat )|+ => $expr_arm:expr ),+ ) => { /// match $expr { /// $( /// $( $pat => $expr_arm, )+ /// )+ /// } /// }; /// } /// /// fn main() { /// let result: Result = Err(42); /// let int: i64 = match_any!(result, Ok(i) | Err(i) => i.into()); /// assert_eq!(int, 42); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In Rust 2021, the `pat` matcher will match additional patterns, which include the `|` character. pub RUST_2021_INCOMPATIBLE_OR_PATTERNS, Allow, "detects usage of old versions of or-patterns", @future_incompatible = FutureIncompatibleInfo { reference: "", reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021), }; } declare_lint! { /// The `rust_2021_prelude_collisions` lint detects the usage of trait methods which are ambiguous /// with traits added to the prelude in future editions. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(rust_2021_prelude_collisions)] /// /// trait Foo { /// fn try_into(self) -> Result; /// } /// /// impl Foo for &str { /// fn try_into(self) -> Result { /// Ok(String::from(self)) /// } /// } /// /// fn main() { /// let x: String = "3".try_into().unwrap(); /// // ^^^^^^^^ /// // This call to try_into matches both Foo:try_into and TryInto::try_into as /// // `TryInto` has been added to the Rust prelude in 2021 edition. /// println!("{}", x); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In Rust 2021, one of the important introductions is the [prelude changes], which add /// `TryFrom`, `TryInto`, and `FromIterator` into the standard library's prelude. Since this /// results in an ambiguity as to which method/function to call when an existing `try_into` /// method is called via dot-call syntax or a `try_from`/`from_iter` associated function /// is called directly on a type. /// /// [prelude changes]: https://blog.rust-lang.org/inside-rust/2021/03/04/planning-rust-2021.html#prelude-changes pub RUST_2021_PRELUDE_COLLISIONS, Allow, "detects the usage of trait methods which are ambiguous with traits added to the \ prelude in future editions", @future_incompatible = FutureIncompatibleInfo { reference: "", reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021), }; } declare_lint! { /// The `rust_2021_prefixes_incompatible_syntax` lint detects identifiers that will be parsed as a /// prefix instead in Rust 2021. /// /// ### Example /// /// ```rust,edition2018,compile_fail /// #![deny(rust_2021_prefixes_incompatible_syntax)] /// /// macro_rules! m { /// (z $x:expr) => (); /// } /// /// m!(z"hey"); /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In Rust 2015 and 2018, `z"hey"` is two tokens: the identifier `z` /// followed by the string literal `"hey"`. In Rust 2021, the `z` is /// considered a prefix for `"hey"`. /// /// This lint suggests to add whitespace between the `z` and `"hey"` tokens /// to keep them separated in Rust 2021. // Allow this lint -- rustdoc doesn't yet support threading edition into this lint's parser. #[allow(rustdoc::invalid_rust_codeblocks)] pub RUST_2021_PREFIXES_INCOMPATIBLE_SYNTAX, Allow, "identifiers that will be parsed as a prefix in Rust 2021", @future_incompatible = FutureIncompatibleInfo { reference: "", reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021), }; crate_level_only } declare_lint! { /// The `unsupported_calling_conventions` lint is output whenever there is a use of the /// `stdcall`, `fastcall`, `thiscall`, `vectorcall` calling conventions (or their unwind /// variants) on targets that cannot meaningfully be supported for the requested target. /// /// For example `stdcall` does not make much sense for a x86_64 or, more apparently, powerpc /// code, because this calling convention was never specified for those targets. /// /// Historically MSVC toolchains have fallen back to the regular C calling convention for /// targets other than x86, but Rust doesn't really see a similar need to introduce a similar /// hack across many more targets. /// /// ### Example /// /// ```rust,ignore (needs specific targets) /// extern "stdcall" fn stdcall() {} /// ``` /// /// This will produce: /// /// ```text /// warning: use of calling convention not supported on this target /// --> $DIR/unsupported.rs:39:1 /// | /// LL | extern "stdcall" fn stdcall() {} /// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ /// | /// = note: `#[warn(unsupported_calling_conventions)]` on by default /// = warning: this was previously accepted by the compiler but is being phased out; /// it will become a hard error in a future release! /// = note: for more information, see issue ... /// ``` /// /// ### Explanation /// /// On most of the targets the behaviour of `stdcall` and similar calling conventions is not /// defined at all, but was previously accepted due to a bug in the implementation of the /// compiler. pub UNSUPPORTED_CALLING_CONVENTIONS, Warn, "use of unsupported calling convention", @future_incompatible = FutureIncompatibleInfo { reference: "issue #87678 ", }; } declare_lint! { /// The `break_with_label_and_loop` lint detects labeled `break` expressions with /// an unlabeled loop as their value expression. /// /// ### Example /// /// ```rust /// 'label: loop { /// break 'label loop { break 42; }; /// }; /// ``` /// /// {{produces}} /// /// ### Explanation /// /// In Rust, loops can have a label, and `break` expressions can refer to that label to /// break out of specific loops (and not necessarily the innermost one). `break` expressions /// can also carry a value expression, which can be another loop. A labeled `break` with an /// unlabeled loop as its value expression is easy to confuse with an unlabeled break with /// a labeled loop and is thus discouraged (but allowed for compatibility); use parentheses /// around the loop expression to silence this warning. Unlabeled `break` expressions with /// labeled loops yield a hard error, which can also be silenced by wrapping the expression /// in parentheses. pub BREAK_WITH_LABEL_AND_LOOP, Warn, "`break` expression with label and unlabeled loop as value expression" } declare_lint! { /// The `non_exhaustive_omitted_patterns` lint detects when a wildcard (`_` or `..`) in a /// pattern for a `#[non_exhaustive]` struct or enum is reachable. /// /// ### Example /// /// ```rust,ignore (needs separate crate) /// // crate A /// #[non_exhaustive] /// pub enum Bar { /// A, /// B, // added variant in non breaking change /// } /// /// // in crate B /// #![feature(non_exhaustive_omitted_patterns_lint)] /// /// match Bar::A { /// Bar::A => {}, /// #[warn(non_exhaustive_omitted_patterns)] /// _ => {}, /// } /// ``` /// /// This will produce: /// /// ```text /// warning: reachable patterns not covered of non exhaustive enum /// --> $DIR/reachable-patterns.rs:70:9 /// | /// LL | _ => {} /// | ^ pattern `B` not covered /// | /// note: the lint level is defined here /// --> $DIR/reachable-patterns.rs:69:16 /// | /// LL | #[warn(non_exhaustive_omitted_patterns)] /// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ /// = help: ensure that all possible cases are being handled by adding the suggested match arms /// = note: the matched value is of type `Bar` and the `non_exhaustive_omitted_patterns` attribute was found /// ``` /// /// ### Explanation /// /// Structs and enums tagged with `#[non_exhaustive]` force the user to add a /// (potentially redundant) wildcard when pattern-matching, to allow for future /// addition of fields or variants. The `non_exhaustive_omitted_patterns` lint /// detects when such a wildcard happens to actually catch some fields/variants. /// In other words, when the match without the wildcard would not be exhaustive. /// This lets the user be informed if new fields/variants were added. pub NON_EXHAUSTIVE_OMITTED_PATTERNS, Allow, "detect when patterns of types marked `non_exhaustive` are missed", @feature_gate = sym::non_exhaustive_omitted_patterns_lint; } declare_lint! { /// The `text_direction_codepoint_in_comment` lint detects Unicode codepoints in comments that /// change the visual representation of text on screen in a way that does not correspond to /// their on memory representation. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(text_direction_codepoint_in_comment)] /// fn main() { /// println!("{:?}"); // '‮'); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Unicode allows changing the visual flow of text on screen in order to support scripts that /// are written right-to-left, but a specially crafted comment can make code that will be /// compiled appear to be part of a comment, depending on the software used to read the code. /// To avoid potential problems or confusion, such as in CVE-2021-42574, by default we deny /// their use. pub TEXT_DIRECTION_CODEPOINT_IN_COMMENT, Deny, "invisible directionality-changing codepoints in comment" } declare_lint! { /// The `deref_into_dyn_supertrait` lint is output whenever there is a use of the /// `Deref` implementation with a `dyn SuperTrait` type as `Output`. /// /// These implementations will become shadowed when the `trait_upcasting` feature is stablized. /// The `deref` functions will no longer be called implicitly, so there might be behavior change. /// /// ### Example /// /// ```rust,compile_fail /// #![deny(deref_into_dyn_supertrait)] /// #![allow(dead_code)] /// /// use core::ops::Deref; /// /// trait A {} /// trait B: A {} /// impl<'a> Deref for dyn 'a + B { /// type Target = dyn A; /// fn deref(&self) -> &Self::Target { /// todo!() /// } /// } /// /// fn take_a(_: &dyn A) { } /// /// fn take_b(b: &dyn B) { /// take_a(b); /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// The dyn upcasting coercion feature adds new coercion rules, taking priority /// over certain other coercion rules, which will cause some behavior change. pub DEREF_INTO_DYN_SUPERTRAIT, Warn, "`Deref` implementation usage with a supertrait trait object for output might be shadowed in the future", @future_incompatible = FutureIncompatibleInfo { reference: "issue #89460 ", }; }