//! 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, declare_tool_lint}; use rustc_span::edition::Edition; use rustc_span::symbol::sym; 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 ", edition: None, }; 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 ", edition: None, }; } 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. When possible, /// the compiler will attempt to detect situations where code can be /// evaluated at compile-time to generate more efficient code. While /// evaluating such code, if it detects that the code will unconditionally /// panic, this usually indicates that it is doing something incorrectly. /// If this lint is allowed, then the code will not be evaluated at /// compile-time, and instead continue to generate code to evaluate at /// runtime, which may panic during runtime. 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)] /// let x: &'static i32 = &(1 / 0); /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This lint detects code that is very likely incorrect. If this lint is /// allowed, then the code will not be evaluated at compile-time, and /// instead continue to generate code to evaluate at runtime, which may /// panic during runtime. /// /// Note that this lint may trigger in either inside or outside of a /// [const context]. Outside of a [const context], the compiler can /// sometimes evaluate an expression at compile-time in order to generate /// more efficient code. As the compiler becomes better at doing this, it /// needs to decide what to do when it encounters code that it knows for /// certain will panic or is otherwise incorrect. Making this a hard error /// would prevent existing code that exhibited this behavior from /// compiling, breaking backwards-compatibility. However, this is almost /// certainly incorrect code, so this is a deny-by-default lint. For more /// details, see [RFC 1229] and [issue #28238]. /// /// Note that there are several other more specific lints associated with /// compile-time evaluation, such as [`arithmetic_overflow`], /// [`unconditional_panic`]. /// /// [const context]: https://doc.rust-lang.org/reference/const_eval.html#const-context /// [RFC 1229]: https://github.com/rust-lang/rfcs/blob/master/text/1229-compile-time-asserts.md /// [issue #28238]: https://github.com/rust-lang/rust/issues/28238 /// [`arithmetic_overflow`]: deny-by-default.html#arithmetic-overflow /// [`unconditional_panic`]: deny-by-default.html#unconditional-panic pub CONST_ERR, Deny, "constant evaluation detected erroneous expression", 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 `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(unsued)]`) 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_patterns` lint detects `match` arms that have /// [range patterns] that overlap. /// /// [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. 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_PATTERNS, Warn, "detects overlapping patterns" } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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; /// } /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// Creating a reference to an insufficiently aligned packed field is /// [undefined behavior] and should be disallowed. /// /// This lint is "allow" by default because there is no stable /// alternative, and it is not yet certain how widespread existing code /// will trigger this lint. /// /// See [issue #27060] for more discussion. /// /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html /// [issue #27060]: https://github.com/rust-lang/rust/issues/27060 pub UNALIGNED_REFERENCES, Allow, "detects unaligned references to fields of packed structs", } 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 `safe_packed_borrows` lint detects borrowing a field in the /// interior of a packed structure with alignment other than 1. /// /// ### Example /// /// ```rust /// #[repr(packed)] /// pub struct Unaligned(pub T); /// /// pub struct Foo { /// start: u8, /// data: Unaligned, /// } /// /// fn main() { /// let x = Foo { start: 0, data: Unaligned(1) }; /// let y = &x.data.0; /// } /// ``` /// /// {{produces}} /// /// ### Explanation /// /// This type of borrow is unsafe and can cause errors on some platforms /// and violates some assumptions made by the compiler. This was /// previously allowed unintentionally. This is a [future-incompatible] /// lint to transition this to a hard error in the future. See [issue /// #46043] for more details, including guidance on how to solve the /// problem. /// /// [issue #46043]: https://github.com/rust-lang/rust/issues/46043 /// [future-incompatible]: ../index.md#future-incompatible-lints pub SAFE_PACKED_BORROWS, Warn, "safe borrows of fields of packed structs were erroneously allowed", @future_incompatible = FutureIncompatibleInfo { reference: "issue #46043 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: Some(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 /// 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" } 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 ", edition: Some(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 ", edition: None, }; } 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 ", edition: None, // 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 detects [irrefutable /// patterns] in [if-let] and [while-let] statements. /// /// /// /// ### Example /// /// ```rust /// 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 `broken_intra_doc_links` lint detects failures in resolving /// intra-doc link targets. This is a `rustdoc` only lint, see the /// documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#broken_intra_doc_links pub BROKEN_INTRA_DOC_LINKS, Warn, "failures in resolving intra-doc link targets" } declare_lint! { /// This is a subset of `broken_intra_doc_links` that warns when linking from /// a public item to a private one. This is a `rustdoc` only lint, see the /// documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#private_intra_doc_links pub PRIVATE_INTRA_DOC_LINKS, Warn, "linking from a public item to a private one" } declare_lint! { /// The `invalid_codeblock_attributes` lint detects code block attributes /// in documentation examples that have potentially mis-typed values. This /// is a `rustdoc` only lint, see the documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_codeblock_attributes pub INVALID_CODEBLOCK_ATTRIBUTES, Warn, "codeblock attribute looks a lot like a known one" } declare_lint! { /// The `missing_crate_level_docs` lint detects if documentation is /// missing at the crate root. This is a `rustdoc` only lint, see the /// documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#missing_crate_level_docs pub MISSING_CRATE_LEVEL_DOCS, Allow, "detects crates with no crate-level documentation" } declare_lint! { /// The `missing_doc_code_examples` lint detects publicly-exported items /// without code samples in their documentation. This is a `rustdoc` only /// lint, see the documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#missing_doc_code_examples pub MISSING_DOC_CODE_EXAMPLES, Allow, "detects publicly-exported items without code samples in their documentation" } declare_lint! { /// The `private_doc_tests` lint detects code samples in docs of private /// items not documented by `rustdoc`. This is a `rustdoc` only lint, see /// the documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#private_doc_tests pub PRIVATE_DOC_TESTS, Allow, "detects code samples in docs of private items not documented by rustdoc" } declare_lint! { /// The `invalid_html_tags` lint detects invalid HTML tags. This is a /// `rustdoc` only lint, see the documentation in the [rustdoc book]. /// /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_html_tags pub INVALID_HTML_TAGS, Allow, "detects invalid HTML tags in doc comments" } 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 ", edition: None, }; } 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, Warn, "detects proc macro derives using inaccessible names from parent modules", @future_incompatible = FutureIncompatibleInfo { reference: "issue #50504 ", edition: None, }; } 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 ", edition: None, }; 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 `unsafe_op_in_unsafe_fn` lint detects unsafe operations in unsafe /// functions without an explicit unsafe block. This lint only works on /// the [**nightly channel**] with the /// `#![feature(unsafe_block_in_unsafe_fn)]` feature. /// /// [**nightly channel**]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html /// /// ### Example /// /// ```rust,compile_fail /// #![feature(unsafe_block_in_unsafe_fn)] /// #![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 because it has not yet been /// stabilized, and is not yet complete. 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", @feature_gate = sym::unsafe_block_in_unsafe_fn; } 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 ", edition: None, }; } 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 ", edition: None, }; } 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 accientally allowed, but is being phased out. pub UNINHABITED_STATIC, Warn, "uninhabited static", @future_incompatible = FutureIncompatibleInfo { reference: "issue #74840 ", edition: None, }; } declare_tool_lint! { pub rustc::INEFFECTIVE_UNSTABLE_TRAIT_IMPL, Deny, "detects `#[unstable]` on stable trait implementations for stable types" } declare_lint_pass! { /// Does nothing as a lint pass, but registers some `Lint`s /// that are used by other parts of the compiler. HardwiredLints => [ 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_PATTERNS, 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, SAFE_PACKED_BORROWS, PATTERNS_IN_FNS_WITHOUT_BODY, 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, BROKEN_INTRA_DOC_LINKS, INVALID_CODEBLOCK_ATTRIBUTES, MISSING_CRATE_LEVEL_DOCS, MISSING_DOC_CODE_EXAMPLES, INVALID_HTML_TAGS, PRIVATE_DOC_TESTS, 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, ASM_SUB_REGISTER, UNSAFE_OP_IN_UNSAFE_FN, INCOMPLETE_INCLUDE, CENUM_IMPL_DROP_CAST, CONST_EVALUATABLE_UNCHECKED, INEFFECTIVE_UNSTABLE_TRAIT_IMPL, UNINHABITED_STATIC, FUNCTION_ITEM_REFERENCES, ] } 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_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);