默认为Deny的Lints

Rustc 默认为Deny的Lints

英文原文地址： https://doc.rust-lang.org/rustc/lints/listing/deny-by-default.html

默认情况下，这些 lint 都设置为’deny’级别。

exceeding-bitshifts

此 lint 检测到移位超出了类型的位数。一些触发此 lint 的示例代码：

1_i32 << 32;

这将产生：

error: bitshift exceeds the type's number of bits
 --> src/main.rs:2:5
  |
2 |     1_i32 << 32;
  |     ^^^^^^^^^^^
  |

invalid-type-param-default

此 lint 检测在无效位置中，允许的类型参数默认值错误。一些触发此 lint 的示例代码：

fn foo<T=i32>(t: T) {}

这将产生：

error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions.
 --> src/main.rs:4:8
  |
4 | fn foo<T=i32>(t: T) {}
  |        ^
  |
  = note: #[deny(invalid_type_param_default)] 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 #36887 <https://github.com/rust-lang/rust/issues/36887>

legacy-constructor-visibility

RFC 1506修改了一些可见性规则，并改变了 struct 构造函数的可见性。一些触发此 lint 的示例代码：

mod m {
    pub struct S(u8);

    fn f() {
        // this is trying to use S from the 'use' line, but because the `u8` is
        // not pub, it is private
        ::S;
    }
}

use m::S;

这将产生：

error: private struct constructors are not usable through re-exports in outer modules
 --> src/main.rs:5:9
  |
5 |         ::S;
  |         ^^^
  |
  = note: #[deny(legacy_constructor_visibility)] 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 #39207 <https://github.com/rust-lang/rust/issues/39207>

legacy-directory-ownership

发出 legacy_directory_ownership 时发出

有一个带有＃[path]属性的非内联模块（例如#[path = "foo.rs"]mod bar;），
模块的文件（上例中的“foo.rs”）是未命名为“mod.rs”，并且
模块的文件包含一个＃[path]属性的非内联模块。

可以通过将父模块重命名为“mod.rs”，并将其移动到其自己的目录（如果合适的话）来修复警告。

missing-fragment-specifier

当一个未使用的macro_rules!宏定义模式出现时，会发出 missing_fragment_specifier 警告，因其有一个元变量（例如$e）后面没有片段说明符（例如:expr）。

通过删除未使用的macro_rules!宏定义模式，可以始终修复此警告。

mutable-transmutes

这种 lint 抓取&T到&mut T的转化，因为它是未定义的行为。一些触发此 lint 的示例代码：

unsafe {
    let y = std::mem::transmute::<&i32, &mut i32>(&5);
}

这将产生：

error: mutating transmuted &mut T from &T may cause undefined behavior, consider instead using an UnsafeCell
 --> src/main.rs:3:17
  |
3 |         let y = std::mem::transmute::<&i32, &mut i32>(&5);
  |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |

no-mangle-const-items

这个 lint 检测到任何带#[no_mangle]属性的const项。常量确实没有导出符号，因此，这可能意味着您打算使用static不是const。一些触发此 lint 的示例代码：

#[no_mangle]
const FOO: i32 = 5;

这将产生：

error: const items should never be #[no_mangle]
 --> src/main.rs:3:1
  |
3 | const FOO: i32 = 5;
  | -----^^^^^^^^^^^^^^
  | |
  | help: try a static value: `pub static`
  |

overflowing-literals

此 lint 检测其类型的字面值超出范围。一些触发此 lint 的示例代码：

let x: u8 = 1000;

这将产生：

error: literal out of range for u8
 --> src/main.rs:2:17
  |
2 |     let x: u8 = 1000;
  |                 ^^^^
  |

parenthesized-params-in-types-and-modules

此 lint 检测到不正确的括号。一些触发此 lint 的示例代码：

let x = 5 as usize();

这将产生：

error: parenthesized parameters may only be used with a trait
 --> src/main.rs:2:21
  |
2 |   let x = 5 as usize();
  |                     ^^
  |
  = note: #[deny(parenthesized_params_in_types_and_modules)] 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 #42238 <https://github.com/rust-lang/rust/issues/42238>

要修复它，请删除多个()。

pub-use-of-private-extern-crate

此 lint 检测重新导出一个私有extern crate的特定情况;

safe-extern-statics

在旧版本的 Rust 中，允许extern static以安全代码访问，会存在安全问题。这个 lint 现在抓住并否认这种代码。

unknown-crate-types

此 lint 检测到在一个#[crate_type]指示中，发现一个未知箱类型。一些触发此 lint 的示例代码：

#![crate_type="lol"]

这将产生：

error: invalid `crate_type` value
 --> src/lib.rs:1:1
  |
1 | #![crate_type="lol"]
  | ^^^^^^^^^^^^^^^^^^^^
  |

incoherent-fundamental-impls

此 lint 检测到错误允许的潜在冲突的 impl。一些触发此 lint 的示例代码：

pub trait Trait1<X> {
    type Output;
}

pub trait Trait2<X> {}

pub struct A;

impl<X, T> Trait1<X> for T where T: Trait2<X> {
    type Output = ();
}

impl<X> Trait1<Box<X>> for A {
    type Output = i32;
}

这将产生：

error: conflicting implementations of trait `Trait1<std::boxed::Box<_>>` for type `A`: (E0119)
  --> src/main.rs:13:1
   |
9  | impl<X, T> Trait1<X> for T where T: Trait2<X> {
   | --------------------------------------------- first implementation here
...
13 | impl<X> Trait1<Box<X>> for A {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `A`
   |
   = note: #[deny(incoherent_fundamental_impls)] 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 #46205 <https://github.com/rust-lang/rust/issues/46205>