1 // ignore-tidy-linelength
2 #![allow(non_snake_case)]
4 // Error messages for EXXXX errors.
5 // Each message should start and end with a new line, and be wrapped to 80 characters.
6 // In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
7 register_long_diagnostics! {
9 Trait objects like `Box<Trait>` can only be constructed when certain
10 requirements are satisfied by the trait in question.
12 Trait objects are a form of dynamic dispatch and use a dynamically sized type
13 for the inner type. So, for a given trait `Trait`, when `Trait` is treated as a
14 type, as in `Box<Trait>`, the inner type is 'unsized'. In such cases the boxed
15 pointer is a 'fat pointer' that contains an extra pointer to a table of methods
16 (among other things) for dynamic dispatch. This design mandates some
17 restrictions on the types of traits that are allowed to be used in trait
18 objects, which are collectively termed as 'object safety' rules.
20 Attempting to create a trait object for a non object-safe trait will trigger
23 There are various rules:
25 ### The trait cannot require `Self: Sized`
27 When `Trait` is treated as a type, the type does not implement the special
28 `Sized` trait, because the type does not have a known size at compile time and
29 can only be accessed behind a pointer. Thus, if we have a trait like the
33 trait Foo where Self: Sized {
38 We cannot create an object of type `Box<Foo>` or `&Foo` since in this case
39 `Self` would not be `Sized`.
41 Generally, `Self: Sized` is used to indicate that the trait should not be used
42 as a trait object. If the trait comes from your own crate, consider removing
45 ### Method references the `Self` type in its arguments or return type
47 This happens when a trait has a method like the following:
51 fn foo(&self) -> Self;
54 impl Trait for String {
55 fn foo(&self) -> Self {
61 fn foo(&self) -> Self {
67 (Note that `&self` and `&mut self` are okay, it's additional `Self` types which
70 In such a case, the compiler cannot predict the return type of `foo()` in a
71 situation like the following:
75 fn foo(&self) -> Self;
78 fn call_foo(x: Box<Trait>) {
79 let y = x.foo(); // What type is y?
84 If only some methods aren't object-safe, you can add a `where Self: Sized` bound
85 on them to mark them as explicitly unavailable to trait objects. The
86 functionality will still be available to all other implementers, including
87 `Box<Trait>` which is itself sized (assuming you `impl Trait for Box<Trait>`).
91 fn foo(&self) -> Self where Self: Sized;
96 Now, `foo()` can no longer be called on a trait object, but you will now be
97 allowed to make a trait object, and that will be able to call any object-safe
98 methods. With such a bound, one can still call `foo()` on types implementing
99 that trait that aren't behind trait objects.
101 ### Method has generic type parameters
103 As mentioned before, trait objects contain pointers to method tables. So, if we
111 impl Trait for String {
125 At compile time each implementation of `Trait` will produce a table containing
126 the various methods (and other items) related to the implementation.
128 This works fine, but when the method gains generic parameters, we can have a
131 Usually, generic parameters get _monomorphized_. For example, if I have
139 The machine code for `foo::<u8>()`, `foo::<bool>()`, `foo::<String>()`, or any
140 other type substitution is different. Hence the compiler generates the
141 implementation on-demand. If you call `foo()` with a `bool` parameter, the
142 compiler will only generate code for `foo::<bool>()`. When we have additional
143 type parameters, the number of monomorphized implementations the compiler
144 generates does not grow drastically, since the compiler will only generate an
145 implementation if the function is called with unparametrized substitutions
146 (i.e., substitutions where none of the substituted types are themselves
149 However, with trait objects we have to make a table containing _every_ object
150 that implements the trait. Now, if it has type parameters, we need to add
151 implementations for every type that implements the trait, and there could
152 theoretically be an infinite number of types.
158 fn foo<T>(&self, on: T);
162 impl Trait for String {
163 fn foo<T>(&self, on: T) {
169 fn foo<T>(&self, on: T) {
174 // 8 more implementations
177 Now, if we have the following code:
179 ```compile_fail,E0038
180 # trait Trait { fn foo<T>(&self, on: T); }
181 # impl Trait for String { fn foo<T>(&self, on: T) {} }
182 # impl Trait for u8 { fn foo<T>(&self, on: T) {} }
183 # impl Trait for bool { fn foo<T>(&self, on: T) {} }
185 fn call_foo(thing: Box<Trait>) {
186 thing.foo(true); // this could be any one of the 8 types above
192 We don't just need to create a table of all implementations of all methods of
193 `Trait`, we need to create such a table, for each different type fed to
194 `foo()`. In this case this turns out to be (10 types implementing `Trait`)*(3
195 types being fed to `foo()`) = 30 implementations!
197 With real world traits these numbers can grow drastically.
199 To fix this, it is suggested to use a `where Self: Sized` bound similar to the
200 fix for the sub-error above if you do not intend to call the method with type
205 fn foo<T>(&self, on: T) where Self: Sized;
210 If this is not an option, consider replacing the type parameter with another
211 trait object (e.g., if `T: OtherTrait`, use `on: Box<OtherTrait>`). If the
212 number of types you intend to feed to this method is limited, consider manually
213 listing out the methods of different types.
215 ### Method has no receiver
217 Methods that do not take a `self` parameter can't be called since there won't be
218 a way to get a pointer to the method table for them.
226 This could be called as `<Foo as Foo>::foo()`, which would not be able to pick
229 Adding a `Self: Sized` bound to these methods will generally make this compile.
233 fn foo() -> u8 where Self: Sized;
237 ### The trait cannot contain associated constants
239 Just like static functions, associated constants aren't stored on the method
240 table. If the trait or any subtrait contain an associated constant, they cannot
241 be made into an object.
243 ```compile_fail,E0038
251 A simple workaround is to use a helper method instead:
259 ### The trait cannot use `Self` as a type parameter in the supertrait listing
261 This is similar to the second sub-error, but subtler. It happens in situations
267 trait Trait: Super<Self> {
272 impl Super<Foo> for Foo{}
274 impl Trait for Foo {}
277 Here, the supertrait might have methods as follows:
281 fn get_a(&self) -> A; // note that this is object safe!
285 If the trait `Foo` was deriving from something like `Super<String>` or
286 `Super<T>` (where `Foo` itself is `Foo<T>`), this is okay, because given a type
287 `get_a()` will definitely return an object of that type.
289 However, if it derives from `Super<Self>`, even though `Super` is object safe,
290 the method `get_a()` would return an object of unknown type when called on the
291 function. `Self` type parameters let us make object safe traits no longer safe,
292 so they are forbidden when specifying supertraits.
294 There's no easy fix for this, generally code will need to be refactored so that
295 you no longer need to derive from `Super<Self>`.
299 When defining a recursive struct or enum, any use of the type being defined
300 from inside the definition must occur behind a pointer (like `Box` or `&`).
301 This is because structs and enums must have a well-defined size, and without
302 the pointer, the size of the type would need to be unbounded.
304 Consider the following erroneous definition of a type for a list of bytes:
306 ```compile_fail,E0072
307 // error, invalid recursive struct type
310 tail: Option<ListNode>,
314 This type cannot have a well-defined size, because it needs to be arbitrarily
315 large (since we would be able to nest `ListNode`s to any depth). Specifically,
318 size of `ListNode` = 1 byte for `head`
319 + 1 byte for the discriminant of the `Option`
323 One way to fix this is by wrapping `ListNode` in a `Box`, like so:
328 tail: Option<Box<ListNode>>,
332 This works because `Box` is a pointer, so its size is well-known.
336 This error indicates that the compiler was unable to sensibly evaluate an
337 constant expression that had to be evaluated. Attempting to divide by 0
338 or causing integer overflow are two ways to induce this error. For example:
340 ```compile_fail,E0080
347 Ensure that the expressions given can be evaluated as the desired integer type.
348 See the FFI section of the Reference for more information about using a custom
351 https://doc.rust-lang.org/reference.html#ffi-attributes
355 This error indicates that a lifetime is missing from a type. If it is an error
356 inside a function signature, the problem may be with failing to adhere to the
357 lifetime elision rules (see below).
359 Here are some simple examples of where you'll run into this error:
361 ```compile_fail,E0106
362 struct Foo1 { x: &bool }
363 // ^ expected lifetime parameter
364 struct Foo2<'a> { x: &'a bool } // correct
367 // ^^^^ expected lifetime parameter
368 impl<'a> Foo2<'a> {} // correct
370 struct Bar1 { x: Foo2 }
371 // ^^^^ expected lifetime parameter
372 struct Bar2<'a> { x: Foo2<'a> } // correct
374 enum Baz1 { A(u8), B(&bool), }
375 // ^ expected lifetime parameter
376 enum Baz2<'a> { A(u8), B(&'a bool), } // correct
379 // ^ expected lifetime parameter
380 type MyStr2<'a> = &'a str; // correct
383 Lifetime elision is a special, limited kind of inference for lifetimes in
384 function signatures which allows you to leave out lifetimes in certain cases.
385 For more background on lifetime elision see [the book][book-le].
387 The lifetime elision rules require that any function signature with an elided
388 output lifetime must either have
390 - exactly one input lifetime
391 - or, multiple input lifetimes, but the function must also be a method with a
392 `&self` or `&mut self` receiver
394 In the first case, the output lifetime is inferred to be the same as the unique
395 input lifetime. In the second case, the lifetime is instead inferred to be the
396 same as the lifetime on `&self` or `&mut self`.
398 Here are some examples of elision errors:
400 ```compile_fail,E0106
401 // error, no input lifetimes
404 // error, `x` and `y` have distinct lifetimes inferred
405 fn bar(x: &str, y: &str) -> &str { }
407 // error, `y`'s lifetime is inferred to be distinct from `x`'s
408 fn baz<'a>(x: &'a str, y: &str) -> &str { }
411 Lifetime elision in implementation headers was part of the lifetime elision
412 RFC. It is, however, [currently unimplemented][iss15872].
414 [book-le]: https://doc.rust-lang.org/book/ch10-03-lifetime-syntax.html#lifetime-elision
415 [iss15872]: https://github.com/rust-lang/rust/issues/15872
419 There are conflicting trait implementations for the same type.
420 Example of erroneous code:
422 ```compile_fail,E0119
424 fn get(&self) -> usize;
427 impl<T> MyTrait for T {
428 fn get(&self) -> usize { 0 }
435 impl MyTrait for Foo { // error: conflicting implementations of trait
436 // `MyTrait` for type `Foo`
437 fn get(&self) -> usize { self.value }
441 When looking for the implementation for the trait, the compiler finds
442 both the `impl<T> MyTrait for T` where T is all types and the `impl
443 MyTrait for Foo`. Since a trait cannot be implemented multiple times,
444 this is an error. So, when you write:
448 fn get(&self) -> usize;
451 impl<T> MyTrait for T {
452 fn get(&self) -> usize { 0 }
456 This makes the trait implemented on all types in the scope. So if you
457 try to implement it on another one after that, the implementations will
462 fn get(&self) -> usize;
465 impl<T> MyTrait for T {
466 fn get(&self) -> usize { 0 }
474 f.get(); // the trait is implemented so we can use it
479 // This shouldn't really ever trigger since the repeated value error comes first
481 A binary can only have one entry point, and by default that entry point is the
482 function `main()`. If there are multiple such functions, please rename one.
486 More than one function was declared with the `#[main]` attribute.
488 Erroneous code example:
490 ```compile_fail,E0137
497 fn f() {} // error: multiple functions with a #[main] attribute
500 This error indicates that the compiler found multiple functions with the
501 `#[main]` attribute. This is an error because there must be a unique entry
502 point into a Rust program. Example:
513 More than one function was declared with the `#[start]` attribute.
515 Erroneous code example:
517 ```compile_fail,E0138
521 fn foo(argc: isize, argv: *const *const u8) -> isize {}
524 fn f(argc: isize, argv: *const *const u8) -> isize {}
525 // error: multiple 'start' functions
528 This error indicates that the compiler found multiple functions with the
529 `#[start]` attribute. This is an error because there must be a unique entry
530 point into a Rust program. Example:
536 fn foo(argc: isize, argv: *const *const u8) -> isize { 0 } // ok!
541 #### Note: this error code is no longer emitted by the compiler.
543 There are various restrictions on transmuting between types in Rust; for example
544 types being transmuted must have the same size. To apply all these restrictions,
545 the compiler must know the exact types that may be transmuted. When type
546 parameters are involved, this cannot always be done.
548 So, for example, the following is not allowed:
551 use std::mem::transmute;
553 struct Foo<T>(Vec<T>);
555 fn foo<T>(x: Vec<T>) {
556 // we are transmuting between Vec<T> and Foo<F> here
557 let y: Foo<T> = unsafe { transmute(x) };
558 // do something with y
562 In this specific case there's a good chance that the transmute is harmless (but
563 this is not guaranteed by Rust). However, when alignment and enum optimizations
564 come into the picture, it's quite likely that the sizes may or may not match
565 with different type parameter substitutions. It's not possible to check this for
566 _all_ possible types, so `transmute()` simply only accepts types without any
567 unsubstituted type parameters.
569 If you need this, there's a good chance you're doing something wrong. Keep in
570 mind that Rust doesn't guarantee much about the layout of different structs
571 (even two structs with identical declarations may have different layouts). If
572 there is a solution that avoids the transmute entirely, try it instead.
574 If it's possible, hand-monomorphize the code by writing the function for each
575 possible type substitution. It's possible to use traits to do this cleanly,
579 use std::mem::transmute;
581 struct Foo<T>(Vec<T>);
583 trait MyTransmutableType: Sized {
584 fn transmute(_: Vec<Self>) -> Foo<Self>;
587 impl MyTransmutableType for u8 {
588 fn transmute(x: Vec<u8>) -> Foo<u8> {
589 unsafe { transmute(x) }
593 impl MyTransmutableType for String {
594 fn transmute(x: Vec<String>) -> Foo<String> {
595 unsafe { transmute(x) }
599 // ... more impls for the types you intend to transmute
601 fn foo<T: MyTransmutableType>(x: Vec<T>) {
602 let y: Foo<T> = <T as MyTransmutableType>::transmute(x);
603 // do something with y
607 Each impl will be checked for a size match in the transmute as usual, and since
608 there are no unbound type parameters involved, this should compile unless there
609 is a size mismatch in one of the impls.
611 It is also possible to manually transmute:
615 # let v = Some("value");
616 # type SomeType = &'static [u8];
618 ptr::read(&v as *const _ as *const SomeType) // `v` transmuted to `SomeType`
623 Note that this does not move `v` (unlike `transmute`), and may need a
624 call to `mem::forget(v)` in case you want to avoid destructors being called.
628 A lang item was redefined.
630 Erroneous code example:
632 ```compile_fail,E0152
633 #![feature(lang_items)]
636 struct Foo; // error: duplicate lang item found: `arc`
639 Lang items are already implemented in the standard library. Unless you are
640 writing a free-standing application (e.g., a kernel), you do not need to provide
643 You can build a free-standing crate by adding `#![no_std]` to the crate
646 ```ignore (only-for-syntax-highlight)
650 See also the [unstable book][1].
652 [1]: https://doc.rust-lang.org/unstable-book/language-features/lang-items.html#writing-an-executable-without-stdlib
656 A generic type was described using parentheses rather than angle brackets.
659 ```compile_fail,E0214
661 let v: Vec(&str) = vec!["foo"];
665 This is not currently supported: `v` should be defined as `Vec<&str>`.
666 Parentheses are currently only used with generic types when defining parameters
667 for `Fn`-family traits.
671 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
672 message for when a particular trait isn't implemented on a type placed in a
673 position that needs that trait. For example, when the following code is
677 #![feature(on_unimplemented)]
679 fn foo<T: Index<u8>>(x: T){}
681 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
682 trait Index<Idx> { /* ... */ }
684 foo(true); // `bool` does not implement `Index<u8>`
687 There will be an error about `bool` not implementing `Index<u8>`, followed by a
688 note saying "the type `bool` cannot be indexed by `u8`".
690 As you can see, you can specify type parameters in curly braces for
691 substitution with the actual types (using the regular format string syntax) in
692 a given situation. Furthermore, `{Self}` will substitute to the type (in this
693 case, `bool`) that we tried to use.
695 This error appears when the curly braces contain an identifier which doesn't
696 match with any of the type parameters or the string `Self`. This might happen
697 if you misspelled a type parameter, or if you intended to use literal curly
698 braces. If it is the latter, escape the curly braces with a second curly brace
699 of the same type; e.g., a literal `{` is `{{`.
703 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
704 message for when a particular trait isn't implemented on a type placed in a
705 position that needs that trait. For example, when the following code is
709 #![feature(on_unimplemented)]
711 fn foo<T: Index<u8>>(x: T){}
713 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
714 trait Index<Idx> { /* ... */ }
716 foo(true); // `bool` does not implement `Index<u8>`
719 there will be an error about `bool` not implementing `Index<u8>`, followed by a
720 note saying "the type `bool` cannot be indexed by `u8`".
722 As you can see, you can specify type parameters in curly braces for
723 substitution with the actual types (using the regular format string syntax) in
724 a given situation. Furthermore, `{Self}` will substitute to the type (in this
725 case, `bool`) that we tried to use.
727 This error appears when the curly braces do not contain an identifier. Please
728 add one of the same name as a type parameter. If you intended to use literal
729 braces, use `{{` and `}}` to escape them.
733 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
734 message for when a particular trait isn't implemented on a type placed in a
735 position that needs that trait. For example, when the following code is
739 #![feature(on_unimplemented)]
741 fn foo<T: Index<u8>>(x: T){}
743 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
744 trait Index<Idx> { /* ... */ }
746 foo(true); // `bool` does not implement `Index<u8>`
749 there will be an error about `bool` not implementing `Index<u8>`, followed by a
750 note saying "the type `bool` cannot be indexed by `u8`".
752 For this to work, some note must be specified. An empty attribute will not do
753 anything, please remove the attribute or add some helpful note for users of the
758 When using a lifetime like `'a` in a type, it must be declared before being
761 These two examples illustrate the problem:
763 ```compile_fail,E0261
764 // error, use of undeclared lifetime name `'a`
765 fn foo(x: &'a str) { }
768 // error, use of undeclared lifetime name `'a`
773 These can be fixed by declaring lifetime parameters:
780 fn foo<'a>(x: &'a str) {}
783 Impl blocks declare lifetime parameters separately. You need to add lifetime
784 parameters to an impl block if you're implementing a type that has a lifetime
785 parameter of its own.
788 ```compile_fail,E0261
793 // error, use of undeclared lifetime name `'a`
795 fn foo<'a>(x: &'a str) {}
799 This is fixed by declaring the impl block like this:
808 fn foo(x: &'a str) {}
814 Declaring certain lifetime names in parameters is disallowed. For example,
815 because the `'static` lifetime is a special built-in lifetime name denoting
816 the lifetime of the entire program, this is an error:
818 ```compile_fail,E0262
819 // error, invalid lifetime parameter name `'static`
820 fn foo<'static>(x: &'static str) { }
825 A lifetime name cannot be declared more than once in the same scope. For
828 ```compile_fail,E0263
829 // error, lifetime name `'a` declared twice in the same scope
830 fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str) { }
835 An unknown external lang item was used. Erroneous code example:
837 ```compile_fail,E0264
838 #![feature(lang_items)]
841 #[lang = "cake"] // error: unknown external lang item: `cake`
846 A list of available external lang items is available in
847 `src/librustc/middle/weak_lang_items.rs`. Example:
850 #![feature(lang_items)]
853 #[lang = "panic_impl"] // ok!
860 This is because of a type mismatch between the associated type of some
861 trait (e.g., `T::Bar`, where `T` implements `trait Quux { type Bar; }`)
862 and another type `U` that is required to be equal to `T::Bar`, but is not.
865 Here is a basic example:
867 ```compile_fail,E0271
868 trait Trait { type AssociatedType; }
870 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
874 impl Trait for i8 { type AssociatedType = &'static str; }
879 Here is that same example again, with some explanatory comments:
881 ```compile_fail,E0271
882 trait Trait { type AssociatedType; }
884 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
885 // ~~~~~~~~ ~~~~~~~~~~~~~~~~~~
887 // This says `foo` can |
888 // only be used with |
890 // implements `Trait`. |
892 // This says not only must
893 // `T` be an impl of `Trait`
894 // but also that the impl
895 // must assign the type `u32`
896 // to the associated type.
900 impl Trait for i8 { type AssociatedType = &'static str; }
901 //~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
906 // ... but it is an implementation
907 // that assigns `&'static str` to
908 // the associated type.
911 // Here, we invoke `foo` with an `i8`, which does not satisfy
912 // the constraint `<i8 as Trait>::AssociatedType=u32`, and
913 // therefore the type-checker complains with this error code.
916 To avoid those issues, you have to make the types match correctly.
917 So we can fix the previous examples like this:
921 trait Trait { type AssociatedType; }
923 fn foo<T>(t: T) where T: Trait<AssociatedType = &'static str> {
927 impl Trait for i8 { type AssociatedType = &'static str; }
932 let vs = vec![1, 2, 3, 4];
944 This error occurs when there was a recursive trait requirement that overflowed
945 before it could be evaluated. Often this means that there is unbounded
946 recursion in resolving some type bounds.
948 For example, in the following code:
950 ```compile_fail,E0275
955 impl<T> Foo for T where Bar<T>: Foo {}
958 To determine if a `T` is `Foo`, we need to check if `Bar<T>` is `Foo`. However,
959 to do this check, we need to determine that `Bar<Bar<T>>` is `Foo`. To
960 determine this, we check if `Bar<Bar<Bar<T>>>` is `Foo`, and so on. This is
961 clearly a recursive requirement that can't be resolved directly.
963 Consider changing your trait bounds so that they're less self-referential.
967 This error occurs when a bound in an implementation of a trait does not match
968 the bounds specified in the original trait. For example:
970 ```compile_fail,E0276
976 fn foo<T>(x: T) where T: Copy {}
980 Here, all types implementing `Foo` must have a method `foo<T>(x: T)` which can
981 take any type `T`. However, in the `impl` for `bool`, we have added an extra
982 bound that `T` is `Copy`, which isn't compatible with the original trait.
984 Consider removing the bound from the method or adding the bound to the original
985 method definition in the trait.
989 You tried to use a type which doesn't implement some trait in a place which
990 expected that trait. Erroneous code example:
992 ```compile_fail,E0277
993 // here we declare the Foo trait with a bar method
998 // we now declare a function which takes an object implementing the Foo trait
999 fn some_func<T: Foo>(foo: T) {
1004 // we now call the method with the i32 type, which doesn't implement
1006 some_func(5i32); // error: the trait bound `i32 : Foo` is not satisfied
1010 In order to fix this error, verify that the type you're using does implement
1018 fn some_func<T: Foo>(foo: T) {
1019 foo.bar(); // we can now use this method since i32 implements the
1023 // we implement the trait on the i32 type
1029 some_func(5i32); // ok!
1033 Or in a generic context, an erroneous code example would look like:
1035 ```compile_fail,E0277
1036 fn some_func<T>(foo: T) {
1037 println!("{:?}", foo); // error: the trait `core::fmt::Debug` is not
1038 // implemented for the type `T`
1042 // We now call the method with the i32 type,
1043 // which *does* implement the Debug trait.
1048 Note that the error here is in the definition of the generic function: Although
1049 we only call it with a parameter that does implement `Debug`, the compiler
1050 still rejects the function: It must work with all possible input types. In
1051 order to make this example compile, we need to restrict the generic type we're
1057 // Restrict the input type to types that implement Debug.
1058 fn some_func<T: fmt::Debug>(foo: T) {
1059 println!("{:?}", foo);
1063 // Calling the method is still fine, as i32 implements Debug.
1066 // This would fail to compile now:
1067 // struct WithoutDebug;
1068 // some_func(WithoutDebug);
1072 Rust only looks at the signature of the called function, as such it must
1073 already specify all requirements that will be used for every type parameter.
1077 #### Note: this error code is no longer emitted by the compiler.
1079 You tried to supply a type which doesn't implement some trait in a location
1080 which expected that trait. This error typically occurs when working with
1081 `Fn`-based types. Erroneous code example:
1084 fn foo<F: Fn(usize)>(x: F) { }
1087 // type mismatch: ... implements the trait `core::ops::Fn<(String,)>`,
1088 // but the trait `core::ops::Fn<(usize,)>` is required
1090 foo(|y: String| { });
1094 The issue in this case is that `foo` is defined as accepting a `Fn` with one
1095 argument of type `String`, but the closure we attempted to pass to it requires
1096 one arguments of type `usize`.
1100 This error indicates that type inference did not result in one unique possible
1101 type, and extra information is required. In most cases this can be provided
1102 by adding a type annotation. Sometimes you need to specify a generic type
1105 A common example is the `collect` method on `Iterator`. It has a generic type
1106 parameter with a `FromIterator` bound, which for a `char` iterator is
1107 implemented by `Vec` and `String` among others. Consider the following snippet
1108 that reverses the characters of a string:
1110 ```compile_fail,E0282
1111 let x = "hello".chars().rev().collect();
1114 In this case, the compiler cannot infer what the type of `x` should be:
1115 `Vec<char>` and `String` are both suitable candidates. To specify which type to
1116 use, you can use a type annotation on `x`:
1119 let x: Vec<char> = "hello".chars().rev().collect();
1122 It is not necessary to annotate the full type. Once the ambiguity is resolved,
1123 the compiler can infer the rest:
1126 let x: Vec<_> = "hello".chars().rev().collect();
1129 Another way to provide the compiler with enough information, is to specify the
1130 generic type parameter:
1133 let x = "hello".chars().rev().collect::<Vec<char>>();
1136 Again, you need not specify the full type if the compiler can infer it:
1139 let x = "hello".chars().rev().collect::<Vec<_>>();
1142 Apart from a method or function with a generic type parameter, this error can
1143 occur when a type parameter of a struct or trait cannot be inferred. In that
1144 case it is not always possible to use a type annotation, because all candidates
1145 have the same return type. For instance:
1147 ```compile_fail,E0282
1158 let number = Foo::bar();
1163 This will fail because the compiler does not know which instance of `Foo` to
1164 call `bar` on. Change `Foo::bar()` to `Foo::<T>::bar()` to resolve the error.
1168 This error occurs when the compiler doesn't have enough information
1169 to unambiguously choose an implementation.
1173 ```compile_fail,E0283
1180 impl Generator for Impl {
1181 fn create() -> u32 { 1 }
1186 impl Generator for AnotherImpl {
1187 fn create() -> u32 { 2 }
1191 let cont: u32 = Generator::create();
1192 // error, impossible to choose one of Generator trait implementation
1193 // Should it be Impl or AnotherImpl, maybe something else?
1197 To resolve this error use the concrete type:
1206 impl Generator for AnotherImpl {
1207 fn create() -> u32 { 2 }
1211 let gen1 = AnotherImpl::create();
1213 // if there are multiple methods with same name (different traits)
1214 let gen2 = <AnotherImpl as Generator>::create();
1220 This error occurs when the compiler was unable to infer the concrete type of a
1221 variable. It can occur for several cases, the most common of which is a
1222 mismatch in the expected type that the compiler inferred for a variable's
1223 initializing expression, and the actual type explicitly assigned to the
1228 ```compile_fail,E0308
1229 let x: i32 = "I am not a number!";
1230 // ~~~ ~~~~~~~~~~~~~~~~~~~~
1232 // | initializing expression;
1233 // | compiler infers type `&str`
1235 // type `i32` assigned to variable `x`
1240 The type definition contains some field whose type
1241 requires an outlives annotation. Outlives annotations
1242 (e.g., `T: 'a`) are used to guarantee that all the data in T is valid
1243 for at least the lifetime `'a`. This scenario most commonly
1244 arises when the type contains an associated type reference
1245 like `<T as SomeTrait<'a>>::Output`, as shown in this example:
1247 ```compile_fail,E0309
1248 // This won't compile because the applicable impl of
1249 // `SomeTrait` (below) requires that `T: 'a`, but the struct does
1250 // not have a matching where-clause.
1252 foo: <T as SomeTrait<'a>>::Output,
1255 trait SomeTrait<'a> {
1259 impl<'a, T> SomeTrait<'a> for T
1267 Here, the where clause `T: 'a` that appears on the impl is not known to be
1268 satisfied on the struct. To make this example compile, you have to add
1269 a where-clause like `T: 'a` to the struct definition:
1276 foo: <T as SomeTrait<'a>>::Output
1279 trait SomeTrait<'a> {
1283 impl<'a, T> SomeTrait<'a> for T
1293 Types in type definitions have lifetimes associated with them that represent
1294 how long the data stored within them is guaranteed to be live. This lifetime
1295 must be as long as the data needs to be alive, and missing the constraint that
1296 denotes this will cause this error.
1298 ```compile_fail,E0310
1299 // This won't compile because T is not constrained to the static lifetime
1300 // the reference needs
1306 This will compile, because it has the constraint on the type parameter:
1309 struct Foo<T: 'static> {
1316 This error occurs when an `if` expression without an `else` block is used in a
1317 context where a type other than `()` is expected, for example a `let`
1320 ```compile_fail,E0317
1323 let a = if x == 5 { 1 };
1327 An `if` expression without an `else` block has the type `()`, so this is a type
1328 error. To resolve it, add an `else` block having the same type as the `if`
1333 This error indicates that some types or traits depend on each other
1334 and therefore cannot be constructed.
1336 The following example contains a circular dependency between two traits:
1338 ```compile_fail,E0391
1339 trait FirstTrait : SecondTrait {
1343 trait SecondTrait : FirstTrait {
1350 #### Note: this error code is no longer emitted by the compiler.
1352 In Rust 1.3, the default object lifetime bounds are expected to change, as
1353 described in [RFC 1156]. You are getting a warning because the compiler
1354 thinks it is possible that this change will cause a compilation error in your
1355 code. It is possible, though unlikely, that this is a false alarm.
1357 The heart of the change is that where `&'a Box<SomeTrait>` used to default to
1358 `&'a Box<SomeTrait+'a>`, it now defaults to `&'a Box<SomeTrait+'static>` (here,
1359 `SomeTrait` is the name of some trait type). Note that the only types which are
1360 affected are references to boxes, like `&Box<SomeTrait>` or
1361 `&[Box<SomeTrait>]`. More common types like `&SomeTrait` or `Box<SomeTrait>`
1364 To silence this warning, edit your code to use an explicit bound. Most of the
1365 time, this means that you will want to change the signature of a function that
1366 you are calling. For example, if the error is reported on a call like `foo(x)`,
1367 and `foo` is defined as follows:
1370 # trait SomeTrait {}
1371 fn foo(arg: &Box<SomeTrait>) { /* ... */ }
1374 You might change it to:
1377 # trait SomeTrait {}
1378 fn foo<'a>(arg: &'a Box<SomeTrait+'a>) { /* ... */ }
1381 This explicitly states that you expect the trait object `SomeTrait` to contain
1382 references (with a maximum lifetime of `'a`).
1384 [RFC 1156]: https://github.com/rust-lang/rfcs/blob/master/text/1156-adjust-default-object-bounds.md
1388 An invalid lint attribute has been given. Erroneous code example:
1390 ```compile_fail,E0452
1391 #![allow(foo = "")] // error: malformed lint attribute
1394 Lint attributes only accept a list of identifiers (where each identifier is a
1395 lint name). Ensure the attribute is of this form:
1398 #![allow(foo)] // ok!
1400 #![allow(foo, foo2)] // ok!
1405 A lint check attribute was overruled by a `forbid` directive set as an
1406 attribute on an enclosing scope, or on the command line with the `-F` option.
1408 Example of erroneous code:
1410 ```compile_fail,E0453
1411 #![forbid(non_snake_case)]
1413 #[allow(non_snake_case)]
1415 let MyNumber = 2; // error: allow(non_snake_case) overruled by outer
1416 // forbid(non_snake_case)
1420 The `forbid` lint setting, like `deny`, turns the corresponding compiler
1421 warning into a hard error. Unlike `deny`, `forbid` prevents itself from being
1422 overridden by inner attributes.
1424 If you're sure you want to override the lint check, you can change `forbid` to
1425 `deny` (or use `-D` instead of `-F` if the `forbid` setting was given as a
1426 command-line option) to allow the inner lint check attribute:
1429 #![deny(non_snake_case)]
1431 #[allow(non_snake_case)]
1433 let MyNumber = 2; // ok!
1437 Otherwise, edit the code to pass the lint check, and remove the overruled
1441 #![forbid(non_snake_case)]
1450 A lifetime bound was not satisfied.
1452 Erroneous code example:
1454 ```compile_fail,E0478
1455 // Check that the explicit lifetime bound (`'SnowWhite`, in this example) must
1456 // outlive all the superbounds from the trait (`'kiss`, in this example).
1458 trait Wedding<'t>: 't { }
1460 struct Prince<'kiss, 'SnowWhite> {
1461 child: Box<Wedding<'kiss> + 'SnowWhite>,
1462 // error: lifetime bound not satisfied
1466 In this example, the `'SnowWhite` lifetime is supposed to outlive the `'kiss`
1467 lifetime but the declaration of the `Prince` struct doesn't enforce it. To fix
1468 this issue, you need to specify it:
1471 trait Wedding<'t>: 't { }
1473 struct Prince<'kiss, 'SnowWhite: 'kiss> { // You say here that 'kiss must live
1474 // longer than 'SnowWhite.
1475 child: Box<Wedding<'kiss> + 'SnowWhite>, // And now it's all good!
1481 A reference has a longer lifetime than the data it references.
1483 Erroneous code example:
1485 ```compile_fail,E0491
1486 trait SomeTrait<'a> {
1490 impl<'a, T> SomeTrait<'a> for T {
1491 type Output = &'a T; // compile error E0491
1495 Here, the problem is that a reference type like `&'a T` is only valid
1496 if all the data in T outlives the lifetime `'a`. But this impl as written
1497 is applicable to any lifetime `'a` and any type `T` -- we have no guarantee
1498 that `T` outlives `'a`. To fix this, you can add a where clause like
1502 trait SomeTrait<'a> {
1506 impl<'a, T> SomeTrait<'a> for T
1510 type Output = &'a T; // compile error E0491
1516 A lifetime name is shadowing another lifetime name. Erroneous code example:
1518 ```compile_fail,E0496
1524 fn f<'a>(x: &'a i32) { // error: lifetime name `'a` shadows a lifetime
1525 // name that is already in scope
1530 Please change the name of one of the lifetimes to remove this error. Example:
1538 fn f<'b>(x: &'b i32) { // ok!
1548 A stability attribute was used outside of the standard library. Erroneous code
1552 #[stable] // error: stability attributes may not be used outside of the
1557 It is not possible to use stability attributes outside of the standard library.
1558 Also, for now, it is not possible to write deprecation messages either.
1562 Transmute with two differently sized types was attempted. Erroneous code
1565 ```compile_fail,E0512
1566 fn takes_u8(_: u8) {}
1569 unsafe { takes_u8(::std::mem::transmute(0u16)); }
1570 // error: cannot transmute between types of different sizes,
1571 // or dependently-sized types
1575 Please use types with same size or use the expected type directly. Example:
1578 fn takes_u8(_: u8) {}
1581 unsafe { takes_u8(::std::mem::transmute(0i8)); } // ok!
1583 unsafe { takes_u8(0u8); } // ok!
1589 This error indicates that a `#[repr(..)]` attribute was placed on an
1592 Examples of erroneous code:
1594 ```compile_fail,E0517
1602 struct Foo {bar: bool, baz: bool}
1610 * The `#[repr(C)]` attribute can only be placed on structs and enums.
1611 * The `#[repr(packed)]` and `#[repr(simd)]` attributes only work on structs.
1612 * The `#[repr(u8)]`, `#[repr(i16)]`, etc attributes only work on enums.
1614 These attributes do not work on typedefs, since typedefs are just aliases.
1616 Representations like `#[repr(u8)]`, `#[repr(i64)]` are for selecting the
1617 discriminant size for enums with no data fields on any of the variants, e.g.
1618 `enum Color {Red, Blue, Green}`, effectively setting the size of the enum to
1619 the size of the provided type. Such an enum can be cast to a value of the same
1620 type as well. In short, `#[repr(u8)]` makes the enum behave like an integer
1621 with a constrained set of allowed values.
1623 Only field-less enums can be cast to numerical primitives, so this attribute
1624 will not apply to structs.
1626 `#[repr(packed)]` reduces padding to make the struct size smaller. The
1627 representation of enums isn't strictly defined in Rust, and this attribute
1628 won't work on enums.
1630 `#[repr(simd)]` will give a struct consisting of a homogeneous series of machine
1631 types (i.e., `u8`, `i32`, etc) a representation that permits vectorization via
1632 SIMD. This doesn't make much sense for enums since they don't consist of a
1633 single list of data.
1637 This error indicates that an `#[inline(..)]` attribute was incorrectly placed
1638 on something other than a function or method.
1640 Examples of erroneous code:
1642 ```compile_fail,E0518
1652 `#[inline]` hints the compiler whether or not to attempt to inline a method or
1653 function. By default, the compiler does a pretty good job of figuring this out
1654 itself, but if you feel the need for annotations, `#[inline(always)]` and
1655 `#[inline(never)]` can override or force the compiler's decision.
1657 If you wish to apply this attribute to all methods in an impl, manually annotate
1658 each method; it is not possible to annotate the entire impl with an `#[inline]`
1663 The lang attribute is intended for marking special items that are built-in to
1664 Rust itself. This includes special traits (like `Copy` and `Sized`) that affect
1665 how the compiler behaves, as well as special functions that may be automatically
1666 invoked (such as the handler for out-of-bounds accesses when indexing a slice).
1667 Erroneous code example:
1669 ```compile_fail,E0522
1670 #![feature(lang_items)]
1673 fn cookie() -> ! { // error: definition of an unknown language item: `cookie`
1680 A closure was used but didn't implement the expected trait.
1682 Erroneous code example:
1684 ```compile_fail,E0525
1688 fn bar<T: Fn(u32)>(_: T) {}
1692 let closure = |_| foo(x); // error: expected a closure that implements
1693 // the `Fn` trait, but this closure only
1694 // implements `FnOnce`
1699 In the example above, `closure` is an `FnOnce` closure whereas the `bar`
1700 function expected an `Fn` closure. In this case, it's simple to fix the issue,
1701 you just have to implement `Copy` and `Clone` traits on `struct X` and it'll
1705 #[derive(Clone, Copy)] // We implement `Clone` and `Copy` traits.
1709 fn bar<T: Fn(u32)>(_: T) {}
1713 let closure = |_| foo(x);
1714 bar(closure); // ok!
1718 To understand better how closures work in Rust, read:
1719 https://doc.rust-lang.org/book/ch13-01-closures.html
1723 The `main` function was incorrectly declared.
1725 Erroneous code example:
1727 ```compile_fail,E0580
1728 fn main(x: i32) { // error: main function has wrong type
1733 The `main` function prototype should never take arguments.
1742 If you want to get command-line arguments, use `std::env::args`. To exit with a
1743 specified exit code, use `std::process::exit`.
1747 Abstract return types (written `impl Trait` for some trait `Trait`) are only
1748 allowed as function and inherent impl return types.
1750 Erroneous code example:
1752 ```compile_fail,E0562
1754 let count_to_ten: impl Iterator<Item=usize> = 0..10;
1755 // error: `impl Trait` not allowed outside of function and inherent method
1757 for i in count_to_ten {
1763 Make sure `impl Trait` only appears in return-type position.
1766 fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
1771 for i in count_to_n(10) { // ok!
1777 See [RFC 1522] for more details.
1779 [RFC 1522]: https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md
1783 Per [RFC 401][rfc401], if you have a function declaration `foo`:
1786 // For the purposes of this explanation, all of these
1787 // different kinds of `fn` declarations are equivalent:
1789 fn foo(x: S) { /* ... */ }
1790 # #[cfg(for_demonstration_only)]
1791 extern "C" { fn foo(x: S); }
1792 # #[cfg(for_demonstration_only)]
1793 impl S { fn foo(self) { /* ... */ } }
1796 the type of `foo` is **not** `fn(S)`, as one might expect.
1797 Rather, it is a unique, zero-sized marker type written here as `typeof(foo)`.
1798 However, `typeof(foo)` can be _coerced_ to a function pointer `fn(S)`,
1799 so you rarely notice this:
1804 let x: fn(S) = foo; // OK, coerces
1807 The reason that this matter is that the type `fn(S)` is not specific to
1808 any particular function: it's a function _pointer_. So calling `x()` results
1809 in a virtual call, whereas `foo()` is statically dispatched, because the type
1810 of `foo` tells us precisely what function is being called.
1812 As noted above, coercions mean that most code doesn't have to be
1813 concerned with this distinction. However, you can tell the difference
1814 when using **transmute** to convert a fn item into a fn pointer.
1816 This is sometimes done as part of an FFI:
1818 ```compile_fail,E0591
1819 extern "C" fn foo(userdata: Box<i32>) {
1823 # fn callback(_: extern "C" fn(*mut i32)) {}
1824 # use std::mem::transmute;
1826 let f: extern "C" fn(*mut i32) = transmute(foo);
1831 Here, transmute is being used to convert the types of the fn arguments.
1832 This pattern is incorrect because, because the type of `foo` is a function
1833 **item** (`typeof(foo)`), which is zero-sized, and the target type (`fn()`)
1834 is a function pointer, which is not zero-sized.
1835 This pattern should be rewritten. There are a few possible ways to do this:
1837 - change the original fn declaration to match the expected signature,
1838 and do the cast in the fn body (the preferred option)
1839 - cast the fn item fo a fn pointer before calling transmute, as shown here:
1842 # extern "C" fn foo(_: Box<i32>) {}
1843 # use std::mem::transmute;
1845 let f: extern "C" fn(*mut i32) = transmute(foo as extern "C" fn(_));
1846 let f: extern "C" fn(*mut i32) = transmute(foo as usize); // works too
1850 The same applies to transmutes to `*mut fn()`, which were observedin practice.
1851 Note though that use of this type is generally incorrect.
1852 The intention is typically to describe a function pointer, but just `fn()`
1853 alone suffices for that. `*mut fn()` is a pointer to a fn pointer.
1854 (Since these values are typically just passed to C code, however, this rarely
1855 makes a difference in practice.)
1857 [rfc401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md
1861 You tried to supply an `Fn`-based type with an incorrect number of arguments
1862 than what was expected.
1864 Erroneous code example:
1866 ```compile_fail,E0593
1867 fn foo<F: Fn()>(x: F) { }
1870 // [E0593] closure takes 1 argument but 0 arguments are required
1877 No `main` function was found in a binary crate. To fix this error, add a
1878 `main` function. For example:
1882 // Your program will start here.
1883 println!("Hello world!");
1887 If you don't know the basics of Rust, you can go look to the Rust Book to get
1888 started: https://doc.rust-lang.org/book/
1892 An unknown lint was used on the command line.
1897 rustc -D bogus omse_file.rs
1900 Maybe you just misspelled the lint name or the lint doesn't exist anymore.
1901 Either way, try to update/remove it in order to fix the error.
1905 This error code indicates a mismatch between the lifetimes appearing in the
1906 function signature (i.e., the parameter types and the return type) and the
1907 data-flow found in the function body.
1909 Erroneous code example:
1911 ```compile_fail,E0621
1912 fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 { // error: explicit lifetime
1913 // required in the type of
1915 if x > y { x } else { y }
1919 In the code above, the function is returning data borrowed from either `x` or
1920 `y`, but the `'a` annotation indicates that it is returning data only from `x`.
1921 To fix the error, the signature and the body must be made to match. Typically,
1922 this is done by updating the function signature. So, in this case, we change
1923 the type of `y` to `&'a i32`, like so:
1926 fn foo<'a>(x: &'a i32, y: &'a i32) -> &'a i32 {
1927 if x > y { x } else { y }
1931 Now the signature indicates that the function data borrowed from either `x` or
1932 `y`. Alternatively, you could change the body to not return data from `y`:
1935 fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 {
1942 The `#![feature]` attribute specified an unknown feature.
1944 Erroneous code example:
1946 ```compile_fail,E0635
1947 #![feature(nonexistent_rust_feature)] // error: unknown feature
1953 A `#![feature]` attribute was declared multiple times.
1955 Erroneous code example:
1957 ```compile_fail,E0636
1958 #![allow(stable_features)]
1960 #![feature(rust1)] // error: the feature `rust1` has already been declared
1966 A closure or generator was constructed that references its own type.
1970 ```compile-fail,E0644
1979 // Here, when `x` is called, the parameter `y` is equal to `x`.
1984 Rust does not permit a closure to directly reference its own type,
1985 either through an argument (as in the example above) or by capturing
1986 itself through its environment. This restriction helps keep closure
1987 inference tractable.
1989 The easiest fix is to rewrite your closure into a top-level function,
1990 or into a method. In some cases, you may also be able to have your
1991 closure call itself by capturing a `&Fn()` object or `fn()` pointer
1992 that refers to itself. That is permitting, since the closure would be
1993 invoking itself via a virtual call, and hence does not directly
1994 reference its own *type*.
1999 A `repr(transparent)` type was also annotated with other, incompatible
2000 representation hints.
2002 Erroneous code example:
2004 ```compile_fail,E0692
2005 #[repr(transparent, C)] // error: incompatible representation hints
2009 A type annotated as `repr(transparent)` delegates all representation concerns to
2010 another type, so adding more representation hints is contradictory. Remove
2011 either the `transparent` hint or the other hints, like this:
2014 #[repr(transparent)]
2018 Alternatively, move the other attributes to the contained type:
2027 #[repr(transparent)]
2028 struct FooWrapper(Foo);
2031 Note that introducing another `struct` just to have a place for the other
2032 attributes may have unintended side effects on the representation:
2035 #[repr(transparent)]
2041 #[repr(transparent)]
2042 struct Grams2(Float); // this is not equivalent to `Grams` above
2045 Here, `Grams2` is a not equivalent to `Grams` -- the former transparently wraps
2046 a (non-transparent) struct containing a single float, while `Grams` is a
2047 transparent wrapper around a float. This can make a difference for the ABI.
2051 The `impl Trait` return type captures lifetime parameters that do not
2052 appear within the `impl Trait` itself.
2054 Erroneous code example:
2056 ```compile-fail,E0700
2057 use std::cell::Cell;
2061 impl<'a, 'b> Trait<'b> for Cell<&'a u32> { }
2063 fn foo<'x, 'y>(x: Cell<&'x u32>) -> impl Trait<'y>
2070 Here, the function `foo` returns a value of type `Cell<&'x u32>`,
2071 which references the lifetime `'x`. However, the return type is
2072 declared as `impl Trait<'y>` -- this indicates that `foo` returns
2073 "some type that implements `Trait<'y>`", but it also indicates that
2074 the return type **only captures data referencing the lifetime `'y`**.
2075 In this case, though, we are referencing data with lifetime `'x`, so
2076 this function is in error.
2078 To fix this, you must reference the lifetime `'x` from the return
2079 type. For example, changing the return type to `impl Trait<'y> + 'x`
2083 use std::cell::Cell;
2087 impl<'a,'b> Trait<'b> for Cell<&'a u32> { }
2089 fn foo<'x, 'y>(x: Cell<&'x u32>) -> impl Trait<'y> + 'x
2098 This error indicates that a `#[non_exhaustive]` attribute was incorrectly placed
2099 on something other than a struct or enum.
2101 Examples of erroneous code:
2103 ```compile_fail,E0701
2104 # #![feature(non_exhaustive)]
2112 This error indicates that a `#[lang = ".."]` attribute was placed
2113 on the wrong type of item.
2115 Examples of erroneous code:
2117 ```compile_fail,E0718
2118 #![feature(lang_items)]
2128 register_diagnostics! {
2129 // E0006, // merged with E0005
2130 // E0101, // replaced with E0282
2131 // E0102, // replaced with E0282
2134 // E0272, // on_unimplemented #0
2135 // E0273, // on_unimplemented #1
2136 // E0274, // on_unimplemented #2
2137 E0278, // requirement is not satisfied
2138 E0279, // requirement is not satisfied
2139 E0280, // requirement is not satisfied
2140 E0284, // cannot resolve type
2141 // E0285, // overflow evaluation builtin bounds
2142 // E0296, // replaced with a generic attribute input check
2143 // E0300, // unexpanded macro
2144 // E0304, // expected signed integer constant
2145 // E0305, // expected constant
2146 E0311, // thing may not live long enough
2147 E0312, // lifetime of reference outlives lifetime of borrowed content
2148 E0313, // lifetime of borrowed pointer outlives lifetime of captured variable
2149 E0314, // closure outlives stack frame
2150 E0315, // cannot invoke closure outside of its lifetime
2151 E0316, // nested quantification of lifetimes
2152 E0320, // recursive overflow during dropck
2153 E0473, // dereference of reference outside its lifetime
2154 E0474, // captured variable `..` does not outlive the enclosing closure
2155 E0475, // index of slice outside its lifetime
2156 E0476, // lifetime of the source pointer does not outlive lifetime bound...
2157 E0477, // the type `..` does not fulfill the required lifetime...
2158 E0479, // the type `..` (provided as the value of a type parameter) is...
2159 E0480, // lifetime of method receiver does not outlive the method call
2160 E0481, // lifetime of function argument does not outlive the function call
2161 E0482, // lifetime of return value does not outlive the function call
2162 E0483, // lifetime of operand does not outlive the operation
2163 E0484, // reference is not valid at the time of borrow
2164 E0485, // automatically reference is not valid at the time of borrow
2165 E0486, // type of expression contains references that are not valid during...
2166 E0487, // unsafe use of destructor: destructor might be called while...
2167 E0488, // lifetime of variable does not enclose its declaration
2168 E0489, // type/lifetime parameter not in scope here
2169 E0490, // a value of type `..` is borrowed for too long
2170 E0495, // cannot infer an appropriate lifetime due to conflicting requirements
2171 E0566, // conflicting representation hints
2172 E0623, // lifetime mismatch where both parameters are anonymous regions
2173 E0628, // generators cannot have explicit arguments
2174 E0631, // type mismatch in closure arguments
2175 E0637, // "'_" is not a valid lifetime bound
2176 E0657, // `impl Trait` can only capture lifetimes bound at the fn level
2177 E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
2178 E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
2179 E0697, // closures cannot be static
2180 E0707, // multiple elided lifetimes used in arguments of `async fn`
2181 E0708, // `async` non-`move` closures with arguments are not currently supported
2182 E0709, // multiple different lifetimes used in arguments of `async fn`
2183 E0710, // an unknown tool name found in scoped lint
2184 E0711, // a feature has been declared with conflicting stability attributes
2185 // E0702, // replaced with a generic attribute input check