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 [book-le]: https://doc.rust-lang.org/book/ch10-03-lifetime-syntax.html#lifetime-elision
415 There are conflicting trait implementations for the same type.
416 Example of erroneous code:
418 ```compile_fail,E0119
420 fn get(&self) -> usize;
423 impl<T> MyTrait for T {
424 fn get(&self) -> usize { 0 }
431 impl MyTrait for Foo { // error: conflicting implementations of trait
432 // `MyTrait` for type `Foo`
433 fn get(&self) -> usize { self.value }
437 When looking for the implementation for the trait, the compiler finds
438 both the `impl<T> MyTrait for T` where T is all types and the `impl
439 MyTrait for Foo`. Since a trait cannot be implemented multiple times,
440 this is an error. So, when you write:
444 fn get(&self) -> usize;
447 impl<T> MyTrait for T {
448 fn get(&self) -> usize { 0 }
452 This makes the trait implemented on all types in the scope. So if you
453 try to implement it on another one after that, the implementations will
458 fn get(&self) -> usize;
461 impl<T> MyTrait for T {
462 fn get(&self) -> usize { 0 }
470 f.get(); // the trait is implemented so we can use it
475 // This shouldn't really ever trigger since the repeated value error comes first
477 A binary can only have one entry point, and by default that entry point is the
478 function `main()`. If there are multiple such functions, please rename one.
482 More than one function was declared with the `#[main]` attribute.
484 Erroneous code example:
486 ```compile_fail,E0137
493 fn f() {} // error: multiple functions with a #[main] attribute
496 This error indicates that the compiler found multiple functions with the
497 `#[main]` attribute. This is an error because there must be a unique entry
498 point into a Rust program. Example:
509 More than one function was declared with the `#[start]` attribute.
511 Erroneous code example:
513 ```compile_fail,E0138
517 fn foo(argc: isize, argv: *const *const u8) -> isize {}
520 fn f(argc: isize, argv: *const *const u8) -> isize {}
521 // error: multiple 'start' functions
524 This error indicates that the compiler found multiple functions with the
525 `#[start]` attribute. This is an error because there must be a unique entry
526 point into a Rust program. Example:
532 fn foo(argc: isize, argv: *const *const u8) -> isize { 0 } // ok!
537 #### Note: this error code is no longer emitted by the compiler.
539 There are various restrictions on transmuting between types in Rust; for example
540 types being transmuted must have the same size. To apply all these restrictions,
541 the compiler must know the exact types that may be transmuted. When type
542 parameters are involved, this cannot always be done.
544 So, for example, the following is not allowed:
547 use std::mem::transmute;
549 struct Foo<T>(Vec<T>);
551 fn foo<T>(x: Vec<T>) {
552 // we are transmuting between Vec<T> and Foo<F> here
553 let y: Foo<T> = unsafe { transmute(x) };
554 // do something with y
558 In this specific case there's a good chance that the transmute is harmless (but
559 this is not guaranteed by Rust). However, when alignment and enum optimizations
560 come into the picture, it's quite likely that the sizes may or may not match
561 with different type parameter substitutions. It's not possible to check this for
562 _all_ possible types, so `transmute()` simply only accepts types without any
563 unsubstituted type parameters.
565 If you need this, there's a good chance you're doing something wrong. Keep in
566 mind that Rust doesn't guarantee much about the layout of different structs
567 (even two structs with identical declarations may have different layouts). If
568 there is a solution that avoids the transmute entirely, try it instead.
570 If it's possible, hand-monomorphize the code by writing the function for each
571 possible type substitution. It's possible to use traits to do this cleanly,
575 use std::mem::transmute;
577 struct Foo<T>(Vec<T>);
579 trait MyTransmutableType: Sized {
580 fn transmute(_: Vec<Self>) -> Foo<Self>;
583 impl MyTransmutableType for u8 {
584 fn transmute(x: Vec<u8>) -> Foo<u8> {
585 unsafe { transmute(x) }
589 impl MyTransmutableType for String {
590 fn transmute(x: Vec<String>) -> Foo<String> {
591 unsafe { transmute(x) }
595 // ... more impls for the types you intend to transmute
597 fn foo<T: MyTransmutableType>(x: Vec<T>) {
598 let y: Foo<T> = <T as MyTransmutableType>::transmute(x);
599 // do something with y
603 Each impl will be checked for a size match in the transmute as usual, and since
604 there are no unbound type parameters involved, this should compile unless there
605 is a size mismatch in one of the impls.
607 It is also possible to manually transmute:
611 # let v = Some("value");
612 # type SomeType = &'static [u8];
614 ptr::read(&v as *const _ as *const SomeType) // `v` transmuted to `SomeType`
619 Note that this does not move `v` (unlike `transmute`), and may need a
620 call to `mem::forget(v)` in case you want to avoid destructors being called.
624 A lang item was redefined.
626 Erroneous code example:
628 ```compile_fail,E0152
629 #![feature(lang_items)]
632 struct Foo; // error: duplicate lang item found: `arc`
635 Lang items are already implemented in the standard library. Unless you are
636 writing a free-standing application (e.g., a kernel), you do not need to provide
639 You can build a free-standing crate by adding `#![no_std]` to the crate
642 ```ignore (only-for-syntax-highlight)
646 See also the [unstable book][1].
648 [1]: https://doc.rust-lang.org/unstable-book/language-features/lang-items.html#writing-an-executable-without-stdlib
652 A generic type was described using parentheses rather than angle brackets.
655 ```compile_fail,E0214
657 let v: Vec(&str) = vec!["foo"];
661 This is not currently supported: `v` should be defined as `Vec<&str>`.
662 Parentheses are currently only used with generic types when defining parameters
663 for `Fn`-family traits.
667 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
668 message for when a particular trait isn't implemented on a type placed in a
669 position that needs that trait. For example, when the following code is
673 #![feature(on_unimplemented)]
675 fn foo<T: Index<u8>>(x: T){}
677 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
678 trait Index<Idx> { /* ... */ }
680 foo(true); // `bool` does not implement `Index<u8>`
683 There will be an error about `bool` not implementing `Index<u8>`, followed by a
684 note saying "the type `bool` cannot be indexed by `u8`".
686 As you can see, you can specify type parameters in curly braces for
687 substitution with the actual types (using the regular format string syntax) in
688 a given situation. Furthermore, `{Self}` will substitute to the type (in this
689 case, `bool`) that we tried to use.
691 This error appears when the curly braces contain an identifier which doesn't
692 match with any of the type parameters or the string `Self`. This might happen
693 if you misspelled a type parameter, or if you intended to use literal curly
694 braces. If it is the latter, escape the curly braces with a second curly brace
695 of the same type; e.g., a literal `{` is `{{`.
699 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
700 message for when a particular trait isn't implemented on a type placed in a
701 position that needs that trait. For example, when the following code is
705 #![feature(on_unimplemented)]
707 fn foo<T: Index<u8>>(x: T){}
709 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
710 trait Index<Idx> { /* ... */ }
712 foo(true); // `bool` does not implement `Index<u8>`
715 there will be an error about `bool` not implementing `Index<u8>`, followed by a
716 note saying "the type `bool` cannot be indexed by `u8`".
718 As you can see, you can specify type parameters in curly braces for
719 substitution with the actual types (using the regular format string syntax) in
720 a given situation. Furthermore, `{Self}` will substitute to the type (in this
721 case, `bool`) that we tried to use.
723 This error appears when the curly braces do not contain an identifier. Please
724 add one of the same name as a type parameter. If you intended to use literal
725 braces, use `{{` and `}}` to escape them.
729 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
730 message for when a particular trait isn't implemented on a type placed in a
731 position that needs that trait. For example, when the following code is
735 #![feature(on_unimplemented)]
737 fn foo<T: Index<u8>>(x: T){}
739 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
740 trait Index<Idx> { /* ... */ }
742 foo(true); // `bool` does not implement `Index<u8>`
745 there will be an error about `bool` not implementing `Index<u8>`, followed by a
746 note saying "the type `bool` cannot be indexed by `u8`".
748 For this to work, some note must be specified. An empty attribute will not do
749 anything, please remove the attribute or add some helpful note for users of the
754 When using a lifetime like `'a` in a type, it must be declared before being
757 These two examples illustrate the problem:
759 ```compile_fail,E0261
760 // error, use of undeclared lifetime name `'a`
761 fn foo(x: &'a str) { }
764 // error, use of undeclared lifetime name `'a`
769 These can be fixed by declaring lifetime parameters:
776 fn foo<'a>(x: &'a str) {}
779 Impl blocks declare lifetime parameters separately. You need to add lifetime
780 parameters to an impl block if you're implementing a type that has a lifetime
781 parameter of its own.
784 ```compile_fail,E0261
789 // error, use of undeclared lifetime name `'a`
791 fn foo<'a>(x: &'a str) {}
795 This is fixed by declaring the impl block like this:
804 fn foo(x: &'a str) {}
810 Declaring certain lifetime names in parameters is disallowed. For example,
811 because the `'static` lifetime is a special built-in lifetime name denoting
812 the lifetime of the entire program, this is an error:
814 ```compile_fail,E0262
815 // error, invalid lifetime parameter name `'static`
816 fn foo<'static>(x: &'static str) { }
821 A lifetime name cannot be declared more than once in the same scope. For
824 ```compile_fail,E0263
825 // error, lifetime name `'a` declared twice in the same scope
826 fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str) { }
831 An unknown external lang item was used. Erroneous code example:
833 ```compile_fail,E0264
834 #![feature(lang_items)]
837 #[lang = "cake"] // error: unknown external lang item: `cake`
842 A list of available external lang items is available in
843 `src/librustc/middle/weak_lang_items.rs`. Example:
846 #![feature(lang_items)]
849 #[lang = "panic_impl"] // ok!
856 This is because of a type mismatch between the associated type of some
857 trait (e.g., `T::Bar`, where `T` implements `trait Quux { type Bar; }`)
858 and another type `U` that is required to be equal to `T::Bar`, but is not.
861 Here is a basic example:
863 ```compile_fail,E0271
864 trait Trait { type AssociatedType; }
866 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
870 impl Trait for i8 { type AssociatedType = &'static str; }
875 Here is that same example again, with some explanatory comments:
877 ```compile_fail,E0271
878 trait Trait { type AssociatedType; }
880 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
881 // ~~~~~~~~ ~~~~~~~~~~~~~~~~~~
883 // This says `foo` can |
884 // only be used with |
886 // implements `Trait`. |
888 // This says not only must
889 // `T` be an impl of `Trait`
890 // but also that the impl
891 // must assign the type `u32`
892 // to the associated type.
896 impl Trait for i8 { type AssociatedType = &'static str; }
897 //~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
902 // ... but it is an implementation
903 // that assigns `&'static str` to
904 // the associated type.
907 // Here, we invoke `foo` with an `i8`, which does not satisfy
908 // the constraint `<i8 as Trait>::AssociatedType=u32`, and
909 // therefore the type-checker complains with this error code.
912 To avoid those issues, you have to make the types match correctly.
913 So we can fix the previous examples like this:
917 trait Trait { type AssociatedType; }
919 fn foo<T>(t: T) where T: Trait<AssociatedType = &'static str> {
923 impl Trait for i8 { type AssociatedType = &'static str; }
928 let vs = vec![1, 2, 3, 4];
940 This error occurs when there was a recursive trait requirement that overflowed
941 before it could be evaluated. Often this means that there is unbounded
942 recursion in resolving some type bounds.
944 For example, in the following code:
946 ```compile_fail,E0275
951 impl<T> Foo for T where Bar<T>: Foo {}
954 To determine if a `T` is `Foo`, we need to check if `Bar<T>` is `Foo`. However,
955 to do this check, we need to determine that `Bar<Bar<T>>` is `Foo`. To
956 determine this, we check if `Bar<Bar<Bar<T>>>` is `Foo`, and so on. This is
957 clearly a recursive requirement that can't be resolved directly.
959 Consider changing your trait bounds so that they're less self-referential.
963 This error occurs when a bound in an implementation of a trait does not match
964 the bounds specified in the original trait. For example:
966 ```compile_fail,E0276
972 fn foo<T>(x: T) where T: Copy {}
976 Here, all types implementing `Foo` must have a method `foo<T>(x: T)` which can
977 take any type `T`. However, in the `impl` for `bool`, we have added an extra
978 bound that `T` is `Copy`, which isn't compatible with the original trait.
980 Consider removing the bound from the method or adding the bound to the original
981 method definition in the trait.
985 You tried to use a type which doesn't implement some trait in a place which
986 expected that trait. Erroneous code example:
988 ```compile_fail,E0277
989 // here we declare the Foo trait with a bar method
994 // we now declare a function which takes an object implementing the Foo trait
995 fn some_func<T: Foo>(foo: T) {
1000 // we now call the method with the i32 type, which doesn't implement
1002 some_func(5i32); // error: the trait bound `i32 : Foo` is not satisfied
1006 In order to fix this error, verify that the type you're using does implement
1014 fn some_func<T: Foo>(foo: T) {
1015 foo.bar(); // we can now use this method since i32 implements the
1019 // we implement the trait on the i32 type
1025 some_func(5i32); // ok!
1029 Or in a generic context, an erroneous code example would look like:
1031 ```compile_fail,E0277
1032 fn some_func<T>(foo: T) {
1033 println!("{:?}", foo); // error: the trait `core::fmt::Debug` is not
1034 // implemented for the type `T`
1038 // We now call the method with the i32 type,
1039 // which *does* implement the Debug trait.
1044 Note that the error here is in the definition of the generic function: Although
1045 we only call it with a parameter that does implement `Debug`, the compiler
1046 still rejects the function: It must work with all possible input types. In
1047 order to make this example compile, we need to restrict the generic type we're
1053 // Restrict the input type to types that implement Debug.
1054 fn some_func<T: fmt::Debug>(foo: T) {
1055 println!("{:?}", foo);
1059 // Calling the method is still fine, as i32 implements Debug.
1062 // This would fail to compile now:
1063 // struct WithoutDebug;
1064 // some_func(WithoutDebug);
1068 Rust only looks at the signature of the called function, as such it must
1069 already specify all requirements that will be used for every type parameter.
1073 #### Note: this error code is no longer emitted by the compiler.
1075 You tried to supply a type which doesn't implement some trait in a location
1076 which expected that trait. This error typically occurs when working with
1077 `Fn`-based types. Erroneous code example:
1080 fn foo<F: Fn(usize)>(x: F) { }
1083 // type mismatch: ... implements the trait `core::ops::Fn<(String,)>`,
1084 // but the trait `core::ops::Fn<(usize,)>` is required
1086 foo(|y: String| { });
1090 The issue in this case is that `foo` is defined as accepting a `Fn` with one
1091 argument of type `String`, but the closure we attempted to pass to it requires
1092 one arguments of type `usize`.
1096 This error indicates that type inference did not result in one unique possible
1097 type, and extra information is required. In most cases this can be provided
1098 by adding a type annotation. Sometimes you need to specify a generic type
1101 A common example is the `collect` method on `Iterator`. It has a generic type
1102 parameter with a `FromIterator` bound, which for a `char` iterator is
1103 implemented by `Vec` and `String` among others. Consider the following snippet
1104 that reverses the characters of a string:
1106 ```compile_fail,E0282
1107 let x = "hello".chars().rev().collect();
1110 In this case, the compiler cannot infer what the type of `x` should be:
1111 `Vec<char>` and `String` are both suitable candidates. To specify which type to
1112 use, you can use a type annotation on `x`:
1115 let x: Vec<char> = "hello".chars().rev().collect();
1118 It is not necessary to annotate the full type. Once the ambiguity is resolved,
1119 the compiler can infer the rest:
1122 let x: Vec<_> = "hello".chars().rev().collect();
1125 Another way to provide the compiler with enough information, is to specify the
1126 generic type parameter:
1129 let x = "hello".chars().rev().collect::<Vec<char>>();
1132 Again, you need not specify the full type if the compiler can infer it:
1135 let x = "hello".chars().rev().collect::<Vec<_>>();
1138 Apart from a method or function with a generic type parameter, this error can
1139 occur when a type parameter of a struct or trait cannot be inferred. In that
1140 case it is not always possible to use a type annotation, because all candidates
1141 have the same return type. For instance:
1143 ```compile_fail,E0282
1154 let number = Foo::bar();
1159 This will fail because the compiler does not know which instance of `Foo` to
1160 call `bar` on. Change `Foo::bar()` to `Foo::<T>::bar()` to resolve the error.
1164 This error occurs when the compiler doesn't have enough information
1165 to unambiguously choose an implementation.
1169 ```compile_fail,E0283
1176 impl Generator for Impl {
1177 fn create() -> u32 { 1 }
1182 impl Generator for AnotherImpl {
1183 fn create() -> u32 { 2 }
1187 let cont: u32 = Generator::create();
1188 // error, impossible to choose one of Generator trait implementation
1189 // Should it be Impl or AnotherImpl, maybe something else?
1193 To resolve this error use the concrete type:
1202 impl Generator for AnotherImpl {
1203 fn create() -> u32 { 2 }
1207 let gen1 = AnotherImpl::create();
1209 // if there are multiple methods with same name (different traits)
1210 let gen2 = <AnotherImpl as Generator>::create();
1216 This error occurs when the compiler was unable to infer the concrete type of a
1217 variable. It can occur for several cases, the most common of which is a
1218 mismatch in the expected type that the compiler inferred for a variable's
1219 initializing expression, and the actual type explicitly assigned to the
1224 ```compile_fail,E0308
1225 let x: i32 = "I am not a number!";
1226 // ~~~ ~~~~~~~~~~~~~~~~~~~~
1228 // | initializing expression;
1229 // | compiler infers type `&str`
1231 // type `i32` assigned to variable `x`
1236 The type definition contains some field whose type
1237 requires an outlives annotation. Outlives annotations
1238 (e.g., `T: 'a`) are used to guarantee that all the data in T is valid
1239 for at least the lifetime `'a`. This scenario most commonly
1240 arises when the type contains an associated type reference
1241 like `<T as SomeTrait<'a>>::Output`, as shown in this example:
1243 ```compile_fail,E0309
1244 // This won't compile because the applicable impl of
1245 // `SomeTrait` (below) requires that `T: 'a`, but the struct does
1246 // not have a matching where-clause.
1248 foo: <T as SomeTrait<'a>>::Output,
1251 trait SomeTrait<'a> {
1255 impl<'a, T> SomeTrait<'a> for T
1263 Here, the where clause `T: 'a` that appears on the impl is not known to be
1264 satisfied on the struct. To make this example compile, you have to add
1265 a where-clause like `T: 'a` to the struct definition:
1272 foo: <T as SomeTrait<'a>>::Output
1275 trait SomeTrait<'a> {
1279 impl<'a, T> SomeTrait<'a> for T
1289 Types in type definitions have lifetimes associated with them that represent
1290 how long the data stored within them is guaranteed to be live. This lifetime
1291 must be as long as the data needs to be alive, and missing the constraint that
1292 denotes this will cause this error.
1294 ```compile_fail,E0310
1295 // This won't compile because T is not constrained to the static lifetime
1296 // the reference needs
1302 This will compile, because it has the constraint on the type parameter:
1305 struct Foo<T: 'static> {
1312 This error occurs when an `if` expression without an `else` block is used in a
1313 context where a type other than `()` is expected, for example a `let`
1316 ```compile_fail,E0317
1319 let a = if x == 5 { 1 };
1323 An `if` expression without an `else` block has the type `()`, so this is a type
1324 error. To resolve it, add an `else` block having the same type as the `if`
1329 This error indicates that some types or traits depend on each other
1330 and therefore cannot be constructed.
1332 The following example contains a circular dependency between two traits:
1334 ```compile_fail,E0391
1335 trait FirstTrait : SecondTrait {
1339 trait SecondTrait : FirstTrait {
1346 #### Note: this error code is no longer emitted by the compiler.
1348 In Rust 1.3, the default object lifetime bounds are expected to change, as
1349 described in [RFC 1156]. You are getting a warning because the compiler
1350 thinks it is possible that this change will cause a compilation error in your
1351 code. It is possible, though unlikely, that this is a false alarm.
1353 The heart of the change is that where `&'a Box<SomeTrait>` used to default to
1354 `&'a Box<SomeTrait+'a>`, it now defaults to `&'a Box<SomeTrait+'static>` (here,
1355 `SomeTrait` is the name of some trait type). Note that the only types which are
1356 affected are references to boxes, like `&Box<SomeTrait>` or
1357 `&[Box<SomeTrait>]`. More common types like `&SomeTrait` or `Box<SomeTrait>`
1360 To silence this warning, edit your code to use an explicit bound. Most of the
1361 time, this means that you will want to change the signature of a function that
1362 you are calling. For example, if the error is reported on a call like `foo(x)`,
1363 and `foo` is defined as follows:
1366 # trait SomeTrait {}
1367 fn foo(arg: &Box<SomeTrait>) { /* ... */ }
1370 You might change it to:
1373 # trait SomeTrait {}
1374 fn foo<'a>(arg: &'a Box<SomeTrait+'a>) { /* ... */ }
1377 This explicitly states that you expect the trait object `SomeTrait` to contain
1378 references (with a maximum lifetime of `'a`).
1380 [RFC 1156]: https://github.com/rust-lang/rfcs/blob/master/text/1156-adjust-default-object-bounds.md
1384 An invalid lint attribute has been given. Erroneous code example:
1386 ```compile_fail,E0452
1387 #![allow(foo = "")] // error: malformed lint attribute
1390 Lint attributes only accept a list of identifiers (where each identifier is a
1391 lint name). Ensure the attribute is of this form:
1394 #![allow(foo)] // ok!
1396 #![allow(foo, foo2)] // ok!
1401 A lint check attribute was overruled by a `forbid` directive set as an
1402 attribute on an enclosing scope, or on the command line with the `-F` option.
1404 Example of erroneous code:
1406 ```compile_fail,E0453
1407 #![forbid(non_snake_case)]
1409 #[allow(non_snake_case)]
1411 let MyNumber = 2; // error: allow(non_snake_case) overruled by outer
1412 // forbid(non_snake_case)
1416 The `forbid` lint setting, like `deny`, turns the corresponding compiler
1417 warning into a hard error. Unlike `deny`, `forbid` prevents itself from being
1418 overridden by inner attributes.
1420 If you're sure you want to override the lint check, you can change `forbid` to
1421 `deny` (or use `-D` instead of `-F` if the `forbid` setting was given as a
1422 command-line option) to allow the inner lint check attribute:
1425 #![deny(non_snake_case)]
1427 #[allow(non_snake_case)]
1429 let MyNumber = 2; // ok!
1433 Otherwise, edit the code to pass the lint check, and remove the overruled
1437 #![forbid(non_snake_case)]
1446 A lifetime bound was not satisfied.
1448 Erroneous code example:
1450 ```compile_fail,E0478
1451 // Check that the explicit lifetime bound (`'SnowWhite`, in this example) must
1452 // outlive all the superbounds from the trait (`'kiss`, in this example).
1454 trait Wedding<'t>: 't { }
1456 struct Prince<'kiss, 'SnowWhite> {
1457 child: Box<Wedding<'kiss> + 'SnowWhite>,
1458 // error: lifetime bound not satisfied
1462 In this example, the `'SnowWhite` lifetime is supposed to outlive the `'kiss`
1463 lifetime but the declaration of the `Prince` struct doesn't enforce it. To fix
1464 this issue, you need to specify it:
1467 trait Wedding<'t>: 't { }
1469 struct Prince<'kiss, 'SnowWhite: 'kiss> { // You say here that 'kiss must live
1470 // longer than 'SnowWhite.
1471 child: Box<Wedding<'kiss> + 'SnowWhite>, // And now it's all good!
1477 A reference has a longer lifetime than the data it references.
1479 Erroneous code example:
1481 ```compile_fail,E0491
1482 trait SomeTrait<'a> {
1486 impl<'a, T> SomeTrait<'a> for T {
1487 type Output = &'a T; // compile error E0491
1491 Here, the problem is that a reference type like `&'a T` is only valid
1492 if all the data in T outlives the lifetime `'a`. But this impl as written
1493 is applicable to any lifetime `'a` and any type `T` -- we have no guarantee
1494 that `T` outlives `'a`. To fix this, you can add a where clause like
1498 trait SomeTrait<'a> {
1502 impl<'a, T> SomeTrait<'a> for T
1506 type Output = &'a T; // compile error E0491
1512 A lifetime name is shadowing another lifetime name. Erroneous code example:
1514 ```compile_fail,E0496
1520 fn f<'a>(x: &'a i32) { // error: lifetime name `'a` shadows a lifetime
1521 // name that is already in scope
1526 Please change the name of one of the lifetimes to remove this error. Example:
1534 fn f<'b>(x: &'b i32) { // ok!
1544 A stability attribute was used outside of the standard library. Erroneous code
1548 #[stable] // error: stability attributes may not be used outside of the
1553 It is not possible to use stability attributes outside of the standard library.
1554 Also, for now, it is not possible to write deprecation messages either.
1558 Transmute with two differently sized types was attempted. Erroneous code
1561 ```compile_fail,E0512
1562 fn takes_u8(_: u8) {}
1565 unsafe { takes_u8(::std::mem::transmute(0u16)); }
1566 // error: cannot transmute between types of different sizes,
1567 // or dependently-sized types
1571 Please use types with same size or use the expected type directly. Example:
1574 fn takes_u8(_: u8) {}
1577 unsafe { takes_u8(::std::mem::transmute(0i8)); } // ok!
1579 unsafe { takes_u8(0u8); } // ok!
1585 This error indicates that a `#[repr(..)]` attribute was placed on an
1588 Examples of erroneous code:
1590 ```compile_fail,E0517
1598 struct Foo {bar: bool, baz: bool}
1606 * The `#[repr(C)]` attribute can only be placed on structs and enums.
1607 * The `#[repr(packed)]` and `#[repr(simd)]` attributes only work on structs.
1608 * The `#[repr(u8)]`, `#[repr(i16)]`, etc attributes only work on enums.
1610 These attributes do not work on typedefs, since typedefs are just aliases.
1612 Representations like `#[repr(u8)]`, `#[repr(i64)]` are for selecting the
1613 discriminant size for enums with no data fields on any of the variants, e.g.
1614 `enum Color {Red, Blue, Green}`, effectively setting the size of the enum to
1615 the size of the provided type. Such an enum can be cast to a value of the same
1616 type as well. In short, `#[repr(u8)]` makes the enum behave like an integer
1617 with a constrained set of allowed values.
1619 Only field-less enums can be cast to numerical primitives, so this attribute
1620 will not apply to structs.
1622 `#[repr(packed)]` reduces padding to make the struct size smaller. The
1623 representation of enums isn't strictly defined in Rust, and this attribute
1624 won't work on enums.
1626 `#[repr(simd)]` will give a struct consisting of a homogeneous series of machine
1627 types (i.e., `u8`, `i32`, etc) a representation that permits vectorization via
1628 SIMD. This doesn't make much sense for enums since they don't consist of a
1629 single list of data.
1633 This error indicates that an `#[inline(..)]` attribute was incorrectly placed
1634 on something other than a function or method.
1636 Examples of erroneous code:
1638 ```compile_fail,E0518
1648 `#[inline]` hints the compiler whether or not to attempt to inline a method or
1649 function. By default, the compiler does a pretty good job of figuring this out
1650 itself, but if you feel the need for annotations, `#[inline(always)]` and
1651 `#[inline(never)]` can override or force the compiler's decision.
1653 If you wish to apply this attribute to all methods in an impl, manually annotate
1654 each method; it is not possible to annotate the entire impl with an `#[inline]`
1659 The lang attribute is intended for marking special items that are built-in to
1660 Rust itself. This includes special traits (like `Copy` and `Sized`) that affect
1661 how the compiler behaves, as well as special functions that may be automatically
1662 invoked (such as the handler for out-of-bounds accesses when indexing a slice).
1663 Erroneous code example:
1665 ```compile_fail,E0522
1666 #![feature(lang_items)]
1669 fn cookie() -> ! { // error: definition of an unknown language item: `cookie`
1676 A closure was used but didn't implement the expected trait.
1678 Erroneous code example:
1680 ```compile_fail,E0525
1684 fn bar<T: Fn(u32)>(_: T) {}
1688 let closure = |_| foo(x); // error: expected a closure that implements
1689 // the `Fn` trait, but this closure only
1690 // implements `FnOnce`
1695 In the example above, `closure` is an `FnOnce` closure whereas the `bar`
1696 function expected an `Fn` closure. In this case, it's simple to fix the issue,
1697 you just have to implement `Copy` and `Clone` traits on `struct X` and it'll
1701 #[derive(Clone, Copy)] // We implement `Clone` and `Copy` traits.
1705 fn bar<T: Fn(u32)>(_: T) {}
1709 let closure = |_| foo(x);
1710 bar(closure); // ok!
1714 To understand better how closures work in Rust, read:
1715 https://doc.rust-lang.org/book/ch13-01-closures.html
1719 The `main` function was incorrectly declared.
1721 Erroneous code example:
1723 ```compile_fail,E0580
1724 fn main(x: i32) { // error: main function has wrong type
1729 The `main` function prototype should never take arguments.
1738 If you want to get command-line arguments, use `std::env::args`. To exit with a
1739 specified exit code, use `std::process::exit`.
1743 Abstract return types (written `impl Trait` for some trait `Trait`) are only
1744 allowed as function and inherent impl return types.
1746 Erroneous code example:
1748 ```compile_fail,E0562
1750 let count_to_ten: impl Iterator<Item=usize> = 0..10;
1751 // error: `impl Trait` not allowed outside of function and inherent method
1753 for i in count_to_ten {
1759 Make sure `impl Trait` only appears in return-type position.
1762 fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
1767 for i in count_to_n(10) { // ok!
1773 See [RFC 1522] for more details.
1775 [RFC 1522]: https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md
1779 Per [RFC 401][rfc401], if you have a function declaration `foo`:
1782 // For the purposes of this explanation, all of these
1783 // different kinds of `fn` declarations are equivalent:
1785 fn foo(x: S) { /* ... */ }
1786 # #[cfg(for_demonstration_only)]
1787 extern "C" { fn foo(x: S); }
1788 # #[cfg(for_demonstration_only)]
1789 impl S { fn foo(self) { /* ... */ } }
1792 the type of `foo` is **not** `fn(S)`, as one might expect.
1793 Rather, it is a unique, zero-sized marker type written here as `typeof(foo)`.
1794 However, `typeof(foo)` can be _coerced_ to a function pointer `fn(S)`,
1795 so you rarely notice this:
1800 let x: fn(S) = foo; // OK, coerces
1803 The reason that this matter is that the type `fn(S)` is not specific to
1804 any particular function: it's a function _pointer_. So calling `x()` results
1805 in a virtual call, whereas `foo()` is statically dispatched, because the type
1806 of `foo` tells us precisely what function is being called.
1808 As noted above, coercions mean that most code doesn't have to be
1809 concerned with this distinction. However, you can tell the difference
1810 when using **transmute** to convert a fn item into a fn pointer.
1812 This is sometimes done as part of an FFI:
1814 ```compile_fail,E0591
1815 extern "C" fn foo(userdata: Box<i32>) {
1819 # fn callback(_: extern "C" fn(*mut i32)) {}
1820 # use std::mem::transmute;
1822 let f: extern "C" fn(*mut i32) = transmute(foo);
1827 Here, transmute is being used to convert the types of the fn arguments.
1828 This pattern is incorrect because, because the type of `foo` is a function
1829 **item** (`typeof(foo)`), which is zero-sized, and the target type (`fn()`)
1830 is a function pointer, which is not zero-sized.
1831 This pattern should be rewritten. There are a few possible ways to do this:
1833 - change the original fn declaration to match the expected signature,
1834 and do the cast in the fn body (the preferred option)
1835 - cast the fn item fo a fn pointer before calling transmute, as shown here:
1838 # extern "C" fn foo(_: Box<i32>) {}
1839 # use std::mem::transmute;
1841 let f: extern "C" fn(*mut i32) = transmute(foo as extern "C" fn(_));
1842 let f: extern "C" fn(*mut i32) = transmute(foo as usize); // works too
1846 The same applies to transmutes to `*mut fn()`, which were observedin practice.
1847 Note though that use of this type is generally incorrect.
1848 The intention is typically to describe a function pointer, but just `fn()`
1849 alone suffices for that. `*mut fn()` is a pointer to a fn pointer.
1850 (Since these values are typically just passed to C code, however, this rarely
1851 makes a difference in practice.)
1853 [rfc401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md
1857 You tried to supply an `Fn`-based type with an incorrect number of arguments
1858 than what was expected.
1860 Erroneous code example:
1862 ```compile_fail,E0593
1863 fn foo<F: Fn()>(x: F) { }
1866 // [E0593] closure takes 1 argument but 0 arguments are required
1873 No `main` function was found in a binary crate. To fix this error, add a
1874 `main` function. For example:
1878 // Your program will start here.
1879 println!("Hello world!");
1883 If you don't know the basics of Rust, you can go look to the Rust Book to get
1884 started: https://doc.rust-lang.org/book/
1888 An unknown lint was used on the command line.
1893 rustc -D bogus omse_file.rs
1896 Maybe you just misspelled the lint name or the lint doesn't exist anymore.
1897 Either way, try to update/remove it in order to fix the error.
1901 This error code indicates a mismatch between the lifetimes appearing in the
1902 function signature (i.e., the parameter types and the return type) and the
1903 data-flow found in the function body.
1905 Erroneous code example:
1907 ```compile_fail,E0621
1908 fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 { // error: explicit lifetime
1909 // required in the type of
1911 if x > y { x } else { y }
1915 In the code above, the function is returning data borrowed from either `x` or
1916 `y`, but the `'a` annotation indicates that it is returning data only from `x`.
1917 To fix the error, the signature and the body must be made to match. Typically,
1918 this is done by updating the function signature. So, in this case, we change
1919 the type of `y` to `&'a i32`, like so:
1922 fn foo<'a>(x: &'a i32, y: &'a i32) -> &'a i32 {
1923 if x > y { x } else { y }
1927 Now the signature indicates that the function data borrowed from either `x` or
1928 `y`. Alternatively, you could change the body to not return data from `y`:
1931 fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 {
1938 The `#![feature]` attribute specified an unknown feature.
1940 Erroneous code example:
1942 ```compile_fail,E0635
1943 #![feature(nonexistent_rust_feature)] // error: unknown feature
1949 A `#![feature]` attribute was declared multiple times.
1951 Erroneous code example:
1953 ```compile_fail,E0636
1954 #![allow(stable_features)]
1956 #![feature(rust1)] // error: the feature `rust1` has already been declared
1962 A closure or generator was constructed that references its own type.
1966 ```compile-fail,E0644
1975 // Here, when `x` is called, the parameter `y` is equal to `x`.
1980 Rust does not permit a closure to directly reference its own type,
1981 either through an argument (as in the example above) or by capturing
1982 itself through its environment. This restriction helps keep closure
1983 inference tractable.
1985 The easiest fix is to rewrite your closure into a top-level function,
1986 or into a method. In some cases, you may also be able to have your
1987 closure call itself by capturing a `&Fn()` object or `fn()` pointer
1988 that refers to itself. That is permitting, since the closure would be
1989 invoking itself via a virtual call, and hence does not directly
1990 reference its own *type*.
1995 A `repr(transparent)` type was also annotated with other, incompatible
1996 representation hints.
1998 Erroneous code example:
2000 ```compile_fail,E0692
2001 #[repr(transparent, C)] // error: incompatible representation hints
2005 A type annotated as `repr(transparent)` delegates all representation concerns to
2006 another type, so adding more representation hints is contradictory. Remove
2007 either the `transparent` hint or the other hints, like this:
2010 #[repr(transparent)]
2014 Alternatively, move the other attributes to the contained type:
2023 #[repr(transparent)]
2024 struct FooWrapper(Foo);
2027 Note that introducing another `struct` just to have a place for the other
2028 attributes may have unintended side effects on the representation:
2031 #[repr(transparent)]
2037 #[repr(transparent)]
2038 struct Grams2(Float); // this is not equivalent to `Grams` above
2041 Here, `Grams2` is a not equivalent to `Grams` -- the former transparently wraps
2042 a (non-transparent) struct containing a single float, while `Grams` is a
2043 transparent wrapper around a float. This can make a difference for the ABI.
2047 The `impl Trait` return type captures lifetime parameters that do not
2048 appear within the `impl Trait` itself.
2050 Erroneous code example:
2052 ```compile-fail,E0700
2053 use std::cell::Cell;
2057 impl<'a, 'b> Trait<'b> for Cell<&'a u32> { }
2059 fn foo<'x, 'y>(x: Cell<&'x u32>) -> impl Trait<'y>
2066 Here, the function `foo` returns a value of type `Cell<&'x u32>`,
2067 which references the lifetime `'x`. However, the return type is
2068 declared as `impl Trait<'y>` -- this indicates that `foo` returns
2069 "some type that implements `Trait<'y>`", but it also indicates that
2070 the return type **only captures data referencing the lifetime `'y`**.
2071 In this case, though, we are referencing data with lifetime `'x`, so
2072 this function is in error.
2074 To fix this, you must reference the lifetime `'x` from the return
2075 type. For example, changing the return type to `impl Trait<'y> + 'x`
2079 use std::cell::Cell;
2083 impl<'a,'b> Trait<'b> for Cell<&'a u32> { }
2085 fn foo<'x, 'y>(x: Cell<&'x u32>) -> impl Trait<'y> + 'x
2094 This error indicates that a `#[non_exhaustive]` attribute was incorrectly placed
2095 on something other than a struct or enum.
2097 Examples of erroneous code:
2099 ```compile_fail,E0701
2100 # #![feature(non_exhaustive)]
2108 This error indicates that a `#[lang = ".."]` attribute was placed
2109 on the wrong type of item.
2111 Examples of erroneous code:
2113 ```compile_fail,E0718
2114 #![feature(lang_items)]
2124 register_diagnostics! {
2125 // E0006, // merged with E0005
2126 // E0101, // replaced with E0282
2127 // E0102, // replaced with E0282
2130 // E0272, // on_unimplemented #0
2131 // E0273, // on_unimplemented #1
2132 // E0274, // on_unimplemented #2
2133 E0278, // requirement is not satisfied
2134 E0279, // requirement is not satisfied
2135 E0280, // requirement is not satisfied
2136 E0284, // cannot resolve type
2137 // E0285, // overflow evaluation builtin bounds
2138 // E0296, // replaced with a generic attribute input check
2139 // E0300, // unexpanded macro
2140 // E0304, // expected signed integer constant
2141 // E0305, // expected constant
2142 E0311, // thing may not live long enough
2143 E0312, // lifetime of reference outlives lifetime of borrowed content
2144 E0313, // lifetime of borrowed pointer outlives lifetime of captured variable
2145 E0314, // closure outlives stack frame
2146 E0315, // cannot invoke closure outside of its lifetime
2147 E0316, // nested quantification of lifetimes
2148 E0320, // recursive overflow during dropck
2149 E0473, // dereference of reference outside its lifetime
2150 E0474, // captured variable `..` does not outlive the enclosing closure
2151 E0475, // index of slice outside its lifetime
2152 E0476, // lifetime of the source pointer does not outlive lifetime bound...
2153 E0477, // the type `..` does not fulfill the required lifetime...
2154 E0479, // the type `..` (provided as the value of a type parameter) is...
2155 E0480, // lifetime of method receiver does not outlive the method call
2156 E0481, // lifetime of function argument does not outlive the function call
2157 E0482, // lifetime of return value does not outlive the function call
2158 E0483, // lifetime of operand does not outlive the operation
2159 E0484, // reference is not valid at the time of borrow
2160 E0485, // automatically reference is not valid at the time of borrow
2161 E0486, // type of expression contains references that are not valid during...
2162 E0487, // unsafe use of destructor: destructor might be called while...
2163 E0488, // lifetime of variable does not enclose its declaration
2164 E0489, // type/lifetime parameter not in scope here
2165 E0490, // a value of type `..` is borrowed for too long
2166 E0495, // cannot infer an appropriate lifetime due to conflicting requirements
2167 E0566, // conflicting representation hints
2168 E0623, // lifetime mismatch where both parameters are anonymous regions
2169 E0628, // generators cannot have explicit arguments
2170 E0631, // type mismatch in closure arguments
2171 E0637, // "'_" is not a valid lifetime bound
2172 E0657, // `impl Trait` can only capture lifetimes bound at the fn level
2173 E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
2174 E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
2175 E0697, // closures cannot be static
2176 E0707, // multiple elided lifetimes used in arguments of `async fn`
2177 E0708, // `async` non-`move` closures with arguments are not currently supported
2178 E0709, // multiple different lifetimes used in arguments of `async fn`
2179 E0710, // an unknown tool name found in scoped lint
2180 E0711, // a feature has been declared with conflicting stability attributes
2181 // E0702, // replaced with a generic attribute input check