1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 #![allow(non_snake_case)]
13 // Error messages for EXXXX errors.
14 // Each message should start and end with a new line, and be wrapped to 80 characters.
15 // In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
16 register_long_diagnostics! {
18 This error indicates that an attempt was made to divide by zero (or take the
19 remainder of a zero divisor) in a static or constant expression. Erroneous
25 const X: i32 = 42 / 0;
26 // error: attempt to divide by zero in a constant expression
31 Trait objects like `Box<Trait>` can only be constructed when certain
32 requirements are satisfied by the trait in question.
34 Trait objects are a form of dynamic dispatch and use a dynamically sized type
35 for the inner type. So, for a given trait `Trait`, when `Trait` is treated as a
36 type, as in `Box<Trait>`, the inner type is 'unsized'. In such cases the boxed
37 pointer is a 'fat pointer' that contains an extra pointer to a table of methods
38 (among other things) for dynamic dispatch. This design mandates some
39 restrictions on the types of traits that are allowed to be used in trait
40 objects, which are collectively termed as 'object safety' rules.
42 Attempting to create a trait object for a non object-safe trait will trigger
45 There are various rules:
47 ### The trait cannot require `Self: Sized`
49 When `Trait` is treated as a type, the type does not implement the special
50 `Sized` trait, because the type does not have a known size at compile time and
51 can only be accessed behind a pointer. Thus, if we have a trait like the
55 trait Foo where Self: Sized {
60 We cannot create an object of type `Box<Foo>` or `&Foo` since in this case
61 `Self` would not be `Sized`.
63 Generally, `Self : Sized` is used to indicate that the trait should not be used
64 as a trait object. If the trait comes from your own crate, consider removing
67 ### Method references the `Self` type in its arguments or return type
69 This happens when a trait has a method like the following:
73 fn foo(&self) -> Self;
76 impl Trait for String {
77 fn foo(&self) -> Self {
83 fn foo(&self) -> Self {
89 (Note that `&self` and `&mut self` are okay, it's additional `Self` types which
92 In such a case, the compiler cannot predict the return type of `foo()` in a
93 situation like the following:
97 fn foo(&self) -> Self;
100 fn call_foo(x: Box<Trait>) {
101 let y = x.foo(); // What type is y?
106 If only some methods aren't object-safe, you can add a `where Self: Sized` bound
107 on them to mark them as explicitly unavailable to trait objects. The
108 functionality will still be available to all other implementers, including
109 `Box<Trait>` which is itself sized (assuming you `impl Trait for Box<Trait>`).
113 fn foo(&self) -> Self where Self: Sized;
118 Now, `foo()` can no longer be called on a trait object, but you will now be
119 allowed to make a trait object, and that will be able to call any object-safe
120 methods. With such a bound, one can still call `foo()` on types implementing
121 that trait that aren't behind trait objects.
123 ### Method has generic type parameters
125 As mentioned before, trait objects contain pointers to method tables. So, if we
133 impl Trait for String {
147 At compile time each implementation of `Trait` will produce a table containing
148 the various methods (and other items) related to the implementation.
150 This works fine, but when the method gains generic parameters, we can have a
153 Usually, generic parameters get _monomorphized_. For example, if I have
161 The machine code for `foo::<u8>()`, `foo::<bool>()`, `foo::<String>()`, or any
162 other type substitution is different. Hence the compiler generates the
163 implementation on-demand. If you call `foo()` with a `bool` parameter, the
164 compiler will only generate code for `foo::<bool>()`. When we have additional
165 type parameters, the number of monomorphized implementations the compiler
166 generates does not grow drastically, since the compiler will only generate an
167 implementation if the function is called with unparametrized substitutions
168 (i.e., substitutions where none of the substituted types are themselves
171 However, with trait objects we have to make a table containing _every_ object
172 that implements the trait. Now, if it has type parameters, we need to add
173 implementations for every type that implements the trait, and there could
174 theoretically be an infinite number of types.
180 fn foo<T>(&self, on: T);
184 impl Trait for String {
185 fn foo<T>(&self, on: T) {
191 fn foo<T>(&self, on: T) {
196 // 8 more implementations
199 Now, if we have the following code:
201 ```compile_fail,E0038
202 # trait Trait { fn foo<T>(&self, on: T); }
203 # impl Trait for String { fn foo<T>(&self, on: T) {} }
204 # impl Trait for u8 { fn foo<T>(&self, on: T) {} }
205 # impl Trait for bool { fn foo<T>(&self, on: T) {} }
207 fn call_foo(thing: Box<Trait>) {
208 thing.foo(true); // this could be any one of the 8 types above
214 We don't just need to create a table of all implementations of all methods of
215 `Trait`, we need to create such a table, for each different type fed to
216 `foo()`. In this case this turns out to be (10 types implementing `Trait`)*(3
217 types being fed to `foo()`) = 30 implementations!
219 With real world traits these numbers can grow drastically.
221 To fix this, it is suggested to use a `where Self: Sized` bound similar to the
222 fix for the sub-error above if you do not intend to call the method with type
227 fn foo<T>(&self, on: T) where Self: Sized;
232 If this is not an option, consider replacing the type parameter with another
233 trait object (e.g. if `T: OtherTrait`, use `on: Box<OtherTrait>`). If the number
234 of types you intend to feed to this method is limited, consider manually listing
235 out the methods of different types.
237 ### Method has no receiver
239 Methods that do not take a `self` parameter can't be called since there won't be
240 a way to get a pointer to the method table for them.
248 This could be called as `<Foo as Foo>::foo()`, which would not be able to pick
251 Adding a `Self: Sized` bound to these methods will generally make this compile.
255 fn foo() -> u8 where Self: Sized;
259 ### The trait cannot contain associated constants
261 Just like static functions, associated constants aren't stored on the method
262 table. If the trait or any subtrait contain an associated constant, they cannot
263 be made into an object.
265 ```compile_fail,E0038
273 A simple workaround is to use a helper method instead:
281 ### The trait cannot use `Self` as a type parameter in the supertrait listing
283 This is similar to the second sub-error, but subtler. It happens in situations
289 trait Trait: Super<Self> {
294 impl Super<Foo> for Foo{}
296 impl Trait for Foo {}
299 Here, the supertrait might have methods as follows:
303 fn get_a(&self) -> A; // note that this is object safe!
307 If the trait `Foo` was deriving from something like `Super<String>` or
308 `Super<T>` (where `Foo` itself is `Foo<T>`), this is okay, because given a type
309 `get_a()` will definitely return an object of that type.
311 However, if it derives from `Super<Self>`, even though `Super` is object safe,
312 the method `get_a()` would return an object of unknown type when called on the
313 function. `Self` type parameters let us make object safe traits no longer safe,
314 so they are forbidden when specifying supertraits.
316 There's no easy fix for this, generally code will need to be refactored so that
317 you no longer need to derive from `Super<Self>`.
321 When defining a recursive struct or enum, any use of the type being defined
322 from inside the definition must occur behind a pointer (like `Box` or `&`).
323 This is because structs and enums must have a well-defined size, and without
324 the pointer, the size of the type would need to be unbounded.
326 Consider the following erroneous definition of a type for a list of bytes:
328 ```compile_fail,E0072
329 // error, invalid recursive struct type
332 tail: Option<ListNode>,
336 This type cannot have a well-defined size, because it needs to be arbitrarily
337 large (since we would be able to nest `ListNode`s to any depth). Specifically,
340 size of `ListNode` = 1 byte for `head`
341 + 1 byte for the discriminant of the `Option`
345 One way to fix this is by wrapping `ListNode` in a `Box`, like so:
350 tail: Option<Box<ListNode>>,
354 This works because `Box` is a pointer, so its size is well-known.
358 This error indicates that the compiler was unable to sensibly evaluate an
359 constant expression that had to be evaluated. Attempting to divide by 0
360 or causing integer overflow are two ways to induce this error. For example:
362 ```compile_fail,E0080
369 Ensure that the expressions given can be evaluated as the desired integer type.
370 See the FFI section of the Reference for more information about using a custom
373 https://doc.rust-lang.org/reference.html#ffi-attributes
377 This error indicates that a lifetime is missing from a type. If it is an error
378 inside a function signature, the problem may be with failing to adhere to the
379 lifetime elision rules (see below).
381 Here are some simple examples of where you'll run into this error:
383 ```compile_fail,E0106
384 struct Foo1 { x: &bool }
385 // ^ expected lifetime parameter
386 struct Foo2<'a> { x: &'a bool } // correct
388 struct Bar1 { x: Foo2 }
389 // ^^^^ expected lifetime parameter
390 struct Bar2<'a> { x: Foo2<'a> } // correct
392 enum Baz1 { A(u8), B(&bool), }
393 // ^ expected lifetime parameter
394 enum Baz2<'a> { A(u8), B(&'a bool), } // correct
397 // ^ expected lifetime parameter
398 type MyStr2<'a> = &'a str; // correct
401 Lifetime elision is a special, limited kind of inference for lifetimes in
402 function signatures which allows you to leave out lifetimes in certain cases.
403 For more background on lifetime elision see [the book][book-le].
405 The lifetime elision rules require that any function signature with an elided
406 output lifetime must either have
408 - exactly one input lifetime
409 - or, multiple input lifetimes, but the function must also be a method with a
410 `&self` or `&mut self` receiver
412 In the first case, the output lifetime is inferred to be the same as the unique
413 input lifetime. In the second case, the lifetime is instead inferred to be the
414 same as the lifetime on `&self` or `&mut self`.
416 Here are some examples of elision errors:
418 ```compile_fail,E0106
419 // error, no input lifetimes
422 // error, `x` and `y` have distinct lifetimes inferred
423 fn bar(x: &str, y: &str) -> &str { }
425 // error, `y`'s lifetime is inferred to be distinct from `x`'s
426 fn baz<'a>(x: &'a str, y: &str) -> &str { }
429 Lifetime elision in implementation headers was part of the lifetime elision
430 RFC. It is, however, [currently unimplemented][iss15872].
432 [book-le]: https://doc.rust-lang.org/nightly/book/first-edition/lifetimes.html#lifetime-elision
433 [iss15872]: https://github.com/rust-lang/rust/issues/15872
437 There are conflicting trait implementations for the same type.
438 Example of erroneous code:
440 ```compile_fail,E0119
442 fn get(&self) -> usize;
445 impl<T> MyTrait for T {
446 fn get(&self) -> usize { 0 }
453 impl MyTrait for Foo { // error: conflicting implementations of trait
454 // `MyTrait` for type `Foo`
455 fn get(&self) -> usize { self.value }
459 When looking for the implementation for the trait, the compiler finds
460 both the `impl<T> MyTrait for T` where T is all types and the `impl
461 MyTrait for Foo`. Since a trait cannot be implemented multiple times,
462 this is an error. So, when you write:
466 fn get(&self) -> usize;
469 impl<T> MyTrait for T {
470 fn get(&self) -> usize { 0 }
474 This makes the trait implemented on all types in the scope. So if you
475 try to implement it on another one after that, the implementations will
480 fn get(&self) -> usize;
483 impl<T> MyTrait for T {
484 fn get(&self) -> usize { 0 }
492 f.get(); // the trait is implemented so we can use it
497 // This shouldn't really ever trigger since the repeated value error comes first
499 A binary can only have one entry point, and by default that entry point is the
500 function `main()`. If there are multiple such functions, please rename one.
504 More than one function was declared with the `#[main]` attribute.
506 Erroneous code example:
508 ```compile_fail,E0137
515 fn f() {} // error: multiple functions with a #[main] attribute
518 This error indicates that the compiler found multiple functions with the
519 `#[main]` attribute. This is an error because there must be a unique entry
520 point into a Rust program. Example:
531 More than one function was declared with the `#[start]` attribute.
533 Erroneous code example:
535 ```compile_fail,E0138
539 fn foo(argc: isize, argv: *const *const u8) -> isize {}
542 fn f(argc: isize, argv: *const *const u8) -> isize {}
543 // error: multiple 'start' functions
546 This error indicates that the compiler found multiple functions with the
547 `#[start]` attribute. This is an error because there must be a unique entry
548 point into a Rust program. Example:
554 fn foo(argc: isize, argv: *const *const u8) -> isize { 0 } // ok!
559 #### Note: this error code is no longer emitted by the compiler.
561 There are various restrictions on transmuting between types in Rust; for example
562 types being transmuted must have the same size. To apply all these restrictions,
563 the compiler must know the exact types that may be transmuted. When type
564 parameters are involved, this cannot always be done.
566 So, for example, the following is not allowed:
569 use std::mem::transmute;
571 struct Foo<T>(Vec<T>);
573 fn foo<T>(x: Vec<T>) {
574 // we are transmuting between Vec<T> and Foo<F> here
575 let y: Foo<T> = unsafe { transmute(x) };
576 // do something with y
580 In this specific case there's a good chance that the transmute is harmless (but
581 this is not guaranteed by Rust). However, when alignment and enum optimizations
582 come into the picture, it's quite likely that the sizes may or may not match
583 with different type parameter substitutions. It's not possible to check this for
584 _all_ possible types, so `transmute()` simply only accepts types without any
585 unsubstituted type parameters.
587 If you need this, there's a good chance you're doing something wrong. Keep in
588 mind that Rust doesn't guarantee much about the layout of different structs
589 (even two structs with identical declarations may have different layouts). If
590 there is a solution that avoids the transmute entirely, try it instead.
592 If it's possible, hand-monomorphize the code by writing the function for each
593 possible type substitution. It's possible to use traits to do this cleanly,
597 use std::mem::transmute;
599 struct Foo<T>(Vec<T>);
601 trait MyTransmutableType: Sized {
602 fn transmute(_: Vec<Self>) -> Foo<Self>;
605 impl MyTransmutableType for u8 {
606 fn transmute(x: Vec<u8>) -> Foo<u8> {
607 unsafe { transmute(x) }
611 impl MyTransmutableType for String {
612 fn transmute(x: Vec<String>) -> Foo<String> {
613 unsafe { transmute(x) }
617 // ... more impls for the types you intend to transmute
619 fn foo<T: MyTransmutableType>(x: Vec<T>) {
620 let y: Foo<T> = <T as MyTransmutableType>::transmute(x);
621 // do something with y
625 Each impl will be checked for a size match in the transmute as usual, and since
626 there are no unbound type parameters involved, this should compile unless there
627 is a size mismatch in one of the impls.
629 It is also possible to manually transmute:
633 # let v = Some("value");
634 # type SomeType = &'static [u8];
636 ptr::read(&v as *const _ as *const SomeType) // `v` transmuted to `SomeType`
641 Note that this does not move `v` (unlike `transmute`), and may need a
642 call to `mem::forget(v)` in case you want to avoid destructors being called.
646 A lang item was redefined.
648 Erroneous code example:
650 ```compile_fail,E0152
651 #![feature(lang_items)]
653 #[lang = "panic_fmt"]
654 struct Foo; // error: duplicate lang item found: `panic_fmt`
657 Lang items are already implemented in the standard library. Unless you are
658 writing a free-standing application (e.g. a kernel), you do not need to provide
661 You can build a free-standing crate by adding `#![no_std]` to the crate
664 ```ignore (only-for-syntax-highlight)
668 See also https://doc.rust-lang.org/book/first-edition/no-stdlib.html
672 A generic type was described using parentheses rather than angle brackets.
675 ```compile_fail,E0214
677 let v: Vec(&str) = vec!["foo"];
681 This is not currently supported: `v` should be defined as `Vec<&str>`.
682 Parentheses are currently only used with generic types when defining parameters
683 for `Fn`-family traits.
687 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
688 message for when a particular trait isn't implemented on a type placed in a
689 position that needs that trait. For example, when the following code is
693 #![feature(on_unimplemented)]
695 fn foo<T: Index<u8>>(x: T){}
697 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
698 trait Index<Idx> { /* ... */ }
700 foo(true); // `bool` does not implement `Index<u8>`
703 There will be an error about `bool` not implementing `Index<u8>`, followed by a
704 note saying "the type `bool` cannot be indexed by `u8`".
706 As you can see, you can specify type parameters in curly braces for
707 substitution with the actual types (using the regular format string syntax) in
708 a given situation. Furthermore, `{Self}` will substitute to the type (in this
709 case, `bool`) that we tried to use.
711 This error appears when the curly braces contain an identifier which doesn't
712 match with any of the type parameters or the string `Self`. This might happen
713 if you misspelled a type parameter, or if you intended to use literal curly
714 braces. If it is the latter, escape the curly braces with a second curly brace
715 of the same type; e.g. a literal `{` is `{{`.
719 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
720 message for when a particular trait isn't implemented on a type placed in a
721 position that needs that trait. For example, when the following code is
725 #![feature(on_unimplemented)]
727 fn foo<T: Index<u8>>(x: T){}
729 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
730 trait Index<Idx> { /* ... */ }
732 foo(true); // `bool` does not implement `Index<u8>`
735 there will be an error about `bool` not implementing `Index<u8>`, followed by a
736 note saying "the type `bool` cannot be indexed by `u8`".
738 As you can see, you can specify type parameters in curly braces for
739 substitution with the actual types (using the regular format string syntax) in
740 a given situation. Furthermore, `{Self}` will substitute to the type (in this
741 case, `bool`) that we tried to use.
743 This error appears when the curly braces do not contain an identifier. Please
744 add one of the same name as a type parameter. If you intended to use literal
745 braces, use `{{` and `}}` to escape them.
749 The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
750 message for when a particular trait isn't implemented on a type placed in a
751 position that needs that trait. For example, when the following code is
755 #![feature(on_unimplemented)]
757 fn foo<T: Index<u8>>(x: T){}
759 #[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
760 trait Index<Idx> { /* ... */ }
762 foo(true); // `bool` does not implement `Index<u8>`
765 there will be an error about `bool` not implementing `Index<u8>`, followed by a
766 note saying "the type `bool` cannot be indexed by `u8`".
768 For this to work, some note must be specified. An empty attribute will not do
769 anything, please remove the attribute or add some helpful note for users of the
774 When using a lifetime like `'a` in a type, it must be declared before being
777 These two examples illustrate the problem:
779 ```compile_fail,E0261
780 // error, use of undeclared lifetime name `'a`
781 fn foo(x: &'a str) { }
784 // error, use of undeclared lifetime name `'a`
789 These can be fixed by declaring lifetime parameters:
792 fn foo<'a>(x: &'a str) {}
801 Declaring certain lifetime names in parameters is disallowed. For example,
802 because the `'static` lifetime is a special built-in lifetime name denoting
803 the lifetime of the entire program, this is an error:
805 ```compile_fail,E0262
806 // error, invalid lifetime parameter name `'static`
807 fn foo<'static>(x: &'static str) { }
812 A lifetime name cannot be declared more than once in the same scope. For
815 ```compile_fail,E0263
816 // error, lifetime name `'a` declared twice in the same scope
817 fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str) { }
822 An unknown external lang item was used. Erroneous code example:
824 ```compile_fail,E0264
825 #![feature(lang_items)]
828 #[lang = "cake"] // error: unknown external lang item: `cake`
833 A list of available external lang items is available in
834 `src/librustc/middle/weak_lang_items.rs`. Example:
837 #![feature(lang_items)]
840 #[lang = "panic_fmt"] // ok!
847 This is because of a type mismatch between the associated type of some
848 trait (e.g. `T::Bar`, where `T` implements `trait Quux { type Bar; }`)
849 and another type `U` that is required to be equal to `T::Bar`, but is not.
852 Here is a basic example:
854 ```compile_fail,E0271
855 trait Trait { type AssociatedType; }
857 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
861 impl Trait for i8 { type AssociatedType = &'static str; }
866 Here is that same example again, with some explanatory comments:
868 ```compile_fail,E0271
869 trait Trait { type AssociatedType; }
871 fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
872 // ~~~~~~~~ ~~~~~~~~~~~~~~~~~~
874 // This says `foo` can |
875 // only be used with |
877 // implements `Trait`. |
879 // This says not only must
880 // `T` be an impl of `Trait`
881 // but also that the impl
882 // must assign the type `u32`
883 // to the associated type.
887 impl Trait for i8 { type AssociatedType = &'static str; }
888 //~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
893 // ... but it is an implementation
894 // that assigns `&'static str` to
895 // the associated type.
898 // Here, we invoke `foo` with an `i8`, which does not satisfy
899 // the constraint `<i8 as Trait>::AssociatedType=u32`, and
900 // therefore the type-checker complains with this error code.
903 Here is a more subtle instance of the same problem, that can
904 arise with for-loops in Rust:
907 let vs: Vec<i32> = vec![1, 2, 3, 4];
916 The above fails because of an analogous type mismatch,
917 though may be harder to see. Again, here are some
918 explanatory comments for the same example:
922 let vs = vec![1, 2, 3, 4];
924 // `for`-loops use a protocol based on the `Iterator`
925 // trait. Each item yielded in a `for` loop has the
926 // type `Iterator::Item` -- that is, `Item` is the
927 // associated type of the concrete iterator impl.
931 // | We borrow `vs`, iterating over a sequence of
932 // | *references* of type `&Elem` (where `Elem` is
933 // | vector's element type). Thus, the associated
934 // | type `Item` must be a reference `&`-type ...
936 // ... and `v` has the type `Iterator::Item`, as dictated by
937 // the `for`-loop protocol ...
943 // ... but *here*, `v` is forced to have some integral type;
944 // only types like `u8`,`i8`,`u16`,`i16`, et cetera can
945 // match the pattern `1` ...
950 // ... therefore, the compiler complains, because it sees
951 // an attempt to solve the equations
952 // `some integral-type` = type-of-`v`
953 // = `Iterator::Item`
954 // = `&Elem` (i.e. `some reference type`)
956 // which cannot possibly all be true.
962 To avoid those issues, you have to make the types match correctly.
963 So we can fix the previous examples like this:
967 trait Trait { type AssociatedType; }
969 fn foo<T>(t: T) where T: Trait<AssociatedType = &'static str> {
973 impl Trait for i8 { type AssociatedType = &'static str; }
978 let vs = vec![1, 2, 3, 4];
990 This error occurs when there was a recursive trait requirement that overflowed
991 before it could be evaluated. Often this means that there is unbounded
992 recursion in resolving some type bounds.
994 For example, in the following code:
996 ```compile_fail,E0275
1001 impl<T> Foo for T where Bar<T>: Foo {}
1004 To determine if a `T` is `Foo`, we need to check if `Bar<T>` is `Foo`. However,
1005 to do this check, we need to determine that `Bar<Bar<T>>` is `Foo`. To
1006 determine this, we check if `Bar<Bar<Bar<T>>>` is `Foo`, and so on. This is
1007 clearly a recursive requirement that can't be resolved directly.
1009 Consider changing your trait bounds so that they're less self-referential.
1013 This error occurs when a bound in an implementation of a trait does not match
1014 the bounds specified in the original trait. For example:
1016 ```compile_fail,E0276
1022 fn foo<T>(x: T) where T: Copy {}
1026 Here, all types implementing `Foo` must have a method `foo<T>(x: T)` which can
1027 take any type `T`. However, in the `impl` for `bool`, we have added an extra
1028 bound that `T` is `Copy`, which isn't compatible with the original trait.
1030 Consider removing the bound from the method or adding the bound to the original
1031 method definition in the trait.
1035 You tried to use a type which doesn't implement some trait in a place which
1036 expected that trait. Erroneous code example:
1038 ```compile_fail,E0277
1039 // here we declare the Foo trait with a bar method
1044 // we now declare a function which takes an object implementing the Foo trait
1045 fn some_func<T: Foo>(foo: T) {
1050 // we now call the method with the i32 type, which doesn't implement
1052 some_func(5i32); // error: the trait bound `i32 : Foo` is not satisfied
1056 In order to fix this error, verify that the type you're using does implement
1064 fn some_func<T: Foo>(foo: T) {
1065 foo.bar(); // we can now use this method since i32 implements the
1069 // we implement the trait on the i32 type
1075 some_func(5i32); // ok!
1079 Or in a generic context, an erroneous code example would look like:
1081 ```compile_fail,E0277
1082 fn some_func<T>(foo: T) {
1083 println!("{:?}", foo); // error: the trait `core::fmt::Debug` is not
1084 // implemented for the type `T`
1088 // We now call the method with the i32 type,
1089 // which *does* implement the Debug trait.
1094 Note that the error here is in the definition of the generic function: Although
1095 we only call it with a parameter that does implement `Debug`, the compiler
1096 still rejects the function: It must work with all possible input types. In
1097 order to make this example compile, we need to restrict the generic type we're
1103 // Restrict the input type to types that implement Debug.
1104 fn some_func<T: fmt::Debug>(foo: T) {
1105 println!("{:?}", foo);
1109 // Calling the method is still fine, as i32 implements Debug.
1112 // This would fail to compile now:
1113 // struct WithoutDebug;
1114 // some_func(WithoutDebug);
1118 Rust only looks at the signature of the called function, as such it must
1119 already specify all requirements that will be used for every type parameter.
1123 #### Note: this error code is no longer emitted by the compiler.
1125 You tried to supply a type which doesn't implement some trait in a location
1126 which expected that trait. This error typically occurs when working with
1127 `Fn`-based types. Erroneous code example:
1130 fn foo<F: Fn(usize)>(x: F) { }
1133 // type mismatch: ... implements the trait `core::ops::Fn<(String,)>`,
1134 // but the trait `core::ops::Fn<(usize,)>` is required
1136 foo(|y: String| { });
1140 The issue in this case is that `foo` is defined as accepting a `Fn` with one
1141 argument of type `String`, but the closure we attempted to pass to it requires
1142 one arguments of type `usize`.
1146 This error indicates that type inference did not result in one unique possible
1147 type, and extra information is required. In most cases this can be provided
1148 by adding a type annotation. Sometimes you need to specify a generic type
1151 A common example is the `collect` method on `Iterator`. It has a generic type
1152 parameter with a `FromIterator` bound, which for a `char` iterator is
1153 implemented by `Vec` and `String` among others. Consider the following snippet
1154 that reverses the characters of a string:
1156 ```compile_fail,E0282
1157 let x = "hello".chars().rev().collect();
1160 In this case, the compiler cannot infer what the type of `x` should be:
1161 `Vec<char>` and `String` are both suitable candidates. To specify which type to
1162 use, you can use a type annotation on `x`:
1165 let x: Vec<char> = "hello".chars().rev().collect();
1168 It is not necessary to annotate the full type. Once the ambiguity is resolved,
1169 the compiler can infer the rest:
1172 let x: Vec<_> = "hello".chars().rev().collect();
1175 Another way to provide the compiler with enough information, is to specify the
1176 generic type parameter:
1179 let x = "hello".chars().rev().collect::<Vec<char>>();
1182 Again, you need not specify the full type if the compiler can infer it:
1185 let x = "hello".chars().rev().collect::<Vec<_>>();
1188 Apart from a method or function with a generic type parameter, this error can
1189 occur when a type parameter of a struct or trait cannot be inferred. In that
1190 case it is not always possible to use a type annotation, because all candidates
1191 have the same return type. For instance:
1193 ```compile_fail,E0282
1204 let number = Foo::bar();
1209 This will fail because the compiler does not know which instance of `Foo` to
1210 call `bar` on. Change `Foo::bar()` to `Foo::<T>::bar()` to resolve the error.
1214 This error occurs when the compiler doesn't have enough information
1215 to unambiguously choose an implementation.
1219 ```compile_fail,E0283
1226 impl Generator for Impl {
1227 fn create() -> u32 { 1 }
1232 impl Generator for AnotherImpl {
1233 fn create() -> u32 { 2 }
1237 let cont: u32 = Generator::create();
1238 // error, impossible to choose one of Generator trait implementation
1239 // Impl or AnotherImpl? Maybe anything else?
1243 To resolve this error use the concrete type:
1252 impl Generator for AnotherImpl {
1253 fn create() -> u32 { 2 }
1257 let gen1 = AnotherImpl::create();
1259 // if there are multiple methods with same name (different traits)
1260 let gen2 = <AnotherImpl as Generator>::create();
1266 This error indicates that the given recursion limit could not be parsed. Ensure
1267 that the value provided is a positive integer between quotes.
1269 Erroneous code example:
1271 ```compile_fail,E0296
1277 And a working example:
1280 #![recursion_limit="1000"]
1287 This error occurs when the compiler was unable to infer the concrete type of a
1288 variable. It can occur for several cases, the most common of which is a
1289 mismatch in the expected type that the compiler inferred for a variable's
1290 initializing expression, and the actual type explicitly assigned to the
1295 ```compile_fail,E0308
1296 let x: i32 = "I am not a number!";
1297 // ~~~ ~~~~~~~~~~~~~~~~~~~~
1299 // | initializing expression;
1300 // | compiler infers type `&str`
1302 // type `i32` assigned to variable `x`
1307 Types in type definitions have lifetimes associated with them that represent
1308 how long the data stored within them is guaranteed to be live. This lifetime
1309 must be as long as the data needs to be alive, and missing the constraint that
1310 denotes this will cause this error.
1312 ```compile_fail,E0309
1313 // This won't compile because T is not constrained, meaning the data
1314 // stored in it is not guaranteed to last as long as the reference
1320 This will compile, because it has the constraint on the type parameter:
1323 struct Foo<'a, T: 'a> {
1328 To see why this is important, consider the case where `T` is itself a reference
1329 (e.g., `T = &str`). If we don't include the restriction that `T: 'a`, the
1330 following code would be perfectly legal:
1332 ```compile_fail,E0309
1338 let v = "42".to_string();
1339 let f = Foo{foo: &v};
1341 println!("{}", f.foo); // but we've already dropped v!
1347 Types in type definitions have lifetimes associated with them that represent
1348 how long the data stored within them is guaranteed to be live. This lifetime
1349 must be as long as the data needs to be alive, and missing the constraint that
1350 denotes this will cause this error.
1352 ```compile_fail,E0310
1353 // This won't compile because T is not constrained to the static lifetime
1354 // the reference needs
1360 This will compile, because it has the constraint on the type parameter:
1363 struct Foo<T: 'static> {
1370 This error occurs when an `if` expression without an `else` block is used in a
1371 context where a type other than `()` is expected, for example a `let`
1374 ```compile_fail,E0317
1377 let a = if x == 5 { 1 };
1381 An `if` expression without an `else` block has the type `()`, so this is a type
1382 error. To resolve it, add an `else` block having the same type as the `if`
1387 This error indicates that some types or traits depend on each other
1388 and therefore cannot be constructed.
1390 The following example contains a circular dependency between two traits:
1392 ```compile_fail,E0391
1393 trait FirstTrait : SecondTrait {
1397 trait SecondTrait : FirstTrait {
1404 #### Note: this error code is no longer emitted by the compiler.
1406 In Rust 1.3, the default object lifetime bounds are expected to change, as
1407 described in [RFC 1156]. You are getting a warning because the compiler
1408 thinks it is possible that this change will cause a compilation error in your
1409 code. It is possible, though unlikely, that this is a false alarm.
1411 The heart of the change is that where `&'a Box<SomeTrait>` used to default to
1412 `&'a Box<SomeTrait+'a>`, it now defaults to `&'a Box<SomeTrait+'static>` (here,
1413 `SomeTrait` is the name of some trait type). Note that the only types which are
1414 affected are references to boxes, like `&Box<SomeTrait>` or
1415 `&[Box<SomeTrait>]`. More common types like `&SomeTrait` or `Box<SomeTrait>`
1418 To silence this warning, edit your code to use an explicit bound. Most of the
1419 time, this means that you will want to change the signature of a function that
1420 you are calling. For example, if the error is reported on a call like `foo(x)`,
1421 and `foo` is defined as follows:
1424 # trait SomeTrait {}
1425 fn foo(arg: &Box<SomeTrait>) { /* ... */ }
1428 You might change it to:
1431 # trait SomeTrait {}
1432 fn foo<'a>(arg: &'a Box<SomeTrait+'a>) { /* ... */ }
1435 This explicitly states that you expect the trait object `SomeTrait` to contain
1436 references (with a maximum lifetime of `'a`).
1438 [RFC 1156]: https://github.com/rust-lang/rfcs/blob/master/text/1156-adjust-default-object-bounds.md
1442 An invalid lint attribute has been given. Erroneous code example:
1444 ```compile_fail,E0452
1445 #![allow(foo = "")] // error: malformed lint attribute
1448 Lint attributes only accept a list of identifiers (where each identifier is a
1449 lint name). Ensure the attribute is of this form:
1452 #![allow(foo)] // ok!
1454 #![allow(foo, foo2)] // ok!
1459 A lint check attribute was overruled by a `forbid` directive set as an
1460 attribute on an enclosing scope, or on the command line with the `-F` option.
1462 Example of erroneous code:
1464 ```compile_fail,E0453
1465 #![forbid(non_snake_case)]
1467 #[allow(non_snake_case)]
1469 let MyNumber = 2; // error: allow(non_snake_case) overruled by outer
1470 // forbid(non_snake_case)
1474 The `forbid` lint setting, like `deny`, turns the corresponding compiler
1475 warning into a hard error. Unlike `deny`, `forbid` prevents itself from being
1476 overridden by inner attributes.
1478 If you're sure you want to override the lint check, you can change `forbid` to
1479 `deny` (or use `-D` instead of `-F` if the `forbid` setting was given as a
1480 command-line option) to allow the inner lint check attribute:
1483 #![deny(non_snake_case)]
1485 #[allow(non_snake_case)]
1487 let MyNumber = 2; // ok!
1491 Otherwise, edit the code to pass the lint check, and remove the overruled
1495 #![forbid(non_snake_case)]
1504 A lifetime bound was not satisfied.
1506 Erroneous code example:
1508 ```compile_fail,E0478
1509 // Check that the explicit lifetime bound (`'SnowWhite`, in this example) must
1510 // outlive all the superbounds from the trait (`'kiss`, in this example).
1512 trait Wedding<'t>: 't { }
1514 struct Prince<'kiss, 'SnowWhite> {
1515 child: Box<Wedding<'kiss> + 'SnowWhite>,
1516 // error: lifetime bound not satisfied
1520 In this example, the `'SnowWhite` lifetime is supposed to outlive the `'kiss`
1521 lifetime but the declaration of the `Prince` struct doesn't enforce it. To fix
1522 this issue, you need to specify it:
1525 trait Wedding<'t>: 't { }
1527 struct Prince<'kiss, 'SnowWhite: 'kiss> { // You say here that 'kiss must live
1528 // longer than 'SnowWhite.
1529 child: Box<Wedding<'kiss> + 'SnowWhite>, // And now it's all good!
1535 A reference has a longer lifetime than the data it references.
1537 Erroneous code example:
1539 ```compile_fail,E0491
1540 // struct containing a reference requires a lifetime parameter,
1541 // because the data the reference points to must outlive the struct (see E0106)
1546 // However, a nested struct like this, the signature itself does not tell
1547 // whether 'a outlives 'b or the other way around.
1548 // So it could be possible that 'b of reference outlives 'a of the data.
1549 struct Nested<'a, 'b> {
1550 ref_struct: &'b Struct<'a>, // compile error E0491
1554 To fix this issue, you can specify a bound to the lifetime like below:
1561 // 'a: 'b means 'a outlives 'b
1562 struct Nested<'a: 'b, 'b> {
1563 ref_struct: &'b Struct<'a>,
1569 A lifetime name is shadowing another lifetime name. Erroneous code example:
1571 ```compile_fail,E0496
1577 fn f<'a>(x: &'a i32) { // error: lifetime name `'a` shadows a lifetime
1578 // name that is already in scope
1583 Please change the name of one of the lifetimes to remove this error. Example:
1591 fn f<'b>(x: &'b i32) { // ok!
1601 A stability attribute was used outside of the standard library. Erroneous code
1605 #[stable] // error: stability attributes may not be used outside of the
1610 It is not possible to use stability attributes outside of the standard library.
1611 Also, for now, it is not possible to write deprecation messages either.
1615 Transmute with two differently sized types was attempted. Erroneous code
1618 ```compile_fail,E0512
1619 fn takes_u8(_: u8) {}
1622 unsafe { takes_u8(::std::mem::transmute(0u16)); }
1623 // error: transmute called with types of different sizes
1627 Please use types with same size or use the expected type directly. Example:
1630 fn takes_u8(_: u8) {}
1633 unsafe { takes_u8(::std::mem::transmute(0i8)); } // ok!
1635 unsafe { takes_u8(0u8); } // ok!
1641 This error indicates that a `#[repr(..)]` attribute was placed on an
1644 Examples of erroneous code:
1646 ```compile_fail,E0517
1654 struct Foo {bar: bool, baz: bool}
1662 * The `#[repr(C)]` attribute can only be placed on structs and enums.
1663 * The `#[repr(packed)]` and `#[repr(simd)]` attributes only work on structs.
1664 * The `#[repr(u8)]`, `#[repr(i16)]`, etc attributes only work on enums.
1666 These attributes do not work on typedefs, since typedefs are just aliases.
1668 Representations like `#[repr(u8)]`, `#[repr(i64)]` are for selecting the
1669 discriminant size for enums with no data fields on any of the variants, e.g.
1670 `enum Color {Red, Blue, Green}`, effectively setting the size of the enum to
1671 the size of the provided type. Such an enum can be cast to a value of the same
1672 type as well. In short, `#[repr(u8)]` makes the enum behave like an integer
1673 with a constrained set of allowed values.
1675 Only field-less enums can be cast to numerical primitives, so this attribute
1676 will not apply to structs.
1678 `#[repr(packed)]` reduces padding to make the struct size smaller. The
1679 representation of enums isn't strictly defined in Rust, and this attribute
1680 won't work on enums.
1682 `#[repr(simd)]` will give a struct consisting of a homogeneous series of machine
1683 types (i.e. `u8`, `i32`, etc) a representation that permits vectorization via
1684 SIMD. This doesn't make much sense for enums since they don't consist of a
1685 single list of data.
1689 This error indicates that an `#[inline(..)]` attribute was incorrectly placed
1690 on something other than a function or method.
1692 Examples of erroneous code:
1694 ```compile_fail,E0518
1704 `#[inline]` hints the compiler whether or not to attempt to inline a method or
1705 function. By default, the compiler does a pretty good job of figuring this out
1706 itself, but if you feel the need for annotations, `#[inline(always)]` and
1707 `#[inline(never)]` can override or force the compiler's decision.
1709 If you wish to apply this attribute to all methods in an impl, manually annotate
1710 each method; it is not possible to annotate the entire impl with an `#[inline]`
1715 The lang attribute is intended for marking special items that are built-in to
1716 Rust itself. This includes special traits (like `Copy` and `Sized`) that affect
1717 how the compiler behaves, as well as special functions that may be automatically
1718 invoked (such as the handler for out-of-bounds accesses when indexing a slice).
1719 Erroneous code example:
1721 ```compile_fail,E0522
1722 #![feature(lang_items)]
1725 fn cookie() -> ! { // error: definition of an unknown language item: `cookie`
1732 A closure was used but didn't implement the expected trait.
1734 Erroneous code example:
1736 ```compile_fail,E0525
1740 fn bar<T: Fn(u32)>(_: T) {}
1744 let closure = |_| foo(x); // error: expected a closure that implements
1745 // the `Fn` trait, but this closure only
1746 // implements `FnOnce`
1751 In the example above, `closure` is an `FnOnce` closure whereas the `bar`
1752 function expected an `Fn` closure. In this case, it's simple to fix the issue,
1753 you just have to implement `Copy` and `Clone` traits on `struct X` and it'll
1757 #[derive(Clone, Copy)] // We implement `Clone` and `Copy` traits.
1761 fn bar<T: Fn(u32)>(_: T) {}
1765 let closure = |_| foo(x);
1766 bar(closure); // ok!
1770 To understand better how closures work in Rust, read:
1771 https://doc.rust-lang.org/book/first-edition/closures.html
1775 The `main` function was incorrectly declared.
1777 Erroneous code example:
1779 ```compile_fail,E0580
1780 fn main() -> i32 { // error: main function has wrong type
1785 The `main` function prototype should never take arguments or return type.
1794 If you want to get command-line arguments, use `std::env::args`. To exit with a
1795 specified exit code, use `std::process::exit`.
1799 Abstract return types (written `impl Trait` for some trait `Trait`) are only
1800 allowed as function return types.
1802 Erroneous code example:
1804 ```compile_fail,E0562
1805 #![feature(conservative_impl_trait)]
1808 let count_to_ten: impl Iterator<Item=usize> = 0..10;
1809 // error: `impl Trait` not allowed outside of function and inherent method
1811 for i in count_to_ten {
1817 Make sure `impl Trait` only appears in return-type position.
1820 #![feature(conservative_impl_trait)]
1822 fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
1827 for i in count_to_n(10) { // ok!
1833 See [RFC 1522] for more details.
1835 [RFC 1522]: https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md
1839 Per [RFC 401][rfc401], if you have a function declaration `foo`:
1842 // For the purposes of this explanation, all of these
1843 // different kinds of `fn` declarations are equivalent:
1845 fn foo(x: S) { /* ... */ }
1846 # #[cfg(for_demonstration_only)]
1847 extern "C" { fn foo(x: S); }
1848 # #[cfg(for_demonstration_only)]
1849 impl S { fn foo(self) { /* ... */ } }
1852 the type of `foo` is **not** `fn(S)`, as one might expect.
1853 Rather, it is a unique, zero-sized marker type written here as `typeof(foo)`.
1854 However, `typeof(foo)` can be _coerced_ to a function pointer `fn(S)`,
1855 so you rarely notice this:
1860 let x: fn(S) = foo; // OK, coerces
1863 The reason that this matter is that the type `fn(S)` is not specific to
1864 any particular function: it's a function _pointer_. So calling `x()` results
1865 in a virtual call, whereas `foo()` is statically dispatched, because the type
1866 of `foo` tells us precisely what function is being called.
1868 As noted above, coercions mean that most code doesn't have to be
1869 concerned with this distinction. However, you can tell the difference
1870 when using **transmute** to convert a fn item into a fn pointer.
1872 This is sometimes done as part of an FFI:
1874 ```compile_fail,E0591
1875 extern "C" fn foo(userdata: Box<i32>) {
1879 # fn callback(_: extern "C" fn(*mut i32)) {}
1880 # use std::mem::transmute;
1882 let f: extern "C" fn(*mut i32) = transmute(foo);
1887 Here, transmute is being used to convert the types of the fn arguments.
1888 This pattern is incorrect because, because the type of `foo` is a function
1889 **item** (`typeof(foo)`), which is zero-sized, and the target type (`fn()`)
1890 is a function pointer, which is not zero-sized.
1891 This pattern should be rewritten. There are a few possible ways to do this:
1893 - change the original fn declaration to match the expected signature,
1894 and do the cast in the fn body (the prefered option)
1895 - cast the fn item fo a fn pointer before calling transmute, as shown here:
1898 # extern "C" fn foo(_: Box<i32>) {}
1899 # use std::mem::transmute;
1901 let f: extern "C" fn(*mut i32) = transmute(foo as extern "C" fn(_));
1902 let f: extern "C" fn(*mut i32) = transmute(foo as usize); // works too
1906 The same applies to transmutes to `*mut fn()`, which were observedin practice.
1907 Note though that use of this type is generally incorrect.
1908 The intention is typically to describe a function pointer, but just `fn()`
1909 alone suffices for that. `*mut fn()` is a pointer to a fn pointer.
1910 (Since these values are typically just passed to C code, however, this rarely
1911 makes a difference in practice.)
1913 [rfc401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md
1917 You tried to supply an `Fn`-based type with an incorrect number of arguments
1918 than what was expected.
1920 Erroneous code example:
1922 ```compile_fail,E0593
1923 fn foo<F: Fn()>(x: F) { }
1926 // [E0593] closure takes 1 argument but 0 arguments are required
1933 No `main` function was found in a binary crate. To fix this error, add a
1934 `main` function. For example:
1938 // Your program will start here.
1939 println!("Hello world!");
1943 If you don't know the basics of Rust, you can go look to the Rust Book to get
1944 started: https://doc.rust-lang.org/book/
1948 An unknown lint was used on the command line.
1953 rustc -D bogus omse_file.rs
1956 Maybe you just misspelled the lint name or the lint doesn't exist anymore.
1957 Either way, try to update/remove it in order to fix the error.
1961 This error code indicates a mismatch between the lifetimes appearing in the
1962 function signature (i.e., the parameter types and the return type) and the
1963 data-flow found in the function body.
1965 Erroneous code example:
1967 ```compile_fail,E0621
1968 fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 { // error: explicit lifetime
1969 // required in the type of
1971 if x > y { x } else { y }
1975 In the code above, the function is returning data borrowed from either `x` or
1976 `y`, but the `'a` annotation indicates that it is returning data only from `x`.
1977 To fix the error, the signature and the body must be made to match. Typically,
1978 this is done by updating the function signature. So, in this case, we change
1979 the type of `y` to `&'a i32`, like so:
1982 fn foo<'a>(x: &'a i32, y: &'a i32) -> &'a i32 {
1983 if x > y { x } else { y }
1987 Now the signature indicates that the function data borrowed from either `x` or
1988 `y`. Alternatively, you could change the body to not return data from `y`:
1991 fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 {
1998 A closure or generator was constructed that references its own type.
2002 ```compile-fail,E0644
2011 // Here, when `x` is called, the parameter `y` is equal to `x`.
2016 Rust does not permit a closure to directly reference its own type,
2017 either through an argument (as in the example above) or by capturing
2018 itself through its environment. This restriction helps keep closure
2019 inference tractable.
2021 The easiest fix is to rewrite your closure into a top-level function,
2022 or into a method. In some cases, you may also be able to have your
2023 closure call itself by capturing a `&Fn()` object or `fn()` pointer
2024 that refers to itself. That is permitting, since the closure would be
2025 invoking itself via a virtual call, and hence does not directly
2026 reference its own *type*.
2031 A `repr(transparent)` type was also annotated with other, incompatible
2032 representation hints.
2034 Erroneous code example:
2036 ```compile_fail,E0692
2037 #![feature(repr_transparent)]
2039 #[repr(transparent, C)] // error: incompatible representation hints
2043 A type annotated as `repr(transparent)` delegates all representation concerns to
2044 another type, so adding more representation hints is contradictory. Remove
2045 either the `transparent` hint or the other hints, like this:
2048 #![feature(repr_transparent)]
2050 #[repr(transparent)]
2054 Alternatively, move the other attributes to the contained type:
2057 #![feature(repr_transparent)]
2065 #[repr(transparent)]
2066 struct FooWrapper(Foo);
2069 Note that introducing another `struct` just to have a place for the other
2070 attributes may have unintended side effects on the representation:
2073 #![feature(repr_transparent)]
2075 #[repr(transparent)]
2081 #[repr(transparent)]
2082 struct Grams2(Float); // this is not equivalent to `Grams` above
2085 Here, `Grams2` is a not equivalent to `Grams` -- the former transparently wraps
2086 a (non-transparent) struct containing a single float, while `Grams` is a
2087 transparent wrapper around a float. This can make a difference for the ABI.
2093 register_diagnostics! {
2094 // E0006 // merged with E0005
2095 // E0101, // replaced with E0282
2096 // E0102, // replaced with E0282
2099 // E0272, // on_unimplemented #0
2100 // E0273, // on_unimplemented #1
2101 // E0274, // on_unimplemented #2
2102 E0278, // requirement is not satisfied
2103 E0279, // requirement is not satisfied
2104 E0280, // requirement is not satisfied
2105 E0284, // cannot resolve type
2106 // E0285, // overflow evaluation builtin bounds
2107 // E0300, // unexpanded macro
2108 // E0304, // expected signed integer constant
2109 // E0305, // expected constant
2110 E0311, // thing may not live long enough
2111 E0312, // lifetime of reference outlives lifetime of borrowed content
2112 E0313, // lifetime of borrowed pointer outlives lifetime of captured variable
2113 E0314, // closure outlives stack frame
2114 E0315, // cannot invoke closure outside of its lifetime
2115 E0316, // nested quantification of lifetimes
2116 E0320, // recursive overflow during dropck
2117 E0473, // dereference of reference outside its lifetime
2118 E0474, // captured variable `..` does not outlive the enclosing closure
2119 E0475, // index of slice outside its lifetime
2120 E0476, // lifetime of the source pointer does not outlive lifetime bound...
2121 E0477, // the type `..` does not fulfill the required lifetime...
2122 E0479, // the type `..` (provided as the value of a type parameter) is...
2123 E0480, // lifetime of method receiver does not outlive the method call
2124 E0481, // lifetime of function argument does not outlive the function call
2125 E0482, // lifetime of return value does not outlive the function call
2126 E0483, // lifetime of operand does not outlive the operation
2127 E0484, // reference is not valid at the time of borrow
2128 E0485, // automatically reference is not valid at the time of borrow
2129 E0486, // type of expression contains references that are not valid during...
2130 E0487, // unsafe use of destructor: destructor might be called while...
2131 E0488, // lifetime of variable does not enclose its declaration
2132 E0489, // type/lifetime parameter not in scope here
2133 E0490, // a value of type `..` is borrowed for too long
2134 E0495, // cannot infer an appropriate lifetime due to conflicting requirements
2135 E0566, // conflicting representation hints
2136 E0623, // lifetime mismatch where both parameters are anonymous regions
2137 E0628, // generators cannot have explicit arguments
2138 E0631, // type mismatch in closure arguments
2139 E0637, // "'_" is not a valid lifetime bound
2140 E0657, // `impl Trait` can only capture lifetimes bound at the fn level
2141 E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
2142 E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
2144 E0906, // closures cannot be static