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. Each message should start and end with a
14 // new line, and be wrapped to 80 characters. In vim you can `:set tw=80` and
15 // use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
16 register_long_diagnostics! {
19 Type parameter defaults can only use parameters that occur before them.
20 Erroneous code example:
23 struct Foo<T=U, U=()> {
27 // error: type parameters with a default cannot use forward declared
31 Since type parameters are evaluated in-order, you may be able to fix this issue
35 struct Foo<U=(), T=U> {
41 Please also verify that this wasn't because of a name-clash and rename the type
46 ## Note: this error code is no longer emitted by the compiler.
48 Imports (`use` statements) are not allowed after non-item statements, such as
49 variable declarations and expression statements.
51 Here is an example that demonstrates the error:
55 // Variable declaration before import
62 The solution is to declare the imports at the top of the block, function, or
65 Here is the previous example again, with the correct order:
75 See the Declaration Statements section of the reference for more information
76 about what constitutes an Item declaration and what does not:
78 https://doc.rust-lang.org/reference.html#statements
82 ## Note: this error code is no longer emitted by the compiler.
84 Two items of the same name cannot be imported without rebinding one of the
85 items under a new local name.
87 An example of this error:
91 use bar::*; // error, do `use foo::baz as quux` instead on the previous line
106 Two items of the same name cannot be imported without rebinding one of the
107 items under a new local name.
109 Erroneous code example:
111 ```compile_fail,E0252
113 use bar::baz; // error, do `use bar::baz as quux` instead
126 You can use aliases in order to fix this error. Example:
129 use foo::baz as foo_baz;
143 Or you can reference the item with its parent:
149 let x = foo::baz; // ok!
163 Attempt was made to import an unimportable value. This can happen when trying
164 to import a method from a trait.
166 Erroneous code example:
168 ```compile_fail,E0253
175 use foo::MyTrait::do_something;
176 // error: `do_something` is not directly importable
181 It's invalid to directly import methods belonging to a trait or concrete type.
185 Attempt was made to import an item whereas an extern crate with this name has
186 already been imported.
188 Erroneous code example:
190 ```compile_fail,E0254
191 extern crate collections;
194 pub trait collections {
199 use foo::collections; // error: an extern crate named `collections` has already
200 // been imported in this module
205 To fix issue issue, you have to rename at least one of the two imports.
209 extern crate collections as libcollections; // ok!
212 pub trait collections {
217 use foo::collections;
224 You can't import a value whose name is the same as another value defined in the
227 Erroneous code example:
229 ```compile_fail,E0255
230 use bar::foo; // error: an item named `foo` is already in scope
241 You can use aliases in order to fix this error. Example:
244 use bar::foo as bar_foo; // ok!
255 Or you can reference the item with its parent:
265 bar::foo(); // we get the item by referring to its parent
271 ## Note: this error code is no longer emitted by the compiler.
273 You can't import a type or module when the name of the item being imported is
274 the same as another type or submodule defined in the module.
276 An example of this error:
279 use foo::Bar; // error
292 The name chosen for an external crate conflicts with another external crate
293 that has been imported into the current module.
295 Erroneous code example:
297 ```compile_fail,E0259
299 extern crate libc as std;
304 The solution is to choose a different name that doesn't conflict with any
305 external crate imported into the current module.
311 extern crate libc as other_name;
316 The name for an item declaration conflicts with an external crate's name.
318 Erroneous code example:
326 There are two possible solutions:
328 Solution #1: Rename the item.
336 Solution #2: Import the crate with a different name.
339 extern crate abc as xyz;
344 See the Declaration Statements section of the reference for more information
345 about what constitutes an Item declaration and what does not:
347 https://doc.rust-lang.org/reference.html#statements
351 Private items cannot be publicly re-exported. This error indicates that you
352 attempted to `pub use` a type or value that was not itself public.
354 Erroneous code example:
366 The solution to this problem is to ensure that the items that you are
367 re-exporting are themselves marked with `pub`:
371 pub const X: u32 = 1;
379 See the 'Use Declarations' section of the reference for more information on
382 https://doc.rust-lang.org/reference.html#use-declarations
386 Private modules cannot be publicly re-exported. This error indicates that you
387 attempted to `pub use` a module that was not itself public.
389 Erroneous code example:
391 ```compile_fail,E0365
393 pub const X: u32 = 1;
401 The solution to this problem is to ensure that the module that you are
402 re-exporting is itself marked with `pub`:
406 pub const X: u32 = 1;
414 See the 'Use Declarations' section of the reference for more information
417 https://doc.rust-lang.org/reference.html#use-declarations
421 Inner items do not inherit type parameters from the functions they are embedded
424 Erroneous code example:
426 ```compile_fail,E0401
428 fn bar(y: T) { // T is defined in the "outer" function
437 ```compile_fail,E0401
439 type MaybeT = Option<T>;
446 ```compile_fail,E0401
455 Items inside functions are basically just like top-level items, except
456 that they can only be used from the function they are in.
458 There are a couple of solutions for this.
460 If the item is a function, you may use a closure:
464 let bar = |y: T| { // explicit type annotation may not be necessary
471 For a generic item, you can copy over the parameters:
484 type MaybeT<T> = Option<T>;
488 Be sure to copy over any bounds as well:
491 fn foo<T: Copy>(x: T) {
492 fn bar<T: Copy>(y: T) {
500 fn foo<T: Copy>(x: T) {
501 struct Foo<T: Copy> {
507 This may require additional type hints in the function body.
509 In case the item is a function inside an `impl`, defining a private helper
510 function might be easier:
514 pub fn foo(&self, x: T) {
518 fn bar(&self, y: T) {
524 For default impls in traits, the private helper solution won't work, however
525 closures or copying the parameters should still work.
529 Some type parameters have the same name.
531 Erroneous code example:
533 ```compile_fail,E0403
534 fn foo<T, T>(s: T, u: T) {} // error: the name `T` is already used for a type
535 // parameter in this type parameter list
538 Please verify that none of the type parameterss are misspelled, and rename any
539 clashing parameters. Example:
542 fn foo<T, Y>(s: T, u: Y) {} // ok!
547 You tried to implement something which was not a trait on an object.
549 Erroneous code example:
551 ```compile_fail,E0404
555 impl Foo for Bar {} // error: `Foo` is not a trait
558 Please verify that you didn't misspell the trait's name or otherwise use the
559 wrong identifier. Example:
567 impl Foo for Bar { // ok!
568 // functions implementation
574 The code refers to a trait that is not in scope.
576 Erroneous code example:
578 ```compile_fail,E0405
581 impl SomeTrait for Foo {} // error: trait `SomeTrait` is not in scope
584 Please verify that the name of the trait wasn't misspelled and ensure that it
585 was imported. Example:
589 use some_file::SomeTrait;
598 impl SomeTrait for Foo { // ok!
599 // implements functions
605 A definition of a method not in the implemented trait was given in a trait
608 Erroneous code example:
610 ```compile_fail,E0407
619 fn b() {} // error: method `b` is not a member of trait `Foo`
623 Please verify you didn't misspell the method name and you used the correct
624 trait. First example:
660 An "or" pattern was used where the variable bindings are not consistently bound
663 Erroneous code example:
665 ```compile_fail,E0408
667 Some(y) | None => { /* use y */ } // error: variable `y` from pattern #1 is
668 // not bound in pattern #2
673 Here, `y` is bound to the contents of the `Some` and can be used within the
674 block corresponding to the match arm. However, in case `x` is `None`, we have
675 not specified what `y` is, and the block will use a nonexistent variable.
677 To fix this error, either split into multiple match arms:
682 Some(y) => { /* use y */ }
683 None => { /* ... */ }
687 or, bind the variable to a field of the same type in all sub-patterns of the
693 (0, y) | (y, 0) => { /* use y */}
698 In this example, if `x` matches the pattern `(0, _)`, the second field is set
699 to `y`. If it matches `(_, 0)`, the first field is set to `y`; so in all
700 cases `y` is set to some value.
704 An "or" pattern was used where the variable bindings are not consistently bound
707 Erroneous code example:
709 ```compile_fail,E0409
712 (0, ref y) | (y, 0) => { /* use y */} // error: variable `y` is bound with
713 // different mode in pattern #2
714 // than in pattern #1
719 Here, `y` is bound by-value in one case and by-reference in the other.
721 To fix this error, just use the same mode in both cases.
722 Generally using `ref` or `ref mut` where not already used will fix this:
727 (0, ref y) | (ref y, 0) => { /* use y */}
732 Alternatively, split the pattern:
737 (y, 0) => { /* use y */ }
738 (0, ref y) => { /* use y */}
745 The `Self` keyword was used outside an impl or a trait.
747 Erroneous code example:
749 ```compile_fail,E0411
750 <Self>::foo; // error: use of `Self` outside of an impl or trait
753 The `Self` keyword represents the current type, which explains why it can only
754 be used inside an impl or a trait. It gives access to the associated items of a
763 fn bar() -> Self::Bar; // like this
767 However, be careful when two types have a common associated type:
778 trait Baz : Foo + Foo2 {
779 fn bar() -> Self::Bar;
780 // error: ambiguous associated type `Bar` in bounds of `Self`
784 This problem can be solved by specifying from which trait we want to use the
796 trait Baz : Foo + Foo2 {
797 fn bar() -> <Self as Foo>::Bar; // ok!
803 The type name used is not in scope.
805 Erroneous code examples:
807 ```compile_fail,E0412
808 impl Something {} // error: type name `Something` is not in scope
813 fn bar(N); // error: type name `N` is not in scope
818 fn foo(x: T) {} // type name `T` is not in scope
821 To fix this error, please verify you didn't misspell the type name, you did
822 declare it or imported it into the scope. Examples:
827 impl Something {} // ok!
834 fn bar(Self::N); // ok!
839 fn foo<T>(x: T) {} // ok!
844 More than one function parameter have the same name.
846 Erroneous code example:
848 ```compile_fail,E0415
849 fn foo(f: i32, f: i32) {} // error: identifier `f` is bound more than
850 // once in this parameter list
853 Please verify you didn't misspell parameters' name. Example:
856 fn foo(f: i32, g: i32) {} // ok!
861 An identifier is bound more than once in a pattern.
863 Erroneous code example:
865 ```compile_fail,E0416
867 (x, x) => {} // error: identifier `x` is bound more than once in the
872 Please verify you didn't misspell identifiers' name. Example:
880 Or maybe did you mean to unify? Consider using a guard:
884 (x, x2, see) if x == x2 => { /* A and B are equal, do one thing */ }
885 (y, z, see) => { /* A and B unequal; do another thing */ }
891 You are trying to use an identifier that is either undefined or not a struct.
892 Erroneous code example:
894 ```compile_fail,E0422
896 let x = Foo { x: 1, y: 2 };
900 In this case, `Foo` is undefined, so it inherently isn't anything, and
901 definitely not a struct.
906 let x = foo { x: 1, y: 2 };
910 In this case, `foo` is defined, but is not a struct, so Rust can't use it as
915 A `struct` variant name was used like a function name.
917 Erroneous code example:
919 ```compile_fail,E0423
920 struct Foo { a: bool };
923 // error: `Foo` is a struct variant name, but this expression uses
924 // it like a function name
927 Please verify you didn't misspell the name of what you actually wanted to use
931 fn Foo() -> u32 { 0 }
933 let f = Foo(); // ok!
938 The `self` keyword was used in a static method.
940 Erroneous code example:
942 ```compile_fail,E0424
949 self.bar(); // error: `self` is not available in a static method.
954 Please check if the method's argument list should have contained `self`,
955 `&self`, or `&mut self` (in case you didn't want to create a static
956 method), and add it if so. Example:
972 An unresolved name was used.
974 Erroneous code examples:
976 ```compile_fail,E0425
977 something_that_doesnt_exist::foo;
978 // error: unresolved name `something_that_doesnt_exist::foo`
984 Self; // error: unresolved name `Self`
990 let x = unknown_variable; // error: unresolved name `unknown_variable`
993 Please verify that the name wasn't misspelled and ensure that the
994 identifier being referred to is valid for the given situation. Example:
997 enum something_that_does_exist {
1005 mod something_that_does_exist {
1006 pub static foo : i32 = 0i32;
1009 something_that_does_exist::foo; // ok!
1015 let unknown_variable = 12u32;
1016 let x = unknown_variable; // ok!
1019 If the item is not defined in the current module, it must be imported using a
1020 `use` statement, like so:
1027 If the item you are importing is not defined in some super-module of the
1028 current module, then it must also be declared as public (e.g., `pub fn`).
1032 An undeclared label was used.
1034 Erroneous code example:
1036 ```compile_fail,E0426
1038 break 'a; // error: use of undeclared label `'a`
1042 Please verify you spelt or declare the label correctly. Example:
1052 A type or module has been defined more than once.
1054 Erroneous code example:
1056 ```compile_fail,E0428
1058 struct Bar; // error: duplicate definition of value `Bar`
1061 Please verify you didn't misspell the type/module's name or remove/rename the
1062 duplicated one. Example:
1071 The `self` keyword cannot appear alone as the last segment in a `use`
1074 Erroneous code example:
1076 ```compile_fail,E0429
1077 use std::fmt::self; // error: `self` imports are only allowed within a { } list
1080 To use a namespace itself in addition to some of its members, `self` may appear
1081 as part of a brace-enclosed list of imports:
1084 use std::fmt::{self, Debug};
1087 If you only want to import the namespace, do so directly:
1095 The `self` import appears more than once in the list.
1097 Erroneous code example:
1099 ```compile_fail,E0430
1100 use something::{self, self}; // error: `self` import can only appear once in
1104 Please verify you didn't misspell the import name or remove the duplicated
1105 `self` import. Example:
1108 use something::self; // ok!
1113 An invalid `self` import was made.
1115 Erroneous code example:
1117 ```compile_fail,E0431
1118 use {self}; // error: `self` import can only appear in an import list with a
1122 You cannot import the current module into itself, please remove this import
1123 or verify you didn't misspell it.
1127 An import was unresolved.
1129 Erroneous code example:
1131 ```compile_fail,E0432
1132 use something::Foo; // error: unresolved import `something::Foo`.
1135 Paths in `use` statements are relative to the crate root. To import items
1136 relative to the current and parent modules, use the `self::` and `super::`
1137 prefixes, respectively. Also verify that you didn't misspell the import
1138 name and that the import exists in the module from where you tried to
1142 use self::something::Foo; // ok!
1149 Or, if you tried to use a module from an external crate, you may have missed
1150 the `extern crate` declaration (which is usually placed in the crate root):
1153 extern crate homura; // Required to use the `homura` crate
1160 An undeclared type or module was used.
1162 Erroneous code example:
1164 ```compile_fail,E0433
1165 let map = HashMap::new();
1166 // error: failed to resolve. Use of undeclared type or module `HashMap`
1169 Please verify you didn't misspell the type/module's name or that you didn't
1170 forgot to import it:
1174 use std::collections::HashMap; // HashMap has been imported.
1175 let map: HashMap<u32, u32> = HashMap::new(); // So it can be used!
1180 This error indicates that a variable usage inside an inner function is invalid
1181 because the variable comes from a dynamic environment. Inner functions do not
1182 have access to their containing environment.
1184 Erroneous code example:
1186 ```compile_fail,E0434
1190 y // error: can't capture dynamic environment in a fn item; use the
1191 // || { ... } closure form instead.
1196 Functions do not capture local variables. To fix this error, you can replace the
1197 function with a closure:
1208 or replace the captured variable with a constant or a static item:
1212 static mut X: u32 = 4;
1225 A non-constant value was used in a constant expression.
1227 Erroneous code example:
1229 ```compile_fail,E0435
1231 let a: [u8; foo]; // error: attempt to use a non-constant value in a constant
1234 To fix this error, please replace the value with a constant. Example:
1237 let a: [u8; 42]; // ok!
1243 const FOO: usize = 42;
1244 let a: [u8; FOO]; // ok!
1249 Trait implementations can only implement associated types that are members of
1250 the trait in question. This error indicates that you attempted to implement
1251 an associated type whose name does not match the name of any associated type
1254 Erroneous code example:
1256 ```compile_fail,E0437
1264 The solution to this problem is to remove the extraneous associated type:
1274 Trait implementations can only implement associated constants that are
1275 members of the trait in question. This error indicates that you
1276 attempted to implement an associated constant whose name does not
1277 match the name of any associated constant in the trait.
1279 Erroneous code example:
1281 ```compile_fail,E0438
1282 #![feature(associated_consts)]
1287 const BAR: bool = true;
1291 The solution to this problem is to remove the extraneous associated constant:
1301 Macro import declarations were malformed.
1303 Erroneous code examples:
1305 ```compile_fail,E0466
1306 #[macro_use(a_macro(another_macro))] // error: invalid import declaration
1307 extern crate core as some_crate;
1309 #[macro_use(i_want = "some_macros")] // error: invalid import declaration
1310 extern crate core as another_crate;
1313 This is a syntax error at the level of attribute declarations. The proper
1314 syntax for macro imports is the following:
1319 macro_rules! get_tacos {
1324 macro_rules! get_pimientos {
1329 #[macro_use(get_tacos, get_pimientos)] // It imports `get_tacos` and
1330 extern crate some_crate; // `get_pimientos` macros from some_crate
1333 If you would like to import all exported macros, write `macro_use` with no
1338 Macro reexport declarations were empty or malformed.
1340 Erroneous code examples:
1342 ```compile_fail,E0467
1343 #[macro_reexport] // error: no macros listed for export
1344 extern crate core as macros_for_good;
1346 #[macro_reexport(fun_macro = "foo")] // error: not a macro identifier
1347 extern crate core as other_macros_for_good;
1350 This is a syntax error at the level of attribute declarations.
1352 Currently, `macro_reexport` requires at least one macro name to be listed.
1353 Unlike `macro_use`, listing no names does not reexport all macros from the
1356 Decide which macros you would like to export and list them properly.
1358 These are proper reexport declarations:
1361 #[macro_reexport(some_macro, another_macro)]
1362 extern crate macros_for_good;
1367 A non-root module attempts to import macros from another crate.
1369 Example of erroneous code:
1371 ```compile_fail,E0468
1373 #[macro_use(helpful_macro)] // error: must be at crate root to import
1374 extern crate core; // macros from another crate
1375 helpful_macro!(...);
1379 Only `extern crate` imports at the crate root level are allowed to import
1382 Either move the macro import to crate root or do without the foreign macros.
1386 #[macro_use(helpful_macro)]
1387 extern crate some_crate;
1396 A macro listed for import was not found.
1398 Erroneous code example:
1400 ```compile_fail,E0469
1401 #[macro_use(drink, be_merry)] // error: imported macro not found
1402 extern crate collections;
1409 Either the listed macro is not contained in the imported crate, or it is not
1410 exported from the given crate.
1412 This could be caused by a typo. Did you misspell the macro's name?
1414 Double-check the names of the macros listed for import, and that the crate
1415 in question exports them.
1417 A working version would be:
1420 // In some_crate crate:
1427 macro_rules! drink {
1432 #[macro_use(eat, drink)]
1433 extern crate some_crate; //ok!
1438 A macro listed for reexport was not found.
1440 Erroneous code example:
1442 ```compile_fail,E0470
1443 #[macro_reexport(drink, be_merry)]
1444 extern crate collections;
1451 Either the listed macro is not contained in the imported crate, or it is not
1452 exported from the given crate.
1454 This could be caused by a typo. Did you misspell the macro's name?
1456 Double-check the names of the macros listed for reexport, and that the crate
1457 in question exports them.
1462 // In some_crate crate:
1469 macro_rules! drink {
1474 #[macro_reexport(eat, drink)]
1475 extern crate some_crate;
1480 A binding shadowed something it shouldn't.
1482 Erroneous code example:
1484 ```compile_fail,E0530
1485 static TEST: i32 = 0;
1487 let r: (i32, i32) = (0, 0);
1489 TEST => {} // error: match bindings cannot shadow statics
1493 To fix this error, just change the binding's name in order to avoid shadowing
1494 one of the following:
1497 * struct/enum variant
1505 static TEST: i32 = 0;
1507 let r: (i32, i32) = (0, 0);
1509 something => {} // ok!
1515 Pattern arm did not match expected kind.
1517 Erroneous code example:
1519 ```compile_fail,E0532
1525 fn print_on_failure(state: &State) {
1527 // error: expected unit struct/variant or constant, found tuple
1528 // variant `State::Failed`
1529 State::Failed => println!("Failed"),
1535 To fix this error, ensure the match arm kind is the same as the expression
1546 fn print_on_failure(state: &State) {
1548 State::Failed(ref msg) => println!("Failed with {}", msg),
1557 register_diagnostics! {
1558 // E0153, unused error code
1559 // E0157, unused error code
1562 // E0402, // cannot use an outer type parameter in this context
1563 // E0406, merged into 420
1564 // E0410, merged into 408
1565 // E0413, merged into 530
1566 // E0414, merged into 530
1567 // E0417, merged into 532
1568 // E0418, merged into 532
1569 // E0419, merged into 531
1570 // E0420, merged into 532
1571 // E0421, merged into 531
1572 E0531, // unresolved pattern path kind `name`
1573 // E0427, merged into 530