diagnostics: Fix E0303 explanation.

[rust.git] / src / librustc / diagnostics.rs

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![allow(non_snake_case)]

// Error messages for EXXXX errors.
// Each message should start and end with a new line, and be wrapped to 80 characters.
// In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
register_long_diagnostics! {

E0001: r##"
This error suggests that the expression arm corresponding to the noted pattern
will never be reached as for all possible values of the expression being
matched, one of the preceding patterns will match.

This means that perhaps some of the preceding patterns are too general, this one
is too specific or the ordering is incorrect.
"##,

E0002: r##"
This error indicates that an empty match expression is illegal because the type
it is matching on is non-empty (there exist values of this type). In safe code
it is impossible to create an instance of an empty type, so empty match
expressions are almost never desired.  This error is typically fixed by adding
one or more cases to the match expression.

An example of an empty type is `enum Empty { }`.
"##,

E0003: r##"
Not-a-Number (NaN) values cannot be compared for equality and hence can never
match the input to a match expression. To match against NaN values, you should
instead use the `is_nan` method in a guard, as in: `x if x.is_nan() => ...`
"##,

E0004: r##"
This error indicates that the compiler cannot guarantee a matching pattern for
one or more possible inputs to a match expression. Guaranteed matches are
required in order to assign values to match expressions, or alternatively,
determine the flow of execution.

If you encounter this error you must alter your patterns so that every possible
value of the input type is matched. For types with a small number of variants
(like enums) you should probably cover all cases explicitly. Alternatively, the
underscore `_` wildcard pattern can be added after all other patterns to match
"anything else".
"##,

// FIXME: Remove duplication here?
E0005: r##"
Patterns used to bind names must be irrefutable, that is, they must guarantee
that a name will be extracted in all cases. If you encounter this error you
probably need to use a `match` or `if let` to deal with the possibility of
failure.
"##,

E0006: r##"
Patterns used to bind names must be irrefutable, that is, they must guarantee
that a name will be extracted in all cases. If you encounter this error you
probably need to use a `match` or `if let` to deal with the possibility of
failure.
"##,

E0007: r##"
This error indicates that the bindings in a match arm would require a value to
be moved into more than one location, thus violating unique ownership. Code like
the following is invalid as it requires the entire `Option<String>` to be moved
into a variable called `op_string` while simultaneously requiring the inner
String to be moved into a variable called `s`.

```
let x = Some("s".to_string());
match x {
    op_string @ Some(s) => ...
    None => ...
}
```

See also Error 303.
"##,

E0008: r##"
Names bound in match arms retain their type in pattern guards. As such, if a
name is bound by move in a pattern, it should also be moved to wherever it is
referenced in the pattern guard code. Doing so however would prevent the name
from being available in the body of the match arm. Consider the following:

```
match Some("hi".to_string()) {
    Some(s) if s.len() == 0 => // use s.
    ...
}
```

The variable `s` has type `String`, and its use in the guard is as a variable of
type `String`. The guard code effectively executes in a separate scope to the
body of the arm, so the value would be moved into this anonymous scope and
therefore become unavailable in the body of the arm. Although this example seems
innocuous, the problem is most clear when considering functions that take their
argument by value.

```
match Some("hi".to_string()) {
    Some(s) if { drop(s); false } => (),
    Some(s) => // use s.
    ...
}
```

The value would be dropped in the guard then become unavailable not only in the
body of that arm but also in all subsequent arms! The solution is to bind by
reference when using guards or refactor the entire expression, perhaps by
putting the condition inside the body of the arm.
"##,

E0009: r##"
In a pattern, all values that don't implement the `Copy` trait have to be bound
the same way. The goal here is to avoid binding simultaneously by-move and
by-ref.

This limitation may be removed in a future version of Rust.

Wrong example:

```
struct X { x: (), }

let x = Some((X { x: () }, X { x: () }));
match x {
    Some((y, ref z)) => {},
    None => panic!()
}
```

You have two solutions:

Solution #1: Bind the pattern's values the same way.

```
struct X { x: (), }

let x = Some((X { x: () }, X { x: () }));
match x {
    Some((ref y, ref z)) => {},
    // or Some((y, z)) => {}
    None => panic!()
}
```

Solution #2: Implement the `Copy` trait for the `X` structure.

However, please keep in mind that the first solution should be preferred.

```
#[derive(Clone, Copy)]
struct X { x: (), }

let x = Some((X { x: () }, X { x: () }));
match x {
    Some((y, ref z)) => {},
    None => panic!()
}
```
"##,

E0010: r##"
The value of statics and constants must be known at compile time, and they live
for the entire lifetime of a program. Creating a boxed value allocates memory on
the heap at runtime, and therefore cannot be done at compile time.
"##,

E0011: r##"
Initializers for constants and statics are evaluated at compile time.
User-defined operators rely on user-defined functions, which cannot be evaluated
at compile time.

Bad example:

```
use std::ops::Index;

struct Foo { a: u8 }

impl Index<u8> for Foo {
    type Output = u8;

    fn index<'a>(&'a self, idx: u8) -> &'a u8 { &self.a }
}

const a: Foo = Foo { a: 0u8 };
const b: u8 = a[0]; // Index trait is defined by the user, bad!
```

Only operators on builtin types are allowed.

Example:

```
const a: &'static [i32] = &[1, 2, 3];
const b: i32 = a[0]; // Good!
```
"##,

E0013: r##"
Static and const variables can refer to other const variables. But a const
variable cannot refer to a static variable. For example, `Y` cannot refer to `X`
here:

```
static X: i32 = 42;
const Y: i32 = X;
```

To fix this, the value can be extracted as a const and then used:

```
const A: i32 = 42;
static X: i32 = A;
const Y: i32 = A;
```
"##,

E0014: r##"
Constants can only be initialized by a constant value or, in a future
version of Rust, a call to a const function. This error indicates the use
of a path (like a::b, or x) denoting something other than one of these
allowed items. Example:

```
const FOO: i32 = { let x = 0; x }; // 'x' isn't a constant nor a function!
```

To avoid it, you have to replace the non-constant value:

```
const FOO: i32 = { const X : i32 = 0; X };
// or even:
const FOO: i32 = { 0 }; // but brackets are useless here
```
"##,

E0015: r##"
The only functions that can be called in static or constant expressions are
`const` functions. Rust currently does not support more general compile-time
function execution.

See [RFC 911] for more details on the design of `const fn`s.

[RFC 911]: https://github.com/rust-lang/rfcs/blob/master/text/0911-const-fn.md
"##,

E0016: r##"
Blocks in constants may only contain items (such as constant, function
definition, etc...) and a tail expression. Example:

```
const FOO: i32 = { let x = 0; x }; // 'x' isn't an item!
```

To avoid it, you have to replace the non-item object:

```
const FOO: i32 = { const X : i32 = 0; X };
```
"##,

E0018: r##"
The value of static and const variables must be known at compile time. You
can't cast a pointer as an integer because we can't know what value the
address will take.

However, pointers to other constants' addresses are allowed in constants,
example:

```
const X: u32 = 50;
const Y: *const u32 = &X;
```

Therefore, casting one of these non-constant pointers to an integer results
in a non-constant integer which lead to this error. Example:

```
const X: u32 = 1;
const Y: usize = &X as *const u32 as usize;
println!("{}", Y);
```
"##,

E0019: r##"
A function call isn't allowed in the const's initialization expression
because the expression's value must be known at compile-time. Example of
erroneous code:

```
enum Test {
    V1
}

impl Test {
    fn test(&self) -> i32 {
        12
    }
}

fn main() {
    const FOO: Test = Test::V1;

    const A: i32 = FOO.test(); // You can't call Test::func() here !
}
```

Remember: you can't use a function call inside a const's initialization
expression! However, you can totally use it elsewhere you want:

```
fn main() {
    const FOO: Test = Test::V1;

    FOO.func(); // here is good
    let x = FOO.func(); // or even here!
}
```
"##,

E0020: r##"
This error indicates that an attempt was made to divide by zero (or take the
remainder of a zero divisor) in a static or constant expression.
"##,

E0079: r##"
Enum variants which contain no data can be given a custom integer
representation. This error indicates that the value provided is not an
integer literal and is therefore invalid.
"##,

E0080: r##"
This error indicates that the compiler was unable to sensibly evaluate an
integer expression provided as an enum discriminant. Attempting to divide by 0
or causing integer overflow are two ways to induce this error. For example:

```
enum Enum {
    X = (1 << 500),
    Y = (1 / 0)
}
```

Ensure that the expressions given can be evaluated as the desired integer type.
See the FFI section of the Reference for more information about using a custom
integer type:

https://doc.rust-lang.org/reference.html#ffi-attributes
"##,

E0109: r##"
You tried to give a type parameter to a type which doesn't need it. Erroneous
code example:

```
type X = u32<i32>; // error: type parameters are not allowed on this type
```

Please check that you used the correct type and recheck its definition. Perhaps
it doesn't need the type parameter.
Example:

```
type X = u32; // ok!
```
"##,

E0110: r##"
You tried to give a lifetime parameter to a type which doesn't need it.
Erroneous code example:

```
type X = u32<'static>; // error: lifetime parameters are not allowed on
                       //        this type
```

Please check that you used the correct type and recheck its definition,
perhaps it doesn't need the lifetime parameter. Example:

```
type X = u32; // ok!
```
"##,

E0133: r##"
Using unsafe functionality, such as dereferencing raw pointers and calling
functions via FFI or marked as unsafe, is potentially dangerous and disallowed
by safety checks. These safety checks can be relaxed for a section of the code
by wrapping the unsafe instructions with an `unsafe` block. For instance:

```
unsafe fn f() { return; }

fn main() {
    unsafe { f(); }
}
```

See also https://doc.rust-lang.org/book/unsafe.html
"##,

E0137: r##"
This error indicates that the compiler found multiple functions with the
`#[main]` attribute. This is an error because there must be a unique entry
point into a Rust program.
"##,

E0152: r##"
Lang items are already implemented in the standard library. Unless you are
writing a free-standing application (e.g. a kernel), you do not need to provide
them yourself.

You can build a free-standing crate by adding `#![no_std]` to the crate
attributes:

```
#![feature(no_std)]
#![no_std]
```

See also https://doc.rust-lang.org/book/no-stdlib.html
"##,

E0158: r##"
`const` and `static` mean different things. A `const` is a compile-time
constant, an alias for a literal value. This property means you can match it
directly within a pattern.

The `static` keyword, on the other hand, guarantees a fixed location in memory.
This does not always mean that the value is constant. For example, a global
mutex can be declared `static` as well.

If you want to match against a `static`, consider using a guard instead:

```
static FORTY_TWO: i32 = 42;
match Some(42) {
    Some(x) if x == FORTY_TWO => ...
    ...
}
```
"##,

E0161: r##"
In Rust, you can only move a value when its size is known at compile time.

To work around this restriction, consider "hiding" the value behind a reference:
either `&x` or `&mut x`. Since a reference has a fixed size, this lets you move
it around as usual.
"##,

E0162: r##"
An if-let pattern attempts to match the pattern, and enters the body if the
match was successful. If the match is irrefutable (when it cannot fail to
match), use a regular `let`-binding instead. For instance:

```
struct Irrefutable(i32);
let irr = Irrefutable(0);

// This fails to compile because the match is irrefutable.
if let Irrefutable(x) = irr {
    // This body will always be executed.
    foo(x);
}

// Try this instead:
let Irrefutable(x) = irr;
foo(x);
```
"##,

E0165: r##"
A while-let pattern attempts to match the pattern, and enters the body if the
match was successful. If the match is irrefutable (when it cannot fail to
match), use a regular `let`-binding inside a `loop` instead. For instance:

```
struct Irrefutable(i32);
let irr = Irrefutable(0);

// This fails to compile because the match is irrefutable.
while let Irrefutable(x) = irr {
    ...
}

// Try this instead:
loop {
    let Irrefutable(x) = irr;
    ...
}
```
"##,

E0170: r##"
Enum variants are qualified by default. For example, given this type:

```
enum Method {
    GET,
    POST
}
```

you would match it using:

```
match m {
    Method::GET => ...
    Method::POST => ...
}
```

If you don't qualify the names, the code will bind new variables named "GET" and
"POST" instead. This behavior is likely not what you want, so `rustc` warns when
that happens.

Qualified names are good practice, and most code works well with them. But if
you prefer them unqualified, you can import the variants into scope:

```
use Method::*;
enum Method { GET, POST }
```
"##,

E0261: r##"
When using a lifetime like `'a` in a type, it must be declared before being
used.

These two examples illustrate the problem:

```
// error, use of undeclared lifetime name `'a`
fn foo(x: &'a str) { }

struct Foo {
    // error, use of undeclared lifetime name `'a`
    x: &'a str,
}
```

These can be fixed by declaring lifetime parameters:

```
fn foo<'a>(x: &'a str) { }

struct Foo<'a> {
    x: &'a str,
}
```
"##,

E0262: r##"
Declaring certain lifetime names in parameters is disallowed. For example,
because the `'static` lifetime is a special built-in lifetime name denoting
the lifetime of the entire program, this is an error:

```
// error, illegal lifetime parameter name `'static`
fn foo<'static>(x: &'static str) { }
```
"##,

E0263: r##"
A lifetime name cannot be declared more than once in the same scope. For
example:

```
// error, lifetime name `'a` declared twice in the same scope
fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str) { }
```
"##,

E0265: r##"
This error indicates that a static or constant references itself.
All statics and constants need to resolve to a value in an acyclic manner.

For example, neither of the following can be sensibly compiled:

```
const X: u32 = X;
```

```
const X: u32 = Y;
const Y: u32 = X;
```
"##,

E0267: r##"
This error indicates the use of a loop keyword (`break` or `continue`) inside a
closure but outside of any loop. Erroneous code example:

```
let w = || { break; }; // error: `break` inside of a closure
```

`break` and `continue` keywords can be used as normal inside closures as long as
they are also contained within a loop. To halt the execution of a closure you
should instead use a return statement. Example:

```
let w = || {
    for _ in 0..10 {
        break;
    }
};

w();
```
"##,

E0268: r##"
This error indicates the use of a loop keyword (`break` or `continue`) outside
of a loop. Without a loop to break out of or continue in, no sensible action can
be taken. Erroneous code example:

```
fn some_func() {
    break; // error: `break` outside of loop
}
```

Please verify that you are using `break` and `continue` only in loops. Example:

```
fn some_func() {
    for _ in 0..10 {
        break; // ok!
    }
}
```
"##,

E0271: r##"
This is because of a type mismatch between the associated type of some
trait (e.g. `T::Bar`, where `T` implements `trait Quux { type Bar; }`)
and another type `U` that is required to be equal to `T::Bar`, but is not.
Examples follow.

Here is a basic example:

```
trait Trait { type AssociatedType; }
fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
    println!("in foo");
}
impl Trait for i8 { type AssociatedType = &'static str; }
foo(3_i8);
```

Here is that same example again, with some explanatory comments:

```
trait Trait { type AssociatedType; }

fn foo<T>(t: T) where T: Trait<AssociatedType=u32> {
//                    ~~~~~~~~ ~~~~~~~~~~~~~~~~~~
//                        |            |
//         This says `foo` can         |
//           only be used with         |
//              some type that         |
//         implements `Trait`.         |
//                                     |
//                             This says not only must
//                             `T` be an impl of `Trait`
//                             but also that the impl
//                             must assign the type `u32`
//                             to the associated type.
    println!("in foo");
}

impl Trait for i8 { type AssociatedType = &'static str; }
~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//      |                             |
// `i8` does have                     |
// implementation                     |
// of `Trait`...                      |
//                     ... but it is an implementation
//                     that assigns `&'static str` to
//                     the associated type.

foo(3_i8);
// Here, we invoke `foo` with an `i8`, which does not satisfy
// the constraint `<i8 as Trait>::AssociatedType=u32`, and
// therefore the type-checker complains with this error code.
```

Here is a more subtle instance of the same problem, that can
arise with for-loops in Rust:

```
let vs: Vec<i32> = vec![1, 2, 3, 4];
for v in &vs {
    match v {
        1 => {}
        _ => {}
    }
}
```

The above fails because of an analogous type mismatch,
though may be harder to see. Again, here are some
explanatory comments for the same example:

```
{
    let vs = vec![1, 2, 3, 4];

    // `for`-loops use a protocol based on the `Iterator`
    // trait. Each item yielded in a `for` loop has the
    // type `Iterator::Item` -- that is,I `Item` is the
    // associated type of the concrete iterator impl.
    for v in &vs {
//      ~    ~~~
//      |     |
//      |    We borrow `vs`, iterating over a sequence of
//      |    *references* of type `&Elem` (where `Elem` is
//      |    vector's element type). Thus, the associated
//      |    type `Item` must be a reference `&`-type ...
//      |
//  ... and `v` has the type `Iterator::Item`, as dictated by
//  the `for`-loop protocol ...

        match v {
            1 => {}
//          ~
//          |
// ... but *here*, `v` is forced to have some integral type;
// only types like `u8`,`i8`,`u16`,`i16`, et cetera can
// match the pattern `1` ...

            _ => {}
        }

// ... therefore, the compiler complains, because it sees
// an attempt to solve the equations
// `some integral-type` = type-of-`v`
//                      = `Iterator::Item`
//                      = `&Elem` (i.e. `some reference type`)
//
// which cannot possibly all be true.

    }
}
```

To avoid those issues, you have to make the types match correctly.
So we can fix the previous examples like this:

```
// Basic Example:
trait Trait { type AssociatedType; }
fn foo<T>(t: T) where T: Trait<AssociatedType = &'static str> {
    println!("in foo");
}
impl Trait for i8 { type AssociatedType = &'static str; }
foo(3_i8);

// For-Loop Example:
let vs = vec![1, 2, 3, 4];
for v in &vs {
    match v {
        &1 => {}
        _ => {}
    }
}
```
"##,

E0277: r##"
You tried to use a type which doesn't implement some trait in a place which
expected that trait. Erroneous code example:

```
// here we declare the Foo trait with a bar method
trait Foo {
    fn bar(&self);
}

// we now declare a function which takes an object implementing the Foo trait
fn some_func<T: Foo>(foo: T) {
    foo.bar();
}

fn main() {
    // we now call the method with the i32 type, which doesn't implement
    // the Foo trait
    some_func(5i32); // error: the trait `Foo` is not implemented for the
                     //     type `i32`
}
```

In order to fix this error, verify that the type you're using does implement
the trait. Example:

```
trait Foo {
    fn bar(&self);
}

fn some_func<T: Foo>(foo: T) {
    foo.bar(); // we can now use this method since i32 implements the
               // Foo trait
}

// we implement the trait on the i32 type
impl Foo for i32 {
    fn bar(&self) {}
}

fn main() {
    some_func(5i32); // ok!
}
```
"##,

E0282: r##"
This error indicates that type inference did not result in one unique possible
type, and extra information is required. In most cases this can be provided
by adding a type annotation. Sometimes you need to specify a generic type
parameter manually.

A common example is the `collect` method on `Iterator`. It has a generic type
parameter with a `FromIterator` bound, which for a `char` iterator is
implemented by `Vec` and `String` among others. Consider the following snippet
that reverses the characters of a string:

```
let x = "hello".chars().rev().collect();
```

In this case, the compiler cannot infer what the type of `x` should be:
`Vec<char>` and `String` are both suitable candidates. To specify which type to
use, you can use a type annotation on `x`:

```
let x: Vec<char> = "hello".chars().rev().collect();
```

It is not necessary to annotate the full type. Once the ambiguity is resolved,
the compiler can infer the rest:

```
let x: Vec<_> = "hello".chars().rev().collect();
```

Another way to provide the compiler with enough information, is to specify the
generic type parameter:

```
let x = "hello".chars().rev().collect::<Vec<char>>();
```

Again, you need not specify the full type if the compiler can infer it:

```
let x = "hello".chars().rev().collect::<Vec<_>>();
```

Apart from a method or function with a generic type parameter, this error can
occur when a type parameter of a struct or trait cannot be inferred. In that
case it is not always possible to use a type annotation, because all candidates
have the same return type. For instance:

```
struct Foo<T> {
    // Some fields omitted.
}

impl<T> Foo<T> {
    fn bar() -> i32 {
        0
    }

    fn baz() {
        let number = Foo::bar();
    }
}
```

This will fail because the compiler does not know which instance of `Foo` to
call `bar` on. Change `Foo::bar()` to `Foo::<T>::bar()` to resolve the error.
"##,

E0296: r##"
This error indicates that the given recursion limit could not be parsed. Ensure
that the value provided is a positive integer between quotes, like so:

```
#![recursion_limit="1000"]
```
"##,

E0297: r##"
Patterns used to bind names must be irrefutable. That is, they must guarantee
that a name will be extracted in all cases. Instead of pattern matching the
loop variable, consider using a `match` or `if let` inside the loop body. For
instance:

```
// This fails because `None` is not covered.
for Some(x) in xs {
    ...
}

// Match inside the loop instead:
for item in xs {
    match item {
        Some(x) => ...
        None => ...
    }
}

// Or use `if let`:
for item in xs {
    if let Some(x) = item {
        ...
    }
}
```
"##,

E0301: r##"
Mutable borrows are not allowed in pattern guards, because matching cannot have
side effects. Side effects could alter the matched object or the environment
on which the match depends in such a way, that the match would not be
exhaustive. For instance, the following would not match any arm if mutable
borrows were allowed:

```
match Some(()) {
    None => { },
    option if option.take().is_none() => { /* impossible, option is `Some` */ },
    Some(_) => { } // When the previous match failed, the option became `None`.
}
```
"##,

E0302: r##"
Assignments are not allowed in pattern guards, because matching cannot have
side effects. Side effects could alter the matched object or the environment
on which the match depends in such a way, that the match would not be
exhaustive. For instance, the following would not match any arm if assignments
were allowed:

```
match Some(()) {
    None => { },
    option if { option = None; false } { },
    Some(_) => { } // When the previous match failed, the option became `None`.
}
```
"##,

E0303: r##"
In certain cases it is possible for sub-bindings to violate memory safety.
Updates to the borrow checker in a future version of Rust may remove this
restriction, but for now patterns must be rewritten without sub-bindings.

```
// Before.
match Some("hi".to_string()) {
    ref op_string_ref @ Some(ref s) => ...
    None => ...
}

// After.
match Some("hi".to_string()) {
    Some(ref s) => {
        let op_string_ref = &Some(s);
        ...
    }
    None => ...
}
```

The `op_string_ref` binding has type `&Option<&String>` in both cases.

See also https://github.com/rust-lang/rust/issues/14587
"##,

E0306: r##"
In an array literal `[x; N]`, `N` is the number of elements in the array. This
number cannot be negative.
"##,

E0307: r##"
The length of an array is part of its type. For this reason, this length must be
a compile-time constant.
"##,

E0308: r##"
This error occurs when the compiler was unable to infer the concrete type of a
variable. It can occur for several cases, the most common of which is a
mismatch in the expected type that the compiler inferred for a variable's
initializing expression, and the actual type explicitly assigned to the
variable.

For example:

```
let x: i32 = "I am not a number!";
//     ~~~   ~~~~~~~~~~~~~~~~~~~~
//      |             |
//      |    initializing expression;
//      |    compiler infers type `&str`
//      |
//    type `i32` assigned to variable `x`
```
"##,

E0309: r##"
Types in type definitions have lifetimes associated with them that represent
how long the data stored within them is guaranteed to be live. This lifetime
must be as long as the data needs to be alive, and missing the constraint that
denotes this will cause this error.

```
// This won't compile because T is not constrained, meaning the data
// stored in it is not guaranteed to last as long as the reference
struct Foo<'a, T> {
    foo: &'a T
}

// This will compile, because it has the constraint on the type parameter
struct Foo<'a, T: 'a> {
    foo: &'a T
}
```
"##,

E0310: r##"
Types in type definitions have lifetimes associated with them that represent
how long the data stored within them is guaranteed to be live. This lifetime
must be as long as the data needs to be alive, and missing the constraint that
denotes this will cause this error.

```
// This won't compile because T is not constrained to the static lifetime
// the reference needs
struct Foo<T> {
    foo: &'static T
}

// This will compile, because it has the constraint on the type parameter
struct Foo<T: 'static> {
    foo: &'static T
}
```
"##,

E0378: r##"
Method calls that aren't calls to inherent `const` methods are disallowed
in statics, constants, and constant functions.

For example:

```
const BAZ: i32 = Foo(25).bar(); // error, `bar` isn't `const`

struct Foo(i32);

impl Foo {
    const fn foo(&self) -> i32 {
        self.bar() // error, `bar` isn't `const`
    }

    fn bar(&self) -> i32 { self.0 }
}
```

For more information about `const fn`'s, see [RFC 911].

[RFC 911]: https://github.com/rust-lang/rfcs/blob/master/text/0911-const-fn.md
"##,

E0394: r##"
From [RFC 246]:

 > It is illegal for a static to reference another static by value. It is
 > required that all references be borrowed.

[RFC 246]: https://github.com/rust-lang/rfcs/pull/246
"##,

E0395: r##"
The value assigned to a constant expression must be known at compile time,
which is not the case when comparing raw pointers. Erroneous code example:

```
static foo: i32 = 42;
static bar: i32 = 43;

static baz: bool = { (&foo as *const i32) == (&bar as *const i32) };
// error: raw pointers cannot be compared in statics!
```

Please check that the result of the comparison can be determined at compile time
or isn't assigned to a constant expression. Example:

```
static foo: i32 = 42;
static bar: i32 = 43;

let baz: bool = { (&foo as *const i32) == (&bar as *const i32) };
// baz isn't a constant expression so it's ok
```
"##,

E0396: r##"
The value assigned to a constant expression must be known at compile time,
which is not the case when dereferencing raw pointers. Erroneous code
example:

```
const foo: i32 = 42;
const baz: *const i32 = (&foo as *const i32);

const deref: i32 = *baz;
// error: raw pointers cannot be dereferenced in constants
```

To fix this error, please do not assign this value to a constant expression.
Example:

```
const foo: i32 = 42;
const baz: *const i32 = (&foo as *const i32);

unsafe { let deref: i32 = *baz; }
// baz isn't a constant expression so it's ok
```

You'll also note that this assignment must be done in an unsafe block!
"##,

E0397: r##"
It is not allowed for a mutable static to allocate or have destructors. For
example:

```
// error: mutable statics are not allowed to have boxes
static mut FOO: Option<Box<usize>> = None;

// error: mutable statics are not allowed to have destructors
static mut BAR: Option<Vec<i32>> = None;
```
"##,

E0398: r##"
In Rust 1.3, the default object lifetime bounds are expected to
change, as described in RFC #1156 [1]. You are getting a warning
because the compiler thinks it is possible that this change will cause
a compilation error in your code. It is possible, though unlikely,
that this is a false alarm.

The heart of the change is that where `&'a Box<SomeTrait>` used to
default to `&'a Box<SomeTrait+'a>`, it now defaults to `&'a
Box<SomeTrait+'static>` (here, `SomeTrait` is the name of some trait
type). Note that the only types which are affected are references to
boxes, like `&Box<SomeTrait>` or `&[Box<SomeTrait>]`.  More common
types like `&SomeTrait` or `Box<SomeTrait>` are unaffected.

To silence this warning, edit your code to use an explicit bound.
Most of the time, this means that you will want to change the
signature of a function that you are calling. For example, if
the error is reported on a call like `foo(x)`, and `foo` is
defined as follows:

```
fn foo(arg: &Box<SomeTrait>) { ... }
```

you might change it to:

```
fn foo<'a>(arg: &Box<SomeTrait+'a>) { ... }
```

This explicitly states that you expect the trait object `SomeTrait` to
contain references (with a maximum lifetime of `'a`).

[1]: https://github.com/rust-lang/rfcs/pull/1156
"##

}


register_diagnostics! {
    E0017,
    E0022,
    E0038,
//  E0134,
//  E0135,
    E0136,
    E0138,
    E0139,
    E0264, // unknown external lang item
    E0269, // not all control paths return a value
    E0270, // computation may converge in a function marked as diverging
    E0272, // rustc_on_unimplemented attribute refers to non-existent type parameter
    E0273, // rustc_on_unimplemented must have named format arguments
    E0274, // rustc_on_unimplemented must have a value
    E0275, // overflow evaluating requirement
    E0276, // requirement appears on impl method but not on corresponding trait method
    E0278, // requirement is not satisfied
    E0279, // requirement is not satisfied
    E0280, // requirement is not satisfied
    E0281, // type implements trait but other trait is required
    E0283, // cannot resolve type
    E0284, // cannot resolve type
    E0285, // overflow evaluation builtin bounds
    E0298, // mismatched types between arms
    E0299, // mismatched types between arms
    E0300, // unexpanded macro
    E0304, // expected signed integer constant
    E0305, // expected constant
    E0311, // thing may not live long enough
    E0312, // lifetime of reference outlives lifetime of borrowed content
    E0313, // lifetime of borrowed pointer outlives lifetime of captured variable
    E0314, // closure outlives stack frame
    E0315, // cannot invoke closure outside of its lifetime
    E0316, // nested quantification of lifetimes
    E0370, // discriminant overflow
    E0400  // overloaded derefs are not allowed in constants
}