# Enum rustc_error_messages::DiagnosticMessage

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    pub enum DiagnosticMessage {
        Str(Cow<'static, str>),
        Eager(Cow<'static, str>),
        FluentIdentifier(Cow<'static, str>, Option<Cow<'static, str>>),
    }

Expand description

Abstraction over a message in a diagnostic to support both translatable and non-translatable diagnostic messages.

Intended to be removed once diagnostics are entirely translatable.

## Variants§

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### Str(Cow<'static, str>)

Non-translatable diagnostic message.

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### Eager(Cow<'static, str>)

Translatable message which has already been translated eagerly.

Some diagnostics have repeated subdiagnostics where the same interpolated variables would be instantiated multiple times with different values. As translation normally happens immediately prior to emission, after the diagnostic and subdiagnostic derive logic has run, the setting of diagnostic arguments in the derived code will overwrite previous variable values and only the final value will be set when translation occurs - resulting in incorrect diagnostics. Eager translation results in translation for a subdiagnostic happening immediately after the subdiagnostic derive’s logic has been run. This variant stores messages which have been translated eagerly.

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### FluentIdentifier(Cow<'static, str>, Option<Cow<'static, str>>)

Identifier for a Fluent message (with optional attribute) corresponding to the diagnostic message.

https://projectfluent.org/fluent/guide/hello.html https://projectfluent.org/fluent/guide/attributes.html

## Implementations§

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### impl DiagnosticMessage

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#### pub fn with_subdiagnostic_message(&self, sub: SubdiagnosticMessage) -> Self

Given a `SubdiagnosticMessage` which may contain a Fluent attribute, create a new `DiagnosticMessage` that combines that attribute with the Fluent identifier of `self`.

- If the `SubdiagnosticMessage` is non-translatable then return the message as a `DiagnosticMessage`.
- If `self` is non-translatable then return `self`’s message.

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#### pub fn as_str(&self) -> Option<&str>

## Trait Implementations§

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### impl Clone for DiagnosticMessage

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#### fn clone(&self) -> DiagnosticMessage

Returns a copy of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for DiagnosticMessage

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl<__D: SpanDecoder> Decodable<__D> for DiagnosticMessage

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#### fn decode(__decoder: &mut __D) -> Self

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### impl<__E: SpanEncoder> Encodable<__E> for DiagnosticMessage

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#### fn encode(&self, __encoder: &mut __E)

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### impl From<&'static str> for DiagnosticMessage

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#### fn from(s: &'static str) -> Self

Converts to this type from the input type.
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### impl From<Cow<'static, str>> for DiagnosticMessage

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#### fn from(s: Cow<'static, str>) -> Self

Converts to this type from the input type.
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### impl<F: FnOnce() -> String> From<DelayDm<F>> for DiagnosticMessage

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#### fn from(DelayDm: DelayDm<F>) -> Self

Converts to this type from the input type.
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### impl From<String> for DiagnosticMessage

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#### fn from(s: String) -> Self

Converts to this type from the input type.
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### impl Hash for DiagnosticMessage

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#### fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given `Hasher`. Read more
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#### fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
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### impl Into<SubdiagnosticMessage> for DiagnosticMessage

Translating into a subdiagnostic message from a diagnostic message is a little strange - but the subdiagnostic functions (e.g. `span_label`) take a `SubdiagnosticMessage` and the subdiagnostic derive refers to typed identifiers that are `DiagnosticMessage`s, so need to be able to convert between these, as much as they’ll be converted back into `DiagnosticMessage` using `with_subdiagnostic_message` eventually. Don’t use this other than for the derive.

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#### fn into(self) -> SubdiagnosticMessage

Converts this type into the (usually inferred) input type.
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### impl PartialEq for DiagnosticMessage

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#### fn eq(&self, other: &DiagnosticMessage) -> bool

This method tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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### impl Eq for DiagnosticMessage

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### impl StructuralEq for DiagnosticMessage

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### impl StructuralPartialEq for DiagnosticMessage

## Auto Trait Implementations§

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### impl RefUnwindSafe for DiagnosticMessage

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### impl Send for DiagnosticMessage

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### impl Sync for DiagnosticMessage

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### impl Unpin for DiagnosticMessage

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### impl UnwindSafe for DiagnosticMessage

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 48 bytes

Size for each variant:

- `Str`: 32 bytes
- `Eager`: 32 bytes
- `FluentIdentifier`: 48 bytes