Struct darling::util::SpannedValue

pub struct SpannedValue<T> { /* private fields */ }

A value and an associated position in source code. The main use case for this is to preserve position information to emit warnings from proc macros. You can use a SpannedValue<T> as a field in any struct that implements or derives any of darling’s core traits.

To access the underlying value, use the struct’s Deref implementation.

Defaulting

This type is meant to be used in conjunction with attribute-extracted options, but the user may not always explicitly set those options in their source code. In this case, using Default::default() will create an instance which points to Span::call_site().

Implementations

impl<T> SpannedValue<T>

pub fn new(value: T, span: Span) -> SpannedValue<T>

pub fn span(&self) -> Span

Get the source code location referenced by this struct.

pub fn map_ref<U>(&self, map_fn: impl FnOnce(&T) -> U) -> SpannedValue<U>

Apply a mapping function to a reference to the spanned value.

Trait Implementations

impl<T> AsRef<T> for SpannedValue<T>

pub fn as_ref(&self) -> &T

Performs the conversion.

impl<T> Clone for SpannedValue<T> where
    T: Clone, 

pub fn clone(&self) -> SpannedValue<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> Debug for SpannedValue<T> where
    T: Debug, 

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

Formats the value using the given formatter.

impl<T> Default for SpannedValue<T> where
    T: Default, 

pub fn default() -> SpannedValue<T>

Returns the “default value” for a type.

impl<T> Deref for SpannedValue<T>

type Target = T

The resulting type after dereferencing.

pub fn deref(&self) -> &T

Dereferences the value.

impl<T> DerefMut for SpannedValue<T>

pub fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<T> From<T> for SpannedValue<T> where
    T: Spanned, 

pub fn from(value: T) -> SpannedValue<T>

Performs the conversion.

impl<T> FromDeriveInput for SpannedValue<T> where
    T: FromDeriveInput, 

pub fn from_derive_input(value: &DeriveInput) -> Result<SpannedValue<T>, Error>

Create an instance from syn::DeriveInput, or return an error.

impl<T> FromField for SpannedValue<T> where
    T: FromField, 

pub fn from_field(value: &Field) -> Result<SpannedValue<T>, Error>

impl<T> FromGenericParam for SpannedValue<T> where
    T: FromGenericParam, 

pub fn from_generic_param(
    value: &GenericParam
) -> Result<SpannedValue<T>, Error>

impl<T> FromGenerics for SpannedValue<T> where
    T: FromGenerics, 

pub fn from_generics(value: &Generics) -> Result<SpannedValue<T>, Error>

impl<T> FromMeta for SpannedValue<T> where
    T: FromMeta, 

pub fn from_meta(value: &Meta) -> Result<SpannedValue<T>, Error>

Create an instance from a syn::Meta by dispatching to the format-appropriate trait function. This generally should not be overridden by implementers.

fn from_nested_meta(item: &NestedMeta) -> Result<Self, Error>

fn from_none() -> Option<Self>

When a field is omitted from a parent meta-item, from_none is used to attempt recovery before a missing field error is generated.

fn from_word() -> Result<Self, Error>

Create an instance from the presence of the word in the attribute with no additional options specified.

fn from_list(items: &[NestedMeta]) -> Result<Self, Error>

Create an instance from a list of nested meta items.

fn from_value(value: &Lit) -> Result<Self, Error>

Create an instance from a literal value of either foo = "bar" or foo("bar"). This dispatches to the appropriate method based on the type of literal encountered, and generally should not be overridden by implementers.

fn from_char(value: char) -> Result<Self, Error>

Create an instance from a char literal in a value position.

fn from_string(value: &str) -> Result<Self, Error>

Create an instance from a string literal in a value position.

fn from_bool(value: bool) -> Result<Self, Error>

Create an instance from a bool literal in a value position.

impl<T> FromTypeParam for SpannedValue<T> where
    T: FromTypeParam, 

pub fn from_type_param(value: &TypeParam) -> Result<SpannedValue<T>, Error>

impl<T> FromVariant for SpannedValue<T> where
    T: FromVariant, 

pub fn from_variant(value: &Variant) -> Result<SpannedValue<T>, Error>

Create an instance from syn::Variant, or return an error.

impl<T> Spanned for SpannedValue<T>

pub fn span(&self) -> Span

Returns a Span covering the complete contents of this syntax tree node, or Span::call_site() if this node is empty.

impl<T> Copy for SpannedValue<T> where
    T: Copy,