Struct Callable 

pub struct Callable { /* private fields */ }

Either a path or a closure.

This type is useful for options that historically took a path, e.g. #[darling(with = ...)] or #[serde(skip_serializing_if = ...)] and now want to also allow using a closure to avoid needing a separate function declaration.

In darling, this value is wrapped in core::convert::identity before usage; this allows treatment of the closure and path cases as equivalent, and prevents a closure from accessing locals in the generated code.

Trait Implementations

impl AsRef<Expr> for Callable

fn as_ref(&self) -> &Expr

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for Callable

fn clone(&self) -> Callable

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Callable

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

Formats the value using the given formatter.

impl From<Callable> for Expr

fn from(value: Callable) -> Self

Converts to this type from the input type.

impl From<ExprClosure> for Callable

fn from(value: ExprClosure) -> Self

Converts to this type from the input type.

impl From<ExprPath> for Callable

fn from(value: ExprPath) -> Self

Converts to this type from the input type.

impl FromMeta for Callable

fn from_expr(expr: &Expr) -> Result<Self>

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

fn from_meta(item: &Meta) -> Result<Self>

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_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>

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

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

Create an instance from a list of nested meta items.

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

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>

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

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

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

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

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

impl ToTokens for Callable

fn to_tokens(&self, tokens: &mut TokenStream)

Write self to the given TokenStream.

fn to_token_stream(&self) -> TokenStream

Convert self directly into a TokenStream object.

fn into_token_stream(self) -> TokenStream

where Self: Sized,

Convert self directly into a TokenStream object.