Struct PreservedStrExpr

#[repr(transparent)]
pub struct PreservedStrExpr(pub Expr);

A wrapper around Expr that preserves the original expression without evaluating it.

For compatibility reasons, darling evaluates the expression inside string literals, which might be undesirable. In many cases, [darling::util::parse_expr::preserve_str_literal] can be used. However, when using Expr inside a container (such as a HashMap), it is not possible to use it.

This wrapper preserves the original expression without evaluating it.

Example

#[derive(FromMeta)]
#[darling(attributes(demo))]
struct Demo {
    option: Option<HashMap<syn::Ident, PreservedStrExpr>>,
}

Tuple Fields

0: Expr

Trait Implementations

impl Clone for PreservedStrExpr

fn clone(&self) -> PreservedStrExpr

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PreservedStrExpr

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

Formats the value using the given formatter.

impl From<Expr> for PreservedStrExpr

fn from(value: Expr) -> PreservedStrExpr

Converts to this type from the input type.

impl From<PreservedStrExpr> for Expr

fn from(value: PreservedStrExpr) -> Expr

Converts to this type from the input type.

impl FromMeta for PreservedStrExpr

fn from_expr(expr: &Expr) -> Result<PreservedStrExpr, Error>

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

fn from_meta(item: &Meta) -> Result<Self, 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_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 Hash for PreservedStrExpr

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

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for PreservedStrExpr

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

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl ToTokens for PreservedStrExpr

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.

impl Eq for PreservedStrExpr

impl StructuralPartialEq for PreservedStrExpr