Enum MaybeExpr

pub enum MaybeExpr<T, TExpr = TokenStream> {
    None,
    Value(T),
    Expr(TExpr),
}

This replaces the idiom Option<Either<CurlyBraced<TokenStream>, T>> commonly used in parsing contents that may be expressions.

Variants

None

Value(T)

Expr(TExpr)

Implementations

impl<T, TExpr> MaybeExpr<T, TExpr>

pub fn is_some(&self) -> bool

pub fn is_none(&self) -> bool

pub fn get(&self) -> Option<ValueOrExpr<'_, T, TExpr>>

Trait Implementations

impl<T: Clone, TExpr: Clone> Clone for MaybeExpr<T, TExpr>

fn clone(&self) -> MaybeExpr<T, TExpr>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug, TExpr: Debug> Debug for MaybeExpr<T, TExpr>

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

Formats the value using the given formatter.

impl<T, TExpr> Default for MaybeExpr<T, TExpr>

fn default() -> MaybeExpr<T, TExpr>

Returns the “default value” for a type.

impl<T: FromMacro, TExpr: FromMacro> FromMacro for MaybeExpr<T, TExpr>

fn from_one(tt: TokenTree) -> Result<Self, Error>

This will be called if there is only one item

const PREFER_MANY: bool = false

Hint to All and similar extractors to disable length validation.

fn from_many(tokens: TokenStream) -> Result<Self, Error>

This will be called if there is more than one item.

fn peek(tt: &TokenTree) -> bool

Look ahead and determine parsability.