Enum attribute_derive::utils::FlagOrValue

pub enum FlagOrValue<T> {
    None,
    Flag,
    Value(T),
}

FromAttr value that can be used both as a flag and with a value.

When parameter is specified both as flag and as value, the value will dominate.

#[derive(FromAttr)]
struct Test {
    param: FlagOrValue<String>,
}

assert_eq!(
    Test::from_args(quote!(param)).unwrap().param,
    FlagOrValue::Flag
);
assert_eq!(
    Test::from_args(quote!(param = "value")).unwrap().param,
    FlagOrValue::Value("value".into())
);
assert_eq!(
    Test::from_args(quote!(param, param = "value", param))
        .unwrap()
        .param,
    FlagOrValue::Value("value".into())
);
assert_eq!(Test::from_args(quote!()).unwrap().param, FlagOrValue::None);

Variants

None

Was not specified.

Flag

Was specified as a flag, i.e., without a value.

Value(T)

Was specified with a value.

Implementations

impl<T> FlagOrValue<T>

pub fn is_none(&self) -> bool

Was not specified.

pub fn is_flag(&self) -> bool

Was specified as a flag, i.e., without a value.

pub fn is_value(&self) -> bool

Was specified with a value.

pub fn into_value(self) -> Option<T>

Returns value if set.

pub fn as_value(&self) -> Option<&T>

Returns value if set.

pub fn map_value<I>(self, map: impl FnOnce(T) -> I) -> FlagOrValue<I>

Maps the value if present.

Trait Implementations

impl<T: AttributeBase> AttributeBase for FlagOrValue<T>

type Partial = Partial<FlagOrValue<<T as AttributeBase>::Partial>>

Partial type for this attribute. In most cases this can be Self, unless the attribute can be parsed in multiple on-its-own-incomplete parts or needs special handling on the conversion.

impl<T: AttributeValue> AttributeNamed for FlagOrValue<T>

fn parse_named( name: &'static str, input: ParseStream<'_> ) -> Result<Option<Named<SpannedValue<Self::Partial>>>>

Parses an attribute containing Self called name.

const PREFERRED_OPEN_DELIMITER: &'static str = " = "

What open delimiter to use when providing error messages.

const PREFERRED_CLOSE_DELIMITER: &'static str = ""

What close delimiter to use when providing error messages.

impl<T: Debug> Debug for FlagOrValue<T>

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

Formats the value using the given formatter.

impl<T> Default for FlagOrValue<T>

fn default() -> FlagOrValue<T>

Returns the “default value” for a type.

impl<T: FromAttr> FromAttr for FlagOrValue<T>

fn parse_partial(input: ParseStream<'_>) -> Result<Self::Partial>

Actual implementation for parsing the attribute. This is the only function required to implement in this trait and derived by the FromAttr derive macro.

fn from_attribute(attr: impl Borrow<Attribute>) -> Result<Self>

Parses from a single attribute. Ignoring the name.

fn from_input(input: impl Into<TokenStream>) -> Result<Self>

Parses a TokenStream.

fn parse_input(input: ParseStream<'_>) -> Result<Self>

Parses input as the complete attribute.

fn from_attribute_partial(attr: impl Borrow<Attribute>) -> Result<Self::Partial>

Like parse_partial but instead takes an Attribute.

impl<T: FromPartial<P>, P> FromPartial<Partial<FlagOrValue<P>>> for FlagOrValue<T>

fn from(partial: Partial<FlagOrValue<P>>) -> Result<Self>

Creates Self from T.

fn from_option( partial: Option<Partial<FlagOrValue<P>>>, _: &str ) -> Result<Self>

Creates Self from optional T.

fn join( first: Option<SpannedValue<Partial<FlagOrValue<P>>>>, second: SpannedValue<Partial<FlagOrValue<P>>>, specified_twice_error: &str ) -> Result<Option<SpannedValue<Partial<FlagOrValue<P>>>>>

Defines how two arguments for the same parameter should be handled.

impl<T: Ord> Ord for FlagOrValue<T>

fn cmp(&self, other: &FlagOrValue<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl<T: PartialEq> PartialEq for FlagOrValue<T>

fn eq(&self, other: &FlagOrValue<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

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.

impl<T: PartialOrd> PartialOrd for FlagOrValue<T>

fn partial_cmp(&self, other: &FlagOrValue<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

This method tests less than (for self and other) and is used by the < operator.

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

This method tests less than or equal to (for self and other) and is used by the <= operator.

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

This method tests greater than (for self and other) and is used by the > operator.

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

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T> Transpose<Option<FlagOrValue<T>>> for FlagOrValue<Option<T>>

fn transpose(self) -> Option<FlagOrValue<T>>

Should behave equivalent to the built-in transpose functions available on Result<Option> and Option<Result>.

impl<T, E> Transpose<Result<FlagOrValue<T>, E>> for FlagOrValue<Result<T, E>>

fn transpose(self) -> Result<FlagOrValue<T>, E>

Should behave equivalent to the built-in transpose functions available on Result<Option> and Option<Result>.

impl<T: Eq> Eq for FlagOrValue<T>

impl<T> StructuralPartialEq for FlagOrValue<T>