Trait attribute_derive::ConvertParsed

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pub trait ConvertParsedwhere
    Self: Sized,
    Self::Type: Error,{
    type Type;

    // Required method
    fn convert(value: Self::Type) -> Result<Self>;

    // Provided methods
    fn default_by_default() -> bool { ... }
    fn default() -> Self { ... }
    fn as_flag() -> Option<Self::Type> { ... }
    fn aggregate(
        this: Option<IdentValue<Self::Type>>,
        other: Option<IdentValue<Self::Type>>,
        error_msg: &str
    ) -> Result<Option<IdentValue<Self::Type>>> { ... }
}

Expand description

Helper trait to convert syn types implementing Parse like LitStr to rust types like String

You probably don’t need to implement this trait, as most syn types like LitStr and Type or that have a direct equivalent in those like String, char or f32 are already implemented. A special treatment have Vecs which are parsed using the helper Array with the syntax [a, b, c] and Options that will be None if not specified and Some when the value is specified via the attribute. It is not specified via Some(value) but as just value.

Required Associated Types§

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type Type

The type this can be converted from

Required Methods§

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fn convert(value: Self::Type) -> Result<Self>

This takes Self::Type and converts it to Self.

This can return an error, e.g. when parsing an integer too large for a u8 into an u8

Provided Methods§

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fn default_by_default() -> bool

Should values of this type return their default when they are not specified even when the default flag is not specified (only returns true for Option, Vec and bool currently)

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fn default() -> Self

The default value, this is necessary to implement the implicit default behavior of Option and bool.

This is necessary as the Default trait cannot be used in expanded code, but normally you can easily implement it using it:

impl ConvertParsed for bool {
    fn default() -> Self {
        Default::default()
    }
}

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fn as_flag() -> Option<Self::Type>

Returns the value when this type is specified as flag i.e. just #[attr(default)] instead of #[attr(default=true)]. This relies on Self::default.

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fn aggregate( this: Option<IdentValue<Self::Type>>, other: Option<IdentValue<Self::Type>>, error_msg: &str ) -> Result<Option<IdentValue<Self::Type>>>

Should values of this type be aggregated instead of conflict if specified multiple times

Currently this is only implemented for Arrays

Trait attribute_derive::ConvertParsed

Required Associated Types§

type Type

Required Methods§

fn convert(value: Self::Type) -> Result<Self>

Provided Methods§

fn default_by_default() -> bool

fn default() -> Self

fn as_flag() -> Option<Self::Type>

fn aggregate( this: Option<IdentValue<Self::Type>>, other: Option<IdentValue<Self::Type>>, error_msg: &str ) -> Result<Option<IdentValue<Self::Type>>>

Implementations on Foreign Types§

impl<Output, Parsed> ConvertParsed for Vec<Output>where Output: ConvertParsed<Type = Parsed>, Parsed: Clone,

type Type = Array<Parsed>

fn convert(array: Array<Parsed>) -> Result<Self>

fn aggregate( this: Option<IdentValue<Self::Type>>, other: Option<IdentValue<Self::Type>>, _: &str ) -> Result<Option<IdentValue<Self::Type>>>

impl ConvertParsed for Underscore

type Type = Underscore

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ExprYield

type Type = ExprYield

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Variant

type Type = Variant

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ExprArray

type Type = ExprArray

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ExprMacro

type Type = ExprMacro

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ExprTryBlock

type Type = ExprTryBlock

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for FieldsNamed

type Type = FieldsNamed

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for TypeParam

type Type = TypeParam

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Shl

type Type = Shl

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Try

type Type = Try

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Question

type Type = Question

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ExprTuple

type Type = ExprTuple

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Ge

type Type = Ge

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Unsafe

type Type = Unsafe

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for TraitBound

type Type = TraitBound

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ExprAsync

type Type = ExprAsync

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Virtual

type Type = Virtual

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for ConstParam

type Type = ConstParam

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Typeof

type Type = Typeof

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for SlashEq

type Type = SlashEq

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Tilde

type Type = Tilde

fn convert(s: Self) -> Result<Self>

impl ConvertParsed for Super

type Type = Super