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 ConvertParsed for AndAnd

type Type = AndAnd

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

impl ConvertParsed for Return

type Type = Return

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

impl ConvertParsed for Not

type Type = Not

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

impl ConvertParsed for LitStr

type Type = LitStr

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

impl ConvertParsed for i16

type Type = LitInt

fn convert(value: LitInt) -> Result<i16>

impl ConvertParsed for Trait

type Type = Trait

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

impl ConvertParsed for Question

type Type = Question

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

impl ConvertParsed for Yield

type Type = Yield

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

impl ConvertParsed for ExprIf

type Type = ExprIf

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

impl ConvertParsed for Override

type Type = Override

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

impl ConvertParsed for ExprTryBlock

type Type = ExprTryBlock

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

impl ConvertParsed for u128

type Type = LitInt

fn convert(value: LitInt) -> Result<u128>

impl ConvertParsed for Typeof

type Type = Typeof

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

impl ConvertParsed for DotDot

type Type = DotDot

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

impl ConvertParsed for TokenStream

type Type = TokenStream

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

impl ConvertParsed for ExprBinary

type Type = ExprBinary

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

impl ConvertParsed for SlashEq

type Type = SlashEq

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

impl ConvertParsed for ExprRepeat

type Type = ExprRepeat

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

impl ConvertParsed for Union

type Type = Union

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

impl ConvertParsed for Punct

type Type = Punct

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

impl ConvertParsed for TokenTree

type Type = TokenTree

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

impl ConvertParsed for Shl

type Type = Shl

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

impl ConvertParsed for LitByteStr

type Type = LitByteStr

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