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 Match

type Type = Match

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

impl ConvertParsed for MinusEq

type Type = MinusEq

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

impl ConvertParsed for Or

type Type = Or

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

impl ConvertParsed for ExprLet

type Type = ExprLet

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

impl ConvertParsed for ExprIndex

type Type = ExprIndex

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

impl ConvertParsed for Meta

type Type = Meta

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

impl ConvertParsed for MetaNameValue

type Type = MetaNameValue

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

impl ConvertParsed for ExprLoop

type Type = ExprLoop

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

impl ConvertParsed for TypeGroup

type Type = TypeGroup

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

impl ConvertParsed for ExprReturn

type Type = ExprReturn

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

impl ConvertParsed for ExprBinary

type Type = ExprBinary

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

impl ConvertParsed for Async

type Type = Async

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

impl ConvertParsed for ExprClosure

type Type = ExprClosure

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

impl ConvertParsed for Ident

type Type = Ident

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

impl ConvertParsed for PathSep

type Type = PathSep

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

impl ConvertParsed for f32

type Type = LitFloat

fn convert(value: LitFloat) -> Result<f32>

impl ConvertParsed for SlashEq

type Type = SlashEq

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

impl ConvertParsed for Do

type Type = Do

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

impl ConvertParsed for Return

type Type = Return

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

impl ConvertParsed for AndAnd

type Type = AndAnd

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

impl ConvertParsed for WhereClause

type Type = WhereClause

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

impl ConvertParsed for isize

type Type = LitInt

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

impl ConvertParsed for String

type Type = LitStr

fn convert(value: LitStr) -> Result<String>