Struct CustomArg

pub struct CustomArg<T>(pub T);

Allows a type to implement CustomArgFromMeta, a simplified version of TryFromMeta.

Tuple Fields

0: T

Trait Implementations

impl<T> Concat for CustomArg<T>

const NO_DUPLICATES: bool = true

Determines whether a duplicate is allowed or if an error should be thrown.
This logic is handled in the implementation for ArgResult.
Typically only true for primitive types.

fn concat(&mut self, other: Self)

Combines an argument.

impl<T: Debug> Debug for CustomArg<T>

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

Formats the value using the given formatter.

impl<T: Default> Default for CustomArg<T>

fn default() -> Self

Returns the “default value” for a type.

impl<V: SynVersion, T: CustomArgFromMeta<V>> TryFromMeta<V> for CustomArg<T>

type InitialType = CustomArg<T>

This is the initial type and will be converted to Self in the validate function.
For most types this is typically Self but for lists this is a builder.

type Metadata = <V as SynVersion>::ArgMeta

The metadata of an argument or an attribute.

fn try_from_meta(meta: Self::Metadata) -> ArgResult<Self::InitialType>

Looks for values & errors in the metadata.
The returned result is added to the argument’s state using the concat method on ArgResult which in turn will call the initial type’s Concat implementation if found.

fn validate( state: ArgResult<Self::InitialType>, arg_name: &'static str, ) -> Result<Self, Vec<Error>>

Converts the initial type to Self or returns found errors.
If the argument is required it should return a missing error.
Wrapper types such as Option can overwrite this.