Trait darling::FromMetaItem

pub trait FromMetaItem {
    fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error> { ... }
    fn from_meta_item(item: &MetaItem) -> Result<Self, Error> { ... }
    fn from_word() -> Result<Self, Error> { ... }
    fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error> { ... }
    fn from_value(value: &Lit) -> Result<Self, Error> { ... }
    fn from_char(value: char) -> Result<Self, Error> { ... }
    fn from_string(value: &str) -> Result<Self, Error> { ... }
    fn from_bool(value: bool) -> Result<Self, Error> { ... }
}

Create an instance from an item in an attribute declaration.

Implementing FromMetaItem

• Do not take a dependency on the ident of the passed-in meta item. The ident will be set by the field name of the containing struct.
• Implement only the from_* methods that you intend to support. The default implementations will return useful errors.

Provided Implementations

bool

• Word with no value specified - becomes true.
• As a boolean literal, e.g. foo = true.
• As a string literal, e.g. foo = "true".

String

• As a string literal, e.g. foo = "hello".
• As a raw string literal, e.g. foo = r#"hello "world""#.

()

• Word with no value specified, e.g. foo. This is best used with Option. See darling::util::Flag for a more strongly-typed alternative.

Option

• Any format produces Some.

Result<T, darling::Error>

• Allows for fallible parsing; will populate the target field with the result of the parse attempt.

Provided Methods

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

Create an instance from a syn::MetaItem by dispatching to the format-appropriate trait function. This generally should not be overridden by implementers.

fn from_word() -> Result<Self, Error>

Create an instance from the presence of the word in the attribute with no additional options specified.

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

Create an instance from a list of nested meta items.

fn from_value(value: &Lit) -> Result<Self, Error>

Create an instance from a literal value of either foo = "bar" or foo("bar"). This dispatches to the appropriate method based on the type of literal encountered, and generally should not be overridden by implementers.

fn from_char(value: char) -> Result<Self, Error>

Create an instance from a char literal in a value position.

fn from_string(value: &str) -> Result<Self, Error>

Create an instance from a string literal in a value position.

fn from_bool(value: bool) -> Result<Self, Error>

Create an instance from a bool literal in a value position.

Implementations on Foreign Types

impl FromMetaItem for i16

fn from_string(s: &str) -> Result<i16, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for u16

fn from_string(s: &str) -> Result<u16, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for i64

fn from_string(s: &str) -> Result<i64, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for bool

fn from_word() -> Result<bool, Error>

fn from_bool(value: bool) -> Result<bool, Error>

fn from_string(value: &str) -> Result<bool, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

impl FromMetaItem for i32

fn from_string(s: &str) -> Result<i32, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for Result<T, MetaItem> where
    T: FromMetaItem, 

Parses the meta-item, and in case of error preserves a copy of the input for later analysis.

fn from_meta_item(item: &MetaItem) -> Result<Result<T, MetaItem>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for Option<T> where
    T: FromMetaItem, 

fn from_meta_item(item: &MetaItem) -> Result<Option<T>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for u32

fn from_string(s: &str) -> Result<u32, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for i8

fn from_string(s: &str) -> Result<i8, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for TyParamBound

fn from_string(value: &str) -> Result<TyParamBound, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for usize

fn from_string(s: &str) -> Result<usize, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for WhereClause

fn from_string(value: &str) -> Result<WhereClause, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for RefCell<T> where
    T: FromMetaItem, 

fn from_meta_item(item: &MetaItem) -> Result<RefCell<T>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for Ident

fn from_string(value: &str) -> Result<Ident, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for AtomicBool

fn from_meta_item(mi: &MetaItem) -> Result<AtomicBool, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for String

fn from_string(s: &str) -> Result<String, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for Rc<T> where
    T: FromMetaItem, 

fn from_meta_item(item: &MetaItem) -> Result<Rc<T>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for u64

fn from_string(s: &str) -> Result<u64, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<V> FromMetaItem for HashMap<String, V, RandomState> where
    V: FromMetaItem, 

fn from_list(
    nested: &[NestedMetaItem]
) -> Result<HashMap<String, V, RandomState>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for Result<T, Error> where
    T: FromMetaItem, 

fn from_meta_item(item: &MetaItem) -> Result<Result<T, Error>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for ForwardAttrs

fn from_word() -> Result<ForwardAttrs, Error>

fn from_list(nested: &[NestedMetaItem]) -> Result<ForwardAttrs, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for RenameRule

fn from_string(value: &str) -> Result<RenameRule, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for Box<T> where
    T: FromMetaItem, 

fn from_meta_item(item: &MetaItem) -> Result<Box<T>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for isize

fn from_string(s: &str) -> Result<isize, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for DataShape

fn from_list(items: &[NestedMetaItem]) -> Result<DataShape, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for u8

fn from_string(s: &str) -> Result<u8, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for Path

fn from_string(value: &str) -> Result<Path, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for ()

fn from_word() -> Result<(), Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for MetaItem

fn from_meta_item(value: &MetaItem) -> Result<MetaItem, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl<T> FromMetaItem for Arc<T> where
    T: FromMetaItem, 

fn from_meta_item(item: &MetaItem) -> Result<Arc<T>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for Vec<WherePredicate>

fn from_string(value: &str) -> Result<Vec<WherePredicate>, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_list(items: &[NestedMetaItem]) -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

impl FromMetaItem for Shape

fn from_list(items: &[NestedMetaItem]) -> Result<Shape, Error>

fn from_nested_meta_item(item: &NestedMetaItem) -> Result<Self, Error>

fn from_meta_item(item: &MetaItem) -> Result<Self, Error>

fn from_word() -> Result<Self, Error>

fn from_value(value: &Lit) -> Result<Self, Error>

fn from_char(value: char) -> Result<Self, Error>

fn from_string(value: &str) -> Result<Self, Error>

fn from_bool(value: bool) -> Result<Self, Error>

Implementors

• impl FromMetaItem for Flag
• impl<T> FromMetaItem for Override<T> where
    T: FromMetaItem, 
• impl FromMetaItem for IdentList
• impl FromMetaItem for Ignored