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//! Structured values.


#![cfg_attr(value_bag_const_type_id, feature(const_type_id))]

#![no_std]

#[cfg(any(feature = "std", test))]
#[macro_use]
#[allow(unused_imports)]
extern crate std;

#[cfg(not(any(feature = "std", test)))]
#[macro_use]
#[allow(unused_imports)]
extern crate core as std;

mod error;
mod fill;
mod impls;
mod internal;

#[cfg(test)]
mod test;

pub use self::{
    error::Error,
    fill::{Fill, Slot},
};

use self::internal::{Inner, Primitive, Visitor};

/// A dynamic structured value.

///

/// # Capturing values

///

/// There are a few ways to capture a value:

///

/// - Using the `ValueBag::capture_*` methods.

/// - Using the standard `From` trait.

/// - Using the `Fill` API.

///

/// ## Using the `ValueBag::capture_*` methods

///

/// `ValueBag` offers a few constructor methods that capture values of different kinds.

/// These methods require a `T: 'static` to support downcasting.

///

/// ```

/// use value_bag::ValueBag;

///

/// let value = ValueBag::capture_debug(&42i32);

///

/// assert_eq!(Some(42), value.to_i32());

/// ```

///

/// ## Using the standard `From` trait

///

/// Standard types that implement `ToValue` also implement `From`.

///

/// ```

/// use value_bag::ValueBag;

///

/// let value = ValueBag::from(42i32);

///

/// assert_eq!(Some(42), value.to_i32());

/// ```

///

/// ```

/// # use std::fmt::Debug;

/// use value_bag::ValueBag;

///

/// let value = ValueBag::from(&42i32 as &dyn Debug);

///

/// assert_eq!(None, value.to_i32());

/// ```

///

/// ## Using the `Fill` API

///

/// The `Fill` trait is a way to bridge APIs that may not be directly

/// compatible with other constructor methods.

///

/// ```

/// use value_bag::{ValueBag, Slot, Fill, Error};

///

/// struct FillSigned;

///

/// impl Fill for FillSigned {

///     fn fill(&self, slot: &mut Slot) -> Result<(), Error> {

///         slot.fill_any(42i32)

///     }

/// }

///

/// let value = ValueBag::from_fill(&FillSigned);

///

/// assert_eq!(Some(42), value.to_i32());

/// ```

///

/// ```

/// # use std::fmt::Debug;

/// use value_bag::{ValueBag, Slot, Fill, Error};

///

/// struct FillDebug;

///

/// impl Fill for FillDebug {

///     fn fill(&self, slot: &mut Slot) -> Result<(), Error> {

///         slot.fill_debug(&42i32 as &dyn Debug)

///     }

/// }

///

/// let value = ValueBag::from_fill(&FillDebug);

///

/// assert_eq!(None, value.to_i32());

/// ```

///

/// # Inspecting values

///

/// Once you have a `ValueBag` there are also a few ways to inspect it:

///

/// - Using the `Debug`, `Display`, `Serialize`, and `Stream` trait implementations.

/// - Using the `ValueBag::to_*` methods.

/// - Using the `ValueBag::downcast_ref` method.

#[derive(Clone)]
pub struct ValueBag<'v> {
    inner: Inner<'v>,
}

impl<'v> ValueBag<'v> {
    /// Get a value from an internal primitive.

    fn from_primitive<T>(value: T) -> Self
    where
        T: Into<Primitive<'v>>,
    {
        ValueBag {
            inner: Inner::Primitive {
                value: value.into(),
            },
        }
    }

    /// Visit the value using an internal visitor.

    fn visit<'a>(&'a self, visitor: &mut dyn Visitor<'a>) -> Result<(), Error> {
        self.inner.visit(visitor)
    }
}