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/// Implement [`Deref`] for a struct.
///
/// The first argument is that of the newtype struct to create the impl for and the second is the
/// deref target type. The third argument is required for non-newtype structs and is the name of the
/// field to deref to. Type parameters require special handling, see examples.
///
/// Also see [`impl_deref_mut`], [`impl_deref_and_mut`], and [`forward_deref_and_mut`].
///
/// # Examples
/// With a newtype struct:
/// ```
/// struct Foo(String);
/// impl_more::impl_deref!(Foo => String);
///
/// let mut foo = Foo("bar".to_owned());
/// assert_eq!(foo.len(), 3);
/// ```
///
/// With a named field struct and type parameter:
/// ```
/// struct MyStruct<T> { msg: T };
/// impl_more::impl_deref!(<T> in MyStruct<T> => msg: T);
///
/// let foo = MyStruct { msg: "two".to_owned() };
/// assert_eq!(foo.len(), 3);
/// ```
///
/// [`Deref`]: std::ops::Deref
/// [`impl_deref_mut`]: crate::impl_deref_mut
/// [`impl_deref_and_mut`]: crate::impl_deref_and_mut
/// [`forward_deref_and_mut`]: crate::forward_deref_and_mut
#[macro_export]
macro_rules! impl_deref {
(<$($generic:ident),+> in $this:ty => $target:ty) => {
impl <$($generic),+> ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.0
}
}
};
(<$($generic:ident),+> in $this:ty => $field:ident : $target:ty) => {
impl <$($generic),+> ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.$field
}
}
};
($this:ty => $target:ty) => {
impl ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.0
}
}
};
($this:ty => $field:ident : $target:ty) => {
impl ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.$field
}
}
};
}
/// Implement [`DerefMut`] for a struct.
///
/// The first argument is that of the struct to create the impl for and this type must also
/// implement [`Deref`]. The second argument is required for non-newtype structs and is the field
/// to deref to.
///
/// This macro has the same type parameter support and format as [`impl_deref`].
///
/// Also see [`impl_deref`], [`impl_deref_and_mut`], and [`forward_deref_and_mut`].
///
/// # Examples
/// With a newtype struct:
/// ```
/// use impl_more::{impl_deref, impl_deref_mut};
///
/// struct Foo(String);
///
/// impl_deref!(Foo => String);
/// impl_deref_mut!(Foo);
///
/// let mut foo = Foo("bar".to_owned());
/// foo.push('!');
///
/// assert_eq!(*foo, "bar!");
/// ```
///
/// With a named field struct and type parameter:
/// ```
/// struct Foo<T> { msg: T };
/// impl_more::impl_deref!(<T> in Foo<T> => msg: T);
/// impl_more::impl_deref_mut!(<T> in Foo<T> => msg);
///
/// let mut foo = Foo { msg: "bar".to_owned() };
/// foo.push('!');
///
/// assert_eq!(*foo, "bar!");
/// ```
///
/// [`Deref`]: std::ops::Deref
/// [`DerefMut`]: std::ops::DerefMut
/// [`impl_deref`]: crate::impl_deref
/// [`impl_deref_and_mut`]: crate::impl_deref_and_mut
/// [`forward_deref_and_mut`]: crate::forward_deref_and_mut
#[macro_export]
macro_rules! impl_deref_mut {
(<$($generic:ident),+> in $this:ty) => {
impl <$($generic),+> ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
};
(<$($generic:ident),+> in $this:ty => $field:ident) => {
impl <$($generic),+> ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.$field
}
}
};
($this:ty) => {
impl ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
};
($this:ty => $field:ident) => {
impl ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.$field
}
}
};
}
/// Implements [`Deref`] and [`DerefMut`] by forwarding through an inner field's implementation.
///
/// Use the `ref <type>` form for deref-ing to types with lifetimes like `&str`. For newtype
/// structs, only the struct name and deref target type is necessary.
///
/// This macro has the same type parameter support and format as [`impl_deref`].
///
/// Also see [`forward_deref_and_mut`].
///
/// # Examples
/// ```
/// struct MyNewTypeStruct(String);
/// impl_more::impl_deref_and_mut!(MyNewTypeStruct => String);
///
/// let foo = MyNewTypeStruct("one".to_owned());
/// let foo_ref: &String = &foo;
///
/// // Unlike `forward_deref_and_mut`, this macro will not forward the deref implementation
/// // through the named type. Even so, in some cases Rust will be able to support these cases.
///
/// let foo_ref: &str = &foo;
///
/// fn accepts_string_slice(_: &str) {}
/// accepts_string_slice(&foo);
/// ```
///
/// [`Deref`]: std::ops::Deref
/// [`DerefMut`]: std::ops::DerefMut
/// [`impl_deref`]: crate::impl_deref
/// [`forward_deref_and_mut`]: crate::forward_deref_and_mut
#[macro_export]
macro_rules! impl_deref_and_mut {
(<$($generic:ident),+> in $this:ty => $target:ty) => {
impl <$($generic),+> ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl <$($generic),+> ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
};
(<$($generic:ident),+> in $this:ty => $field:ident : $target:ty) => {
impl <$($generic),+> ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.$field
}
}
impl <$($generic),+> ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.$field
}
}
};
($this:ty => $target:ty) => {
impl ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
};
($this:ty => $field:ident : $target:ty) => {
impl ::core::ops::Deref for $this {
type Target = $target;
fn deref(&self) -> &Self::Target {
&self.$field
}
}
impl ::core::ops::DerefMut for $this {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.$field
}
}
};
}
/// Implements [`Deref`] and [`DerefMut`] by forwarding through an inner field's implementation.
///
/// Use the `ref <type>` form for deref-ing to types with lifetimes like `&str`. For newtype
/// structs, only the struct name and deref target type is necessary.
///
/// Also see [`impl_deref_and_mut`].
///
/// # Examples
/// With a newtype struct:
/// ```
/// # fn accepts_string_slice(_: &str) {}
/// # fn accepts_mut_string_slice(_: &mut str) {}
/// #
/// struct MyNewTypeStruct(String);
/// impl_more::forward_deref_and_mut!(MyNewTypeStruct => ref str);
/// let mut foo = MyNewTypeStruct("one".to_owned());
/// let foo_ref: &str = &foo;
/// accepts_string_slice(&foo);
/// accepts_mut_string_slice(&mut foo);
/// ```
///
/// [`impl_deref_and_mut`]: crate::impl_deref_and_mut
/// [`Deref`]: std::ops::Deref
/// [`DerefMut`]: std::ops::DerefMut
#[macro_export]
macro_rules! forward_deref_and_mut {
($ty:ty => $target:ty) => {
impl ::core::ops::Deref for $ty {
type Target = $target;
fn deref(&self) -> &Self::Target {
::core::ops::Deref::deref(&self.0)
}
}
impl ::core::ops::DerefMut for $ty {
fn deref_mut(&mut self) -> &mut Self::Target {
::core::ops::DerefMut::deref_mut(&mut self.0)
}
}
};
($ty:ty => ref $target:ty) => {
impl<'__impl_more_a> ::core::ops::Deref for $ty {
type Target = $target;
fn deref(&self) -> &Self::Target {
::core::ops::Deref::deref(&self.0)
}
}
impl<'__impl_more_a> ::core::ops::DerefMut for $ty {
fn deref_mut(&mut self) -> &mut Self::Target {
::core::ops::DerefMut::deref_mut(&mut self.0)
}
}
};
($ty:ty => $field:ident : $target:ty) => {
impl ::core::ops::Deref for $ty {
type Target = $target;
fn deref(&self) -> &Self::Target {
::core::ops::Deref::deref(&self.$field)
}
}
impl ::core::ops::DerefMut for $ty {
fn deref_mut(&mut self) -> &mut Self::Target {
::core::ops::DerefMut::deref_mut(&mut self.$field)
}
}
};
($ty:ty => $field:ident : ref $target:ty) => {
impl<'__impl_more_a> ::core::ops::Deref for $ty {
type Target = $target;
fn deref(&self) -> &Self::Target {
::core::ops::Deref::deref(&self.$field)
}
}
impl<'__impl_more_a> ::core::ops::DerefMut for $ty {
fn deref_mut(&mut self) -> &mut Self::Target {
::core::ops::DerefMut::deref_mut(&mut self.$field)
}
}
};
}
#[cfg(test)]
mod tests {
use alloc::{borrow::ToOwned as _, string::String};
use core::ops::{Deref, DerefMut};
fn accepts_string_slice(_: &str) {}
fn accepts_mut_string_slice(_: &mut str) {}
struct Foo1(String);
impl_deref_and_mut!(Foo1 => String);
static_assertions::assert_impl_all!(
Foo1:
// impls
Deref<Target = String>,
DerefMut<Target = String>,
);
struct Foo2(String);
forward_deref_and_mut!(Foo2 => ref str);
static_assertions::assert_impl_all!(
Foo2:
// impls
Deref,
DerefMut,
);
struct SingleGeneric<T>(T);
impl_deref!(<T> in SingleGeneric<T> => T);
impl_deref_mut!(<T> in SingleGeneric<T>);
static_assertions::assert_impl_all!(
SingleGeneric<usize>:
// impls
Deref<Target = usize>,
DerefMut<Target = usize>,
);
struct SingleGenericCombined<T>(T);
impl_deref_and_mut!(<T> in SingleGenericCombined<T> => T);
static_assertions::assert_impl_all!(
SingleGenericCombined<usize>:
// impls
Deref<Target = usize>,
DerefMut<Target = usize>,
);
struct DoubleGeneric<T, U> {
t: T,
_u: U,
}
impl_deref!(<T, U> in DoubleGeneric<T, U> => t: T);
impl_deref_mut!(<T, U> in DoubleGeneric<T, U> => t);
static_assertions::assert_impl_all!(
DoubleGeneric<usize, u32>:
// impls
Deref<Target = usize>,
DerefMut<Target = usize>,
);
struct DoubleGenericCombined<T, U> {
t: T,
_u: U,
}
impl_deref_and_mut!(<T, U> in DoubleGenericCombined<T, U> => t: T);
static_assertions::assert_impl_all!(
DoubleGenericCombined<usize, u32>:
// impls
Deref<Target = usize>,
DerefMut<Target = usize>,
);
#[test]
fn foo2_impls() {
let mut foo = Foo2("".to_owned());
accepts_string_slice(&foo);
accepts_mut_string_slice(&mut foo);
}
struct Foo3 {
msg: String,
}
forward_deref_and_mut!(Foo3 => msg: ref str);
static_assertions::assert_impl_all!(
Foo3:
// impls
Deref,
DerefMut,
);
#[test]
fn foo3_impls() {
let mut foo = Foo3 { msg: "".to_owned() };
accepts_string_slice(&foo);
accepts_mut_string_slice(&mut foo);
}
}