src/libcore/internal_macros.rs

// implements the unary operator "op &T"
// based on "op T" where T is expected to be `Copy`able
macro_rules! forward_ref_unop {
    (impl $imp:ident, $method:ident for $t:ty) => {
        forward_ref_unop!(impl $imp, $method for $t,
                #[stable(feature = "rust1", since = "1.0.0")]);
    };
    (impl $imp:ident, $method:ident for $t:ty, #[$attr:meta]) => {
        #[$attr]
        impl<'a> $imp for &'a $t {
            type Output = <$t as $imp>::Output;

            #[inline]
            fn $method(self) -> <$t as $imp>::Output {
                $imp::$method(*self)
            }
        }
    }
}

// implements binary operators "&T op U", "T op &U", "&T op &U"
// based on "T op U" where T and U are expected to be `Copy`able
macro_rules! forward_ref_binop {
    (impl $imp:ident, $method:ident for $t:ty, $u:ty) => {
        forward_ref_binop!(impl $imp, $method for $t, $u,
                #[stable(feature = "rust1", since = "1.0.0")]);
    };
    (impl $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
        #[$attr]
        impl<'a> $imp<$u> for &'a $t {
            type Output = <$t as $imp<$u>>::Output;

            #[inline]
            fn $method(self, other: $u) -> <$t as $imp<$u>>::Output {
                $imp::$method(*self, other)
            }
        }

        #[$attr]
        impl<'a> $imp<&'a $u> for $t {
            type Output = <$t as $imp<$u>>::Output;

            #[inline]
            fn $method(self, other: &'a $u) -> <$t as $imp<$u>>::Output {
                $imp::$method(self, *other)
            }
        }

        #[$attr]
        impl<'a, 'b> $imp<&'a $u> for &'b $t {
            type Output = <$t as $imp<$u>>::Output;

            #[inline]
            fn $method(self, other: &'a $u) -> <$t as $imp<$u>>::Output {
                $imp::$method(*self, *other)
            }
        }
    }
}

// implements "T op= &U", based on "T op= U"
// where U is expected to be `Copy`able
macro_rules! forward_ref_op_assign {
    (impl $imp:ident, $method:ident for $t:ty, $u:ty) => {
        forward_ref_op_assign!(impl $imp, $method for $t, $u,
                #[stable(feature = "op_assign_builtins_by_ref", since = "1.22.0")]);
    };
    (impl $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
        #[$attr]
        impl<'a> $imp<&'a $u> for $t {
            #[inline]
            fn $method(&mut self, other: &'a $u) {
                $imp::$method(self, *other);
            }
        }
    }
}