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/// Controls the signature of a setter method,
/// more specifically how `self` is passed and returned.
///
/// It can also be generalized to methods with different parameter sets and return types,
/// e.g. the `build()` method.
#[derive(PartialEq, Eq, Debug, Clone, Copy)]
pub enum BuilderPattern {
    /// E.g. `fn bar(self, bar: Bar) -> Self`.
    Owned,
    /// E.g. `fn bar(&mut self, bar: Bar) -> &mut Self`.
    Mutable,
    /// E.g. `fn bar(&self, bar: Bar) -> Self`.
    ///
    /// Note:
    /// - Needs to `clone` in order to return an _updated_ instance of `Self`.
    /// - There is a great chance that the Rust compiler (LLVM) will
    ///   optimize chained `clone` calls away in release mode.
    ///   Therefore this turns out not to be as bad as it sounds.
    Immutable,
}

impl BuilderPattern {
    /// Returns true if this style of builder needs to be able to clone its
    /// fields during the `build` method.
    pub fn requires_clone(&self) -> bool {
        *self != BuilderPattern::Owned
    }
}

/// Defaults to `Mutable`.
impl Default for BuilderPattern {
    fn default() -> BuilderPattern {
        BuilderPattern::Mutable
    }
}