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    use std::fmt;

    use crate::{capitalize, transform};

    /// This trait defines a title case conversion.
    ///
    /// In Title Case, word boundaries are indicated by spaces, and every word is
    /// capitalized.
    ///
    /// ## Example:
    ///
    /// ```rust
    /// use heck::ToTitleCase;
    ///
    /// let sentence = "We have always lived in slums and holes in the wall.";
    /// assert_eq!(sentence.to_title_case(), "We Have Always Lived In Slums And Holes In The Wall");
    /// ```
    pub trait ToTitleCase: ToOwned {
        /// Convert this type to title case.
        fn to_title_case(&self) -> Self::Owned;
    }

    impl ToTitleCase for str {
        fn to_title_case(&self) -> String {
            AsTitleCase(self).to_string()
        }
    }

    /// This wrapper performs a title case conversion in [`fmt::Display`].
    ///
    /// ## Example:
    ///
    /// ```
    /// use heck::AsTitleCase;
    ///
    /// let sentence = "We have always lived in slums and holes in the wall.";
    /// assert_eq!(format!("{}", AsTitleCase(sentence)), "We Have Always Lived In Slums And Holes In The Wall");
    /// ```
    pub struct AsTitleCase<T: AsRef<str>>(pub T);

    impl<T: AsRef<str>> fmt::Display for AsTitleCase<T> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            transform(self.0.as_ref(), capitalize, |f| write!(f, " "), f)
        }
    }

    #[cfg(test)]
    mod tests {
        use super::ToTitleCase;

        macro_rules! t {
            ($t:ident : $s1:expr => $s2:expr) => {
                #[test]
                fn $t() {
                    assert_eq!($s1.to_title_case(), $s2)
                }
            };
        }

        t!(test1: "CamelCase" => "Camel Case");
        t!(test2: "This is Human case." => "This Is Human Case");
        t!(test3: "MixedUP CamelCase, with some Spaces" => "Mixed Up Camel Case With Some Spaces");
        t!(test4: "mixed_up_ snake_case, with some _spaces" => "Mixed Up Snake Case With Some Spaces");
        t!(test5: "kebab-case" => "Kebab Case");
        t!(test6: "SHOUTY_SNAKE_CASE" => "Shouty Snake Case");
        t!(test7: "snake_case" => "Snake Case");
        t!(test8: "this-contains_ ALLKinds OfWord_Boundaries" => "This Contains All Kinds Of Word Boundaries");
        #[cfg(feature = "unicode")]
        t!(test9: "XΣXΣ baﬄe" => "Xσxς Baﬄe");
        t!(test10: "XMLHttpRequest" => "Xml Http Request");
    }