Remove SmallStr.

It no longer has any uses. If it's needed in the future, it can be
easily reinstated. Or a crate such as `smallstr` can be used, much like
we use `smallvec`.

compiler/rustc_data_structures/src/lib.rs

@@ -68,7 +68,6 @@ pub mod macros;
 pub mod obligation_forest;
 pub mod sip128;
 pub mod small_c_str;
-pub mod small_str;
 pub mod snapshot_map;
 pub mod svh;
 pub use ena::snapshot_vec;

compiler/rustc_data_structures/src/small_str.rs

@@ -1,68 +0,0 @@
-use smallvec::SmallVec;
-
-#[cfg(test)]
-mod tests;
-
-/// Like SmallVec but for strings.
-#[derive(Default)]
-pub struct SmallStr<const N: usize>(SmallVec<[u8; N]>);
-
-impl<const N: usize> SmallStr<N> {
-    #[inline]
-    pub fn new() -> Self {
-        SmallStr(SmallVec::default())
-    }
-
-    #[inline]
-    pub fn push_str(&mut self, s: &str) {
-        self.0.extend_from_slice(s.as_bytes());
-    }
-
-    #[inline]
-    pub fn empty(&self) -> bool {
-        self.0.is_empty()
-    }
-
-    #[inline]
-    pub fn spilled(&self) -> bool {
-        self.0.spilled()
-    }
-
-    #[inline]
-    pub fn as_str(&self) -> &str {
-        unsafe { std::str::from_utf8_unchecked(self.0.as_slice()) }
-    }
-}
-
-impl<const N: usize> std::ops::Deref for SmallStr<N> {
-    type Target = str;
-
-    #[inline]
-    fn deref(&self) -> &str {
-        self.as_str()
-    }
-}
-
-impl<const N: usize, A: AsRef<str>> FromIterator<A> for SmallStr<N> {
-    #[inline]
-    fn from_iter<T>(iter: T) -> Self
-    where
-        T: IntoIterator<Item = A>,
-    {
-        let mut s = SmallStr::default();
-        s.extend(iter);
-        s
-    }
-}
-
-impl<const N: usize, A: AsRef<str>> Extend<A> for SmallStr<N> {
-    #[inline]
-    fn extend<T>(&mut self, iter: T)
-    where
-        T: IntoIterator<Item = A>,
-    {
-        for a in iter.into_iter() {
-            self.push_str(a.as_ref());
-        }
-    }
-}

compiler/rustc_data_structures/src/small_str/tests.rs

@@ -1,20 +0,0 @@
-use super::*;
-
-#[test]
-fn empty() {
-    let s = SmallStr::<1>::new();
-    assert!(s.empty());
-    assert_eq!("", s.as_str());
-    assert!(!s.spilled());
-}
-
-#[test]
-fn from_iter() {
-    let s = ["aa", "bb", "cc"].iter().collect::<SmallStr<6>>();
-    assert_eq!("aabbcc", s.as_str());
-    assert!(!s.spilled());
-
-    let s = ["aa", "bb", "cc", "dd"].iter().collect::<SmallStr<6>>();
-    assert_eq!("aabbccdd", s.as_str());
-    assert!(s.spilled());
-}