1 files changed, 68 insertions, 0 deletions
diff --git a/compiler/rustc_data_structures/src/small_str.rs b/compiler/rustc_data_structures/src/small_str.rs
new file mode 100644
index 000000000..800acb1b0
--- /dev/null
+++ b/compiler/rustc_data_structures/src/small_str.rs
@@ -0,0 +1,68 @@
+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());
+        }
+    }
+}