1 files changed, 37 insertions, 0 deletions

diff --git a/crates/libsyntax2/src/token_set.rs b/crates/libsyntax2/src/token_set.rs
new file mode 100644
index 000000000..c83fba81b
--- /dev/null
+++ b/crates/libsyntax2/src/token_set.rs
@@ -0,0 +1,37 @@
+use SyntaxKind;
+
+#[derive(Clone, Copy)]
+pub(crate) struct TokenSet(pub(crate) u128);
+
+fn mask(kind: SyntaxKind) -> u128 {
+    1u128 << (kind as usize)
+}
+
+impl TokenSet {
+    pub const EMPTY: TokenSet = TokenSet(0);
+
+    pub fn contains(&self, kind: SyntaxKind) -> bool {
+        self.0 & mask(kind) != 0
+    }
+}
+
+#[macro_export]
+macro_rules! token_set {
+    ($($t:ident),*) => { TokenSet($(1u128 << ($t as usize))|*) };
+    ($($t:ident),* ,) => { token_set!($($t),*) };
+}
+
+#[macro_export]
+macro_rules! token_set_union {
+    ($($ts:expr),*) => { TokenSet($($ts.0)|*) };
+    ($($ts:expr),* ,) => { token_set_union!($($ts),*) };
+}
+
+#[test]
+fn token_set_works_for_tokens() {
+    use SyntaxKind::*;
+    let ts = token_set! { EOF, SHEBANG };
+    assert!(ts.contains(EOF));
+    assert!(ts.contains(SHEBANG));
+    assert!(!ts.contains(PLUS));
+}