5 files changed, 14 insertions, 9 deletions

diff --git a/crates/libsyntax2/src/grammar/expressions/atom.rs b/crates/libsyntax2/src/grammar/expressions/atom.rs
index 1488e12a4..fdb4718ba 100644
--- a/crates/libsyntax2/src/grammar/expressions/atom.rs
+++ b/crates/libsyntax2/src/grammar/expressions/atom.rs
@@ -18,7 +18,7 @@ pub(crate) const LITERAL_FIRST: TokenSet =
                STRING, RAW_STRING, BYTE_STRING, RAW_BYTE_STRING];
 
 pub(crate) fn literal(p: &mut Parser) -> Option<CompletedMarker> {
-    if !LITERAL_FIRST.contains(p.current()) {
+    if !p.at_ts(LITERAL_FIRST) {
         return None;
     }
     let m = p.start();
@@ -108,7 +108,7 @@ fn tuple_expr(p: &mut Parser) -> CompletedMarker {
     let mut saw_expr = false;
     while !p.at(EOF) && !p.at(R_PAREN) {
         saw_expr = true;
-        if !EXPR_FIRST.contains(p.current()) {
+        if !p.at_ts(EXPR_FIRST) {
             p.error("expected expression");
             break;
         }
@@ -147,7 +147,7 @@ fn array_expr(p: &mut Parser) -> CompletedMarker {
         if p.at(R_BRACK) {
             break;
         }
-        if !EXPR_FIRST.contains(p.current()) {
+        if !p.at_ts(EXPR_FIRST) {
             p.error("expected expression");
             break;
         }
@@ -360,7 +360,7 @@ fn return_expr(p: &mut Parser) -> CompletedMarker {
     assert!(p.at(RETURN_KW));
     let m = p.start();
     p.bump();
-    if EXPR_FIRST.contains(p.current()) {
+    if p.at_ts(EXPR_FIRST) {
         expr(p);
     }
     m.complete(p, RETURN_EXPR)
@@ -395,7 +395,7 @@ fn break_expr(p: &mut Parser) -> CompletedMarker {
     let m = p.start();
     p.bump();
     p.eat(LIFETIME);
-    if EXPR_FIRST.contains(p.current()) {
+    if p.at_ts(EXPR_FIRST) {
         expr(p);
     }
     m.complete(p, BREAK_EXPR)
diff --git a/crates/libsyntax2/src/grammar/expressions/mod.rs b/crates/libsyntax2/src/grammar/expressions/mod.rs
index f7b9f7086..d5ee91ad8 100644
--- a/crates/libsyntax2/src/grammar/expressions/mod.rs
+++ b/crates/libsyntax2/src/grammar/expressions/mod.rs
@@ -236,7 +236,7 @@ fn lhs(p: &mut Parser, r: Restrictions) -> Option<CompletedMarker> {
         DOTDOT => {
             m = p.start();
             p.bump();
-            if EXPR_FIRST.contains(p.current()) {
+            if p.at_ts(EXPR_FIRST) {
                 expr_bp(p, r, 2);
             }
             return Some(m.complete(p, RANGE_EXPR));
@@ -376,7 +376,7 @@ fn arg_list(p: &mut Parser) {
     let m = p.start();
     p.bump();
     while !p.at(R_PAREN) && !p.at(EOF) {
-        if !EXPR_FIRST.contains(p.current()) {
+        if !p.at_ts(EXPR_FIRST) {
             p.error("expected expression");
             break;
         }
diff --git a/crates/libsyntax2/src/grammar/params.rs b/crates/libsyntax2/src/grammar/params.rs
index bc0cb44ba..903c25939 100644
--- a/crates/libsyntax2/src/grammar/params.rs
+++ b/crates/libsyntax2/src/grammar/params.rs
@@ -48,7 +48,7 @@ fn list_(p: &mut Parser, flavor: Flavor) {
         opt_self_param(p);
     }
     while !p.at(EOF) && !p.at(ket) {
-        if !VALUE_PARAMETER_FIRST.contains(p.current()) {
+        if !p.at_ts(VALUE_PARAMETER_FIRST) {
             p.error("expected value parameter");
             break;
         }
diff --git a/crates/libsyntax2/src/grammar/patterns.rs b/crates/libsyntax2/src/grammar/patterns.rs
index aa20ae8e4..6dd3ab2fa 100644
--- a/crates/libsyntax2/src/grammar/patterns.rs
+++ b/crates/libsyntax2/src/grammar/patterns.rs
@@ -102,7 +102,7 @@ fn tuple_pat_fields(p: &mut Parser) {
         match p.current() {
             DOTDOT => p.bump(),
             _ => {
-                if !PATTERN_FIRST.contains(p.current()) {
+                if !p.at_ts(PATTERN_FIRST) {
                     p.error("expected a pattern");
                     break;
                 }
diff --git a/crates/libsyntax2/src/parser_api.rs b/crates/libsyntax2/src/parser_api.rs
index c4753140e..7d97159dd 100644
--- a/crates/libsyntax2/src/parser_api.rs
+++ b/crates/libsyntax2/src/parser_api.rs
@@ -35,6 +35,11 @@ impl<'t> Parser<'t> {
         self.current() == kind
     }
 
+    /// Checks if the current token is `kind`.
+    pub(crate) fn at_ts(&self, kinds: TokenSet) -> bool {
+        kinds.contains(self.current())
+    }
+
     pub(crate) fn next2(&self) -> Option<(SyntaxKind, SyntaxKind)> {
         self.0.next2()
     }