1 files changed, 11 insertions, 0 deletions
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index fe67b905bf3..b2207f22816 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -121,10 +121,14 @@ where
 }
 
 pub trait CreateTokenStream: sync::Send + sync::Sync {
+    fn add_trailing_semi(&self) -> Box<dyn CreateTokenStream>;
     fn create_token_stream(&self) -> TokenStream;
 }
 
 impl CreateTokenStream for TokenStream {
+    fn add_trailing_semi(&self) -> Box<dyn CreateTokenStream> {
+        panic!("Cannot call `add_trailing_semi` on a `TokenStream`!");
+    }
     fn create_token_stream(&self) -> TokenStream {
         self.clone()
     }
@@ -141,6 +145,13 @@ impl LazyTokenStream {
         LazyTokenStream(Lrc::new(Box::new(inner)))
     }
 
+    /// Extends the captured stream by one token,
+    /// which must be a trailing semicolon. This
+    /// affects the `TokenStream` created by `make_tokenstream`.
+    pub fn add_trailing_semi(&self) -> LazyTokenStream {
+        LazyTokenStream(Lrc::new(self.0.add_trailing_semi()))
+    }
+
     pub fn create_token_stream(&self) -> TokenStream {
         self.0.create_token_stream()
     }