Attach tokens to ast::Stmt

We currently only attach tokens when parsing a `:stmt` matcher for a
`macro_rules!` macro. Proc-macro attributes on statements are still
unstable, and need additional work.

compiler/rustc_parse/src/parser/stmt.rs

@@ -415,7 +415,7 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt {
-        Stmt { id: DUMMY_NODE_ID, kind, span }
+        Stmt { id: DUMMY_NODE_ID, kind, span, tokens: None }
     }
 
     fn mk_stmt_err(&self, span: Span) -> Stmt {