1 files changed, 42 insertions, 0 deletions
diff --git a/vendor/pest_meta/src/optimizer/lister.rs b/vendor/pest_meta/src/optimizer/lister.rs
new file mode 100644
index 000000000..e19885032
--- /dev/null
+++ b/vendor/pest_meta/src/optimizer/lister.rs
@@ -0,0 +1,42 @@
+// pest. The Elegant Parser
+// Copyright (c) 2018 Dragoș Tiselice
+//
+// Licensed under the Apache License, Version 2.0
+// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
+// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. All files in the project carrying such notice may not be copied,
+// modified, or distributed except according to those terms.
+
+use crate::ast::*;
+
+pub fn list(rule: Rule) -> Rule {
+    let Rule { name, ty, expr } = rule;
+    Rule {
+        name,
+        ty,
+        expr: expr.map_bottom_up(|expr| {
+            // TODO: Use box syntax when it gets stabilized.
+            match expr {
+                Expr::Seq(l, r) => match *l {
+                    Expr::Rep(l) => {
+                        let l = *l;
+                        match l {
+                            Expr::Seq(l1, l2) => {
+                                // Converts `(rule ~ rest)* ~ rule` to `rule ~ (rest ~ rule)*`,
+                                // avoiding matching the last `rule` twice.
+                                if l1 == r {
+                                    Expr::Seq(l1, Box::new(Expr::Rep(Box::new(Expr::Seq(l2, r)))))
+                                } else {
+                                    Expr::Seq(Box::new(Expr::Rep(Box::new(Expr::Seq(l1, l2)))), r)
+                                }
+                            }
+                            expr => Expr::Seq(Box::new(Expr::Rep(Box::new(expr))), r),
+                        }
+                    }
+                    expr => Expr::Seq(Box::new(expr), r),
+                },
+                expr => expr,
+            }
+        }),
+    }
+}