From 8c802dcd587d487387c99b057163becc827e0108 Mon Sep 17 00:00:00 2001
From: Stephen Chung <schungx@live.com>
Date: Thu, 1 Jul 2021 12:27:29 +0800
Subject: [PATCH] Fix optimizer bug.

---
 CHANGELOG.md       |  5 +++++
 src/optimize.rs    |  8 +++++++-
 tests/optimizer.rs | 19 +++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1c9fac5..3680c038 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,11 @@ The official version `1.0`.
 
 Almost the same version as `0.20.3` but with deprecated API's removed.
 
+Bug fixes
+---------
+
+* Fixed infinite loop in certain script optimizations.
+
 Breaking changes
 ----------------
 
diff --git a/src/optimize.rs b/src/optimize.rs
index 7830efb7..22a67ac8 100644
--- a/src/optimize.rs
+++ b/src/optimize.rs
@@ -297,8 +297,14 @@ fn optimize_stmt_block(
                             Stmt::Noop(pos)
                         };
                     }
+                    // { ...; stmt; noop } -> done
                     [.., ref second_last_stmt, Stmt::Noop(_)]
-                        if second_last_stmt.returns_value() => {}
+                        if second_last_stmt.returns_value() =>
+                    {
+                        break
+                    }
+                    // { ...; stmt_that_returns; pure_non_value_stmt } -> { ...; stmt_that_returns; noop }
+                    // { ...; stmt; pure_non_value_stmt } -> { ...; stmt }
                     [.., ref second_last_stmt, ref last_stmt]
                         if !last_stmt.returns_value() && is_pure(last_stmt) =>
                     {
diff --git a/tests/optimizer.rs b/tests/optimizer.rs
index 844577b5..dc25ab23 100644
--- a/tests/optimizer.rs
+++ b/tests/optimizer.rs
@@ -2,6 +2,25 @@
 
 use rhai::{Engine, EvalAltResult, OptimizationLevel, INT};
 
+#[test]
+fn test_optimizer() -> Result<(), Box<EvalAltResult>> {
+    let mut engine = Engine::new();
+    engine.set_optimization_level(OptimizationLevel::Full);
+
+    assert_eq!(
+        engine.eval::<INT>(
+            "
+                fn foo(x) { print(x); return; }
+                fn foo2(x) { if x > 0 {} return; }
+                42
+            "
+        )?,
+        42
+    );
+
+    Ok(())
+}
+
 #[test]
 fn test_optimizer_run() -> Result<(), Box<EvalAltResult>> {
     fn run_test(engine: &mut Engine) -> Result<(), Box<EvalAltResult>> {