From 9b56c1ba7809716641f6ba172aa82c267de3a326 Mon Sep 17 00:00:00 2001
From: Stephen Chung <schungx@live.com>
Date: Wed, 4 Aug 2021 17:40:26 +0800
Subject: [PATCH] Optimize loops better.

---
 src/engine.rs   | 29 ++++++++++++++++++++++-------
 src/optimize.rs |  3 +++
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/engine.rs b/src/engine.rs
index cdba7f9f..d72b2dac 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -2542,15 +2542,30 @@ impl Engine {
                 })
             }
 
+            // Loop
+            Stmt::While(Expr::Unit(_), body, _) => loop {
+                if !body.is_empty() {
+                    match self.eval_stmt_block(scope, mods, state, lib, this_ptr, body, true, level)
+                    {
+                        Ok(_) => (),
+                        Err(err) => match *err {
+                            EvalAltResult::LoopBreak(false, _) => (),
+                            EvalAltResult::LoopBreak(true, _) => return Ok(Dynamic::UNIT),
+                            _ => return Err(err),
+                        },
+                    }
+                } else {
+                    #[cfg(not(feature = "unchecked"))]
+                    self.inc_operations(state, body.position())?;
+                }
+            },
+
             // While loop
             Stmt::While(expr, body, _) => loop {
-                let condition = if !expr.is_unit() {
-                    self.eval_expr(scope, mods, state, lib, this_ptr, expr, level)?
-                        .as_bool()
-                        .map_err(|typ| self.make_type_mismatch_err::<bool>(typ, expr.position()))?
-                } else {
-                    true
-                };
+                let condition = self
+                    .eval_expr(scope, mods, state, lib, this_ptr, expr, level)?
+                    .as_bool()
+                    .map_err(|typ| self.make_type_mismatch_err::<bool>(typ, expr.position()))?;
 
                 if !condition {
                     return Ok(Dynamic::UNIT);
diff --git a/src/optimize.rs b/src/optimize.rs
index 3376240e..08f3fadd 100644
--- a/src/optimize.rs
+++ b/src/optimize.rs
@@ -559,6 +559,9 @@ fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: b
         // while expr { block }
         Stmt::While(condition, body, _) => {
             optimize_expr(condition, state, false);
+            if let Expr::BoolConstant(true, pos) = condition {
+                *condition = Expr::Unit(*pos);
+            }
             let block = mem::take(body.statements_mut()).into_vec();
             *body.statements_mut() = optimize_stmt_block(block, state, false, true, false).into();