1 files changed, 49 insertions, 0 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 3e5b524d..22fb330e 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1380,6 +1380,10 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_Seq, function(self, compressor){
+        if (!compressor.option("side_effects"))
+            return self;
+        if (!self.car.has_side_effects())
+            return self.cdr;
         if (compressor.option("cascade")) {
             if (self.car instanceof AST_Assign
                 && !self.car.left.has_side_effects()
@@ -1395,7 +1399,26 @@ merge(Compressor.prototype, {
         return self;
     });
 
+    AST_Unary.DEFMETHOD("lift_sequences", function(compressor){
+        if (compressor.option("sequences")) {
+            if (this.expression instanceof AST_Seq) {
+                var seq = this.expression;
+                var x = seq.to_array();
+                this.expression = x.pop();
+                x.push(this);
+                seq = AST_Seq.from_array(x).transform(compressor);
+                return seq;
+            }
+        }
+        return this;
+    });
+
+    OPT(AST_UnaryPostfix, function(self, compressor){
+        return self.lift_sequences(compressor);
+    });
+
     OPT(AST_UnaryPrefix, function(self, compressor){
+        self = self.lift_sequences(compressor);
         var e = self.expression;
         if (compressor.option("booleans") && compressor.in_boolean_context()) {
             switch (self.operator) {
@@ -1418,7 +1441,32 @@ merge(Compressor.prototype, {
         return self.evaluate(compressor)[0];
     });
 
+    AST_Binary.DEFMETHOD("lift_sequences", function(compressor){
+        if (compressor.option("sequences")) {
+            if (this.left instanceof AST_Seq) {
+                var seq = this.left;
+                var x = seq.to_array();
+                this.left = x.pop();
+                x.push(this);
+                seq = AST_Seq.from_array(x).transform(compressor);
+                return seq;
+            }
+            if (this.right instanceof AST_Seq
+                && !(this.operator == "||" || this.operator == "&&")
+                && !this.left.has_side_effects()) {
+                var seq = this.right;
+                var x = seq.to_array();
+                this.right = x.pop();
+                x.push(this);
+                seq = AST_Seq.from_array(x).transform(compressor);
+                return seq;
+            }
+        }
+        return this;
+    });
+
     OPT(AST_Binary, function(self, compressor){
+        self = self.lift_sequences(compressor);
         if (compressor.option("comparisons")) switch (self.operator) {
           case "===":
           case "!==":
@@ -1557,6 +1605,7 @@ merge(Compressor.prototype, {
 
     var ASSIGN_OPS = [ '+', '-', '/', '*', '%', '>>', '<<', '>>>', '|', '^', '&' ];
     OPT(AST_Assign, function(self, compressor){
+        self = self.lift_sequences(compressor);
         if (self.operator == "="
             && self.left instanceof AST_SymbolRef
             && self.right instanceof AST_Binary