preserve side effects in switch expression (#1694)

fixes #1690

1 files changed, 8 insertions, 7 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 8350ba25..9ed368c7 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2560,10 +2560,9 @@ merge(Compressor.prototype, {
                 fallthrough = !aborts(exact_match);
             }
             while (i < len) extract_declarations_from_unreachable_code(compressor, self.body[i++], decl);
-            if (body.length == 0) return make_node(AST_BlockStatement, self, {
-                body: decl
-            }).optimize(compressor);
-            body[0].body = decl.concat(body[0].body);
+            if (body.length > 0) {
+                body[0].body = decl.concat(body[0].body);
+            }
             self.body = body;
         }
         while (branch = self.body[self.body.length - 1]) {
@@ -2575,9 +2574,11 @@ merge(Compressor.prototype, {
                     && branch.expression.has_side_effects(compressor)) break;
             self.body.pop();
         }
-        if (compressor.option("conditionals") && self.body.length == 0) {
-            return make_node(AST_SimpleStatement, self, {
-                body: self.expression
+        if (decl && self.body.length == 0) {
+            return make_node(AST_BlockStatement, self, {
+                body: decl.concat(make_node(AST_SimpleStatement, self.expression, {
+                    body: self.expression
+                }))
             }).optimize(compressor);
         }
         if (body && body.length == 1 && (body[0] === exact_match || body[0] === default_branch)) {