optimize try-catch-finally (#1731)

- eliminate empty blocks
- flatten out if try-block does not throw

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/compress.js b/lib/compress.js
index e36ff893..be760152 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2606,6 +2606,15 @@ merge(Compressor.prototype, {
 
     OPT(AST_Try, function(self, compressor){
         self.body = tighten_body(self.body, compressor);
+        if (self.bcatch && self.bfinally && all(self.bfinally.body, is_empty)) self.bfinally = null;
+        if (all(self.body, is_empty)) {
+            var body = [];
+            if (self.bcatch) extract_declarations_from_unreachable_code(compressor, self.bcatch, body);
+            if (self.bfinally) body = body.concat(self.bfinally.body);
+            return body.length > 0 ? make_node(AST_BlockStatement, self, {
+                body: body
+            }).optimize(compressor) : make_node(AST_EmptyStatement, self);
+        }
         return self;
     });