fix `dead_code` on exceptional `return` (#2930)

fixes #2929

1 files changed, 11 insertions, 5 deletions

diff --git a/lib/compress.js b/lib/compress.js
index f8e9f916..2cc8282a 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2863,6 +2863,9 @@ merge(Compressor.prototype, {
         def(AST_ObjectProperty, function(compressor){
             return this.value.may_throw(compressor);
         });
+        def(AST_Return, function(compressor){
+            return this.value.may_throw(compressor);
+        });
         def(AST_Sequence, function(compressor){
             return any(this.expressions, compressor);
         });
@@ -2882,8 +2885,7 @@ merge(Compressor.prototype, {
             return !this.is_declared(compressor);
         });
         def(AST_Try, function(compressor){
-            return any(this.body, compressor)
-                || this.bcatch && this.bcatch.may_throw(compressor)
+            return this.bcatch ? this.bcatch.may_throw(compressor) : any(this.body, compressor)
                 || this.bfinally && this.bfinally.may_throw(compressor);
         });
         def(AST_Unary, function(compressor){
@@ -5511,7 +5513,7 @@ merge(Compressor.prototype, {
                 node = parent;
                 parent = compressor.parent(level++);
                 if (parent instanceof AST_Exit) {
-                    if (in_try(level, parent instanceof AST_Throw)) break;
+                    if (in_try(level, parent)) break;
                     if (is_reachable(def.scope, [ def ])) break;
                     if (self.operator == "=") return self.right;
                     def.fixed = false;
@@ -5545,13 +5547,17 @@ merge(Compressor.prototype, {
         }
         return self;
 
-        function in_try(level, no_catch) {
+        function in_try(level, node) {
+            var right = self.right;
+            self.right = make_node(AST_Null, right);
+            var may_throw = node.may_throw(compressor);
+            self.right = right;
             var scope = self.left.definition().scope;
             var parent;
             while ((parent = compressor.parent(level++)) !== scope) {
                 if (parent instanceof AST_Try) {
                     if (parent.bfinally) return true;
-                    if (no_catch && parent.bcatch) return true;
+                    if (may_throw && parent.bcatch) return true;
                 }
             }
         }