fix dead_code on nested try (#2599)

fixes #2597

lib/compress.js

@@ -4751,11 +4751,7 @@ merge(Compressor.prototype, {
                 node = parent;
                 parent = compressor.parent(level++);
                 if (parent instanceof AST_Exit) {
-                    var try_node = find_try(level);
+                    if (in_try(level, parent instanceof AST_Throw)) break;
-                    if (try_node) {
-                        if (try_node.bfinally) break;
-                        if (parent instanceof AST_Throw && try_node.bcatch) break;
-                    }
                     if (self.operator == "=") return self.right;
                     return make_node(AST_Binary, self, {
                         operator: self.operator.slice(0, -1),
@@ -4787,11 +4783,14 @@ merge(Compressor.prototype, {
         }
         return self;
 
-        function find_try(level) {
+        function in_try(level, no_catch) {
             var scope = self.left.definition().scope;
             var parent;
             while ((parent = compressor.parent(level++)) !== scope) {
-                if (parent instanceof AST_Try) return parent;
+                if (parent instanceof AST_Try) {
+                    if (parent.bfinally) return true;
+                    if (no_catch && parent.bcatch) return true;
+                }
             }
         }
     });

test/compress/dead-code.js

@@ -789,3 +789,42 @@ throw_assignment: {
         "caught -9",
     ]
 }
+
+issue_2597: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        function f(b) {
+            try {
+                try {
+                    throw "foo";
+                } catch (e) {
+                    return b = true;
+                }
+            } finally {
+                b && (a = "PASS");
+            }
+        }
+        var a = "FAIL";
+        f();
+        console.log(a);
+    }
+    expect: {
+        function f(b) {
+            try {
+                try {
+                    throw "foo";
+                } catch (e) {
+                    return b = true;
+                }
+            } finally {
+                b && (a = "PASS");
+            }
+        }
+        var a = "FAIL";
+        f();
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+}