fix corner case in unused (#5323)

fixes #5322

lib/compress.js

@@ -6507,28 +6507,29 @@ Compressor.prototype.compress = function(node) {
             if (scope === self) {
                 if (node instanceof AST_DefClass) {
                     var def = node.name.definition();
-                    if ((!drop_funcs || def.exported) && !(def.id in in_use_ids)) {
+                    var drop = drop_funcs && !def.exported;
+                    if (!drop && !(def.id in in_use_ids)) {
                         in_use_ids[def.id] = true;
                         in_use.push(def);
                     }
                     if (node.extends) node.extends.walk(tw);
-                    var is_export = false;
+                    var used = tw.parent() instanceof AST_ExportDefault;
-                    if (tw.parent() instanceof AST_ExportDefault) {
+                    if (used) export_defaults[def.id] = true;
-                        is_export = true;
+                    var values = [];
-                        export_defaults[def.id] = true;
-                    }
                     node.properties.forEach(function(prop) {
                         if (prop.key instanceof AST_Node) prop.key.walk(tw);
-                        if (!prop.value) return;
+                        var value = prop.value;
-                        if (is_export || prop instanceof AST_ClassField && prop.static) {
+                        if (!value) return;
-                            var save_scope = scope;
+                        if (prop instanceof AST_ClassField && prop.static) {
-                            scope = node;
+                            if (!used && value.contains_this()) used = true;
-                            prop.value.walk(tw);
+                            walk_class_prop(value);
-                            scope = save_scope;
                         } else {
-                            initializations.add(def.id, prop.value);
+                            values.push(value);
                         }
                     });
+                    values.forEach(drop && used ? walk_class_prop : function(value) {
+                        initializations.add(def.id, value);
+                    });
                     return true;
                 }
                 if (node instanceof AST_LambdaDefinition) {
@@ -6594,6 +6595,13 @@ Compressor.prototype.compress = function(node) {
                 }
             }
             return scan_ref_scoped(node, descend, true);
+
+            function walk_class_prop(value) {
+                var save_scope = scope;
+                scope = node;
+                value.walk(tw);
+                scope = save_scope;
+            }
         });
         tw.directives = Object.create(compressor.directives);
         self.walk(tw);

test/compress/classes.js

@@ -2449,3 +2449,30 @@ issue_5294_4: {
     expect_stdout: "PASS"
     node_version: ">=12"
 }
+
+issue_5322: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 41;
+        class A {
+            static p() {
+                console.log(++a);
+            }
+            static q = this.p();
+        }
+    }
+    expect: {
+        var a = 41;
+        (class {
+            static p() {
+                console.log(++a);
+            }
+            static q = this.p();
+        });
+    }
+    expect_stdout: "42"
+    node_version: ">=12"
+}