Enforce keyword order between override and static/async

src/compiler/checker.ts

@@ -40471,6 +40471,9 @@ namespace ts {
                         else if (flags & ModifierFlags.Readonly) {
                             return grammarErrorOnNode(modifier, Diagnostics._0_modifier_must_precede_1_modifier, "override", "readonly");
                         }
+                        else if (flags & ModifierFlags.Async) {
+                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_must_precede_1_modifier, "override", "async");
+                        }
                         if (node.kind === SyntaxKind.Parameter) {
                             return grammarErrorOnNode(modifier, Diagnostics._0_modifier_cannot_appear_on_a_parameter, "override");
                         }
@@ -40534,6 +40537,9 @@ namespace ts {
                         else if (flags & ModifierFlags.Abstract) {
                             return grammarErrorOnNode(modifier, Diagnostics._0_modifier_cannot_be_used_with_1_modifier, "static", "abstract");
                         }
+                        else if (flags & ModifierFlags.Override) {
+                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_must_precede_1_modifier, "static", "override");
+                        }
                         flags |= ModifierFlags.Static;
                         lastStatic = modifier;
                         break;

tests/baselines/reference/overrideKeywordOrder.errors.txt

@@ -0,0 +1,41 @@
+tests/cases/conformance/override/overrideKeywordOrder.ts(12,9): error TS1029: 'override' modifier must precede 'async' modifier.
+tests/cases/conformance/override/overrideKeywordOrder.ts(15,12): error TS1029: 'static' modifier must precede 'override' modifier.
+tests/cases/conformance/override/overrideKeywordOrder.ts(19,12): error TS1029: 'public' modifier must precede 'override' modifier.
+tests/cases/conformance/override/overrideKeywordOrder.ts(24,12): error TS1029: 'override' modifier must precede 'readonly' modifier.
+
+
+==== tests/cases/conformance/override/overrideKeywordOrder.ts (4 errors) ====
+    class Base {
+      static s1() {}
+      static s2() {}
+      m1() {}
+      m2() {}
+      p1: any;
+      p2: any;
+    }
+
+    class Test1 extends Base {
+      override async m1() {}
+      async override m2() {} // error
+            ~~~~~~~~
+!!! error TS1029: 'override' modifier must precede 'async' modifier.
+    }
+    class Test2 extends Base {
+      override static s1() {} // error
+               ~~~~~~
+!!! error TS1029: 'static' modifier must precede 'override' modifier.
+      static override s2() {}
+    }
+    class Test3 extends Base {
+      override public m1() {} // error
+               ~~~~~~
+!!! error TS1029: 'public' modifier must precede 'override' modifier.
+      public override m2() {}
+    }
+    class Test4 extends Base {
+      override readonly p1: any;
+      readonly override p2: any; // error
+               ~~~~~~~~
+!!! error TS1029: 'override' modifier must precede 'readonly' modifier.
+    }
+

tests/cases/conformance/override/overrideKeywordOrder.ts

@@ -0,0 +1,28 @@
+// @noTypesAndSymbols: true
+// @noEmit: true
+
+class Base {
+  static s1() {}
+  static s2() {}
+  m1() {}
+  m2() {}
+  p1: any;
+  p2: any;
+}
+
+class Test1 extends Base {
+  override async m1() {}
+  async override m2() {} // error
+}
+class Test2 extends Base {
+  override static s1() {} // error
+  static override s2() {}
+}
+class Test3 extends Base {
+  override public m1() {} // error
+  public override m2() {}
+}
+class Test4 extends Base {
+  override readonly p1: any;
+  readonly override p2: any; // error
+}