Support TS 4.3 override syntax in class (#13097)

* support TS 4.3 `override` syntax in class

* fix types

* fix types

* tweak error message

* update TypeScript commit

* split tests

* add more tests

* update allowlist

* disallow `override` with `declare`

* disallow `override` in non-sub class

* update TypeScript allowlist

* rename error message key

* add more tests

Makefile

@@ -1,6 +1,6 @@
 FLOW_COMMIT = a1f9a4c709dcebb27a5084acf47755fbae699c25
 TEST262_COMMIT = eca69e2c95972a4c5780ef58fe1f1e53e871b9b1
-TYPESCRIPT_COMMIT = 41dc625b0a609eb294b975dd92675e72b2b3fdec
+TYPESCRIPT_COMMIT = dd1ef88d016dc40a145eafc0a1169e7f0a4a9ebe
 
 # Fix color output until TravisCI fixes https://github.com/travis-ci/travis-ci/issues/7967
 export FORCE_COLOR = true

packages/babel-generator/src/generators/typescript.ts

@@ -644,6 +644,10 @@ export function tsPrintClassMemberModifiers(this: Printer, node: any, isField) {
     this.word("declare");
     this.space();
   }
+  if (node.override) {
+    this.word("override");
+    this.space();
+  }
   if (node.accessibility) {
     this.word(node.accessibility);
     this.space();

packages/babel-generator/test/fixtures/typescript/class-modifier-override/input.js

@@ -0,0 +1,8 @@
+class MyClass extends BaseClass {
+  override show() {}
+  override public show() {}
+  public override show() {}
+  override size = 5;
+  override readonly size = 5;
+  readonly override size = 5;
+}

packages/babel-generator/test/fixtures/typescript/class-modifier-override/options.json

@@ -0,0 +1,4 @@
+{
+  "sourceType": "module",
+  "plugins": ["typescript", "classProperties"]
+}

packages/babel-generator/test/fixtures/typescript/class-modifier-override/output.js

@@ -0,0 +1,11 @@
+class MyClass extends BaseClass {
+  override show() {}
+
+  override public show() {}
+
+  override public show() {}
+
+  override size = 5;
+  override readonly size = 5;
+  override readonly size = 5;
+}

packages/babel-parser/src/parser/error-message.js

@@ -128,6 +128,8 @@ export const ErrorMessages = makeErrorTemplates(
       "constructors in/after an Optional Chain are not allowed",
     OptionalChainingNoTemplate:
       "Tagged Template Literals are not allowed in optionalChain",
+    OverrideOnConstructor:
+      "'override' modifier cannot appear on a constructor declaration.",
     ParamDupe: "Argument name clash",
     PatternHasAccessor: "Object pattern can't contain getter or setter",
     PatternHasMethod: "Object pattern can't contain methods",

packages/babel-parser/src/parser/statement.js

@@ -1205,15 +1205,12 @@ export default class StatementParser extends ExpressionParser {
   }
 
   // https://tc39.es/ecma262/#prod-ClassBody
-  parseClassBody(
+  parseClassBody(hadSuperClass: boolean, oldStrict: boolean): N.ClassBody {
-    constructorAllowsSuper: boolean,
-    oldStrict: boolean,
-  ): N.ClassBody {
     this.classScope.enter();
 
     const state: N.ParseClassMemberState = {
-      constructorAllowsSuper,
       hadConstructor: false,
+      hadSuperClass,
     };
     let decorators: N.Decorator[] = [];
     const classBody: N.ClassBody = this.startNode();
@@ -1400,8 +1397,11 @@ export default class StatementParser extends ExpressionParser {
         if (state.hadConstructor && !this.hasPlugin("typescript")) {
           this.raise(key.start, Errors.DuplicateConstructor);
         }
+        if (isConstructor && this.hasPlugin("typescript") && member.override) {
+          this.raise(key.start, Errors.OverrideOnConstructor);
+        }
         state.hadConstructor = true;
-        allowsDirectSuper = state.constructorAllowsSuper;
+        allowsDirectSuper = state.hadSuperClass;
       }
 
       this.pushClassMethod(

packages/babel-parser/src/plugins/typescript/index.js

@@ -41,6 +41,7 @@ type TsModifier =
   | "abstract"
   | "declare"
   | "static"
+  | "override"
   | N.Accessibility;
 
 function nonNull<T>(x: ?T): T {
@@ -86,12 +87,15 @@ const TSErrors = makeErrorTemplates(
     ExpectedAmbientAfterExportDeclare:
       "'export declare' must be followed by an ambient declaration.",
     ImportAliasHasImportType: "An import alias can not use 'import type'",
+    IncompatibleModifiers: "'%0' modifier cannot be used with '%1' modifier.",
     IndexSignatureHasAbstract:
       "Index signatures cannot have the 'abstract' modifier",
     IndexSignatureHasAccessibility:
       "Index signatures cannot have an accessibility modifier ('%0')",
     IndexSignatureHasDeclare:
       "Index signatures cannot have the 'declare' modifier",
+    IndexSignatureHasOverride:
+      "'override' modifier cannot appear on an index signature.",
     IndexSignatureHasStatic:
       "Index signatures cannot have the 'static' modifier",
     InvalidModifierOnTypeMember:
@@ -107,6 +111,8 @@ const TSErrors = makeErrorTemplates(
       "'abstract' modifier can only appear on a class, method, or property declaration.",
     OptionalTypeBeforeRequired:
       "A required element cannot follow an optional element.",
+    OverrideNotInSubClass:
+      "This member cannot have an 'override' modifier because its containing class does not extend another class.",
     PatternIsOptional:
       "A binding pattern parameter cannot be optional in an implementation signature.",
     PrivateElementHasAbstract:
@@ -257,6 +263,16 @@ export default (superClass: Class<Parser>): Class<Parser> =>
               "static",
               "readonly",
             );
+          } else if (
+            (modified.declare && modifier === "override") ||
+            (modified.override && modifier === "declare")
+          ) {
+            this.raise(
+              startPos,
+              TSErrors.IncompatibleModifiers,
+              "declare",
+              "override",
+            );
           }
           modified[modifier] = true;
         }
@@ -622,7 +638,15 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       this.tsParseModifiers(
         node,
         ["readonly"],
-        ["declare", "abstract", "private", "protected", "public", "static"],
+        [
+          "declare",
+          "abstract",
+          "private",
+          "protected",
+          "public",
+          "static",
+          "override",
+        ],
         TSErrors.InvalidModifierOnTypeMember,
       );
 
@@ -2223,6 +2247,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         "private",
         "public",
         "protected",
+        "override",
       ]);
 
       const callParseClassMember = () => {
@@ -2246,6 +2271,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         "readonly",
         "declare",
         "static",
+        "override",
       ]);
 
       if (isStatic) {
@@ -2269,6 +2295,9 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         if ((member: any).declare) {
           this.raise(member.start, TSErrors.IndexSignatureHasDeclare);
         }
+        if ((member: any).override) {
+          this.raise(member.start, TSErrors.IndexSignatureHasOverride);
+        }
 
         return;
       }
@@ -2277,6 +2306,19 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         this.raise(member.start, TSErrors.NonAbstractClassHasAbstractMethod);
       }
 
+      if ((member: any).override) {
+        if (isStatic) {
+          this.raise(
+            member.start,
+            TSErrors.IncompatibleModifiers,
+            "static",
+            "override",
+          );
+        } else if (!state.hadSuperClass) {
+          this.raise(member.start, TSErrors.OverrideNotInSubClass);
+        }
+      }
+
       /*:: invariant(member.type !== "TSIndexSignature") */
 
       super.parseClassMemberWithIsStatic(classBody, member, state, isStatic);

packages/babel-parser/src/types.js

@@ -730,6 +730,7 @@ export type ClassMemberBase = NodeBase &
     computed: boolean,
     // TypeScript only:
     accessibility?: ?Accessibility,
+    override?: ?true,
     abstract?: ?true,
     optional?: ?true,
   };
@@ -807,6 +808,7 @@ export type ClassPrivateProperty = NodeBase & {
   optional?: true,
   definite?: true,
   readonly?: true,
+  override?: true,
 };
 
 export type OptClassDeclaration = ClassBase &
@@ -1536,5 +1538,5 @@ export type ParseSubscriptState = {
 
 export type ParseClassMemberState = {|
   hadConstructor: boolean,
-  constructorAllowsSuper: boolean,
+  hadSuperClass: boolean,
 |};

packages/babel-parser/test/fixtures/typescript/class/modifiers-override-errors/input.ts

@@ -0,0 +1,15 @@
+class MyClass2 extends BaseClass {
+  override constructor() {}
+  override [x: string]: any;
+  override static size = 5;
+  static override size = 5;
+}
+
+declare class MyClass3 extends BaseClass {
+  declare override prop1: any
+  override declare prop2: any
+}
+
+class MyClass4 {
+  override prop: any
+}

packages/babel-parser/test/fixtures/typescript/class/modifiers-override-errors/output.json

@@ -0,0 +1,237 @@
+{
+  "type": "File",
+  "start":0,"end":296,"loc":{"start":{"line":1,"column":0},"end":{"line":15,"column":1}},
+  "errors": [
+    "SyntaxError: 'override' modifier cannot appear on a constructor declaration. (2:11)",
+    "SyntaxError: 'override' modifier cannot appear on an index signature. (3:2)",
+    "SyntaxError: 'static' modifier cannot be used with 'override' modifier. (4:2)",
+    "SyntaxError: 'static' modifier cannot be used with 'override' modifier. (5:2)",
+    "SyntaxError: 'declare' modifier cannot be used with 'override' modifier. (9:10)",
+    "SyntaxError: 'declare' modifier cannot be used with 'override' modifier. (10:11)",
+    "SyntaxError: This member cannot have an 'override' modifier because its containing class does not extend another class. (14:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":296,"loc":{"start":{"line":1,"column":0},"end":{"line":15,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":149,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":14,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":14},"identifierName":"MyClass2"},
+          "name": "MyClass2"
+        },
+        "superClass": {
+          "type": "Identifier",
+          "start":23,"end":32,"loc":{"start":{"line":1,"column":23},"end":{"line":1,"column":32},"identifierName":"BaseClass"},
+          "name": "BaseClass"
+        },
+        "body": {
+          "type": "ClassBody",
+          "start":33,"end":149,"loc":{"start":{"line":1,"column":33},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start":37,"end":62,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":27}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":46,"end":57,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":22},"identifierName":"constructor"},
+                "name": "constructor"
+              },
+              "computed": false,
+              "kind": "constructor",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":60,"end":62,"loc":{"start":{"line":2,"column":25},"end":{"line":2,"column":27}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "TSIndexSignature",
+              "start":65,"end":91,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":28}},
+              "override": true,
+              "parameters": [
+                {
+                  "type": "Identifier",
+                  "start":75,"end":84,"loc":{"start":{"line":3,"column":12},"end":{"line":3,"column":21},"identifierName":"x"},
+                  "name": "x",
+                  "typeAnnotation": {
+                    "type": "TSTypeAnnotation",
+                    "start":76,"end":84,"loc":{"start":{"line":3,"column":13},"end":{"line":3,"column":21}},
+                    "typeAnnotation": {
+                      "type": "TSStringKeyword",
+                      "start":78,"end":84,"loc":{"start":{"line":3,"column":15},"end":{"line":3,"column":21}}
+                    }
+                  }
+                }
+              ],
+              "typeAnnotation": {
+                "type": "TSTypeAnnotation",
+                "start":85,"end":90,"loc":{"start":{"line":3,"column":22},"end":{"line":3,"column":27}},
+                "typeAnnotation": {
+                  "type": "TSAnyKeyword",
+                  "start":87,"end":90,"loc":{"start":{"line":3,"column":24},"end":{"line":3,"column":27}}
+                }
+              }
+            },
+            {
+              "type": "ClassProperty",
+              "start":94,"end":119,"loc":{"start":{"line":4,"column":2},"end":{"line":4,"column":27}},
+              "override": true,
+              "static": true,
+              "key": {
+                "type": "Identifier",
+                "start":110,"end":114,"loc":{"start":{"line":4,"column":18},"end":{"line":4,"column":22},"identifierName":"size"},
+                "name": "size"
+              },
+              "computed": false,
+              "value": {
+                "type": "NumericLiteral",
+                "start":117,"end":118,"loc":{"start":{"line":4,"column":25},"end":{"line":4,"column":26}},
+                "extra": {
+                  "rawValue": 5,
+                  "raw": "5"
+                },
+                "value": 5
+              }
+            },
+            {
+              "type": "ClassProperty",
+              "start":122,"end":147,"loc":{"start":{"line":5,"column":2},"end":{"line":5,"column":27}},
+              "override": true,
+              "static": true,
+              "key": {
+                "type": "Identifier",
+                "start":138,"end":142,"loc":{"start":{"line":5,"column":18},"end":{"line":5,"column":22},"identifierName":"size"},
+                "name": "size"
+              },
+              "computed": false,
+              "value": {
+                "type": "NumericLiteral",
+                "start":145,"end":146,"loc":{"start":{"line":5,"column":25},"end":{"line":5,"column":26}},
+                "extra": {
+                  "rawValue": 5,
+                  "raw": "5"
+                },
+                "value": 5
+              }
+            }
+          ]
+        }
+      },
+      {
+        "type": "ClassDeclaration",
+        "start":151,"end":255,"loc":{"start":{"line":8,"column":0},"end":{"line":11,"column":1}},
+        "declare": true,
+        "id": {
+          "type": "Identifier",
+          "start":165,"end":173,"loc":{"start":{"line":8,"column":14},"end":{"line":8,"column":22},"identifierName":"MyClass3"},
+          "name": "MyClass3"
+        },
+        "superClass": {
+          "type": "Identifier",
+          "start":182,"end":191,"loc":{"start":{"line":8,"column":31},"end":{"line":8,"column":40},"identifierName":"BaseClass"},
+          "name": "BaseClass"
+        },
+        "body": {
+          "type": "ClassBody",
+          "start":192,"end":255,"loc":{"start":{"line":8,"column":41},"end":{"line":11,"column":1}},
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start":196,"end":223,"loc":{"start":{"line":9,"column":2},"end":{"line":9,"column":29}},
+              "declare": true,
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":213,"end":218,"loc":{"start":{"line":9,"column":19},"end":{"line":9,"column":24},"identifierName":"prop1"},
+                "name": "prop1"
+              },
+              "computed": false,
+              "typeAnnotation": {
+                "type": "TSTypeAnnotation",
+                "start":218,"end":223,"loc":{"start":{"line":9,"column":24},"end":{"line":9,"column":29}},
+                "typeAnnotation": {
+                  "type": "TSAnyKeyword",
+                  "start":220,"end":223,"loc":{"start":{"line":9,"column":26},"end":{"line":9,"column":29}}
+                }
+              },
+              "value": null
+            },
+            {
+              "type": "ClassProperty",
+              "start":226,"end":253,"loc":{"start":{"line":10,"column":2},"end":{"line":10,"column":29}},
+              "override": true,
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":243,"end":248,"loc":{"start":{"line":10,"column":19},"end":{"line":10,"column":24},"identifierName":"prop2"},
+                "name": "prop2"
+              },
+              "computed": false,
+              "typeAnnotation": {
+                "type": "TSTypeAnnotation",
+                "start":248,"end":253,"loc":{"start":{"line":10,"column":24},"end":{"line":10,"column":29}},
+                "typeAnnotation": {
+                  "type": "TSAnyKeyword",
+                  "start":250,"end":253,"loc":{"start":{"line":10,"column":26},"end":{"line":10,"column":29}}
+                }
+              },
+              "value": null
+            }
+          ]
+        }
+      },
+      {
+        "type": "ClassDeclaration",
+        "start":257,"end":296,"loc":{"start":{"line":13,"column":0},"end":{"line":15,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":263,"end":271,"loc":{"start":{"line":13,"column":6},"end":{"line":13,"column":14},"identifierName":"MyClass4"},
+          "name": "MyClass4"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":272,"end":296,"loc":{"start":{"line":13,"column":15},"end":{"line":15,"column":1}},
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start":276,"end":294,"loc":{"start":{"line":14,"column":2},"end":{"line":14,"column":20}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":285,"end":289,"loc":{"start":{"line":14,"column":11},"end":{"line":14,"column":15},"identifierName":"prop"},
+                "name": "prop"
+              },
+              "computed": false,
+              "typeAnnotation": {
+                "type": "TSTypeAnnotation",
+                "start":289,"end":294,"loc":{"start":{"line":14,"column":15},"end":{"line":14,"column":20}},
+                "typeAnnotation": {
+                  "type": "TSAnyKeyword",
+                  "start":291,"end":294,"loc":{"start":{"line":14,"column":17},"end":{"line":14,"column":20}}
+                }
+              },
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/class/modifiers-override/input.ts

@@ -0,0 +1,20 @@
+class MyClass extends BaseClass {
+  override show() {}
+  override public show() {}
+  public override show() {}
+  override size = 5;
+  override readonly size = 5;
+  readonly override size = 5;
+
+  override get text() {}
+  override set text(value) {}
+
+  override async fetch() {}
+
+  override [x] = 2
+  override [x]() {}
+}
+
+declare class DeclaredClass extends BaseClass {
+  override test() {}
+}

packages/babel-parser/test/fixtures/typescript/class/modifiers-override/output.json

@@ -0,0 +1,332 @@
+{
+  "type": "File",
+  "start":0,"end":390,"loc":{"start":{"line":1,"column":0},"end":{"line":20,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":390,"loc":{"start":{"line":1,"column":0},"end":{"line":20,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":318,"loc":{"start":{"line":1,"column":0},"end":{"line":16,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":13,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":13},"identifierName":"MyClass"},
+          "name": "MyClass"
+        },
+        "superClass": {
+          "type": "Identifier",
+          "start":22,"end":31,"loc":{"start":{"line":1,"column":22},"end":{"line":1,"column":31},"identifierName":"BaseClass"},
+          "name": "BaseClass"
+        },
+        "body": {
+          "type": "ClassBody",
+          "start":32,"end":318,"loc":{"start":{"line":1,"column":32},"end":{"line":16,"column":1}},
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start":36,"end":54,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":20}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":45,"end":49,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":15},"identifierName":"show"},
+                "name": "show"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":52,"end":54,"loc":{"start":{"line":2,"column":18},"end":{"line":2,"column":20}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":57,"end":82,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":27}},
+              "override": true,
+              "accessibility": "public",
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":73,"end":77,"loc":{"start":{"line":3,"column":18},"end":{"line":3,"column":22},"identifierName":"show"},
+                "name": "show"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":80,"end":82,"loc":{"start":{"line":3,"column":25},"end":{"line":3,"column":27}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":85,"end":110,"loc":{"start":{"line":4,"column":2},"end":{"line":4,"column":27}},
+              "accessibility": "public",
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":101,"end":105,"loc":{"start":{"line":4,"column":18},"end":{"line":4,"column":22},"identifierName":"show"},
+                "name": "show"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":108,"end":110,"loc":{"start":{"line":4,"column":25},"end":{"line":4,"column":27}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassProperty",
+              "start":113,"end":131,"loc":{"start":{"line":5,"column":2},"end":{"line":5,"column":20}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":122,"end":126,"loc":{"start":{"line":5,"column":11},"end":{"line":5,"column":15},"identifierName":"size"},
+                "name": "size"
+              },
+              "computed": false,
+              "value": {
+                "type": "NumericLiteral",
+                "start":129,"end":130,"loc":{"start":{"line":5,"column":18},"end":{"line":5,"column":19}},
+                "extra": {
+                  "rawValue": 5,
+                  "raw": "5"
+                },
+                "value": 5
+              }
+            },
+            {
+              "type": "ClassProperty",
+              "start":134,"end":161,"loc":{"start":{"line":6,"column":2},"end":{"line":6,"column":29}},
+              "override": true,
+              "readonly": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":152,"end":156,"loc":{"start":{"line":6,"column":20},"end":{"line":6,"column":24},"identifierName":"size"},
+                "name": "size"
+              },
+              "computed": false,
+              "value": {
+                "type": "NumericLiteral",
+                "start":159,"end":160,"loc":{"start":{"line":6,"column":27},"end":{"line":6,"column":28}},
+                "extra": {
+                  "rawValue": 5,
+                  "raw": "5"
+                },
+                "value": 5
+              }
+            },
+            {
+              "type": "ClassProperty",
+              "start":164,"end":191,"loc":{"start":{"line":7,"column":2},"end":{"line":7,"column":29}},
+              "readonly": true,
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":182,"end":186,"loc":{"start":{"line":7,"column":20},"end":{"line":7,"column":24},"identifierName":"size"},
+                "name": "size"
+              },
+              "computed": false,
+              "value": {
+                "type": "NumericLiteral",
+                "start":189,"end":190,"loc":{"start":{"line":7,"column":27},"end":{"line":7,"column":28}},
+                "extra": {
+                  "rawValue": 5,
+                  "raw": "5"
+                },
+                "value": 5
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":195,"end":217,"loc":{"start":{"line":9,"column":2},"end":{"line":9,"column":24}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":208,"end":212,"loc":{"start":{"line":9,"column":15},"end":{"line":9,"column":19},"identifierName":"text"},
+                "name": "text"
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":215,"end":217,"loc":{"start":{"line":9,"column":22},"end":{"line":9,"column":24}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":220,"end":247,"loc":{"start":{"line":10,"column":2},"end":{"line":10,"column":29}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":233,"end":237,"loc":{"start":{"line":10,"column":15},"end":{"line":10,"column":19},"identifierName":"text"},
+                "name": "text"
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start":238,"end":243,"loc":{"start":{"line":10,"column":20},"end":{"line":10,"column":25},"identifierName":"value"},
+                  "name": "value"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start":245,"end":247,"loc":{"start":{"line":10,"column":27},"end":{"line":10,"column":29}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":251,"end":276,"loc":{"start":{"line":12,"column":2},"end":{"line":12,"column":27}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":266,"end":271,"loc":{"start":{"line":12,"column":17},"end":{"line":12,"column":22},"identifierName":"fetch"},
+                "name": "fetch"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": true,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":274,"end":276,"loc":{"start":{"line":12,"column":25},"end":{"line":12,"column":27}},
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassProperty",
+              "start":280,"end":296,"loc":{"start":{"line":14,"column":2},"end":{"line":14,"column":18}},
+              "override": true,
+              "static": false,
+              "computed": true,
+              "key": {
+                "type": "Identifier",
+                "start":290,"end":291,"loc":{"start":{"line":14,"column":12},"end":{"line":14,"column":13},"identifierName":"x"},
+                "name": "x"
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":295,"end":296,"loc":{"start":{"line":14,"column":17},"end":{"line":14,"column":18}},
+                "extra": {
+                  "rawValue": 2,
+                  "raw": "2"
+                },
+                "value": 2
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":299,"end":316,"loc":{"start":{"line":15,"column":2},"end":{"line":15,"column":19}},
+              "override": true,
+              "static": false,
+              "computed": true,
+              "key": {
+                "type": "Identifier",
+                "start":309,"end":310,"loc":{"start":{"line":15,"column":12},"end":{"line":15,"column":13},"identifierName":"x"},
+                "name": "x"
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":314,"end":316,"loc":{"start":{"line":15,"column":17},"end":{"line":15,"column":19}},
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      },
+      {
+        "type": "ClassDeclaration",
+        "start":320,"end":390,"loc":{"start":{"line":18,"column":0},"end":{"line":20,"column":1}},
+        "declare": true,
+        "id": {
+          "type": "Identifier",
+          "start":334,"end":347,"loc":{"start":{"line":18,"column":14},"end":{"line":18,"column":27},"identifierName":"DeclaredClass"},
+          "name": "DeclaredClass"
+        },
+        "superClass": {
+          "type": "Identifier",
+          "start":356,"end":365,"loc":{"start":{"line":18,"column":36},"end":{"line":18,"column":45},"identifierName":"BaseClass"},
+          "name": "BaseClass"
+        },
+        "body": {
+          "type": "ClassBody",
+          "start":366,"end":390,"loc":{"start":{"line":18,"column":46},"end":{"line":20,"column":1}},
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start":370,"end":388,"loc":{"start":{"line":19,"column":2},"end":{"line":19,"column":20}},
+              "override": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":379,"end":383,"loc":{"start":{"line":19,"column":11},"end":{"line":19,"column":15},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":386,"end":388,"loc":{"start":{"line":19,"column":18},"end":{"line":19,"column":20}},
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-types/src/ast-types/generated/index.ts

@@ -909,6 +909,7 @@ export interface ClassMethod extends BaseNode {
   accessibility?: "public" | "private" | "protected" | null;
   decorators?: Array<Decorator> | null;
   optional?: boolean | null;
+  override?: boolean;
   returnType?: TypeAnnotation | TSTypeAnnotation | Noop | null;
   typeParameters?:
     | TypeParameterDeclaration
@@ -1535,6 +1536,7 @@ export interface ClassProperty extends BaseNode {
   declare?: boolean | null;
   definite?: boolean | null;
   optional?: boolean | null;
+  override?: boolean;
   readonly?: boolean | null;
 }
 
@@ -1576,6 +1578,7 @@ export interface ClassPrivateMethod extends BaseNode {
   decorators?: Array<Decorator> | null;
   generator?: boolean;
   optional?: boolean | null;
+  override?: boolean;
   returnType?: TypeAnnotation | TSTypeAnnotation | Noop | null;
   typeParameters?:
     | TypeParameterDeclaration
@@ -1668,6 +1671,7 @@ export interface TSDeclareMethod extends BaseNode {
   generator?: boolean;
   kind?: "get" | "set" | "method" | "constructor";
   optional?: boolean | null;
+  override?: boolean;
   static?: boolean;
 }
 

packages/babel-types/src/definitions/core.ts

@@ -1705,6 +1705,9 @@ export const classMethodOrPropertyCommon = {
   static: {
     default: false,
   },
+  override: {
+    default: false,
+  },
   computed: {
     default: false,
   },