Add support for class private methods (#703)

* Add support for class private methods

This commit adds parser support for the TC39 Stage 2 Private Methods
proposal.

This commit also changes "key" in ClassPrivateProperty from an
Identifier to a PrivateName, as well as disallowing #constructor as a
valid private field name.

* Add tests for string literal get/set/async

These should be treated as regular methods and not special get/set/async
behaviour.

* Add tests for class private methods

This also removes a test from the Test262 whitelist that failed before
the changes for private methods support and now passes.

* Modify class private prop tests for PrivateName

* Add class private prop tests for #constructor

* Fix existing ASI test case failure

README.md

@@ -137,6 +137,7 @@ require("babylon").parse("code", {
 | `decorators` (Stage 1) and `decorators2` (Stage 2 [proposal](https://github.com/tc39/proposal-decorators)) | `@a class A {}` |
 | `classProperties` ([proposal](https://github.com/tc39/proposal-class-public-fields)) | `class A { b = 1; }` |
 | `classPrivateProperties` ([proposal](https://github.com/tc39/proposal-private-fields)) | `class A { #b = 1; }` |
+| `classPrivateMethods` ([proposal](https://github.com/tc39/proposal-private-methods)) | `class A { #c() {} }` |
 | `exportExtensions` ([proposal 1](https://github.com/leebyron/ecmascript-export-default-from)), ([proposal 2](https://github.com/leebyron/ecmascript-export-ns-from)) | Proposal 1: `export v from "mod"` Proposal 2: `export * as ns from "mod"` |
 | `asyncGenerators` ([proposal](https://github.com/tc39/proposal-async-iteration)) | `async function*() {}`, `for await (let a of b) {}` |
 | `functionBind` ([proposal](https://github.com/zenparsing/es-function-bind)) | `a::b`, `::console.log` |

ast/spec.md

@@ -90,6 +90,7 @@ These are the core Babylon AST node types.
 - [Classes](#classes)
   - [ClassBody](#classbody)
   - [ClassMethod](#classmethod)
+  - [ClassPrivateMethod](#classprivatemethod)
   - [ClassProperty](#classproperty)
   - [ClassPrivateProperty](#classprivateproperty)
   - [ClassDeclaration](#classdeclaration)
@@ -1032,7 +1033,7 @@ interface Class <: Node {
 ```js
 interface ClassBody <: Node {
   type: "ClassBody";
-  body: [ ClassMethod | ClassProperty | ClassPrivateProperty ];
+  body: [ ClassMethod | ClassPrivateMethod | ClassProperty | ClassPrivateProperty ];
 }
 ```
 
@@ -1049,6 +1050,18 @@ interface ClassMethod <: Function {
 }
 ```
 
+## ClassPrivateMethod
+
+```js
+interface ClassPrivateMethod <: Function {
+  type: "ClassPrivateMethod";
+  key: PrivateName;
+  kind: "method" | "get" | "set";
+  static: boolean;
+  decorators: [ Decorator ];
+}
+```
+
 ## ClassProperty
 
 ```js
@@ -1066,7 +1079,7 @@ interface ClassProperty <: Node {
 ```js
 interface ClassPrivateProperty <: Node {
   type: "ClassPrivateProperty";
-  key: Identifier;
+  key: PrivateName;
   value: Expression;
   static: boolean;
 }

scripts/test262_whitelist.txt

@@ -256,8 +256,6 @@ language/statements/class/definition/early-errors-class-method-await-in-formals.
 language/statements/class/strict-mode/with.js(default)
 language/statements/class/syntax/early-errors/class-body-has-direct-super-missing-class-heritage.js(default)
 language/statements/class/syntax/early-errors/class-body-has-direct-super-missing-class-heritage.js(strict mode)
-language/statements/class/syntax/early-errors/class-body-static-method-get-propname-prototype.js(default)
-language/statements/class/syntax/early-errors/class-body-static-method-get-propname-prototype.js(strict mode)
 language/statements/class/syntax/early-errors/class-definition-evaluation-block-duplicate-binding.js(default)
 language/statements/class/syntax/early-errors/class-definition-evaluation-block-duplicate-binding.js(strict mode)
 language/statements/class/syntax/early-errors/class-definition-evaluation-scriptbody-duplicate-binding.js(default)
@@ -1305,4 +1303,4 @@ language/statements/class/fields-wrapped-in-sc-string-literal-names.js(strict mo
 
 language/statements/labeled/let-identifier-with-newline.js(default)
 language/statements/labeled/value-yield-non-strict-escaped.js(default)
-language/statements/let/syntax/escaped-let.js(default)
+language/statements/let/syntax/escaped-let.js(default)

src/parser/expression.js

@@ -1398,20 +1398,30 @@ export default class ExpressionParser extends LValParser {
   }
 
   parsePropertyName(
-    prop: N.ObjectOrClassMember | N.TsNamedTypeElementBase,
-  ): N.Expression {
+    prop:
+      | N.ObjectOrClassMember
+      | N.ClassPrivateProperty
+      | N.ClassPrivateMethod
+      | N.TsNamedTypeElementBase,
+  ): N.Expression | N.Identifier {
     if (this.eat(tt.bracketL)) {
       prop.computed = true;
       prop.key = this.parseMaybeAssign();
       this.expect(tt.bracketR);
     } else {
-      prop.computed = false;
       const oldInPropertyName = this.state.inPropertyName;
       this.state.inPropertyName = true;
+      // We check if it's valid for it to be a private name when we push it.
       prop.key =
         this.match(tt.num) || this.match(tt.string)
           ? this.parseExprAtom()
-          : this.parseIdentifier(true);
+          : this.parseMaybePrivateName();
+
+      if (prop.key.type !== "PrivateName") {
+        // ClassPrivateProperty is never computed, so we don't assign in that case.
+        prop.computed = false;
+      }
+
       this.state.inPropertyName = oldInPropertyName;
     }