Support ES2022 class-private-fields-in syntax (#1068)

FIX #1067 FEATURE: Support class private fields with the `in` operator. Co-authored-by: 成仕伟 <chengsw@heywhale.com>

Author: Lucian-4a25

acorn-loose/src/expression.js

@@ -131,6 +131,8 @@ lp.parseMaybeUnary = function(sawUnary) {
  this.next()
  node.argument = this.parseMaybeUnary(sawUnary)
  expr = this.finishNode(node, "SpreadElement")
+ } else if (!sawUnary && this.tok.type === tt.privateId) {
+ expr = this.parsePrivateIdent()
  } else {
  expr = this.parseExprSubscripts()
  while (this.tok.type.postfix && !this.canInsertSemicolon()) {

acorn/src/expression.js

@@ -215,6 +215,7 @@ pp.parseExprOp = function(left, leftStartPos, leftStartLoc, minPrec, forInit) {
 }
 
 pp.buildBinary = function(startPos, startLoc, left, right, op, logical) {
+ if (right.type === "PrivateIdentifier") this.raise(right.start, "Private identifier can only be left side of binary expression")
  let node = this.startNodeAt(startPos, startLoc)
  node.left = left
  node.operator = op
@@ -244,6 +245,11 @@ pp.parseMaybeUnary = function(refDestructuringErrors, sawUnary, incDec, forInit)
  this.raiseRecoverable(node.start, "Private fields can not be deleted")
  else sawUnary = true
  expr = this.finishNode(node, update ? "UpdateExpression" : "UnaryExpression")
+ } else if (!sawUnary && this.type === tt.privateId) {
+ if (forInit || this.privateNameStack.length === 0) this.unexpected()
+ expr = this.parsePrivateIdent()
+ // only could be private fields in 'in', such as #x in obj
+ if (this.type !== tt._in) this.unexpected()
  } else {
  expr = this.parseExprSubscripts(refDestructuringErrors, forInit)
  if (this.checkExpressionErrors(refDestructuringErrors)) return expr

bin/run_test262.js

@@ -6,7 +6,6 @@ const parse = require("../acorn").parse
 const unsupportedFeatures = [
  "regexp-match-indices",
  "arbitrary-module-namespace-names",
- "class-fields-private-in",
  "import-assertions"
 ];