Fix minor ParenthesizedExpression-related issues (#1277)

And run test262 test suite with preserveParens enabled

FIX: Fix a bug where some invalid `delete` expressions were let through when the operand
was parenthesized and `preserveParens` was enabled.

acorn/src/expression.js

@@ -242,8 +242,7 @@ pp.parseMaybeUnary = function(refDestructuringErrors, sawUnary, incDec, forInit)
     node.argument = this.parseMaybeUnary(null, true, update, forInit)
     this.checkExpressionErrors(refDestructuringErrors, true)
     if (update) this.checkLValSimple(node.argument)
-    else if (this.strict && node.operator === "delete" &&
-             node.argument.type === "Identifier")
+    else if (this.strict && node.operator === "delete" && isLocalVariableAccess(node.argument))
       this.raiseRecoverable(node.start, "Deleting local variable in strict mode")
     else if (node.operator === "delete" && isPrivateFieldAccess(node.argument))
       this.raiseRecoverable(node.start, "Private fields can not be deleted")
@@ -278,10 +277,18 @@ pp.parseMaybeUnary = function(refDestructuringErrors, sawUnary, incDec, forInit)
   }
 }
 
+function isLocalVariableAccess(node) {
+  return (
+    node.type === "Identifier" ||
+    node.type === "ParenthesizedExpression" && isLocalVariableAccess(node.expression)
+  )
+}
+
 function isPrivateFieldAccess(node) {
   return (
     node.type === "MemberExpression" && node.property.type === "PrivateIdentifier" ||
-    node.type === "ChainExpression" && isPrivateFieldAccess(node.expression)
+    node.type === "ChainExpression" && isPrivateFieldAccess(node.expression) ||
+    node.type === "ParenthesizedExpression" && isPrivateFieldAccess(node.expression)
   )
 }
 

bin/run_test262.js

@@ -10,7 +10,7 @@ function loadList(filename) {
 }
 
 run(
-  (content, {sourceType}) => parse(content, {sourceType, ecmaVersion: "latest"}),
+  (content, {sourceType}) => parse(content, {sourceType, ecmaVersion: "latest", preserveParens: true}),
   {
     testsDirectory: path.dirname(require.resolve("test262/package.json")),
     skip: test => test.attrs.features &&