Further refine handling of await in class fields

FIX: Properly allow await inside an async arrow function inside a class field
initializer.

Issue #1338

Author: marijnh

acorn/src/expression.js

@@ -1043,7 +1043,7 @@ pp.checkUnreserved = function({start, end, name}) {
     this.raiseRecoverable(start, "Cannot use 'yield' as identifier inside a generator")
   if (this.inAsync && name === "await")
     this.raiseRecoverable(start, "Cannot use 'await' as identifier inside an async function")
-  if (this.currentThisScope().inClassFieldInit && name === "arguments")
+  if (this.currentScope().inClassFieldInit && name === "arguments")
     this.raiseRecoverable(start, "Cannot use 'arguments' in class field initializer")
   if (this.inClassStaticBlock && (name === "arguments" || name === "await"))
     this.raise(start, `Cannot use ${name} in class static initialization block`)

acorn/src/state.js

@@ -99,15 +99,14 @@ export class Parser {
 
   get inFunction() { return (this.currentVarScope().flags & SCOPE_FUNCTION) > 0 }
 
-  get inGenerator() { return (this.currentVarScope().flags & SCOPE_GENERATOR) > 0 && !this.currentVarScope().inClassFieldInit }
+  get inGenerator() { return (this.currentVarScope().flags & SCOPE_GENERATOR) > 0 && !this.currentScope().inClassFieldInit }
 
-  get inAsync() { return (this.currentVarScope().flags & SCOPE_ASYNC) > 0 && !this.currentVarScope().inClassFieldInit }
+  get inAsync() { return (this.currentScope().flags & SCOPE_ASYNC) > 0 && !this.currentScope().inClassFieldInit }
 
   get canAwait() {
-    if (this.currentThisScope().inClassFieldInit) return false
     for (let i = this.scopeStack.length - 1; i >= 0; i--) {
       let scope = this.scopeStack[i]
-      if (scope.flags & SCOPE_CLASS_STATIC_BLOCK) return false
+      if (scope.flags & SCOPE_CLASS_STATIC_BLOCK || scope.inClassFieldInit) return false
       if (scope.flags & SCOPE_FUNCTION) return (scope.flags & SCOPE_ASYNC) > 0
     }
     return (this.inModule && this.options.ecmaVersion >= 13) || this.options.allowAwaitOutsideFunction
@@ -123,8 +122,8 @@ export class Parser {
   get treatFunctionsAsVar() { return this.treatFunctionsAsVarInScope(this.currentScope()) }
 
   get allowNewDotTarget() {
-    const {flags, inClassFieldInit} = this.currentThisScope()
-    return (flags & (SCOPE_FUNCTION | SCOPE_CLASS_STATIC_BLOCK)) > 0 || inClassFieldInit
+    const {flags} = this.currentThisScope()
+    return (flags & (SCOPE_FUNCTION | SCOPE_CLASS_STATIC_BLOCK)) > 0 || this.currentScope().inClassFieldInit
   }
 
   get inClassStaticBlock() {

acorn/src/statement.js

@@ -742,7 +742,7 @@ pp.parseClassField = function(field) {
 
   if (this.eat(tt.eq)) {
     // To raise SyntaxError if 'arguments' exists in the initializer.
-    const scope = this.currentThisScope()
+    const scope = this.currentScope()
     const inClassFieldInit = scope.inClassFieldInit
     scope.inClassFieldInit = true
     field.value = this.parseMaybeAssign()

test/tests-asyncawait.js

@@ -3541,4 +3541,11 @@ testFail("4 + async() => 2", "Unexpected token (1:12)", {ecmaVersion: 8, loose:
 
 testFail("async function𝐬 f() {}", "Unexpected token (1:17)", {ecmaVersion: 8})
 
-testFail("async () => class { x = await 1 }", "Cannot use 'await' as identifier inside an async function (1:24)", {ecmaVersion: 2024})
+testFail("async () => class { x = await 1 }", "Unexpected token (1:30)", {ecmaVersion: 2024})
+
+test("async () => class { x = async () => await 1 }", {}, {ecmaVersion: 2024})
+
+test("async () => class { x = await }", {}, {ecmaVersion: 2024})
+
+testFail("async () => class { x = await }", "Cannot use keyword 'await' outside an async function (1:24)",
+         {ecmaVersion: 2024, sourceType: "module"})