Make allowAwaitOutsideFunction more accurate

Fixes an issue where class field initializers could contain await expressions
when the option was enabled, and makes the ecmaVersion >= 13 behavior only
apply to module sources.

Closes #1048

Author: marijnh

acorn-loose/src/expression.js

@@ -113,8 +113,8 @@ lp.parseExprOp = function(left, start, minPrec, noIn, indent, line) {
 lp.parseMaybeUnary = function(sawUnary) {
   let start = this.storeCurrentPos(), expr
   if (this.options.ecmaVersion >= 8 && this.toks.isContextual("await") &&
-    (this.inAsync || (!this.inFunction && this.options.allowAwaitOutsideFunction))
-  ) {
+      (this.inAsync || (this.toks.inModule && this.options.ecmaVersion >= 13) ||
+       (!this.inFunction && this.options.allowAwaitOutsideFunction))) {
     expr = this.parseAwait()
     sawUnary = true
   } else if (this.tok.type.prefix) {

acorn/src/expression.js

@@ -225,7 +225,7 @@ pp.buildBinary = function(startPos, startLoc, left, right, op, logical) {
 
 pp.parseMaybeUnary = function(refDestructuringErrors, sawUnary, incDec) {
   let startPos = this.start, startLoc = this.startLoc, expr
-  if (this.isContextual("await") && (this.inAsync || (!this.inFunction && this.options.allowAwaitOutsideFunction))) {
+  if (this.isContextual("await") && this.canAwait) {
     expr = this.parseAwait()
     sawUnary = true
   } else if (this.type.prefix) {

acorn/src/options.js

@@ -119,8 +119,6 @@ export function getOptions(opts) {
 
   if (options.allowReserved == null)
     options.allowReserved = options.ecmaVersion < 5
-  if (options.allowAwaitOutsideFunction == null)
-    options.allowAwaitOutsideFunction = options.ecmaVersion >= 13
 
   if (isArray(options.onToken)) {
     let tokens = options.onToken

acorn/src/scopeflags.js

@@ -8,7 +8,8 @@ export const
     SCOPE_ARROW = 16,
     SCOPE_SIMPLE_CATCH = 32,
     SCOPE_SUPER = 64,
-    SCOPE_DIRECT_SUPER = 128
+    SCOPE_DIRECT_SUPER = 128,
+    SCOPE_CLASS = 256
 
 export function functionFlags(async, generator) {
   return SCOPE_FUNCTION | (async ? SCOPE_ASYNC : 0) | (generator ? SCOPE_GENERATOR : 0)

acorn/src/state.js

@@ -3,7 +3,10 @@ import {types as tt} from "./tokentype.js"
 import {lineBreak} from "./whitespace.js"
 import {getOptions} from "./options.js"
 import {wordsRegexp} from "./util.js"
-import {SCOPE_TOP, SCOPE_FUNCTION, SCOPE_ASYNC, SCOPE_GENERATOR, SCOPE_SUPER, SCOPE_DIRECT_SUPER} from "./scopeflags.js"
+import {
+  SCOPE_TOP, SCOPE_FUNCTION, SCOPE_ASYNC, SCOPE_CLASS, SCOPE_GENERATOR,
+  SCOPE_SUPER, SCOPE_DIRECT_SUPER
+} from "./scopeflags.js"
 
 export class Parser {
   constructor(options, input, startPos) {
@@ -100,6 +103,14 @@ 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 inAsync() { return (this.currentVarScope().flags & SCOPE_ASYNC) > 0 && !this.currentVarScope().inClassFieldInit }
+  get canAwait() {
+    for (let i = this.scopeStack.length - 1; i >= 0; i--) {
+      let {flags} = this.scopeStack[i]
+      if (flags & SCOPE_FUNCTION) return (flags & SCOPE_ASYNC) > 0
+      if (flags & SCOPE_CLASS) return false
+    }
+    return (this.inModule && this.options.ecmaVersion >= 13) || this.options.allowAwaitOutsideFunction
+  }
   get allowSuper() {
     const {flags, inClassFieldInit} = this.currentThisScope()
     return (flags & SCOPE_SUPER) > 0 || inClassFieldInit || this.options.allowSuperOutsideMethod

acorn/src/statement.js

@@ -4,7 +4,10 @@ import {lineBreak, skipWhiteSpace} from "./whitespace.js"
 import {isIdentifierStart, isIdentifierChar, keywordRelationalOperator} from "./identifier.js"
 import {has} from "./util.js"
 import {DestructuringErrors} from "./parseutil.js"
-import {functionFlags, SCOPE_SIMPLE_CATCH, BIND_SIMPLE_CATCH, BIND_LEXICAL, BIND_VAR, BIND_FUNCTION} from "./scopeflags.js"
+import {
+  functionFlags, SCOPE_SIMPLE_CATCH, SCOPE_CLASS, BIND_SIMPLE_CATCH,
+  BIND_LEXICAL, BIND_VAR, BIND_FUNCTION
+} from "./scopeflags.js"
 
 const pp = Parser.prototype
 
@@ -209,7 +212,7 @@ pp.parseDoStatement = function(node) {
 
 pp.parseForStatement = function(node) {
   this.next()
-  let awaitAt = (this.options.ecmaVersion >= 9 && (this.inAsync || (!this.inFunction && this.options.allowAwaitOutsideFunction)) && this.eatContextual("await")) ? this.lastTokStart : -1
+  let awaitAt = (this.options.ecmaVersion >= 9 && this.canAwait && this.eatContextual("await")) ? this.lastTokStart : -1
   this.labels.push(loopLabel)
   this.enterScope(0)
   this.expect(tt.parenL)
@@ -581,6 +584,7 @@ pp.parseClass = function(node, isStatement) {
   let hadConstructor = false
   classBody.body = []
   this.expect(tt.braceL)
+  this.enterScope(SCOPE_CLASS)
   while (this.type !== tt.braceR) {
     const element = this.parseClassElement(node.superClass !== null)
     if (element) {
@@ -597,6 +601,7 @@ pp.parseClass = function(node, isStatement) {
   this.next()
   node.body = this.finishNode(classBody, "ClassBody")
   this.exitClassBody()
+  this.exitScope()
   return this.finishNode(node, isStatement ? "ClassDeclaration" : "ClassExpression")
 }
 

test/tests-await-top-level.js

@@ -59,7 +59,7 @@ test("await 1", {
       }
     }
   ]
-}, {ecmaVersion: 13})
+}, {ecmaVersion: 13, sourceType: "module"})
 testFail("function foo() {return await 1}", "Unexpected token (1:29)", {ecmaVersion: 13})
 testFail("await 1", "Unexpected token (1:6)", {
   allowAwaitOutsideFunction: false,