Polish parser errors (#12258)

* polish: update AwaitNotInAsyncFunction message

* polish: update YieldInParameter error message

* Apply suggestions from code review

Co-authored-by: Brian Ng <bng412@gmail.com>

* update test fixtures

Co-authored-by: Brian Ng <bng412@gmail.com>

packages/babel-parser/src/parser/error-message.js

@@ -16,8 +16,9 @@ export const ErrorMessages = Object.freeze({
     "Can not use 'await' as identifier inside an async function",
   AwaitExpressionFormalParameter:
     "await is not allowed in async function parameters",
-  AwaitNotInAsyncFunction:
-    "Can not use keyword 'await' outside an async function",
+  AwaitNotInAsyncContext:
+    "'await' is only allowed within async functions and at the top levels of modules",
+  AwaitNotInAsyncFunction: "'await' is only allowed within async functions",
   BadGetterArity: "getter must not have any formal parameters",
   BadSetterArity: "setter must have exactly one formal parameter",
   BadSetterRestParameter:
@@ -210,7 +211,7 @@ export const ErrorMessages = Object.freeze({
   VarRedeclaration: "Identifier '%0' has already been declared",
   YieldBindingIdentifier:
     "Can not use 'yield' as identifier inside a generator",
-  YieldInParameter: "yield is not allowed in generator parameters",
+  YieldInParameter: "Yield expression is not allowed in formal parameters",
   ZeroDigitNumericSeparator:
     "Numeric separator can not be used after leading 0",
 });

packages/babel-parser/src/parser/expression.js

@@ -2343,7 +2343,12 @@ export default class ExpressionParser extends LValParser {
 
     if (reservedTest(word, this.inModule)) {
       if (!this.prodParam.hasAwait && word === "await") {
-        this.raise(startLoc, Errors.AwaitNotInAsyncFunction);
+        this.raise(
+          startLoc,
+          this.hasPlugin("topLevelAwait")
+            ? Errors.AwaitNotInAsyncContext
+            : Errors.AwaitNotInAsyncFunction,
+        );
       } else {
         this.raise(startLoc, Errors.UnexpectedReservedWord, word);
       }