Disallow escape sequences in contextual keywords (#9618)

* Disallow escape sequences in async

* Disallow escape sequences in get, set and async in class

* invalid escape tests

* Update whitelist

* tests for async in parens

* Add test for invalid newline between params and arrow

* Move canInsertSemilcolon() into shouldPArseAsyncArrow

packages/babel-parser/src/plugins/flow.js

@@ -2619,6 +2619,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       startLoc: Position,
       noCalls: ?boolean,
       subscriptState: N.ParseSubscriptState,
+      maybeAsyncArrow: boolean,
     ): N.Expression {
       if (this.match(tt.questionDot) && this.isLookaheadRelational("<")) {
         this.expectPlugin("optionalChaining");
@@ -2671,6 +2672,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         startLoc,
         noCalls,
         subscriptState,
+        maybeAsyncArrow,
       );
     }
 

packages/babel-parser/src/plugins/typescript.js

@@ -1498,6 +1498,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       startLoc: Position,
       noCalls: ?boolean,
       state: N.ParseSubscriptState,
+      maybeAsyncArrow: boolean,
     ): N.Expression {
       if (!this.hasPrecedingLineBreak() && this.match(tt.bang)) {
         this.state.exprAllowed = false;
@@ -1560,7 +1561,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         if (result) return result;
       }
 
-      return super.parseSubscript(base, startPos, startLoc, noCalls, state);
+      return super.parseSubscript(
+        base,
+        startPos,
+        startLoc,
+        noCalls,
+        state,
+        maybeAsyncArrow,
+      );
     }
 
     parseNewArguments(node: N.NewExpression): void {