Revert of Merged: Disallow tail calls from async functions and generators

test/mjsunit/es8/syntactic-tail-call-parsing.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --allow-natives-syntax --harmony-explicit-tailcalls
-// Flags: --harmony-do-expressions --harmony-async-await
+// Flags: --harmony-do-expressions
 "use strict";
 
 var SyntaxErrorTests = [
   { msg: "Unexpected expression inside tail call",
     tests: [
       { src: `()=>{ return continue  foo ; }`,
         err: `                       ^^^`,
       },
       { src: `()=>{ return  continue 42 ; }`,
         err: `                       ^^`,
@@ skipping 104 matching lines @@
       { src: `()=>{ return bar instanceof continue foo() ; }`,
         err: `                            ^^^^^^^^^^^^^^`,
       },
       { src: `()=>{ return continue foo() in bar ; }`,
         err: `             ^^^^^^^^^^^^^^`,
       },
       { src: `()=>{ return bar in continue foo() ; }`,
         err: `                    ^^^^^^^^^^^^^^`,
       },
       { src: `()=>{ function* G() { yield continue foo(); } }`,
-        err: `                                     ^^^^^`,
-      },
-      { src: `()=>{ function* G() { return continue foo(); } }`,
-        err: `                                      ^^^^^`,
+        err: `                            ^^^^^^^^^^^^^^`,
       },
       { src: `()=>{ (1, 2, 3, continue f() ) => {} }`,
         err: `                ^^^^^^^^^^^^`,
       },
       { src: `()=>{ (... continue f()) => {}  }`,
         err: `           ^^^^^^^^^^^^`,
       },
       { src: `()=>{ (a, b, c, ... continue f() ) => {}  }`,
         err: `                    ^^^^^^^^^^^^`,
       },
@@ skipping 86 matching lines @@
       },
       { src: `()=>{ const c = continue  foo() }`,
         err: `                ^^^^^^^^^^^^^^^`,
       },
       { src: `class A {}; class B extends A { constructor() { return continue foo () ; } }`,
         err: `                                                       ^^^^^^^^^^^^^^^`,
       },
       { src: `class A extends continue f () {}; }`,
         err: `                ^^^^^^^^^^^^^`,
       },
-      { src: `async() => continue foo()`,
-        err: `                    ^^^^^`,
-      },
     ],
   },
   { msg: "Tail call expression in try block",
     tests: [
       { src: `()=>{ try { return  continue   f ( ) ; } catch(e) {} }`,
         err: `                    ^^^^^^^^^^^^^^^^`,
       },
       { src: `()=>{ try { try { smth; } catch(e) { return  continue  f( ) ; } }`,
         err: `                                             ^^^^^^^^^^^^^^`,
       },
@@ skipping 56 matching lines @@
   `()=>{ return continue  a.b.c.foo () ; }`,
   `()=>{ return continue  a().b.c().d.foo () ; }`,
   `()=>{ return continue  foo (1)(2)(3, 4) ; }`,
   `()=>{ return continue (0, eval)(); }`,
   `()=>{ return ( continue b() ) ; }`,
   "()=>{ return continue bar`ab cd ef` ; }",
   "()=>{ return continue bar`ab ${cd} ef` ; }",
   `()=>{ return a || continue f() ; }`,
   `()=>{ return a && continue f() ; }`,
   `()=>{ return a , continue f() ; }`,
+  `()=>{ function* G() { return continue foo(); } }`,
   `()=>{ class A { foo() { return continue super.f() ; } } }`,
   `()=>{ function B() { return continue new.target() ; } }`,
   `()=>{ return continue do { x ? foo() : bar() ; }() }`,
   `()=>{ return continue (do { x ? foo() : bar() ; })() }`,
   `()=>{ return do { 1, continue foo() } }`,
   `()=>{ return do { x ? continue foo() : y } }`,
   `()=>{ return a || (b && continue c()); }`,
   `()=>{ return a && (b || continue c()); }`,
   `()=>{ return a || (b ? c : continue d()); }`,
   `()=>{ return 1, 2, 3, a || (b ? c : continue d()); }`,
@@ skipping 54 matching lines @@
 (function() {
   for (var src of NoErrorTests) {
     print("=======================================");
     print("Source   | " + src);
     src = `"use strict"; ` + src;
     Realm.eval(0, src);
     print("PASSED");
     print();
   }
 })();