Fixed a crash when parsing invalid decorator on await expression

Author: Andarist

src/compiler/parser.ts

@@ -7677,7 +7677,9 @@ namespace Parser {
                 flags |= NodeFlags.Using;
                 break;
             case SyntaxKind.AwaitKeyword:
-                Debug.assert(isAwaitUsingDeclaration());
+                if (!isAwaitUsingDeclaration()) {
+                    break;
+                }
                 flags |= NodeFlags.AwaitUsing;
                 nextToken();
                 break;

tests/baselines/reference/decoratorOnAwait.errors.txt

@@ -0,0 +1,11 @@
+decoratorOnAwait.ts(4,7): error TS1134: Variable declaration expected.
+
+
+==== decoratorOnAwait.ts (1 errors) ====
+    declare function dec<T>(target: T): T;
+    
+    @dec
+    await 1
+          ~
+!!! error TS1134: Variable declaration expected.
+    

tests/baselines/reference/decoratorOnAwait.js

@@ -0,0 +1,12 @@
+//// [tests/cases/conformance/decorators/invalid/decoratorOnAwait.ts] ////
+
+//// [decoratorOnAwait.ts]
+declare function dec<T>(target: T): T;
+
+@dec
+await 1
+
+
+//// [decoratorOnAwait.js]
+var ;
+1;

tests/baselines/reference/decoratorOnAwait.symbols

@@ -0,0 +1,15 @@
+//// [tests/cases/conformance/decorators/invalid/decoratorOnAwait.ts] ////
+
+=== decoratorOnAwait.ts ===
+declare function dec<T>(target: T): T;
+>dec : Symbol(dec, Decl(decoratorOnAwait.ts, 0, 0))
+>T : Symbol(T, Decl(decoratorOnAwait.ts, 0, 21))
+>target : Symbol(target, Decl(decoratorOnAwait.ts, 0, 24))
+>T : Symbol(T, Decl(decoratorOnAwait.ts, 0, 21))
+>T : Symbol(T, Decl(decoratorOnAwait.ts, 0, 21))
+
+@dec
+>dec : Symbol(dec, Decl(decoratorOnAwait.ts, 0, 0))
+
+await 1
+

tests/baselines/reference/decoratorOnAwait.types

@@ -0,0 +1,17 @@
+//// [tests/cases/conformance/decorators/invalid/decoratorOnAwait.ts] ////
+
+=== decoratorOnAwait.ts ===
+declare function dec<T>(target: T): T;
+>dec : <T>(target: T) => T
+>    : ^ ^^      ^^ ^^^^^ 
+>target : T
+>       : ^
+
+@dec
+>dec : <T>(target: T) => T
+>    : ^ ^^      ^^ ^^^^^ 
+
+await 1
+>1 : 1
+>  : ^
+

tests/cases/conformance/decorators/invalid/decoratorOnAwait.ts

@@ -0,0 +1,4 @@
+declare function dec<T>(target: T): T;
+
+@dec
+await 1