Allow 'await' at start of statement in Script

src/Compilers/CSharp/Portable/Parser/LanguageParser.cs

@@ -428,7 +428,7 @@ private NamespaceDeclarationSyntax ParseNamespaceDeclaration()
             Debug.Assert(this.CurrentToken.Kind == SyntaxKind.NamespaceKeyword);
             var namespaceToken = this.EatToken(SyntaxKind.NamespaceKeyword);
 
-            if (IsScript || IsInteractive)
+            if (IsScriptOrInteractive)
             {
                 namespaceToken = this.AddError(namespaceToken, ErrorCode.ERR_NamespaceNotAllowedInScript);
             }
@@ -592,7 +592,7 @@ private void ParseNamespaceBody(ref SyntaxToken openBrace, ref NamespaceBodyBuil
             Debug.Assert(!IsInAsync);
 
             bool isGlobal = openBrace == null;
-            bool isGlobalScript = isGlobal && this.IsScript;
+            bool isGlobalScript = isGlobal && this.IsScriptOrInteractive;
 
             var saveTerm = _termState;
             _termState |= TerminatorState.IsNamespaceMemberStartOrStop;
@@ -629,7 +629,7 @@ private void ParseNamespaceBody(ref SyntaxToken openBrace, ref NamespaceBodyBuil
 
                                 var token = this.EatToken();
                                 token = this.AddError(token,
-                                    IsScript ? ErrorCode.ERR_GlobalDefinitionOrStatementExpected : ErrorCode.ERR_EOFExpected);
+                                    IsScriptOrInteractive ? ErrorCode.ERR_GlobalDefinitionOrStatementExpected : ErrorCode.ERR_EOFExpected);
 
                                 this.AddSkippedNamespaceText(ref openBrace, ref body, ref initialBadNodes, token);
                                 reportUnexpectedToken = true;
@@ -738,7 +738,7 @@ private void ParseNamespaceBody(ref SyntaxToken openBrace, ref NamespaceBodyBuil
                                 if (reportUnexpectedToken && !skippedToken.ContainsDiagnostics)
                                 {
                                     skippedToken = this.AddError(skippedToken,
-                                        IsScript ? ErrorCode.ERR_GlobalDefinitionOrStatementExpected : ErrorCode.ERR_EOFExpected);
+                                        IsScriptOrInteractive ? ErrorCode.ERR_GlobalDefinitionOrStatementExpected : ErrorCode.ERR_EOFExpected);
 
                                     // do not report the error multiple times for subsequent tokens:
                                     reportUnexpectedToken = false;
@@ -2230,7 +2230,7 @@ private MemberDeclarationSyntax ParseMemberDeclarationOrStatement(SyntaxKind par
 
             cancellationToken.ThrowIfCancellationRequested();
 
-            bool isGlobalScript = parentKind == SyntaxKind.CompilationUnit && this.IsScript;
+            bool isGlobalScript = parentKind == SyntaxKind.CompilationUnit && this.IsScriptOrInteractive;
             bool acceptStatement = isGlobalScript;
 
             // don't reuse members if they were previously declared under a different type keyword kind
@@ -2498,7 +2498,7 @@ private MemberDeclarationSyntax ParseMemberDeclarationOrStatement(SyntaxKind par
                         return incompleteMember;
                     }
                     else if (parentKind == SyntaxKind.NamespaceDeclaration ||
-                             parentKind == SyntaxKind.CompilationUnit && !IsScript)
+                             parentKind == SyntaxKind.CompilationUnit && !IsScriptOrInteractive)
                     {
                         return this.AddErrorToLastToken(incompleteMember, ErrorCode.ERR_NamespaceUnexpected);
                     }
@@ -4520,7 +4520,7 @@ private void ParseVariableDeclarators(TypeSyntax type, VariableFlags flags, Sepa
             // the reported errors should take into consideration whether or not one expects them in the current context.
             bool variableDeclarationsExpected =
                 parentKind != SyntaxKind.NamespaceDeclaration &&
-                (parentKind != SyntaxKind.CompilationUnit || IsScript);
+                (parentKind != SyntaxKind.CompilationUnit || IsScriptOrInteractive);
 
             ParseVariableDeclarators(type, flags, variables, variableDeclarationsExpected);
         }
@@ -8231,7 +8231,7 @@ private static bool IsExpectedAssignmentOperator(SyntaxKind kind)
 
         private bool IsPossibleAwaitExpressionStatement()
         {
-            return (this.IsInteractive || this.IsInAsync) && this.CurrentToken.ContextualKind == SyntaxKind.AwaitKeyword;
+            return (this.IsScriptOrInteractive || this.IsInAsync) && this.CurrentToken.ContextualKind == SyntaxKind.AwaitKeyword;
         }
 
         private bool IsAwaitExpression()

src/Compilers/CSharp/Portable/Parser/SyntaxParser.cs

@@ -191,11 +191,11 @@ public bool IsInteractive
         }
 
         /// <summary>
-        /// Script - global statements and member declarations allowed, but not expressions.
+        /// Script or interactive - global statements, member declarations, and expressions allowed.
         /// </summary>
-        public bool IsScript
+        public bool IsScriptOrInteractive
         {
-            get { return Options.Kind != SourceCodeKind.Regular; }
+            get { return (Options.Kind == SourceCodeKind.Script) || (Options.Kind == SourceCodeKind.Interactive); }
         }
 
         protected LexerMode Mode

src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncTests.cs

@@ -3605,7 +3605,6 @@ public static Task<T> GetValue<T>()
             CompileAndVerify(comp.WithOptions(TestOptions.ReleaseExe), expectedOutput: "0");
         }
 
-
         [Fact]
         public void AwaitInScriptExpression()
         {
@@ -3615,6 +3614,15 @@ public void AwaitInScriptExpression()
             compilation.VerifyDiagnostics();
         }
 
+        [Fact]
+        public void AwaitInScriptGlobalStatement()
+        {
+            var source =
+@"await System.Threading.Tasks.Task.FromResult(4);";
+            var compilation = CreateCompilationWithMscorlib45(source, parseOptions: TestOptions.Script, options: TestOptions.DebugExe);
+            compilation.VerifyDiagnostics();
+        }
+
         [Fact]
         public void AwaitInScriptDeclaration()
         {
@@ -3641,6 +3649,16 @@ public void AwaitInInteractiveExpression()
             s1.VerifyDiagnostics();
         }
 
+        [Fact]
+        public void AwaitInInteractiveGlobalStatement()
+        {
+            var references = new[] { MscorlibRef_v4_0_30316_17626, SystemCoreRef };
+            var source0 =
+@"await System.Threading.Tasks.Task.FromResult(5);";
+            var s0 = CSharpCompilation.CreateSubmission("s0.dll", SyntaxFactory.ParseSyntaxTree(source0, options: TestOptions.Interactive), references);
+            s0.VerifyDiagnostics();
+        }
+
         [Fact]
         public void AwaitInInteractiveDeclaration()
         {
@@ -3731,7 +3749,6 @@ static void M(int input)
         }
         catch (Exception)
         {
-
         }
     }
 }
@@ -3775,7 +3792,7 @@ public void SwitchOnAwaitedValueString()
 using System;
 
 class Program
-    {
+{
     static void Main()
     {
         M(0).Wait();
@@ -3792,7 +3809,7 @@ static async Task M(int input)
                 return;
         }
     }
-    }
+}
 ";
             var comp = CreateCompilation(source, options: TestOptions.DebugExe);
             CompileAndVerify(comp);