Disallow in script

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -3975,7 +3975,7 @@ You should consider suppressing the warning only if you're sure that you don't w
     <value>Cannot declare namespace in script code</value>
   </data>
   <data name="ERR_GlobalAttributesNotAllowed" xml:space="preserve">
-    <value>Assembly and module attributes are not allowed in this context</value>
+    <value>Assembly, module, and main attributes are not allowed in this context</value>
   </data>
   <data name="ERR_InvalidDelegateType" xml:space="preserve">
     <value>Delegate '{0}' has no invoke method or an invoke method with a return type or parameter types that are not supported.</value>

src/Compilers/CSharp/Portable/Symbols/Symbol_Attributes.cs

@@ -551,6 +551,7 @@ private static bool MatchAttributeTarget(IAttributeTargetSymbol attributeTarget,
                         {
                             case AttributeLocation.Assembly:
                             case AttributeLocation.Module:
+                            case AttributeLocation.Main:
                                 // global attributes are disallowed in interactive code:
                                 diagnostics.Add(ErrorCode.ERR_GlobalAttributesNotAllowed, targetOpt.Identifier.GetLocation());
                                 break;

src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests.cs

@@ -5194,6 +5194,24 @@ public class MyAttribute : Attribute {{ public MyAttribute(string name) {{}} }}
                 });
         }
 
+        [Fact]
+        public void TestMainAttributesInScript()
+        {
+            var compilation = CreateSubmission(@"
+using System;
+[main: My(""one"")]
+
+public class C {}
+public class MyAttribute : Attribute { public MyAttribute(string name) {} }",
+            parseOptions: TestOptions.Script.WithLanguageVersion(LanguageVersion.Preview));
+
+            compilation.VerifyDiagnostics(
+                // (3,2): error CS7026: Assembly and module attributes are not allowed in this context
+                // [main: My("one")]
+                Diagnostic(ErrorCode.ERR_GlobalAttributesNotAllowed, "main").WithLocation(3, 2)
+                );
+        }
+
         #endregion
 
         #region Error Tests