Improve code in AssemblyKeywordRecommender -> IsValidContext

src/Features/CSharp/Portable/Completion/KeywordRecommenders/AssemblyKeywordRecommender.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System.Threading;
-using Microsoft.CodeAnalysis.CSharp.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders
 {
@@ -17,14 +15,21 @@ public AssemblyKeywordRecommender()
 
         protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
         {
-            if (context.IsTypeAttributeContextBefore(SyntaxKind.NamespaceKeyword, cancellationToken))
-            {
-                var token = context.LeftToken;
-                var type = token.GetAncestor<MemberDeclarationSyntax>();
+            var token = context.TargetToken;
 
-                return type == null || type.IsParentKind(SyntaxKind.CompilationUnit);
+            // Note that we pass the token.SpanStart to IsTypeDeclarationContext below. This is a bit subtle,
+            // but we want to be sure that the attribute itself (i.e. the open square bracket, '[') is in a
+            // type declaration context.
+            if (token.Kind() != SyntaxKind.OpenBracketToken)
+                return false;
+            if (token.Parent.Kind() == SyntaxKind.AttributeList)
+            {
+                var previousSyntax = token.GetPreviousToken().Parent;
+                return previousSyntax == null;
             }
-            return false;
+            var nextSyntax = token.GetNextToken().Parent;
+            var currentSyntax = token.Parent;
+            return nextSyntax is NamespaceDeclarationSyntax || currentSyntax is CompilationUnitSyntax;
         }
     }
 }

src/Workspaces/CSharp/Portable/Extensions/ContextQuery/CSharpSyntaxContext.cs

@@ -283,26 +283,6 @@ public bool IsTypeAttributeContext(CancellationToken cancellationToken)
             return false;
         }
 
-        public bool IsTypeAttributeContextBefore(SyntaxKind syntaxKind, CancellationToken cancellationToken)
-        {
-            // cases:
-            //    [ |
-            //    class C {
-            var token = TargetToken;
-
-            // Note that we pass the token.SpanStart to IsTypeDeclarationContext below. This is a bit subtle,
-            // but we want to be sure that the attribute itself (i.e. the open square bracket, '[') is in a
-            // type declaration context.
-            if (token.Kind() == SyntaxKind.OpenBracketToken &&
-                (token.GetNextToken().Kind() == syntaxKind || token.Parent.Kind() == SyntaxKind.AttributeList) &&
-                SyntaxTree.IsTypeDeclarationContext(
-                    token.SpanStart, contextOpt: null, validModifiers: null, validTypeDeclarations: SyntaxKindSet.ClassStructTypeDeclarations, canBePartial: false, cancellationToken: cancellationToken))
-            {
-                return true;
-            }
-
-            return false;
-        }
 
         public bool IsTypeDeclarationContext(
             ISet<SyntaxKind> validModifiers = null,