Simplify type checks.

src/Workspaces/CSharp/Portable/CodeGeneration/CSharpSyntaxGenerator.cs

@@ -2495,13 +2495,7 @@ public override SyntaxNode InsertAccessors(SyntaxNode declaration, int index, IE
         }
 
         internal static AccessorListSyntax GetAccessorList(SyntaxNode declaration)
-            => declaration switch
-            {
-                PropertyDeclarationSyntax property => property.AccessorList,
-                IndexerDeclarationSyntax indexer => indexer.AccessorList,
-                EventDeclarationSyntax @event => @event.AccessorList,
-                _ => null,
-            };
+            => (declaration as BasePropertyDeclarationSyntax)?.AccessorList;
 
         private static bool CanHaveAccessors(SyntaxNode declaration)
             => declaration.Kind() switch
@@ -2513,11 +2507,9 @@ private static bool CanHaveAccessors(SyntaxNode declaration)
             };
 
         private static SyntaxNode WithAccessorList(SyntaxNode declaration, AccessorListSyntax accessorList)
-            => declaration.Kind() switch
+            => declaration switch
             {
-                SyntaxKind.PropertyDeclaration => ((PropertyDeclarationSyntax)declaration).WithAccessorList(accessorList),
-                SyntaxKind.IndexerDeclaration => ((PropertyDeclarationSyntax)declaration).WithAccessorList(accessorList),
-                SyntaxKind.EventDeclaration => ((EventDeclarationSyntax)declaration).WithAccessorList(accessorList),
+                BasePropertyDeclarationSyntax baseProperty => baseProperty.WithAccessorList(accessorList),
                 _ => declaration,
             };
 

src/Workspaces/CSharp/Portable/SemanticModelReuse/CSharpSemanticModelReuseLanguageService.cs

@@ -22,6 +22,7 @@ namespace Microsoft.CodeAnalysis.CSharp.SemanticModelReuse
     internal class CSharpSemanticModelReuseLanguageService : AbstractSemanticModelReuseLanguageService<
         MemberDeclarationSyntax,
         BaseMethodDeclarationSyntax,
+        BasePropertyDeclarationSyntax,
         AccessorDeclarationSyntax>
     {
         [ImportingConstructor]
@@ -32,15 +33,15 @@ public CSharpSemanticModelReuseLanguageService()
 
         protected override ISyntaxFacts SyntaxFacts => CSharpSyntaxFacts.Instance;
 
-        protected override MemberDeclarationSyntax GetAccessorContainerDeclaration(AccessorDeclarationSyntax currentAccessor)
+        protected override BasePropertyDeclarationSyntax GetBasePropertyDeclaration(AccessorDeclarationSyntax accessor)
         {
-            Contract.ThrowIfFalse(currentAccessor.Parent is AccessorListSyntax);
-            Contract.ThrowIfFalse(currentAccessor.Parent.Parent is MemberDeclarationSyntax);
-            return (MemberDeclarationSyntax)currentAccessor.Parent.Parent;
+            Contract.ThrowIfFalse(accessor.Parent is AccessorListSyntax);
+            Contract.ThrowIfFalse(accessor.Parent.Parent is BasePropertyDeclarationSyntax);
+            return (BasePropertyDeclarationSyntax)accessor.Parent.Parent;
         }
 
-        protected override SyntaxList<AccessorDeclarationSyntax> GetAccessors(MemberDeclarationSyntax member)
-            => CSharpSyntaxGenerator.GetAccessorList(member).Accessors;
+        protected override SyntaxList<AccessorDeclarationSyntax> GetAccessors(BasePropertyDeclarationSyntax baseProperty)
+            => baseProperty.AccessorList.Accessors;
 
         public override SyntaxNode? TryGetContainingMethodBodyForSpeculation(SyntaxNode node)
         {

src/Workspaces/Core/Portable/SemanticModelReuse/AbstractSemanticModelReuseLanguageService.cs

@@ -15,9 +15,11 @@ namespace Microsoft.CodeAnalysis.SemanticModelReuse
     internal abstract class AbstractSemanticModelReuseLanguageService<
         TMemberDeclarationSyntax,
         TBaseMethodDeclarationSyntax,
+        TBasePropertyDeclarationSyntax,
         TAccessorDeclarationSyntax> : ISemanticModelReuseLanguageService
         where TMemberDeclarationSyntax : SyntaxNode
         where TBaseMethodDeclarationSyntax : TMemberDeclarationSyntax
+        where TBasePropertyDeclarationSyntax : TMemberDeclarationSyntax
         where TAccessorDeclarationSyntax : SyntaxNode
     {
         protected abstract ISyntaxFacts SyntaxFacts { get; }
@@ -25,8 +27,8 @@ internal abstract class AbstractSemanticModelReuseLanguageService<
         public abstract SyntaxNode? TryGetContainingMethodBodyForSpeculation(SyntaxNode node);
 
         protected abstract Task<SemanticModel?> TryGetSpeculativeSemanticModelWorkerAsync(SemanticModel previousSemanticModel, SyntaxNode currentBodyNode, CancellationToken cancellationToken);
-        protected abstract SyntaxList<TAccessorDeclarationSyntax> GetAccessors(TMemberDeclarationSyntax member);
-        protected abstract TMemberDeclarationSyntax GetAccessorContainerDeclaration(TAccessorDeclarationSyntax currentAccessor);
+        protected abstract SyntaxList<TAccessorDeclarationSyntax> GetAccessors(TBasePropertyDeclarationSyntax baseProperty);
+        protected abstract TBasePropertyDeclarationSyntax GetBasePropertyDeclaration(TAccessorDeclarationSyntax accessor);
 
         public Task<SemanticModel?> TryGetSpeculativeSemanticModelAsync(SemanticModel previousSemanticModel, SyntaxNode currentBodyNode, CancellationToken cancellationToken)
         {
@@ -45,10 +47,10 @@ protected SyntaxNode GetPreviousBodyNode(SyntaxNode previousRoot, SyntaxNode cur
                 // in the case of an accessor, have to find the previous accessor in the previous prop/event corresponding
                 // to the current prop/event.
 
-                var currentContainer = GetAccessorContainerDeclaration(currentAccessor);
+                var currentContainer = GetBasePropertyDeclaration(currentAccessor);
                 var previousContainer = GetPreviousBodyNode(previousRoot, currentRoot, currentContainer);
 
-                if (previousContainer is not TMemberDeclarationSyntax previousMember)
+                if (previousContainer is not TBasePropertyDeclarationSyntax previousMember)
                 {
                     Debug.Fail("Previous container didn't map back to a normal accessor container.");
                     return null;

src/Workspaces/VisualBasic/Portable/SemanticModelReuse/VisualBasicSemanticModelReuseLanguageService.vb

@@ -17,6 +17,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.SemanticModelReuse
         Inherits AbstractSemanticModelReuseLanguageService(Of
             DeclarationStatementSyntax,
             MethodBlockBaseSyntax,
+            DeclarationStatementSyntax,
             AccessorBlockSyntax)
 
         <ImportingConstructor>
@@ -26,8 +27,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.SemanticModelReuse
 
         Protected Overrides ReadOnly Property SyntaxFacts As ISyntaxFacts = VisualBasicSyntaxFacts.Instance
 
-        Protected Overrides Function GetAccessorContainerDeclaration(currentAccessor As AccessorBlockSyntax) As DeclarationStatementSyntax
-            Dim container = currentAccessor.Parent
+        Protected Overrides Function GetBasePropertyDeclaration(accessor As AccessorBlockSyntax) As DeclarationStatementSyntax
+            Dim container = accessor.Parent
             Contract.ThrowIfFalse(TypeOf container Is PropertyBlockSyntax OrElse
                                   TypeOf container Is EventBlockSyntax)
             Return DirectCast(container, DeclarationStatementSyntax)