Use pattern matching.

src/EditorFeatures/Core/GoToDefinition/GoToDefinitionHelpers.cs

@@ -37,14 +37,14 @@ internal static class GoToDefinitionHelpers
             // We can't go to the definition of the alias, so use the target type.
 
             var solution = project.Solution;
-            if (symbol is IAliasSymbol)
+            if (alias != null)
             {
                 var sourceLocations = NavigableItemFactory.GetPreferredSourceLocations(
                     solution, symbol, cancellationToken);
 
                 if (sourceLocations.All(l => project.Solution.GetDocument(l.SourceTree) == null))
                 {
-                    symbol = ((IAliasSymbol)symbol).Target;
+                    symbol = alias.Target;
                 }
             }
 
@@ -63,9 +63,9 @@ internal static class GoToDefinitionHelpers
 
             // If it is a partial method declaration with no body, choose to go to the implementation
             // that has a method body.
-            if (symbol is IMethodSymbol)
+            if (symbol is IMethodSymbol method)
             {
-                symbol = ((IMethodSymbol)symbol).PartialImplementationPart ?? symbol;
+                symbol = method.PartialImplementationPart ?? symbol;
             }
 
             var options = project.Solution.Options;

src/EditorFeatures/Core/Implementation/CallHierarchy/CallHierarchyProvider.cs

@@ -61,11 +61,10 @@ internal partial class CallHierarchyProvider
 
         private ISymbol GetTargetSymbol(ISymbol symbol)
         {
-            if (symbol is IMethodSymbol)
+            if (symbol is IMethodSymbol methodSymbol)
             {
-                var methodSymbol = (IMethodSymbol)symbol;
-                methodSymbol = methodSymbol.ReducedFrom != null ? methodSymbol.ReducedFrom : methodSymbol;
-                methodSymbol = methodSymbol.ConstructedFrom != null ? methodSymbol.ConstructedFrom : methodSymbol;
+                methodSymbol = methodSymbol.ReducedFrom ?? methodSymbol;
+                methodSymbol = methodSymbol.ConstructedFrom ?? methodSymbol;
                 return methodSymbol;
             }
 

src/EditorFeatures/Core/Implementation/Formatting/FormatCommandHandler.cs

@@ -135,9 +135,9 @@ public void ExecuteReturnOrTypeCommand(CommandArgs args, Action nextHandler, Can
                     return;
                 }
             }
-            else if (args is TypeCharCommandArgs)
+            else if (args is TypeCharCommandArgs typeCharArgs)
             {
-                var typedChar = ((TypeCharCommandArgs)args).TypedChar;
+                var typedChar = typeCharArgs.TypedChar;
                 if (!service.SupportsFormattingOnTypedCharacter(document, typedChar) ||
                     !TryFormat(textView, document, service, typedChar, caretPositionMarker, formatOnReturn: false, cancellationToken: cancellationToken))
                 {

src/EditorFeatures/Core/Implementation/IntelliSense/ViewTextSpan.cs

@@ -100,9 +100,8 @@ private static IEnumerable<Span> MapUpToSnapshotRecursive(SnapshotSpan start, IP
                         yield return result;
                     }
                 }
-                else if (source is IProjectionSnapshot)
+                else if (source is IProjectionSnapshot sourceProjection)
                 {
-                    var sourceProjection = source as IProjectionSnapshot;
                     foreach (var span in MapUpToSnapshotRecursive(start, sourceProjection))
                     {
                         foreach (var result in target.MapFromSourceSnapshot(new SnapshotSpan(source, span)))

src/EditorFeatures/Core/Implementation/KeywordHighlighting/AbstractKeywordHighlighter.cs

@@ -18,9 +18,9 @@ internal abstract class AbstractKeywordHighlighter<TNode> : IHighlighter
             {
                 for (var parent = token.Parent; parent != null; parent = parent.Parent)
                 {
-                    if (parent is TNode)
+                    if (parent is TNode parentTNode)
                     {
-                        var highlights = GetHighlights((TNode)parent, cancellationToken);
+                        var highlights = GetHighlights(parentTNode, cancellationToken);
 
                         // Only return them if any of them matched
                         if (highlights.Any(span => span.IntersectsWith(position)))