From 8e4c8eb25209501bbd60428cae5aa067d4e7dcad Mon Sep 17 00:00:00 2001
From: gpetrou <gipetrou@gmail.com>
Date: Mon, 5 Feb 2018 21:20:39 +0000
Subject: [PATCH] Replace is operator with switch pattern matching (#98)

* Replace is operator with switch pattern matching and as operator

* Switch back to is operator
---
 .../Actions/Calls/DefaultOverloadResolver.cs  |  8 ++--
 Src/Microsoft.Dynamic/ComInterop/ComBinder.cs |  4 +-
 .../Runtime/CodeDomCodeGen.cs                 | 41 +++++++++++--------
 Src/Microsoft.Dynamic/Utils/WeakDictionary.cs | 18 ++++----
 .../Runtime/StringDictionaryExpando.cs        |  4 +-
 5 files changed, 42 insertions(+), 33 deletions(-)

diff --git a/Src/Microsoft.Dynamic/Actions/Calls/DefaultOverloadResolver.cs b/Src/Microsoft.Dynamic/Actions/Calls/DefaultOverloadResolver.cs
index 2cbd8ddb..e5616de7 100644
--- a/Src/Microsoft.Dynamic/Actions/Calls/DefaultOverloadResolver.cs
+++ b/Src/Microsoft.Dynamic/Actions/Calls/DefaultOverloadResolver.cs
@@ -220,16 +220,16 @@ private void SplatDictionaryArgument(IList<string> splattedNames, IList<DynamicM
             IDictionaryEnumerator dictEnum = dict.GetEnumerator();
             while (dictEnum.MoveNext()) {
                 DictionaryEntry de = dictEnum.Entry;
-                
-                if (de.Key is string) {
-                    splattedNames.Add((string)de.Key);
+
+                if (de.Key is string s) {
+                    splattedNames.Add(s);
                     splattedArgs.Add(
                         DynamicMetaObject.Create(
                             de.Value,
                             Ast.Call(
                                 AstUtils.Convert(dictMo.Expression, typeof(IDictionary)),
                                 typeof(IDictionary).GetMethod("get_Item"),
-                                AstUtils.Constant(de.Key as string)
+                                AstUtils.Constant(s)
                             )
                         )
                     );
diff --git a/Src/Microsoft.Dynamic/ComInterop/ComBinder.cs b/Src/Microsoft.Dynamic/ComInterop/ComBinder.cs
index 7b77f896..75bf7d63 100644
--- a/Src/Microsoft.Dynamic/ComInterop/ComBinder.cs
+++ b/Src/Microsoft.Dynamic/ComInterop/ComBinder.cs
@@ -299,8 +299,8 @@ private static bool TryGetMetaObjectInvoke(ref DynamicMetaObject instance) {
                 return true;
             }
 
-            if (instance.Value is IPseudoComObject) {
-                instance = ((IPseudoComObject)instance.Value).GetMetaObject(instance.Expression);
+            if (instance.Value is IPseudoComObject o) {
+                instance = o.GetMetaObject(instance.Expression);
                 return true;
             }
 
diff --git a/Src/Microsoft.Dynamic/Runtime/CodeDomCodeGen.cs b/Src/Microsoft.Dynamic/Runtime/CodeDomCodeGen.cs
index 1ab17b42..9f96bc49 100644
--- a/Src/Microsoft.Dynamic/Runtime/CodeDomCodeGen.cs
+++ b/Src/Microsoft.Dynamic/Runtime/CodeDomCodeGen.cs
@@ -20,6 +20,7 @@
 using Microsoft.Scripting.Utils;
 
 namespace Microsoft.Scripting.Runtime {
+
     [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable")] // TODO: fix
     public abstract class CodeDomCodeGen {
         // This is the key used in the UserData of the CodeDom objects to track
@@ -55,43 +56,49 @@ private SourceUnit CreateSourceUnit(LanguageContext context, string path, Source
             return src;
         }
 
-        virtual protected void WriteArgumentReferenceExpression(CodeArgumentReferenceExpression e) {
+        protected virtual void WriteArgumentReferenceExpression(CodeArgumentReferenceExpression e) {
             _writer.Write(e.ParameterName);
         }
 
-        virtual protected void WriteSnippetExpression(CodeSnippetExpression e) {
+        protected virtual void WriteSnippetExpression(CodeSnippetExpression e) {
             _writer.Write(e.Value);
         }
 
-        virtual protected void WriteSnippetStatement(CodeSnippetStatement s) {
+        protected virtual void WriteSnippetStatement(CodeSnippetStatement s) {
             _writer.Write(s.Value);
             _writer.Write('\n');
         }
 
-        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1800:DoNotCastUnnecessarily")] // TODO: fix
         protected void WriteStatement(CodeStatement s) {
             // Save statement source location
             if (s.LinePragma != null) {
                 _writer.MapLocation(s.LinePragma);
             }
 
-            if (s is CodeExpressionStatement) {
-                WriteExpressionStatement((CodeExpressionStatement)s);
-            } else if (s is CodeSnippetStatement) {
-                WriteSnippetStatement((CodeSnippetStatement)s);
+            switch (s) {
+                case CodeExpressionStatement statement:
+                    WriteExpressionStatement(statement);
+                    break;
+                case CodeSnippetStatement statement:
+                    WriteSnippetStatement(statement);
+                    break;
             }
         }
 
-        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1800:DoNotCastUnnecessarily")] // TODO: fix
         protected void WriteExpression(CodeExpression e) {
-            if (e is CodeSnippetExpression) {
-                WriteSnippetExpression((CodeSnippetExpression)e);
-            } else if (e is CodePrimitiveExpression) {
-                WritePrimitiveExpression((CodePrimitiveExpression)e);
-            } else if (e is CodeMethodInvokeExpression) {
-                WriteCallExpression((CodeMethodInvokeExpression)e);
-            } else if (e is CodeArgumentReferenceExpression) {
-                WriteArgumentReferenceExpression((CodeArgumentReferenceExpression)e);
+            switch (e) {
+                case CodeSnippetExpression expression:
+                    WriteSnippetExpression(expression);
+                    break;
+                case CodePrimitiveExpression expression:
+                    WritePrimitiveExpression(expression);
+                    break;
+                case CodeMethodInvokeExpression expression:
+                    WriteCallExpression(expression);
+                    break;
+                case CodeArgumentReferenceExpression expression:
+                    WriteArgumentReferenceExpression(expression);
+                    break;
             }
         }
 
diff --git a/Src/Microsoft.Dynamic/Utils/WeakDictionary.cs b/Src/Microsoft.Dynamic/Utils/WeakDictionary.cs
index 4f068552..e8e2e11b 100644
--- a/Src/Microsoft.Dynamic/Utils/WeakDictionary.cs
+++ b/Src/Microsoft.Dynamic/Utils/WeakDictionary.cs
@@ -380,14 +380,16 @@ public T GetObjectFromId(int id) {
         public int GetIdFromObject(T value) {
             lock (_synchObject) {
                 foreach (KeyValuePair<int, object> kv in _dict) {
-                    if (kv.Value is WeakObject) {
-                        object target = ((WeakObject)kv.Value).Target;
-                        if (target != null && target.Equals(value))
-                            return kv.Key;
-                    } else if (kv.Value is T) {
-                        object target = (T)(kv.Value);
-                        if (target.Equals(value))
-                            return kv.Key;
+                    switch (kv.Value) {
+                        case WeakObject weakObject:
+                            object target = weakObject.Target;
+                            if (target != null && target.Equals(value))
+                                return kv.Key;
+                            break;
+                        case T t:
+                            if (t.Equals(value))
+                                return kv.Key;
+                            break;
                     }
                 }
             }
diff --git a/Src/Microsoft.Scripting/Runtime/StringDictionaryExpando.cs b/Src/Microsoft.Scripting/Runtime/StringDictionaryExpando.cs
index 6d088874..d059a99f 100644
--- a/Src/Microsoft.Scripting/Runtime/StringDictionaryExpando.cs
+++ b/Src/Microsoft.Scripting/Runtime/StringDictionaryExpando.cs
@@ -158,8 +158,8 @@ public override DynamicMetaObject BindDeleteMember(DeleteMemberBinder binder) {
 
         public override IEnumerable<string> GetDynamicMemberNames() {
             foreach (object o in _keys) {
-                if (o is string) {
-                    yield return (string)o;
+                if (o is string s) {
+                    yield return s;
                 }
             }
         }