Enable IDE0020 (Use pattern matching)

eng/CodeAnalysis.src.globalconfig

@@ -1356,7 +1356,7 @@ dotnet_diagnostic.IDE0018.severity = suggestion
 dotnet_diagnostic.IDE0019.severity = suggestion
 
 # IDE0020: Use pattern matching to avoid is check followed by a cast (with variable)
-dotnet_diagnostic.IDE0020.severity = suggestion
+dotnet_diagnostic.IDE0020.severity = warning
 
 # IDE0021: Use expression body for constructors
 dotnet_diagnostic.IDE0021.severity = silent

src/coreclr/nativeaot/System.Private.CoreLib/src/System/RuntimeTypeHandle.cs

@@ -32,9 +32,8 @@ private RuntimeTypeHandle(IntPtr value)
 
         public override bool Equals(object? obj)
         {
-            if (obj is RuntimeTypeHandle)
+            if (obj is RuntimeTypeHandle handle)
             {
-                RuntimeTypeHandle handle = (RuntimeTypeHandle)obj;
                 return Equals(handle);
             }
             return false;

src/coreclr/nativeaot/System.Private.Reflection.Execution/src/Internal/Reflection/Execution/PayForPlayExperience/MissingMetadataExceptionCreator.cs

@@ -99,16 +99,13 @@ public static string ComputeUsefulPertainantIfPossible(object pertainant)
                     return type.ToDisplayStringIfAvailable(null);
             }
 
-            if (pertainant is MemberInfo)
+            if (pertainant is MemberInfo memberInfo)
             {
-                MemberInfo memberInfo = (MemberInfo)pertainant;
-
                 StringBuilder friendlyName = new StringBuilder(memberInfo.DeclaringType.ToDisplayStringIfAvailable(null));
                 friendlyName.Append('.');
                 friendlyName.Append(memberInfo.Name);
-                if (pertainant is MethodBase)
+                if (pertainant is MethodBase method)
                 {
-                    MethodBase method = (MethodBase)pertainant;
                     bool first;
 
                     // write out generic parameters

src/coreclr/nativeaot/System.Private.TypeLoader/src/Internal/Runtime/TypeLoader/TypeBuilder.cs

@@ -266,10 +266,8 @@ internal void PrepareType(TypeDesc type)
 
             bool noExtraPreparation = false; // Set this to true for types which don't need other types to be prepared. I.e GenericTypeDefinitions
 
-            if (type is DefType)
+            if (type is DefType typeAsDefType)
             {
-                DefType typeAsDefType = (DefType)type;
-
                 if (typeAsDefType.HasInstantiation)
                 {
                     if (typeAsDefType.IsTypeDefinition)
@@ -305,10 +303,8 @@ internal void PrepareType(TypeDesc type)
             {
                 PrepareType(((ParameterizedType)type).ParameterType);
 
-                if (type is ArrayType)
+                if (type is ArrayType typeAsArrayType)
                 {
-                    ArrayType typeAsArrayType = (ArrayType)type;
-
                     if (typeAsArrayType.IsSzArray && !typeAsArrayType.ElementType.IsPointer)
                     {
                         TypeDesc.ComputeTemplate(state);
@@ -1326,10 +1322,8 @@ private void FinishRuntimeType(TypeDesc type)
 
             var state = type.GetTypeBuilderState();
 
-            if (type is DefType)
+            if (type is DefType typeAsDefType)
             {
-                DefType typeAsDefType = (DefType)type;
-
                 if (type.HasInstantiation)
                 {
                     // Type definitions don't need any further finishing once created by the EETypeCreator
@@ -1367,10 +1361,8 @@ private void FinishRuntimeType(TypeDesc type)
             }
             else if (type is ParameterizedType)
             {
-                if (type is ArrayType)
+                if (type is ArrayType typeAsSzArrayType)
                 {
-                    ArrayType typeAsSzArrayType = (ArrayType)type;
-
                     state.HalfBakedRuntimeTypeHandle.SetRelatedParameterType(GetRuntimeTypeHandle(typeAsSzArrayType.ElementType));
 
                     state.HalfBakedRuntimeTypeHandle.SetComponentSize(state.ComponentSize.Value);

src/coreclr/nativeaot/System.Private.TypeLoader/src/Internal/Runtime/TypeLoader/TypeBuilderState.cs

@@ -973,10 +973,8 @@ public int? FieldAlignment
                 {
                     return checked((ushort)((DefType)TypeBeingBuilt).InstanceFieldAlignment.AsInt);
                 }
-                else if (TypeBeingBuilt is ArrayType)
+                else if (TypeBeingBuilt is ArrayType arrayType)
                 {
-                    ArrayType arrayType = (ArrayType)TypeBeingBuilt;
-
                     if (arrayType.ElementType is DefType)
                     {
                         return checked((ushort)((DefType)arrayType.ElementType).InstanceFieldAlignment.AsInt);

src/coreclr/nativeaot/System.Private.TypeLoader/src/Internal/Runtime/TypeLoader/TypeLoaderEnvironment.LdTokenResultLookup.cs

@@ -100,9 +100,8 @@ public RuntimeFieldHandleKey(RuntimeTypeHandle declaringType, string fieldName)
 
             public override bool Equals(object obj)
             {
-                if (obj is RuntimeFieldHandleKey)
+                if (obj is RuntimeFieldHandleKey other)
                 {
-                    RuntimeFieldHandleKey other = (RuntimeFieldHandleKey)obj;
                     return Equals(other);
                 }
                 return false;
@@ -145,9 +144,8 @@ public RuntimeMethodHandleKey(RuntimeTypeHandle declaringType, string methodName
 
             public override bool Equals(object obj)
             {
-                if (obj is RuntimeMethodHandleKey)
+                if (obj is RuntimeMethodHandleKey other)
                 {
-                    RuntimeMethodHandleKey other = (RuntimeMethodHandleKey)obj;
                     return Equals(other);
                 }
                 return false;

src/coreclr/nativeaot/System.Private.TypeLoader/src/Internal/TypeSystem/TypeDesc.Runtime.cs

@@ -84,10 +84,8 @@ internal bool RetrieveRuntimeTypeHandleIfPossible()
             if (state != null && state.AttemptedAndFailedToRetrieveTypeHandle)
                 return false;
 
-            if (type is DefType)
+            if (type is DefType typeAsDefType)
             {
-                DefType typeAsDefType = (DefType)type;
-
                 TypeDesc typeDefinition = typeAsDefType.GetTypeDefinition();
                 RuntimeTypeHandle typeDefHandle = typeDefinition.RuntimeTypeHandle;
                 if (typeDefHandle.IsNull())
@@ -155,10 +153,8 @@ internal bool RetrieveRuntimeTypeHandleIfPossible()
                     }
                 }
             }
-            else if (type is ParameterizedType)
+            else if (type is ParameterizedType typeAsParameterType)
             {
-                ParameterizedType typeAsParameterType = (ParameterizedType)type;
-
                 if (typeAsParameterType.ParameterType.RetrieveRuntimeTypeHandleIfPossible())
                 {
                     RuntimeTypeHandle rtth;

src/coreclr/nativeaot/System.Private.TypeLoader/src/Internal/TypeSystem/TypeSystemContext.Runtime.cs

@@ -321,10 +321,8 @@ protected override int GetValueHashCode(MethodDesc value)
 
                 protected override bool CompareKeyToValue(RuntimeMethodKey key, MethodDesc value)
                 {
-                    if (value is RuntimeMethodDesc)
+                    if (value is RuntimeMethodDesc runtimeMethod)
                     {
-                        RuntimeMethodDesc runtimeMethod = (RuntimeMethodDesc)value;
-
                         if (key._unboxingStub != runtimeMethod.UnboxingStub)
                             return false;
 

src/libraries/System.Composition.TypedParts/src/System/Composition/TypedParts/Discovery/DiscoveredPart.cs

@@ -212,9 +212,8 @@ public IDictionary<string, object> GetPartMetadata(TypeInfo partType)
             var partMetadata = new Dictionary<string, object>();
             foreach (var attr in _attributeContext.GetDeclaredAttributes(partType.AsType(), partType))
             {
-                if (attr is PartMetadataAttribute)
+                if (attr is PartMetadataAttribute ma)
                 {
-                    var ma = (PartMetadataAttribute)attr;
                     partMetadata.Add(ma.Name, ma.Value);
                 }
             }

src/libraries/System.Data.Common/src/System/Data/ConstraintCollection.cs

@@ -113,9 +113,8 @@ internal void Add(Constraint constraint, bool addUniqueWhenAddingForeign)
                 }
                 AddUniqueConstraint((UniqueConstraint)constraint);
             }
-            else if (constraint is ForeignKeyConstraint)
+            else if (constraint is ForeignKeyConstraint fk)
             {
-                ForeignKeyConstraint fk = (ForeignKeyConstraint)constraint;
                 if (addUniqueWhenAddingForeign)
                 {
                     UniqueConstraint? key = fk.RelatedTable.Constraints.FindKeyConstraint(fk.RelatedColumnsReference);

src/libraries/System.Data.Common/src/System/Data/DataColumnPropertyDescriptor.cs

@@ -43,16 +43,9 @@ public override AttributeCollection Attributes
 
         public override Type PropertyType => Column.DataType;
 
-        public override bool Equals([NotNullWhen(true)] object? other)
-        {
-            if (other is DataColumnPropertyDescriptor)
-            {
-                DataColumnPropertyDescriptor descriptor = (DataColumnPropertyDescriptor)other;
-                return (descriptor.Column == Column);
-            }
-
-            return false;
-        }
+        public override bool Equals([NotNullWhen(true)] object? other) =>
+            other is DataColumnPropertyDescriptor descriptor &&
+            descriptor.Column == Column;
 
         public override int GetHashCode() => Column.GetHashCode();
 

src/libraries/System.Data.Common/src/System/Data/DataRelation.cs

@@ -796,9 +796,8 @@ internal void ValidateMultipleNestedRelations()
 
                 foreach (Constraint cs in ChildTable.Constraints)
                 {
-                    if (cs is ForeignKeyConstraint)
+                    if (cs is ForeignKeyConstraint fk)
                     {
-                        ForeignKeyConstraint fk = (ForeignKeyConstraint)cs;
                         if (!XmlTreeGen.AutoGenerated(fk, true))
                         {
                             throw ExceptionBuilder.TableCantBeNestedInTwoTables(ChildTable.TableName);

src/libraries/System.Data.Common/src/System/Data/DataRelationPropertyDescriptor.cs

@@ -21,15 +21,9 @@ internal DataRelationPropertyDescriptor(DataRelation dataRelation) : base(dataRe
 
         public override Type PropertyType => typeof(IBindingList);
 
-        public override bool Equals([NotNullWhen(true)] object? other)
-        {
-            if (other is DataRelationPropertyDescriptor)
-            {
-                DataRelationPropertyDescriptor descriptor = (DataRelationPropertyDescriptor)other;
-                return (descriptor.Relation == Relation);
-            }
-            return false;
-        }
+        public override bool Equals([NotNullWhen(true)] object? other) =>
+            other is DataRelationPropertyDescriptor descriptor &&
+            descriptor.Relation == Relation;
 
         public override int GetHashCode() => Relation.GetHashCode();
 

src/libraries/System.Data.Common/src/System/Data/DataTablePropertyDescriptor.cs

@@ -21,15 +21,9 @@ internal DataTablePropertyDescriptor(DataTable dataTable) : base(dataTable.Table
 
         public override Type PropertyType => typeof(IBindingList);
 
-        public override bool Equals([NotNullWhen(true)] object? other)
-        {
-            if (other is DataTablePropertyDescriptor)
-            {
-                DataTablePropertyDescriptor descriptor = (DataTablePropertyDescriptor)other;
-                return (descriptor.Table == Table);
-            }
-            return false;
-        }
+        public override bool Equals([NotNullWhen(true)] object? other) =>
+            other is DataTablePropertyDescriptor descriptor &&
+            descriptor.Table == Table;
 
         public override int GetHashCode() => Table.GetHashCode();
 

src/libraries/System.Data.Common/src/System/Data/Filter/BinaryNode.cs

@@ -83,9 +83,8 @@ internal override ExpressionNode Optimize()
             if (_op == Operators.Is)
             {
                 // only 'Is Null' or 'Is Not Null' are valid
-                if (_right is UnaryNode)
+                if (_right is UnaryNode un)
                 {
-                    UnaryNode un = (UnaryNode)_right;
                     if (un._op != Operators.Not)
                     {
                         throw ExprException.InvalidIsSyntax();

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLBinary.cs

@@ -338,10 +338,8 @@ public SqlGuid ToSqlGuid()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlBinary)
+            if (value is SqlBinary i)
             {
-                SqlBinary i = (SqlBinary)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlBinary));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLBoolean.cs

@@ -441,10 +441,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlBoolean)
+            if (value is SqlBoolean i)
             {
-                SqlBoolean i = (SqlBoolean)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlBoolean));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLByte.cs

@@ -450,10 +450,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlByte)
+            if (value is SqlByte i)
             {
-                SqlByte i = (SqlByte)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlByte));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLDateTime.cs

@@ -597,10 +597,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlDateTime)
+            if (value is SqlDateTime i)
             {
-                SqlDateTime i = (SqlDateTime)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlDateTime));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLDouble.cs

@@ -366,10 +366,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlDouble)
+            if (value is SqlDouble i)
             {
-                SqlDouble i = (SqlDouble)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlDouble));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLGuid.cs

@@ -257,10 +257,8 @@ public SqlBinary ToSqlBinary()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlGuid)
+            if (value is SqlGuid i)
             {
-                SqlGuid i = (SqlGuid)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlGuid));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLInt16.cs

@@ -451,10 +451,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlInt16)
+            if (value is SqlInt16 i)
             {
-                SqlInt16 i = (SqlInt16)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlInt16));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLInt32.cs

@@ -466,10 +466,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlInt32)
+            if (value is SqlInt32 i)
             {
-                SqlInt32 i = (SqlInt32)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlInt32));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLInt64.cs

@@ -525,10 +525,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlInt64)
+            if (value is SqlInt64 i)
             {
-                SqlInt64 i = (SqlInt64)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlInt64));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLMoney.cs

@@ -515,10 +515,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlMoney)
+            if (value is SqlMoney i)
             {
-                SqlMoney i = (SqlMoney)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlMoney));

src/libraries/System.Data.Common/src/System/Data/SQLTypes/SQLSingle.cs

@@ -376,10 +376,8 @@ public SqlString ToSqlString()
         // If object is not of same type, this method throws an ArgumentException.
         public int CompareTo(object? value)
         {
-            if (value is SqlSingle)
+            if (value is SqlSingle i)
             {
-                SqlSingle i = (SqlSingle)value;
-
                 return CompareTo(i);
             }
             throw ADP.WrongType(value!.GetType(), typeof(SqlSingle));