Convert if-else to return statement when pattern matching is used

ChangeLog.md

@@ -33,6 +33,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Do not suggest to make local variable a const when it is used in ref extension method ([RCS1118](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1118.md)) ([#948](https://github.com/josefpihrt/roslynator/pull/948).
 - Fix formatting of argument list ([#952](https://github.com/josefpihrt/roslynator/pull/952).
 - Do not remove async/await when 'using declaration' is used ([#953](https://github.com/josefpihrt/roslynator/pull/953).
+- Convert if-else to return statement when pattern matching is used ([RCS1073](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1073.md)) ([#956](https://github.com/josefpihrt/roslynator/pull/956).
 
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 <!-- Content below does not adhere to 'Keep a Changelog' format -->

src/Common/CSharp/Analysis/If/IfAnalysis.cs

@@ -219,7 +219,7 @@ private static IfAnalysis CreateIfToReturnStatement(
             SemanticModel semanticModel,
             CancellationToken cancellationToken)
         {
-            if ((nullCheck.Style & NullCheckStyles.ComparisonToNull) != 0
+            if ((nullCheck.Style & (NullCheckStyles.ComparisonToNull | NullCheckStyles.IsPattern)) != 0
                 && AreEquivalent(nullCheck.Expression, expression1))
             {
                 return CreateIfToReturnStatement(isNullable: false);

src/Tests/Analyzers.Tests/RCS1073ConvertIfToReturnStatementTests.cs

@@ -76,6 +76,72 @@ bool M()
 ");
         }
 
+        [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.ConvertIfToReturnStatement)]
+        public async Task Test_IfReturn_EqualsToNull()
+        {
+            await VerifyDiagnosticAndFixAsync(@"
+class C
+{
+    string M()
+    {
+        string x = null;
+
+        [|if (x == null)
+        {
+            return null;
+        }
+        else
+        {
+            return x;
+        }|]
+    }
+}
+", @"
+class C
+{
+    string M()
+    {
+        string x = null;
+
+        return x;
+    }
+}
+");
+        }
+
+        [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.ConvertIfToReturnStatement)]
+        public async Task Test_IfReturn_IsNull()
+        {
+            await VerifyDiagnosticAndFixAsync(@"
+class C
+{
+    string M()
+    {
+        string x = null;
+
+        [|if (x is null)
+        {
+            return null;
+        }
+        else
+        {
+            return x;
+        }|]
+    }
+}
+", @"
+class C
+{
+    string M()
+    {
+        string x = null;
+
+        return x;
+    }
+}
+");
+        }
+
         [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.ConvertIfToReturnStatement)]
         public async Task TestNoDiagnostic_IfElseContainsComment()
         {