From b11a3edb5c055e385c75ae1fb47f4498a2719d26 Mon Sep 17 00:00:00 2001
From: Josef Pihrt <josef.pihrt@outlook.com>
Date: Mon, 31 Oct 2022 16:20:05 +0100
Subject: [PATCH] Do not make generic class static if it's inherited (RCS1102)
 (#978)

---
 ChangeLog.md                                      |  1 +
 .../CSharp/Analysis/MakeClassStaticAnalyzer.cs    | 15 ++++++++++++---
 .../RCS1102MakeClassStaticTests.cs                | 13 +++++++++++++
 3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index c7e4d3f48a..eadeaee95f 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -45,6 +45,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Use explicit type from lambda expression ([RCS1008](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1008.md)) ([#967](https://github.com/josefpihrt/roslynator/pull/967).
 - Do not remove constructor if it is decorated with 'UsedImplicitlyAttribute' ([RCS1074](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1074.md)) ([#968](https://github.com/josefpihrt/roslynator/pull/968).
 - Detect argument null check in the form of `ArgumentNullException.ThrowIfNull` ([RR0025](https://github.com/JosefPihrt/Roslynator/blob/main/docs/refactorings/RR0025.md), [RCS1227](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1227.md)) ([#974](https://github.com/josefpihrt/roslynator/pull/974).
+- Do not make generic class static if it's inherited ([RCS1102](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1102.md)) ([#978](https://github.com/josefpihrt/roslynator/pull/978).
 
 -----
 <!-- Content below does not adhere to 'Keep a Changelog' format -->
diff --git a/src/Analyzers/CSharp/Analysis/MakeClassStaticAnalyzer.cs b/src/Analyzers/CSharp/Analysis/MakeClassStaticAnalyzer.cs
index 0d4bd576b4..1b9869b4f7 100644
--- a/src/Analyzers/CSharp/Analysis/MakeClassStaticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analysis/MakeClassStaticAnalyzer.cs
@@ -190,7 +190,8 @@ protected override void VisitType(TypeSyntax node)
             {
                 if (node is IdentifierNameSyntax identifierName)
                 {
-                    if (string.Equals(Symbol.Name, identifierName.Identifier.ValueText, StringComparison.Ordinal)
+                    if (!identifierName.IsVar
+                        && string.Equals(Symbol.Name, identifierName.Identifier.ValueText, StringComparison.Ordinal)
                         && SymbolEqualityComparer.Default.Equals(
                             SemanticModel.GetSymbol(identifierName, CancellationToken)?.OriginalDefinition,
                             Symbol))
@@ -198,10 +199,18 @@ protected override void VisitType(TypeSyntax node)
                         CanBeMadeStatic = false;
                     }
                 }
-                else
+                else if (node is GenericNameSyntax genericName)
                 {
-                    base.VisitType(node);
+                    if (string.Equals(Symbol.Name, genericName.Identifier.ValueText, StringComparison.Ordinal)
+                        && SymbolEqualityComparer.Default.Equals(
+                            SemanticModel.GetSymbol(genericName, CancellationToken)?.OriginalDefinition,
+                            Symbol))
+                    {
+                        CanBeMadeStatic = false;
+                    }
                 }
+
+                base.VisitType(node);
             }
 
             public static MakeClassStaticWalker GetInstance()
diff --git a/src/Tests/Analyzers.Tests/RCS1102MakeClassStaticTests.cs b/src/Tests/Analyzers.Tests/RCS1102MakeClassStaticTests.cs
index 6eb57f8ef5..20584d7242 100644
--- a/src/Tests/Analyzers.Tests/RCS1102MakeClassStaticTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1102MakeClassStaticTests.cs
@@ -161,6 +161,19 @@ static C M()
         return null;
     }
 }
+");
+        }
+
+        [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.MakeClassStatic)]
+        public async Task TestNoDiagnostic_NestedClass()
+        {
+            await VerifyNoDiagnosticAsync(@"
+public class Class1<T>
+{
+    public sealed class Class2 : Class1<T>
+    {
+    }
+}
 ");
         }
     }