REFL044 Expected attribute type. DotNetAnalyzers#182.

README.md

@@ -176,5 +176,9 @@ Analyzers checking System.Reflection
     <td><a href="https://github.com/DotNetAnalyzers/ReflectionAnalyzers/tree/master/documentation/REFL043.md">REFL043</a></td>
     <td>First argument must match type.</td>
   </tr>
+  <tr>
+    <td><a href="https://github.com/DotNetAnalyzers/ReflectionAnalyzers/tree/master/documentation/REFL044.md">REFL044</a></td>
+    <td>Expected attribute type.</td>
+  </tr>
 <table>
 <!-- end generated table -->

ReflectionAnalyzers.Tests/REFL044ExpectedAttributeTypeTests/CodeFix.cs

@@ -0,0 +1,30 @@
+namespace ReflectionAnalyzers.Tests.REFL044ExpectedAttributeTypeTests
+{
+    using Gu.Roslyn.Asserts;
+    using Microsoft.CodeAnalysis.Diagnostics;
+    using NUnit.Framework;
+
+    internal class CodeFix
+    {
+        private static readonly DiagnosticAnalyzer Analyzer = new GetCustomAttributeAnalyzer();
+        private static readonly ExpectedDiagnostic ExpectedDiagnostic = ExpectedDiagnostic.Create(REFL044ExpectedAttributeType.DiagnosticId);
+
+        [Test]
+        public void AttributeGetCustomAttribute()
+        {
+            var code = @"
+namespace RoslynSandbox
+{
+    using System;
+
+    class C
+    {
+        public static bool Bar() => Attribute.GetCustomAttribute(typeof(C), ↓typeof(string)) == null;
+    }
+}";
+
+            var message = "Expected attribute type.";
+            AnalyzerAssert.Diagnostics(Analyzer, ExpectedDiagnostic.WithMessage(message), code);
+        }
+    }
+}

ReflectionAnalyzers.Tests/REFL044ExpectedAttributeTypeTests/ValidCode.cs

@@ -0,0 +1,72 @@
+namespace ReflectionAnalyzers.Tests.REFL044ExpectedAttributeTypeTests
+{
+    using Gu.Roslyn.Asserts;
+    using Microsoft.CodeAnalysis;
+    using Microsoft.CodeAnalysis.Diagnostics;
+    using NUnit.Framework;
+
+    internal class ValidCode
+    {
+        private static readonly DiagnosticAnalyzer Analyzer = new GetCustomAttributeAnalyzer();
+        private static readonly DiagnosticDescriptor Descriptor = REFL044ExpectedAttributeType.Descriptor;
+
+        [Test]
+        public void WhenUsingGeneric()
+        {
+            var code = @"
+namespace RoslynSandbox
+{
+    using System;
+    using System.Reflection;
+
+    class C
+    {
+        public C()
+        {
+            var attribute = typeof(C).GetCustomAttribute<ObsoleteAttribute>();
+        }
+    }
+}";
+            AnalyzerAssert.Valid(Analyzer, Descriptor, code);
+        }
+
+        [Test]
+        public void WhenGetCustomAttributeCast()
+        {
+            var code = @"
+namespace RoslynSandbox
+{
+    using System;
+
+    class C
+    {
+        public C()
+        {
+            var attribute = (ObsoleteAttribute)Attribute.GetCustomAttribute(typeof(C), typeof(ObsoleteAttribute));
+        }
+    }
+}";
+            AnalyzerAssert.Valid(Analyzer, Descriptor, code);
+        }
+
+        [Test]
+        public void WhenGetCustomAttributeAs()
+        {
+            var code = @"
+namespace RoslynSandbox
+{
+    using System;
+
+    class C
+    {
+        public C()
+        {
+            var attribute = Attribute.GetCustomAttribute(typeof(C), typeof(ObsoleteAttribute)) as ObsoleteAttribute;
+        }
+    }
+}";
+
+            AnalyzerAssert.Valid(Analyzer, Descriptor, code);
+        }
+    }
+}

ReflectionAnalyzers.sln

@@ -74,6 +74,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = ".docs", ".docs", "{1C271AF2
 		documentation\REFL041.md = documentation\REFL041.md
 		documentation\REFL042.md = documentation\REFL042.md
 		documentation\REFL043.md = documentation\REFL043.md
+		documentation\REFL044.md = documentation\REFL044.md
 		RELEASE_NOTES.md = RELEASE_NOTES.md
 	EndProjectSection
 EndProject

ReflectionAnalyzers/NodeAnalzers/GetCustomAttributeAnalyzer.cs

@@ -13,7 +13,8 @@ internal class GetCustomAttributeAnalyzer : DiagnosticAnalyzer
         /// <inheritdoc/>
         public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(
             REFL010PreferGenericGetCustomAttribute.Descriptor,
-            REFL012PreferIsDefined.Descriptor);
+            REFL012PreferIsDefined.Descriptor,
+            REFL044ExpectedAttributeType.Descriptor);
 
         /// <inheritdoc/>
         public override void Initialize(AnalysisContext context)
@@ -51,6 +52,14 @@ context.Node is InvocationExpressionSyntax invocation &&
                                 nameof(InvocationExpressionSyntax),
                                 invocationText)));
                 }
+
+                if (!attributeType.Value.IsAssignableTo(context.Compilation.GetTypeByMetadataName("System.Attribute"), context.Compilation))
+                {
+                    context.ReportDiagnostic(
+                        Diagnostic.Create(
+                            REFL044ExpectedAttributeType.Descriptor,
+                            attributeType.Argument.GetLocation()));
+                }
             }
         }
 

ReflectionAnalyzers/REFL044ExpectedAttributeType.cs

@@ -0,0 +1,19 @@
+namespace ReflectionAnalyzers
+{
+    using Microsoft.CodeAnalysis;
+
+    internal static class REFL044ExpectedAttributeType
+    {
+        internal const string DiagnosticId = "REFL044";
+
+        internal static readonly DiagnosticDescriptor Descriptor = new DiagnosticDescriptor(
+            id: DiagnosticId,
+            title: "Expected attribute type.",
+            messageFormat: "Expected attribute type.",
+            category: AnalyzerCategory.SystemReflection,
+            defaultSeverity: DiagnosticSeverity.Warning,
+            isEnabledByDefault: true,
+            description: "Expected attribute type.",
+            helpLinkUri: HelpLink.ForId(DiagnosticId));
+    }
+}

documentation/REFL044.md

@@ -0,0 +1,67 @@
+# REFL044
+## Expected attribute type.
+
+<!-- start generated table -->
+<table>
+  <tr>
+    <td>CheckId</td>
+    <td>REFL044</td>
+  </tr>
+  <tr>
+    <td>Severity</td>
+    <td>Warning</td>
+  </tr>
+  <tr>
+    <td>Enabled</td>
+    <td>true</td>
+  </tr>
+  <tr>
+    <td>Category</td>
+    <td>ReflectionAnalyzers.SystemReflection</td>
+  </tr>
+  <tr>
+    <td>Code</td>
+    <td><a href="https://github.com/DotNetAnalyzers/ReflectionAnalyzers/blob/master/ReflectionAnalyzers/NodeAnalzers/GetCustomAttributeAnalyzer.cs">GetCustomAttributeAnalyzer</a></td>
+  </tr>
+</table>
+<!-- end generated table -->
+
+## Description
+
+Expected attribute type.
+
+## Motivation
+
+ADD MOTIVATION HERE
+
+## How to fix violations
+
+ADD HOW TO FIX VIOLATIONS HERE
+
+<!-- start generated config severity -->
+## Configure severity
+
+### Via ruleset file.
+
+Configure the severity per project, for more info see [MSDN](https://msdn.microsoft.com/en-us/library/dd264949.aspx).
+
+### Via #pragma directive.
+```C#
+#pragma warning disable REFL044 // Expected attribute type.
+Code violating the rule here
+#pragma warning restore REFL044 // Expected attribute type.
+```
+
+Or put this at the top of the file to disable all instances.
+```C#
+#pragma warning disable REFL044 // Expected attribute type.
+```
+
+### Via attribute `[SuppressMessage]`.
+
+```C#
+[System.Diagnostics.CodeAnalysis.SuppressMessage("ReflectionAnalyzers.SystemReflection", 
+    "REFL044:Expected attribute type.", 
+    Justification = "Reason...")]
+```
+<!-- end generated config severity -->