From 908fb804e041fea0b79d0fe4fea62e568b577332 Mon Sep 17 00:00:00 2001
From: Manfred Brands <manfred-brands@users.noreply.github.com>
Date: Tue, 5 Sep 2023 09:56:06 +0800
Subject: [PATCH] Within is allowed on Nullable<T> when T  is supported.

---
 .../WithinUsage/WithinUsageAnalyzerTests.cs       | 15 +++++++++++++++
 .../WithinUsage/WithinUsageAnalyzer.cs            |  6 ++++++
 2 files changed, 21 insertions(+)

diff --git a/src/nunit.analyzers.tests/WithinUsage/WithinUsageAnalyzerTests.cs b/src/nunit.analyzers.tests/WithinUsage/WithinUsageAnalyzerTests.cs
index 12f6419b..6bbb1a40 100644
--- a/src/nunit.analyzers.tests/WithinUsage/WithinUsageAnalyzerTests.cs
+++ b/src/nunit.analyzers.tests/WithinUsage/WithinUsageAnalyzerTests.cs
@@ -272,5 +272,20 @@ public void AnalyzeOnNonGenericCollection()
 
             RoslynAssert.Valid(analyzer, testCode);
         }
+
+        [TestCase("double")]
+        [TestCase("int")]
+        [TestCase("TimeSpan")]
+        public void AnalyzeWhenAppliedToEqualityConstraintForNullableValidTypes(string type)
+        {
+            string testCode = TestUtility.WrapMethodInClassNamespaceAndAddUsings($@"
+                [TestCase(null, null)]
+                public void Test({type}? a, {type}? b)
+                {{
+                    Assert.That(a, Is.EqualTo(b).Within(0.1));
+                }}");
+
+            RoslynAssert.Valid(analyzer, testCode);
+        }
     }
 }
diff --git a/src/nunit.analyzers/WithinUsage/WithinUsageAnalyzer.cs b/src/nunit.analyzers/WithinUsage/WithinUsageAnalyzer.cs
index 6b075d7f..9519a5f5 100644
--- a/src/nunit.analyzers/WithinUsage/WithinUsageAnalyzer.cs
+++ b/src/nunit.analyzers/WithinUsage/WithinUsageAnalyzer.cs
@@ -142,6 +142,12 @@ private static bool IsTypeSupported(ITypeSymbol type, HashSet<ITypeSymbol>? chec
             if (fullName.Equals("System.DateTimeOffset", StringComparison.Ordinal))
                 return true;
 
+            // Check for Nullable<T>
+            if (fullName.Equals("System.Nullable`1", StringComparison.Ordinal))
+            {
+                return IsTypeSupported(namedType.TypeArguments[0]);
+            }
+
             if (fullName.StartsWith("System.Collections.Generic.KeyValuePair`", StringComparison.Ordinal))
             {
                 // We pass tolerance to the Value Type.