fix: wrap with ParenthesizedExpression when casting the subject (#183)

* add test to reproduce #172

* wrap with ParenthesizedExpression when casting the subject

---------

Co-authored-by: Meir Blachman <meblachm@microsoft.com>

Author: Meir017

src/FluentAssertions.Analyzers.Tests/Tips/SanityTests.cs

@@ -258,5 +258,49 @@ public static void Main()
 
             DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(source);
         }
+
+        [TestMethod]
+        [Implemented(Reason = "https://github.com/fluentassertions/fluentassertions.analyzers/issues/172")]
+        public void AssertAreEqualDoesNotCompile()
+        {
+            const string oldSource = @"
+using FluentAssertions;
+using FluentAssertions.Extensions;
+
+namespace TestProject
+{
+    using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+    public class Program
+    {
+        public static void Main()
+        {
+            double x = 5;
+
+            Assert.AreEqual(1, (int)x);
+        }
+    }
+}";
+            const string newSource = @"
+using FluentAssertions;
+using FluentAssertions.Extensions;
+
+namespace TestProject
+{
+    using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+    public class Program
+    {
+        public static void Main()
+        {
+            double x = 5;
+
+            ((int)x).Should().Be(1);
+        }
+    }
+}";
+
+            DiagnosticVerifier.VerifyCSharpFix<AssertAreEqualCodeFix, AssertAreEqualAnalyzer>(oldSource, newSource);
+        }
     }
 }

src/FluentAssertions.Analyzers/Utilities/Expressions.cs

@@ -26,6 +26,14 @@ public static ArgumentSyntax OptionsUsing(ArgumentSyntax comparer)
 
         public static InvocationExpressionSyntax SubjectShould(ExpressionSyntax subject)
         {
+            if (subject.IsKind(SyntaxKind.CastExpression))
+            {
+                return SF.InvocationExpression(
+                    SF.MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, SF.ParenthesizedExpression(subject), SF.IdentifierName("Should")),
+                    SF.ArgumentList()
+                );    
+            }
+
             return SF.InvocationExpression(
                 SF.MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, subject, SF.IdentifierName("Should")),
                 SF.ArgumentList()