fixed issue (#42)

Author: Meir017

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

@@ -11,7 +11,7 @@ public void CountWithPredicate()
         {
             const string assertion = "actual.Count(d => d.Message.Contains(\"a\")).Should().Be(2);";
             var source = GenerateCode.EnumerableCodeBlockAssertion(assertion);
-            
+
             DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(source);
         }
 
@@ -64,6 +64,23 @@ public void DictionaryShouldContainPair_WhenPropertiesOfDifferentVariables_Shoul
             var source = GenerateCode.DictionaryAssertion(assertion);
 
             DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(source);
-    }
+        }
+
+        [TestMethod]
+        [Implemented(Reason = "https://github.com/fluentassertions/fluentassertions.analyzers/issues/41")]
+        public void ExpressionBasedFunction_ShouldNotThrow()
+        {
+            const string source = @"
+public class TestClass
+{
+    private SomeClass CreateSomeClass() => new SomeClass();
+ 
+    public class SomeClass
+    { }
+    public static void Main() { }
+}";
+
+            DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(source);
+        }
     }
 }

src/FluentAssertions.Analyzers/Tips/Collections/CollectionAnalyzer.cs

@@ -5,10 +5,10 @@ namespace FluentAssertions.Analyzers
 {
     public abstract class CollectionAnalyzer : FluentAssertionsAnalyzer
     {
-        protected override bool ShouldAnalyzeVariableType(TypeInfo typeInfo)
+        protected override bool ShouldAnalyzeVariableType(ITypeSymbol type)
         {
-            return typeInfo.ConvertedType.Name != "String"
-                && typeInfo.ConvertedType.AllInterfaces.Any(@interface => @interface.Name == "IEnumerable");
+            return type.Name != "String"
+                && type.AllInterfaces.Any(@interface => @interface.Name == "IEnumerable");
         }
     }
 }

src/FluentAssertions.Analyzers/Tips/Numerics/NumericAnalyzer.cs

@@ -4,9 +4,6 @@ namespace FluentAssertions.Analyzers
 {
     public abstract class NumericAnalyzer : FluentAssertionsAnalyzer
     {
-        protected override bool ShouldAnalyzeVariableType(TypeInfo typeInfo)
-        {
-            return true;
-        }
+        protected override bool ShouldAnalyzeVariableType(ITypeSymbol type) => true;
     }
 }

src/FluentAssertions.Analyzers/Tips/Numerics/NumericShouldBeApproximately.cs

@@ -29,10 +29,8 @@ protected override IEnumerable<FluentAssertionsCSharpSyntaxVisitor> Visitors
         }
 
         private static readonly string[] ValidaTypeNames = { "double", "decimal", "float" };
-        protected override bool ShouldAnalyzeVariableType(TypeInfo typeInfo)
-        {
-            return ValidaTypeNames.Contains(typeInfo.ConvertedType.ToDisplayString(), StringComparer.OrdinalIgnoreCase);
-        }
+        protected override bool ShouldAnalyzeVariableType(ITypeSymbol type)
+            => ValidaTypeNames.Contains(type.ToDisplayString(), StringComparer.OrdinalIgnoreCase);
 
         public class MathAbsShouldBeLessOrEqualToSyntaxVisitor : FluentAssertionsCSharpSyntaxVisitor
         {

src/FluentAssertions.Analyzers/Tips/Strings/StringAnalyzer.cs

@@ -4,9 +4,6 @@ namespace FluentAssertions.Analyzers
 {
     public abstract class StringAnalyzer : FluentAssertionsAnalyzer
     {
-        protected override bool ShouldAnalyzeVariableType(TypeInfo typeInfo)
-        {
-            return typeInfo.ConvertedType.Name == "String";
-        }
+        protected override bool ShouldAnalyzeVariableType(ITypeSymbol type) => type.Name == "String";
     }
 }

src/FluentAssertions.Analyzers/Utilities/FluentAssertionsAnalyzer.cs

@@ -51,18 +51,16 @@ private void AnalyzeCodeBlock(CodeBlockAnalysisContext context)
             }
         }
 
-        protected virtual bool ShouldAnalyzeVariableType(TypeInfo typeInfo)
-        {
-            return true;
-        }
+        protected virtual bool ShouldAnalyzeVariableType(ITypeSymbol type) => true;
 
         protected virtual Diagnostic AnalyzeExpression(ExpressionSyntax expression, SemanticModel semanticModel)
         {
             var variableNameExtractor = new VariableNameExtractor(semanticModel);
             expression.Accept(variableNameExtractor);
 
             var typeInfo = semanticModel.GetTypeInfo(variableNameExtractor.VariableIdentifierName);
-            if (!ShouldAnalyzeVariableType(typeInfo)) return null;
+            if (typeInfo.ConvertedType == null) return null;
+            if (!ShouldAnalyzeVariableType(typeInfo.ConvertedType)) return null;
 
             foreach (var visitor in Visitors)
             {