Enforce MSGH007 for simple generators with parameters and finish SimpleMethodWithParameter test (#82)

* Initial plan

* Add MSGH007 validation for simple generators with parameters

Co-authored-by: dex3r <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: dex3r <[email protected]>

Author: Copilot

EasySourceGenerators.GeneratorTests/SimpleMethodWithParameter.cs

@@ -1,4 +1,8 @@
-namespace EasySourceGenerators.GeneratorTests;
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+
+namespace EasySourceGenerators.GeneratorTests;
 
 public class SimpleMethodWithParameterTests
 {
@@ -22,6 +26,16 @@ private static int SimpleMethodWithParameter_Generator(int someIntParameter)
                         }
                         """;
 
-        //TODO: This should not compile and throw error MSGH007
+        ImmutableArray<Diagnostic> diagnostics = GeneratorTestHelper.GetGeneratorOnlyDiagnostics(source);
+
+        Diagnostic? msgh007 = diagnostics.FirstOrDefault(diagnostic => diagnostic.Id == "MSGH007");
+        Assert.That(msgh007, Is.Not.Null, "Expected MSGH007 for simple generator method with runtime parameter.");
+        Assert.That(msgh007!.Location.IsInSource, Is.True, "MSGH007 should point to generator source.");
+
+        TextSpan span = msgh007.Location.SourceSpan;
+        string highlightedCode = source.Substring(span.Start, span.Length);
+        Assert.That(highlightedCode, Does.Contain("SimpleMethodWithParameter_Generator(int someIntParameter)"));
+        Assert.That(highlightedCode, Does.Not.Contain("return 5;"),
+            "MSGH007 should highlight the generator method signature, not the method body.");
     }
-}
+}

EasySourceGenerators.Generators/GeneratesMethodGenerationPipeline.cs

@@ -1,5 +1,6 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Text;
 using System.Collections.Immutable;
 using static EasySourceGenerators.Generators.Consts;
 
@@ -71,6 +72,21 @@ private static string GenerateSourceForGroup(
                 compilation);
         }
 
+        List<GeneratesMethodGenerationTarget> methodsWithParameters = methods
+            .Where(method => method.Symbol.Parameters.Length > 0)
+            .ToList();
+        if (methodsWithParameters.Count > 0)
+        {
+            foreach (GeneratesMethodGenerationTarget methodWithParameters in methodsWithParameters)
+            {
+                context.ReportDiagnostic(Diagnostic.Create(
+                    GeneratesMethodGeneratorDiagnostics.CannotUseRuntimeParameterForCompileTimeGeneratorError,
+                    GetMethodSignatureLocation(methodWithParameters.Syntax)));
+            }
+
+            return string.Empty;
+        }
+
         return GenerateFromSimplePattern(context, firstMethod, compilation);
     }
 
@@ -105,4 +121,10 @@ private static bool HasAttribute(IMethodSymbol methodSymbol, string fullAttribut
         return methodSymbol.GetAttributes()
             .Any(attribute => attribute.AttributeClass?.ToDisplayString() == fullAttributeTypeName);
     }
+
+    private static Location GetMethodSignatureLocation(MethodDeclarationSyntax methodSyntax)
+    {
+        TextSpan signatureSpan = TextSpan.FromBounds(methodSyntax.SpanStart, methodSyntax.ParameterList.Span.End);
+        return Location.Create(methodSyntax.SyntaxTree, signatureSpan);
+    }
 }