From 3b201c2b04680af5ef88b614604b57603629da1a Mon Sep 17 00:00:00 2001
From: Raul Santos <raulsntos@gmail.com>
Date: Sat, 13 Aug 2022 06:21:27 +0200
Subject: [PATCH] Improve C# signal analyzer errors

Report the specific parameters that are not supported.
---
 .../Godot.SourceGenerators/Common.cs          | 34 ++++++++++++++++---
 .../ScriptSignalsGenerator.cs                 | 25 ++++++++++++--
 2 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/Common.cs b/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/Common.cs
index c1ae9932517..0f8b128da84 100644
--- a/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/Common.cs
+++ b/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/Common.cs
@@ -192,15 +192,15 @@ namespace Godot.SourceGenerators
                 location?.SourceTree?.FilePath));
         }
 
-        public static void ReportSignalDelegateSignatureNotSupported(
+        public static void ReportSignalParameterTypeNotSupported(
             GeneratorExecutionContext context,
-            INamedTypeSymbol delegateSymbol)
+            IParameterSymbol parameterSymbol)
         {
-            var locations = delegateSymbol.Locations;
+            var locations = parameterSymbol.Locations;
             var location = locations.FirstOrDefault(l => l.SourceTree != null) ?? locations.FirstOrDefault();
 
-            string message = "The delegate signature of the signal " +
-                             $"is not supported: '{delegateSymbol.ToDisplayString()}'";
+            string message = "The parameter of the delegate signature of the signal " +
+                             $"is not supported: '{parameterSymbol.ToDisplayString()}'";
 
             string description = $"{message}. Use supported types only or remove the '[Signal]' attribute.";
 
@@ -215,5 +215,29 @@ namespace Godot.SourceGenerators
                 location,
                 location?.SourceTree?.FilePath));
         }
+
+        public static void ReportSignalDelegateSignatureMustReturnVoid(
+            GeneratorExecutionContext context,
+            INamedTypeSymbol delegateSymbol)
+        {
+            var locations = delegateSymbol.Locations;
+            var location = locations.FirstOrDefault(l => l.SourceTree != null) ?? locations.FirstOrDefault();
+
+            string message = "The delegate signature of the signal " +
+                             $"must return void: '{delegateSymbol.ToDisplayString()}'";
+
+            string description = $"{message}. Return void or remove the '[Signal]' attribute.";
+
+            context.ReportDiagnostic(Diagnostic.Create(
+                new DiagnosticDescriptor(id: "GODOT-G0203",
+                    title: message,
+                    messageFormat: message,
+                    category: "Usage",
+                    DiagnosticSeverity.Error,
+                    isEnabledByDefault: true,
+                    description),
+                location,
+                location?.SourceTree?.FilePath));
+        }
     }
 }
diff --git a/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSignalsGenerator.cs b/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSignalsGenerator.cs
index 536ddb02f8a..f1c7706f9c3 100644
--- a/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSignalsGenerator.cs
+++ b/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSignalsGenerator.cs
@@ -148,8 +148,29 @@ namespace Godot.SourceGenerators
 
                 if (invokeMethodData == null)
                 {
-                    // TODO: Better error for incompatible signature. We should indicate incompatible argument types, as we do with exported properties.
-                    Common.ReportSignalDelegateSignatureNotSupported(context, signalDelegateSymbol);
+                    if (signalDelegateSymbol.DelegateInvokeMethod is IMethodSymbol methodSymbol)
+                    {
+                        foreach (var parameter in methodSymbol.Parameters)
+                        {
+                            if (parameter.RefKind != RefKind.None)
+                            {
+                                Common.ReportSignalParameterTypeNotSupported(context, parameter);
+                                continue;
+                            }
+
+                            var marshalType = MarshalUtils.ConvertManagedTypeToMarshalType(parameter.Type, typeCache);
+
+                            if (marshalType == null)
+                            {
+                                Common.ReportSignalParameterTypeNotSupported(context, parameter);
+                            }
+                        }
+
+                        if (!methodSymbol.ReturnsVoid)
+                        {
+                            Common.ReportSignalDelegateSignatureMustReturnVoid(context, signalDelegateSymbol);
+                        }
+                    }
                     continue;
                 }