From 357f8844d6c6894baa84a7b1e47ea8001330c3c6 Mon Sep 17 00:00:00 2001
From: David Maas <contact@pathogenstudios.com>
Date: Sun, 19 Dec 2021 00:25:28 -0600
Subject: [PATCH] Added verification to highlight records which have a vtable
 but no constructors since they can't be initialized from C# yet.

Relates to https://github.com/MochiLibraries/Biohazrd/issues/31
---
 .../CSharpTranslationVerifier.cs              |  8 +++
 .../CSharpTranslationVerifierTests.cs         | 58 +++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/Biohazrd.CSharp/#Transformations/CSharpTranslationVerifier.cs b/Biohazrd.CSharp/#Transformations/CSharpTranslationVerifier.cs
index dcd827f..b8c6bc3 100644
--- a/Biohazrd.CSharp/#Transformations/CSharpTranslationVerifier.cs
+++ b/Biohazrd.CSharp/#Transformations/CSharpTranslationVerifier.cs
@@ -1,6 +1,7 @@
 using Biohazrd.CSharp.Metadata;
 using Biohazrd.Expressions;
 using Biohazrd.Transformation;
+using ClangSharp;
 using ClangSharp.Pathogen;
 using System.Collections.Immutable;
 using System.Linq;
@@ -298,6 +299,13 @@ protected override TransformationResult TransformRecord(TransformationContext co
             else if (declaration.VTable is not null && declaration.VTableField is null)
             { declaration = declaration.WithError("Records should not have a VTable without a VTable field."); }
 
+            // We don't currently provide a way to initialize a virtual type without a constructor
+            // https://github.com/MochiLibraries/Biohazrd/issues/31
+            if (declaration.VTable is not null
+                && !declaration.Members.OfType<TranslatedFunction>().Any(f => f.SpecialFunctionKind is SpecialFunctionKind.Constructor)
+                && declaration.Declaration is not CXXRecordDecl { IsAbstract: true })
+            { declaration = declaration.WithWarning("Virtual records without a constructor cannot be initialized from C#. See https://github.com/MochiLibraries/Biohazrd/issues/31"); }
+
             return base.TransformRecord(context, declaration);
         }
 
diff --git a/Tests/Biohazrd.CSharp.Tests/CSharpTranslationVerifierTests.cs b/Tests/Biohazrd.CSharp.Tests/CSharpTranslationVerifierTests.cs
index aabad80..5d88536 100644
--- a/Tests/Biohazrd.CSharp.Tests/CSharpTranslationVerifierTests.cs
+++ b/Tests/Biohazrd.CSharp.Tests/CSharpTranslationVerifierTests.cs
@@ -385,5 +385,63 @@ public void Constant_UnsupportedConstantNotOk()
             // Unsupported constants should mention the failure reason
             Assert.Single(constant.Diagnostics.Where(d => d.Message.Contains(nameof(Constant_UnsupportedConstantNotOk))));
         }
+
+        [Fact]
+        [RelatedIssue("https://github.com/MochiLibraries/Biohazrd/issues/31")]
+        public void Record_CannotInitializeConstructorlessVirtual()
+        {
+            TranslatedLibrary library = CreateLibrary
+            (@"
+class MyClass
+{
+public:
+    virtual void Test() { }
+};
+"
+            );
+
+            Assert.Empty(library.FindDeclaration<TranslatedRecord>("MyClass").Diagnostics);
+            library = new CSharpTranslationVerifier().Transform(library);
+            Assert.Contains(library.FindDeclaration<TranslatedRecord>("MyClass").Diagnostics, d => d.Severity >= Severity.Warning);
+        }
+
+        [Fact]
+        [RelatedIssue("https://github.com/MochiLibraries/Biohazrd/issues/31")]
+        public void Record_CannotInitializeConstructorlessVirtual_IgnoreAbstract()
+        {
+            TranslatedLibrary library = CreateLibrary
+            (@"
+class MyClass
+{
+public:
+    virtual void Test() = 0;
+};
+"
+            );
+
+            Assert.Empty(library.FindDeclaration<TranslatedRecord>("MyClass").Diagnostics);
+            library = new CSharpTranslationVerifier().Transform(library);
+            Assert.Empty(library.FindDeclaration<TranslatedRecord>("MyClass").Diagnostics);
+        }
+
+        [Fact]
+        [RelatedIssue("https://github.com/MochiLibraries/Biohazrd/issues/31")]
+        public void Record_CannotInitializeConstructorlessVirtual_ExplicitConstructorOk()
+        {
+            TranslatedLibrary library = CreateLibrary
+            (@"
+class MyClass
+{
+public:
+    MyClass() { }
+    virtual void Test() { }
+};
+"
+            );
+
+            Assert.Empty(library.FindDeclaration<TranslatedRecord>("MyClass").Diagnostics);
+            library = new CSharpTranslationVerifier().Transform(library);
+            Assert.Empty(library.FindDeclaration<TranslatedRecord>("MyClass").Diagnostics);
+        }
     }
 }