Fix invalid codegen for bool bitfields

sources/ClangSharp.PInvokeGenerator/PInvokeGenerator.VisitRecordDecl.cs

@@ -1128,6 +1128,12 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
             var currentSize = fieldDecl.Type.Handle.SizeOf;
             var bitfieldName = "_bitfield";
 
+            // A `bool` bitfield cannot be shifted or masked directly and needs an integer
+            // backing store. It is emitted using the same unsigned-integer path as the
+            // equivalently-sized integer type, with the public accessor kept as `bool` and
+            // the conversion done at the get/set boundary.
+            var isBooleanBitfield = fieldDecl.Type.CanonicalType.Kind == CXType_Bool;
+
             Type typeBacking;
             string typeNameBacking;
 
@@ -1149,6 +1155,11 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
                 typeBacking = bitfieldDesc.TypeBacking;
                 typeNameBacking = GetRemappedTypeName(fieldDecl, context: null, typeBacking, out _);
 
+                if (isBooleanBitfield)
+                {
+                    typeNameBacking = "byte";
+                }
+
                 if (parent == recordDecl)
                 {
                     var fieldDesc = new FieldDesc {
@@ -1201,6 +1212,11 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
                 var bitfieldDesc = (index > 0) ? bitfieldDescs[index - 1] : bitfieldDescs[0];
                 typeBacking = bitfieldDesc.TypeBacking;
                 typeNameBacking = GetRemappedTypeName(fieldDecl, context: null, typeBacking, out _);
+
+                if (isBooleanBitfield)
+                {
+                    typeNameBacking = "byte";
+                }
             }
 
             var bitfieldOffset = (currentSize * 8) - remainingBits;
@@ -1216,6 +1232,7 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
 
             switch (builtinTypeBacking.Kind)
             {
+                case CXType_Bool:
                 case CXType_Char_U:
                 case CXType_UChar:
                 case CXType_UShort:
@@ -1315,6 +1332,7 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
 
             switch (builtinType.Kind)
             {
+                case CXType_Bool:
                 case CXType_Char_U:
                 case CXType_UChar:
                 case CXType_UShort:
@@ -1389,6 +1407,16 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
             var name = GetRemappedCursorName(fieldDecl);
             var escapedName = EscapeName(name);
 
+            // The public accessor keeps the original type (e.g. `bool`) while the shift/mask
+            // arithmetic is done against the integer backing type; the two only differ for a
+            // `bool` bitfield, which is converted at the get/set boundary below.
+            var fieldTypeName = typeName;
+
+            if (isBooleanBitfield)
+            {
+                typeName = typeNameBacking;
+            }
+
             var desc = new FieldDesc {
                 AccessSpecifier = accessSpecifier,
                 NativeTypeName = nativeTypeName,
@@ -1409,7 +1437,7 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
 
             _outputBuilder.WriteDivider();
             _outputBuilder.BeginField(in desc);
-            _outputBuilder.WriteRegularField(typeName, escapedName);
+            _outputBuilder.WriteRegularField(fieldTypeName, escapedName);
             _outputBuilder.BeginBody();
 
             var recordDeclName = GetCursorName(recordDecl);
@@ -1461,7 +1489,7 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
                     code.Write(")(");
                 }
 
-                if (needsCastToFinal)
+                if (needsCastToFinal && !isBooleanBitfield)
                 {
                     code.Write('(');
                     code.BeginMarker("typeName");
@@ -1565,6 +1593,11 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
                     code.Write(')');
                 }
 
+                if (isBooleanBitfield)
+                {
+                    code.Write(" != 0");
+                }
+
                 code.WriteSemicolon();
                 code.WriteNewline();
                 _outputBuilder.EndCSharpCode(code);
@@ -1658,6 +1691,10 @@ void VisitBitfieldDecl(FieldDecl fieldDecl, BitfieldDesc[] bitfieldDescs, Record
                     code.Write(typeNameBacking);
                     code.Write(")(value)");
                 }
+                else if (isBooleanBitfield)
+                {
+                    code.Write("(value ? 1 : 0)");
+                }
                 else
                 {
                     code.Write("value");

tests/ClangSharp.PInvokeGenerator.UnitTests/BooleanBitfieldTest.cs

@@ -0,0 +1,140 @@
+// Copyright (c) .NET Foundation and Contributors. All Rights Reserved. Licensed under the MIT License (MIT). See License.md in the repository root for more information.
+
+using System.Threading.Tasks;
+using NUnit.Framework;
+
+namespace ClangSharp.UnitTests;
+
+public sealed class BooleanBitfieldTest : PInvokeGeneratorTest
+{
+    // Regression test for https://github.com/dotnet/clangsharp/issues/508
+    // A `bool` bitfield previously generated invalid C# (a `bool` backing field plus
+    // `bool & int` arithmetic and `(bool)` casts). It should use an integer backing store
+    // with the public accessor kept as `bool`, converting at the get/set boundary. An
+    // adjacent non-bool bitfield must be unaffected.
+    private const string InputContents = @"struct MyStruct
+{
+    bool a : 1;
+    bool b : 1;
+    int c : 2;
+};
+";
+
+    [Test]
+    public Task LatestTest()
+    {
+        var expectedOutputContents = @"namespace ClangSharp.Test
+{
+    public partial struct MyStruct
+    {
+        public byte _bitfield1;
+
+        [NativeTypeName(""bool : 1"")]
+        public bool a
+        {
+            readonly get
+            {
+                return (_bitfield1 & 0x1u) != 0;
+            }
+
+            set
+            {
+                _bitfield1 = (byte)((_bitfield1 & ~0x1u) | ((value ? 1 : 0) & 0x1u));
+            }
+        }
+
+        [NativeTypeName(""bool : 1"")]
+        public bool b
+        {
+            readonly get
+            {
+                return ((_bitfield1 >> 1) & 0x1u) != 0;
+            }
+
+            set
+            {
+                _bitfield1 = (byte)((_bitfield1 & ~(0x1u << 1)) | (((value ? 1 : 0) & 0x1u) << 1));
+            }
+        }
+
+        public int _bitfield2;
+
+        [NativeTypeName(""int : 2"")]
+        public int c
+        {
+            readonly get
+            {
+                return (_bitfield2 << 30) >> 30;
+            }
+
+            set
+            {
+                _bitfield2 = (_bitfield2 & ~0x3) | (value & 0x3);
+            }
+        }
+    }
+}
+";
+
+        return ValidateGeneratedCSharpLatestWindowsBindingsAsync(InputContents, expectedOutputContents);
+    }
+
+    [Test]
+    public Task CompatibleTest()
+    {
+        var expectedOutputContents = @"namespace ClangSharp.Test
+{
+    public partial struct MyStruct
+    {
+        public byte _bitfield1;
+
+        [NativeTypeName(""bool : 1"")]
+        public bool a
+        {
+            get
+            {
+                return (_bitfield1 & 0x1u) != 0;
+            }
+
+            set
+            {
+                _bitfield1 = (byte)((_bitfield1 & ~0x1u) | ((value ? 1 : 0) & 0x1u));
+            }
+        }
+
+        [NativeTypeName(""bool : 1"")]
+        public bool b
+        {
+            get
+            {
+                return ((_bitfield1 >> 1) & 0x1u) != 0;
+            }
+
+            set
+            {
+                _bitfield1 = (byte)((_bitfield1 & ~(0x1u << 1)) | (((value ? 1 : 0) & 0x1u) << 1));
+            }
+        }
+
+        public int _bitfield2;
+
+        [NativeTypeName(""int : 2"")]
+        public int c
+        {
+            get
+            {
+                return (_bitfield2 << 30) >> 30;
+            }
+
+            set
+            {
+                _bitfield2 = (_bitfield2 & ~0x3) | (value & 0x3);
+            }
+        }
+    }
+}
+";
+
+        return ValidateGeneratedCSharpCompatibleWindowsBindingsAsync(InputContents, expectedOutputContents);
+    }
+}