fix: unsafe accessor generic type args

src/Riok.Mapperly/Descriptors/Enumerables/Capacity/EnsureCapacityMethodSetter.cs

@@ -1,3 +1,4 @@
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Riok.Mapperly.Symbols.Members;
 using static Riok.Mapperly.Emit.Syntax.SyntaxFactoryHelper;
@@ -17,7 +18,12 @@ private EnsureCapacityMethodSetter() { }
 
     public bool SupportsCoalesceAssignment => false;
 
-    public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false)
+    public ExpressionSyntax BuildAssignment(
+        ExpressionSyntax? baseAccess,
+        ExpressionSyntax valueToAssign,
+        INamedTypeSymbol? containingType = null,
+        bool coalesceAssignment = false
+    )
     {
         if (baseAccess == null)
             throw new ArgumentNullException(nameof(baseAccess));

src/Riok.Mapperly/Descriptors/UnsafeAccess/UnsafeFieldAccessor.cs

@@ -43,7 +43,7 @@ public MethodDeclarationSyntax BuildAccessorMethod(SourceEmitterContext ctx)
         return ctx.SyntaxFactory.PublicStaticExternMethod(returnType, methodName, parameters, [attribute]);
     }
 
-    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false)
+    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, INamedTypeSymbol? containingType = null, bool nullConditional = false)
     {
         if (baseAccess == null)
             throw new ArgumentNullException(nameof(baseAccess));
@@ -54,7 +54,10 @@ public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullCondi
             return InvocationWithoutIndention(method);
         }
 
-        var genericClassName = GenericName(className).WithTypeArgumentList(TypeArgumentList(symbol.ContainingType.TypeArguments));
+        // Use the passed containingType for type arguments if provided,
+        // otherwise fall back to the symbol's containing type.
+        var typeArgs = containingType?.TypeArguments ?? symbol.ContainingType.TypeArguments;
+        var genericClassName = GenericName(className).WithTypeArgumentList(TypeArgumentList(typeArgs));
         var invocation = InvocationExpression(MemberAccess(genericClassName, methodName))
             .WithArgumentList(ArgumentListWithoutIndention([baseAccess]));
 
@@ -64,9 +67,14 @@ public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullCondi
         return Conditional(IsNotNull(baseAccess), invocation, DefaultLiteral());
     }
 
-    public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false)
+    public ExpressionSyntax BuildAssignment(
+        ExpressionSyntax? baseAccess,
+        ExpressionSyntax valueToAssign,
+        INamedTypeSymbol? containingType = null,
+        bool coalesceAssignment = false
+    )
     {
-        var access = BuildAccess(baseAccess);
+        var access = BuildAccess(baseAccess, containingType);
         return Assignment(access, valueToAssign, coalesceAssignment);
     }
 }

src/Riok.Mapperly/Descriptors/UnsafeAccess/UnsafeGetPropertyAccessor.cs

@@ -46,7 +46,7 @@ public MethodDeclarationSyntax BuildAccessorMethod(SourceEmitterContext ctx)
         );
     }
 
-    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false)
+    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, INamedTypeSymbol? containingType = null, bool nullConditional = false)
     {
         if (baseAccess == null)
             throw new ArgumentNullException(nameof(baseAccess));
@@ -57,7 +57,12 @@ public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullCondi
             return InvocationWithoutIndention(method);
         }
 
-        var genericClassName = GenericName(className).WithTypeArgumentList(TypeArgumentList(symbol.ContainingType.TypeArguments));
+        // Use the passed containingType for type arguments if provided,
+        // otherwise fall back to the symbol's containing type.
+        // This is critical for inherited members where the cached symbol's
+        // type arguments may differ from the actual derived type being mapped.
+        var typeArgs = containingType?.TypeArguments ?? symbol.ContainingType.TypeArguments;
+        var genericClassName = GenericName(className).WithTypeArgumentList(TypeArgumentList(typeArgs));
         var invocation = InvocationExpression(MemberAccess(genericClassName, methodName))
             .WithArgumentList(ArgumentListWithoutIndention([baseAccess]));
 

src/Riok.Mapperly/Descriptors/UnsafeAccess/UnsafeSetPropertyAccessor.cs

@@ -53,7 +53,12 @@ public MethodDeclarationSyntax BuildAccessorMethod(SourceEmitterContext ctx)
         );
     }
 
-    public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false)
+    public ExpressionSyntax BuildAssignment(
+        ExpressionSyntax? baseAccess,
+        ExpressionSyntax valueToAssign,
+        INamedTypeSymbol? containingType = null,
+        bool coalesceAssignment = false
+    )
     {
         if (baseAccess == null)
             throw new ArgumentNullException(nameof(baseAccess));
@@ -63,8 +68,13 @@ public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, Expression
             return InvocationWithoutIndention(MemberAccess(baseAccess, methodName), valueToAssign);
         }
 
+        // Use the passed containingType for type arguments if provided,
+        // otherwise fall back to the symbol's containing type.
+        // This is critical for inherited members where the cached symbol's
+        // type arguments may differ from the actual derived type being mapped.
+        var typeArgs = containingType?.TypeArguments ?? symbol.ContainingType.TypeArguments;
         var args = new[] { baseAccess, valueToAssign };
-        var genericClassName = GenericName(className).WithTypeArgumentList(TypeArgumentList(symbol.ContainingType.TypeArguments));
+        var genericClassName = GenericName(className).WithTypeArgumentList(TypeArgumentList(typeArgs));
         return InvocationExpression(MemberAccess(genericClassName, methodName)).WithArgumentList(ArgumentListWithoutIndention(args));
     }
 }

src/Riok.Mapperly/Symbols/Members/ConstructorParameterMember.cs

@@ -36,5 +36,9 @@ public class ConstructorParameterMember(IParameterSymbol symbol, SymbolAccessor
     public IMemberSetter BuildSetter(UnsafeAccessorContext ctx) =>
         throw new InvalidOperationException($"Cannot create a setter for {nameof(ParameterSourceMember)}");
 
-    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false) => IdentifierName(Name);
+    public ExpressionSyntax BuildAccess(
+        ExpressionSyntax? baseAccess,
+        INamedTypeSymbol? containingType = null,
+        bool nullConditional = false
+    ) => IdentifierName(Name);
 }

src/Riok.Mapperly/Symbols/Members/FieldMember.cs

@@ -54,13 +54,18 @@ public IMemberSetter BuildSetter(UnsafeAccessorContext ctx)
         return ctx.GetOrBuildFieldGetter(this);
     }
 
-    public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false)
+    public ExpressionSyntax BuildAssignment(
+        ExpressionSyntax? baseAccess,
+        ExpressionSyntax valueToAssign,
+        INamedTypeSymbol? containingType = null,
+        bool coalesceAssignment = false
+    )
     {
         var targetMemberRef = BuildAccess(baseAccess);
         return Assignment(targetMemberRef, valueToAssign, coalesceAssignment);
     }
 
-    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false)
+    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, INamedTypeSymbol? containingType = null, bool nullConditional = false)
     {
         if (baseAccess == null)
             return SyntaxFactory.IdentifierName(Name);

src/Riok.Mapperly/Symbols/Members/IMemberGetter.cs

@@ -1,8 +1,9 @@
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 namespace Riok.Mapperly.Symbols.Members;
 
 public interface IMemberGetter
 {
-    ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false);
+    ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, INamedTypeSymbol? containingType = null, bool nullConditional = false);
 }

src/Riok.Mapperly/Symbols/Members/IMemberSetter.cs

@@ -1,3 +1,4 @@
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 namespace Riok.Mapperly.Symbols.Members;
@@ -6,5 +7,10 @@ public interface IMemberSetter
 {
     bool SupportsCoalesceAssignment { get; }
 
-    ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false);
+    ExpressionSyntax BuildAssignment(
+        ExpressionSyntax? baseAccess,
+        ExpressionSyntax valueToAssign,
+        INamedTypeSymbol? containingType = null,
+        bool coalesceAssignment = false
+    );
 }

src/Riok.Mapperly/Symbols/Members/MemberPathGetter.cs

@@ -56,7 +56,7 @@ public static MemberPathGetter Build(SimpleMappingBuilderContext ctx, MemberPath
         {
             return path.AggregateWithPrevious(
                 baseAccess,
-                (expr, prevProp, prop) => prop.Getter.BuildAccess(expr, prevProp.Member?.IsNullable == true)
+                (expr, prevProp, prop) => prop.Getter.BuildAccess(expr, prop.Member.ContainingType, prevProp.Member?.IsNullable == true)
             );
         }
 
@@ -66,12 +66,12 @@ public static MemberPathGetter Build(SimpleMappingBuilderContext ctx, MemberPath
                 baseAccess,
                 (a, b) =>
                     b.Member.Type.IsNullableValueType()
-                        ? MemberAccess(b.Getter.BuildAccess(a), NullableValueProperty)
-                        : b.Getter.BuildAccess(a)
+                        ? MemberAccess(b.Getter.BuildAccess(a, b.Member.ContainingType), NullableValueProperty)
+                        : b.Getter.BuildAccess(a, b.Member.ContainingType)
             );
         }
 
-        return path.Aggregate(baseAccess, (a, b) => b.Getter.BuildAccess(a));
+        return path.Aggregate(baseAccess, (a, b) => b.Getter.BuildAccess(a, b.Member.ContainingType));
     }
 
     /// <summary>
@@ -99,7 +99,7 @@ private BinaryExpressionSyntax BuildNonNullCondition(ExpressionSyntax baseAccess
         var conditions = new List<BinaryExpressionSyntax>();
         foreach (var pathPart in nullablePath)
         {
-            access = pathPart.Getter.BuildAccess(access);
+            access = pathPart.Getter.BuildAccess(access, pathPart.Member.ContainingType);
 
             if (!pathPart.Member.IsNullable)
                 continue;

src/Riok.Mapperly/Symbols/Members/MemberPathSetter.cs

@@ -13,12 +13,19 @@ public class MemberPathSetter
     private readonly NonEmptyMemberPath _memberPath;
     private readonly MemberPathGetter _baseAccessGetter;
     private readonly IMemberSetter _memberSetter;
+    private readonly IMappableMember _member;
 
-    private MemberPathSetter(NonEmptyMemberPath memberPath, MemberPathGetter baseAccessGetter, IMemberSetter memberSetter)
+    private MemberPathSetter(
+        NonEmptyMemberPath memberPath,
+        MemberPathGetter baseAccessGetter,
+        IMemberSetter memberSetter,
+        IMappableMember member
+    )
     {
         _memberPath = memberPath;
         _baseAccessGetter = baseAccessGetter;
         _memberSetter = memberSetter;
+        _member = member;
     }
 
     public bool SupportsCoalesceAssignment => _memberSetter.SupportsCoalesceAssignment;
@@ -30,13 +37,13 @@ public static MemberPathSetter Build(SimpleMappingBuilderContext ctx, NonEmptyMe
         var objectPath = MemberPath.Create(path.RootType, path.ObjectPath.ToList());
         var objectGetter = objectPath.BuildGetter(ctx);
         var memberSetter = path.Member.BuildSetter(ctx.UnsafeAccessorContext);
-        return new MemberPathSetter(path, objectGetter, memberSetter);
+        return new MemberPathSetter(path, objectGetter, memberSetter, path.Member);
     }
 
     public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false)
     {
         baseAccess = _baseAccessGetter.BuildAccess(baseAccess);
-        return _memberSetter.BuildAssignment(baseAccess, valueToAssign, coalesceAssignment);
+        return _memberSetter.BuildAssignment(baseAccess, valueToAssign, _member.ContainingType, coalesceAssignment);
     }
 
     public override bool Equals(object? obj)

src/Riok.Mapperly/Symbols/Members/ParameterSourceMember.cs

@@ -33,7 +33,11 @@ public class ParameterSourceMember(MethodParameter parameter) : IMappableMember,
     public IMemberSetter BuildSetter(UnsafeAccessorContext ctx) =>
         throw new InvalidOperationException($"Cannot create a setter for {nameof(ParameterSourceMember)}");
 
-    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false) => IdentifierName(Name);
+    public ExpressionSyntax BuildAccess(
+        ExpressionSyntax? baseAccess,
+        INamedTypeSymbol? containingType = null,
+        bool nullConditional = false
+    ) => IdentifierName(Name);
 
     public override bool Equals(object? obj)
     {

src/Riok.Mapperly/Symbols/Members/PropertyMember.cs

@@ -64,15 +64,20 @@ public IMemberSetter BuildSetter(UnsafeAccessorContext ctx)
         return ctx.GetOrBuildPropertySetter(this);
     }
 
-    public ExpressionSyntax BuildAssignment(ExpressionSyntax? baseAccess, ExpressionSyntax valueToAssign, bool coalesceAssignment = false)
+    public ExpressionSyntax BuildAssignment(
+        ExpressionSyntax? baseAccess,
+        ExpressionSyntax valueToAssign,
+        INamedTypeSymbol? containingType = null,
+        bool coalesceAssignment = false
+    )
     {
         Debug.Assert(CanSetDirectly);
         ExpressionSyntax targetMember = baseAccess == null ? IdentifierName(Name) : MemberAccess(baseAccess, Name);
 
         return Assignment(targetMember, valueToAssign, coalesceAssignment);
     }
 
-    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, bool nullConditional = false)
+    public ExpressionSyntax BuildAccess(ExpressionSyntax? baseAccess, INamedTypeSymbol? containingType = null, bool nullConditional = false)
     {
         Debug.Assert(CanGetDirectly);
         if (baseAccess == null)

test/Riok.Mapperly.Tests/Mapping/UnsafeAccessorTest.cs

@@ -88,6 +88,29 @@ public Task PrivatePropertyInGenericClassMultipleTypeParametersWithConstraints()
         return TestHelper.VerifyGenerator(source);
     }
 
+    [Fact]
+    public Task ProtectedPropertyInGenericBaseClassWithDifferentInstantiations()
+    {
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            """
+            partial B1 Map1(A1 source);
+            partial B2 Map2(A2 source);
+            """,
+            TestSourceBuilderOptions.WithMemberVisibility(MemberVisibility.All),
+            "interface IA { }",
+            "interface IB : IA { }",
+            "interface IC : IA { }",
+            "class A<T> where T : IA { protected T _value { get; set; } }",
+            "class A1 : A<IB> { }",
+            "class A2 : A<IC> { }",
+            "class B<T> where T : IA { protected T _value { get; set; } }",
+            "class B1 : B<IB> { }",
+            "class B2 : B<IC> { }"
+        );
+
+        return TestHelper.VerifyGenerator(source);
+    }
+
     [Fact]
     public Task ProtectedProperty()
     {

test/Riok.Mapperly.Tests/_snapshots/UnsafeAccessorTest.PrivatePropertyInGenericClassMultiple#Mapper.g.verified.cs

@@ -15,7 +15,7 @@ public partial class Mapper
     partial global::B<float> Map(global::A<float> source)
     {
         var target = new global::B<float>();
-        BAccessor<int>.SetValue(target, AAccessor<int>.GetValue(source));
+        BAccessor<float>.SetValue(target, AAccessor<float>.GetValue(source));
         return target;
     }
 }

test/Riok.Mapperly.Tests/_snapshots/UnsafeAccessorTest.ProtectedPropertyInGenericBaseClassWithDifferentInstantiations#Mapper.g.verified.cs

@@ -0,0 +1,39 @@
+//HintName: Mapper.g.cs
+// <auto-generated />
+#nullable enable
+public partial class Mapper
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    partial global::B1 Map1(global::A1 source)
+    {
+        var target = new global::B1();
+        BAccessor<global::IB>.SetValue(target, AAccessor<global::IB>.GetValue(source));
+        return target;
+    }
+
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    partial global::B2 Map2(global::A2 source)
+    {
+        var target = new global::B2();
+        BAccessor<global::IC>.SetValue(target, AAccessor<global::IC>.GetValue(source));
+        return target;
+    }
+}
+
+[global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+static file class AAccessor<T>
+    where T : global::IA
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Method, Name = "get__value")]
+    public static extern T GetValue(global::A<T> source);
+}
+
+[global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+static file class BAccessor<T>
+    where T : global::IA
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Method, Name = "set__value")]
+    public static extern void SetValue(global::B<T> target, T value);
+}