make MemberMap.DestinationType a regular property, with storage

Author: lbargaoanu

src/AutoMapper/ConstructorMap.cs

@@ -67,11 +67,13 @@ public bool ApplyMap(TypeMap typeMap, IncludedMember includedMember = null)
 [EditorBrowsable(EditorBrowsableState.Never)]
 public class ConstructorParameterMap : MemberMap
 {
-    public ConstructorParameterMap(TypeMap typeMap, ParameterInfo parameter, MemberInfo[] sourceMembers) : base(typeMap)
+    public ConstructorParameterMap(TypeMap typeMap, ParameterInfo parameter, MemberInfo[] sourceMembers) : base(typeMap, parameter.ParameterType)
     {
         Parameter = parameter;
-        var parameterType = parameter.ParameterType;
-        DestinationType = parameterType.IsByRef ? parameterType.GetElementType() : parameterType;
+        if(DestinationType.IsByRef)
+        {
+            DestinationType = DestinationType.GetElementType();
+        }
         if (sourceMembers.Length > 0)
         {
             MapByConvention(sourceMembers);
@@ -82,7 +84,6 @@ public ConstructorParameterMap(TypeMap typeMap, ParameterInfo parameter, MemberI
         }
     }
     public ParameterInfo Parameter { get; }
-    public override Type DestinationType { get; protected set; }
     public override IncludedMember IncludedMember { get; protected set; }
     public override MemberInfo[] SourceMembers { get; set; }
     public override string DestinationName => Parameter.Name;

src/AutoMapper/MemberMap.cs

@@ -6,8 +6,8 @@ namespace AutoMapper;
 public class MemberMap : IValueResolver
 {
     private protected Type _sourceType;
-    protected MemberMap(TypeMap typeMap) => TypeMap = typeMap;
-    internal static readonly MemberMap Instance = new(null);
+    protected MemberMap(TypeMap typeMap, Type destinationType) => (TypeMap, DestinationType) = (typeMap, destinationType);
+    internal static readonly MemberMap Instance = new(null, null);
     public TypeMap TypeMap { get; protected set; }
     public LambdaExpression CustomMapExpression => Resolver?.ProjectToExpression;
     public bool IsResolveConfigured => Resolver != null && Resolver != this;
@@ -22,7 +22,7 @@ public void SetResolver(IValueResolver resolver)
     public virtual MemberInfo[] SourceMembers { get => []; set { } }
     public virtual IncludedMember IncludedMember { get => default; protected set { } }
     public virtual string DestinationName => default;
-    public virtual Type DestinationType { get => default; protected set { } }
+    public Type DestinationType { get; protected set; }
     public virtual TypePair Types() => new(SourceType, DestinationType);
     public bool CanResolveValue => !Ignored && Resolver != null;
     public bool IsMapped => Ignored || Resolver != null;

src/AutoMapper/PathMap.cs

@@ -1,7 +1,8 @@
 namespace AutoMapper;
 [DebuggerDisplay("{DestinationExpression}")]
 [EditorBrowsable(EditorBrowsableState.Never)]
-public sealed class PathMap(LambdaExpression destinationExpression, MemberPath memberPath, TypeMap typeMap) : MemberMap(typeMap)
+public sealed class PathMap(LambdaExpression destinationExpression, MemberPath memberPath, TypeMap typeMap) 
+    : MemberMap(typeMap, memberPath.Last.GetMemberType())
 {
     public PathMap(PathMap pathMap, TypeMap typeMap, IncludedMember includedMember) : this(pathMap.DestinationExpression, pathMap.MemberPath, typeMap)
     {
@@ -13,7 +14,6 @@ public PathMap(PathMap pathMap, TypeMap typeMap, IncludedMember includedMember)
     public override Type SourceType => Resolver.ResolvedType;
     public LambdaExpression DestinationExpression { get; } = destinationExpression;
     public MemberPath MemberPath { get; } = memberPath;
-    public override Type DestinationType => MemberPath.Last.GetMemberType();
     public override string DestinationName => MemberPath.ToString();
     public override bool CanBeSet => ReflectionHelper.CanBeSet(MemberPath.Last);
     public override bool Ignored { get; set; }

src/AutoMapper/PropertyMap.cs

@@ -5,19 +5,15 @@ namespace AutoMapper;
 public sealed class PropertyMap : MemberMap
 {
     private MemberMapDetails _details;
-    public PropertyMap(MemberInfo destinationMember, Type destinationMemberType, TypeMap typeMap) : base(typeMap)
-    {
+    public PropertyMap(MemberInfo destinationMember, Type destinationMemberType, TypeMap typeMap) : base(typeMap, destinationMemberType) =>
         DestinationMember = destinationMember;
-        DestinationType = destinationMemberType;
-    }
-    public PropertyMap(PropertyMap inheritedMappedProperty, TypeMap typeMap) : base(typeMap)
+    public PropertyMap(PropertyMap inheritedMappedProperty, TypeMap typeMap) : base(typeMap, inheritedMappedProperty.DestinationType)
     {
         DestinationMember = inheritedMappedProperty.DestinationMember;
         if (DestinationMember.DeclaringType.ContainsGenericParameters)
         {
             DestinationMember = typeMap.DestinationSetters.Single(m => m.Name == DestinationMember.Name);
         }
-        DestinationType = inheritedMappedProperty.DestinationType;
         if (DestinationType.ContainsGenericParameters)
         {
             DestinationType = DestinationMember.GetMemberType();
@@ -29,7 +25,6 @@ public PropertyMap(PropertyMap includedMemberMap, TypeMap typeMap, IncludedMembe
     private MemberMapDetails Details => _details ??= new();
     public MemberInfo DestinationMember { get; }
     public override string DestinationName => DestinationMember?.Name;
-    public override Type DestinationType { get; protected set; }
     public override MemberInfo[] SourceMembers { get; set; } = [];
     public override bool CanBeSet => DestinationMember.CanBeSet();
     public override bool Ignored { get; set; }