[cdac] Convert TypeHandle to the ITypeHandle interface

docs/design/datacontracts/ManagedTypeSource.md

@@ -21,10 +21,10 @@ bool TryGetTypeInfo(string fullyQualifiedName, out Target.TypeInfo info);
 // Throws InvalidOperationException if the type cannot be resolved.
 Target.TypeInfo GetTypeInfo(string fullyQualifiedName);
 
-// Return true and populate `typeHandle` with the runtime TypeHandle for the type,
+// Return true and populate `typeHandle` with the ITypeHandle for the runtime type,
 // or false if the type cannot be resolved.
-bool TryGetTypeHandle(string fullyQualifiedName, out TypeHandle typeHandle);
-TypeHandle GetTypeHandle(string fullyQualifiedName);
+bool TryGetTypeHandle(string fullyQualifiedName, [NotNullWhen(true)] out ITypeHandle? typeHandle);
+ITypeHandle GetTypeHandle(string fullyQualifiedName);
 
 // Return true and populate `address` with the address of the named static field,
 // or false if the type / field cannot be resolved or its statics storage has not
@@ -68,7 +68,11 @@ they read in their own `### Managed types used` section.
 ``` csharp
 // Type resolution: parse the fully-qualified name, walk System.Private.CoreLib's
 // metadata to locate the TypeDef, then map TypeDef -> MethodTable via the loader.
-bool TryResolveType(string managedFqName, out TypeHandle th, out MetadataReader mdReader, out TypeDefinition typeDef)
+bool TryResolveType(
+    string managedFqName,
+    [NotNullWhen(true)] out ITypeHandle? th,
+    [NotNullWhen(true)] out MetadataReader? mdReader,
+    out TypeDefinition typeDef)
 {
     ILoader loader = target.Contracts.Loader;
     TargetPointer systemAssembly = loader.GetSystemAssembly();
@@ -96,14 +100,14 @@ bool TryResolveType(string managedFqName, out TypeHandle th, out MetadataReader
     return true;
 }
 
-bool TryGetTypeHandle(string fqn, out TypeHandle th)
+bool TryGetTypeHandle(string fqn, [NotNullWhen(true)] out ITypeHandle? th)
 {
     return TryResolveType(fqn, out th, out _, out _);
 }
 
 bool TryGetTypeInfo(string fqn, out Target.TypeInfo info)
 {
-    if (!TryResolveType(fqn, out TypeHandle th, out MetadataReader mdReader, out TypeDefinition typeDef))
+    if (!TryResolveType(fqn, out ITypeHandle? th, out MetadataReader? mdReader, out TypeDefinition typeDef))
         return false;
 
     IRuntimeTypeSystem rts = target.Contracts.RuntimeTypeSystem;
@@ -147,7 +151,7 @@ bool TryGetStaticFieldAddress(string fqn, string fieldName, out TargetPointer ad
     // cannot dereference a small offset-from-zero when the class has not been
     // initialized.
     TargetPointer enclosingMT = rts.GetMTOfEnclosingClass(fdAddr);
-    TypeHandle ctx = rts.GetTypeHandle(enclosingMT);
+    ITypeHandle ctx = rts.GetTypeHandle(enclosingMT);
     CorElementType et = rts.GetFieldDescType(fdAddr);
     bool isGC = et is CorElementType.Class or CorElementType.ValueType;
     TargetPointer @base = isGC
@@ -174,7 +178,7 @@ bool TryGetThreadStaticFieldAddress(string fqn, string fieldName, TargetPointer
     // thread so callers cannot dereference a small offset-from-zero when this
     // thread has not initialized thread-static storage for the type.
     TargetPointer enclosingMT = rts.GetMTOfEnclosingClass(fdAddr);
-    TypeHandle ctx = rts.GetTypeHandle(enclosingMT);
+    ITypeHandle ctx = rts.GetTypeHandle(enclosingMT);
     CorElementType et = rts.GetFieldDescType(fdAddr);
     bool isGC = et is CorElementType.Class or CorElementType.ValueType;
     TargetPointer @base = isGC
@@ -189,7 +193,7 @@ bool TryGetThreadStaticFieldAddress(string fqn, string fieldName, TargetPointer
 
 bool TryGetFieldDesc(string fqn, string fieldName, out TargetPointer fdAddr)
 {
-    if (!TryResolveType(fqn, out TypeHandle th, out _, out _))
+    if (!TryResolveType(fqn, out ITypeHandle th, out _, out _))
     {
         fdAddr = TargetPointer.Null;
         return false;

docs/design/datacontracts/RuntimeMutableTypeSystem.md

@@ -5,7 +5,7 @@ This contract exposes runtime type system information about changes that occurre
 ## APIs of contract
 
 ```csharp
-IEnumerable<TargetPointer> EnumerateAddedFieldDescs(TypeHandle typeHandle, bool staticFields);
+IEnumerable<TargetPointer> EnumerateAddedFieldDescs(ITypeHandle typeHandle, bool staticFields);
 bool IsFieldDescEnCNew(TargetPointer fieldDescPointer);
 bool DoesEnCFieldDescNeedFixup(TargetPointer encFieldDescPointer);
 TargetPointer GetEnCStaticFieldDataAddress(TargetPointer encFieldDescPointer);
@@ -59,7 +59,7 @@ internal enum FieldDescFlags2 : uint
     OffsetMask = 0x07ffffff,
 }
 
-IEnumerable<TargetPointer> EnumerateAddedFieldDescs(TypeHandle typeHandle, bool staticFields)
+IEnumerable<TargetPointer> EnumerateAddedFieldDescs(ITypeHandle typeHandle, bool staticFields)
 {
     // get modulePtr and moduleHandle from typeHandle
     // if there is no EnC data, yield break