Add runtime type access via callWithReflectedType

packages/reflectable/lib/mirrors.dart

@@ -674,7 +674,7 @@ abstract class CombinatorMirror implements Mirror {
 
 /// A [TypeMirror] reflects a Dart language class, typedef,
 /// function type or type variable.
-abstract class TypeMirror implements DeclarationMirror {
+abstract class TypeMirror<T> implements DeclarationMirror {
   /// Returns true if this mirror reflects dynamic, a non-generic class or
   /// typedef, or an instantiated generic class or typedef with support in
   /// the execution mode. Otherwise, returns false.
@@ -817,10 +817,16 @@ abstract class TypeMirror implements DeclarationMirror {
   /// Returns true iff this type mirror represents a potentially non-nullable
   /// type.
   bool get isPotentiallyNonNullable;
+
+  /// Invokes the provided function with the reflected type as a type argument.
+  ///
+  /// Allows executing generic code with the actual runtime type represented
+  /// by this mirror.
+  R callWithReflectedType<R>(R Function<X>() f);
 }
 
 /// A [ClassMirror] reflects a Dart language class.
-abstract class ClassMirror implements TypeMirror, ObjectMirror {
+abstract class ClassMirror<T> implements TypeMirror<T>, ObjectMirror {
   /// A mirror on the superclass on the reflectee.
   ///
   /// If this type is [:Object:], the superclass will be null.
@@ -1077,7 +1083,7 @@ abstract class FunctionTypeMirror implements ClassMirror {
 }
 
 /// A [TypeVariableMirror] represents a type parameter of a generic type.
-abstract class TypeVariableMirror extends TypeMirror {
+abstract class TypeVariableMirror<T> extends TypeMirror<T> {
   /// A mirror on the type that is the upper bound of this type variable.
   ///
   /// Required capabilities: [upperBound] requires a [TypeCapability].

packages/reflectable/lib/reflectable.dart

@@ -40,7 +40,7 @@ abstract class ReflectableInterface {
   ///
   /// Throws a [NoSuchCapabilityError] if the class of [o] has not been marked
   /// for reflection.
-  InstanceMirror reflect(Object o);
+  InstanceMirror reflect<T extends Object>(T o);
 
   /// Returns true if this reflector has capabilities for the given Type.
   bool canReflectType(Type type);

packages/reflectable/lib/src/reflectable_builder_based.dart

@@ -148,14 +148,15 @@ class ReflectorData {
     return typeToTypeMirrorCache[type];
   }
 
-  ClassMirror? classMirrorForInstance(Object? instance) {
+  ClassMirror? classMirrorForInstance<T>(Object? instance) {
     TypeMirror? result = typeMirrorForType(instance.runtimeType);
+
     if (result is ClassMirror) return result;
     // Check if we have a generic class that matches.
     for (TypeMirror typeMirror in _typeToTypeMirrorCache!.values) {
       if (typeMirror is GenericClassMirrorImpl) {
         if (typeMirror._isGenericRuntimeTypeOf(instance)) {
-          return _createInstantiatedGenericClass(
+          return _createInstantiatedGenericClass<T>(
             typeMirror,
             instance.runtimeType,
             null,
@@ -205,15 +206,15 @@ abstract class _DataCaching {
   }
 }
 
-class _InstanceMirrorImpl extends _DataCaching implements InstanceMirror {
+class _InstanceMirrorImpl<T> extends _DataCaching implements InstanceMirror {
   @override
   final ReflectableImpl _reflector;
 
   @override
   final Object? reflectee;
 
   _InstanceMirrorImpl(this.reflectee, this._reflector) {
-    _type = _data.classMirrorForInstance(reflectee) as ClassMirrorBase?;
+    _type = _data.classMirrorForInstance<T>(reflectee) as ClassMirrorBase?;
     if (_type == null) {
       // If there is no `TypeCapability` and also no `InstanceInvokeCapability`
       // then can do almost nothing. Nevertheless, we can still offer a
@@ -390,7 +391,8 @@ class _InstanceMirrorImpl extends _DataCaching implements InstanceMirror {
 
 typedef MethodMirrorProvider = MethodMirror? Function(String methodName);
 
-abstract class ClassMirrorBase extends _DataCaching implements ClassMirror {
+abstract class ClassMirrorBase<T> extends _DataCaching
+    implements ClassMirror<T> {
   /// The reflector which represents the mirror system that this
   /// mirror belongs to.
   @override
@@ -974,9 +976,12 @@ abstract class ClassMirrorBase extends _DataCaching implements ClassMirror {
     if (_superclassIndex == null) return null; // Superclass of [Object].
     return _data.typeMirrors[_superclassIndex] as ClassMirrorBase?;
   }
+
+  @override
+  D callWithReflectedType<D>(D Function<X>() f) => f<T>();
 }
 
-class NonGenericClassMirrorImpl extends ClassMirrorBase {
+class NonGenericClassMirrorImpl<T> extends ClassMirrorBase<T> {
   NonGenericClassMirrorImpl(
     super.simpleName,
     super.qualifiedName,
@@ -1067,7 +1072,7 @@ class NonGenericClassMirrorImpl extends ClassMirrorBase {
 
 typedef InstanceChecker = bool Function(Object?);
 
-class GenericClassMirrorImpl extends ClassMirrorBase {
+class GenericClassMirrorImpl<T> extends ClassMirrorBase<T> {
   /// Used to enable instance checks. Let O be an instance and let C denote the
   /// generic class modeled by this mirror. The check is then such that the
   /// result is true iff there exists a list of type arguments X1..Xk such that
@@ -1216,7 +1221,7 @@ class GenericClassMirrorImpl extends ClassMirrorBase {
   String toString() => 'GenericClassMirrorImpl($qualifiedName)';
 }
 
-class InstantiatedGenericClassMirrorImpl extends ClassMirrorBase {
+class InstantiatedGenericClassMirrorImpl<T> extends ClassMirrorBase<T> {
   final GenericClassMirrorImpl _originalDeclaration;
   final Type? _reflectedType;
 
@@ -1360,11 +1365,14 @@ class InstantiatedGenericClassMirrorImpl extends ClassMirrorBase {
   @override
   int get hashCode => originalDeclaration.hashCode ^ _reflectedType.hashCode;
 
+  @override
+  D callWithReflectedType<D>(D Function<X>() f) => f<T>();
+
   @override
   String toString() => 'InstantiatedGenericClassMirrorImpl($qualifiedName)';
 }
 
-InstantiatedGenericClassMirrorImpl _createInstantiatedGenericClass(
+InstantiatedGenericClassMirrorImpl<T> _createInstantiatedGenericClass<T>(
   GenericClassMirrorImpl genericClassMirror,
   Type? reflectedType,
   List<int>? reflectedTypeArguments, [
@@ -1373,7 +1381,7 @@ InstantiatedGenericClassMirrorImpl _createInstantiatedGenericClass(
   // TODO(eernst) implement: Pass a representation of type arguments to this
   // method, and create an instantiated generic class which includes that
   // information.
-  return InstantiatedGenericClassMirrorImpl(
+  return InstantiatedGenericClassMirrorImpl<T>(
     genericClassMirror.simpleName,
     genericClassMirror.qualifiedName,
     descriptor ?? genericClassMirror._descriptor,
@@ -1573,6 +1581,11 @@ class TypeVariableMirrorImpl extends _DataCaching
     }
     return _data.typeMirrors[_ownerIndex];
   }
+
+  @override
+  D callWithReflectedType<D>(D Function<X>() f) => throw UnsupportedError(
+    'Attempt to call `callWithReflectedType` on type variable $simpleName',
+  );
 }
 
 class LibraryMirrorImpl extends _DataCaching implements LibraryMirror {
@@ -1820,7 +1833,7 @@ class LibraryMirrorImpl extends _DataCaching implements LibraryMirror {
       throw unimplementedError('libraryDependencies');
 }
 
-class MethodMirrorImpl extends _DataCaching implements MethodMirror {
+class MethodMirrorImpl<T> extends _DataCaching implements MethodMirror {
   /// An encoding of the attributes and kind of this mirror.
   final int _descriptor;
 
@@ -1997,7 +2010,7 @@ class MethodMirrorImpl extends _DataCaching implements MethodMirror {
     if (_hasClassReturnType) {
       TypeMirror typeMirror = _data.typeMirrors[_returnTypeIndex];
       return _hasGenericReturnType
-          ? _createInstantiatedGenericClass(
+          ? _createInstantiatedGenericClass<T>(
               typeMirror as GenericClassMirrorImpl,
               null,
               _reflectedTypeArgumentsOfReturnType,
@@ -2307,7 +2320,7 @@ class ImplicitSetterMirrorImpl extends ImplicitAccessorMirrorImpl {
   String toString() => 'ImplicitSetterMirrorImpl($qualifiedName)';
 }
 
-abstract class VariableMirrorBase extends _DataCaching
+abstract class VariableMirrorBase<T> extends _DataCaching
     implements VariableMirror {
   final String _name;
   final int _descriptor;
@@ -2401,15 +2414,15 @@ abstract class VariableMirrorBase extends _DataCaching
       if (typeMirror.isNullable != _isNullable ||
           typeMirror.isNonNullable != _isNonNullable) {
         if (_isGenericType) {
-          return _createInstantiatedGenericClass(
+          return _createInstantiatedGenericClass<T>(
             typeMirror as GenericClassMirrorImpl,
             hasReflectedType ? reflectedType : null,
             _reflectedTypeArguments,
             _descriptor,
           );
         } else {
           var classMirror = typeMirror as NonGenericClassMirrorImpl;
-          return NonGenericClassMirrorImpl(
+          return NonGenericClassMirrorImpl<T>(
             classMirror.simpleName,
             classMirror.qualifiedName,
             _descriptor,
@@ -2431,7 +2444,7 @@ abstract class VariableMirrorBase extends _DataCaching
         }
       } else {
         return _isGenericType
-            ? _createInstantiatedGenericClass(
+            ? _createInstantiatedGenericClass<T>(
                 typeMirror as GenericClassMirrorImpl,
                 hasReflectedType ? reflectedType : null,
                 _reflectedTypeArguments,
@@ -2487,7 +2500,7 @@ abstract class VariableMirrorBase extends _DataCaching
   int get hashCode => simpleName.hashCode ^ owner.hashCode;
 }
 
-class VariableMirrorImpl extends VariableMirrorBase {
+class VariableMirrorImpl<T> extends VariableMirrorBase<T> {
   @override
   DeclarationMirror get owner {
     if (_ownerIndex == noCapabilityIndex) {
@@ -2532,7 +2545,7 @@ class VariableMirrorImpl extends VariableMirrorBase {
   int get hashCode;
 }
 
-class ParameterMirrorImpl extends VariableMirrorBase
+class ParameterMirrorImpl<T> extends VariableMirrorBase<T>
     implements ParameterMirror {
   final Object? _defaultValue;
 
@@ -2601,7 +2614,7 @@ class ParameterMirrorImpl extends VariableMirrorBase
   int get hashCode;
 }
 
-abstract class SpecialTypeMirrorImpl implements TypeMirror {
+abstract class SpecialTypeMirrorImpl<T> implements TypeMirror<T> {
   @override
   bool get isPrivate => false;
 
@@ -2637,11 +2650,14 @@ abstract class SpecialTypeMirrorImpl implements TypeMirror {
 
   @override
   List<Object> get metadata => <Object>[];
+
+  @override
+  D callWithReflectedType<D>(D Function<X>() f) => f<T>();
 }
 
 Type _typeOf<X>() => X;
 
-class DynamicMirrorImpl extends SpecialTypeMirrorImpl {
+class DynamicMirrorImpl extends SpecialTypeMirrorImpl<dynamic> {
   @override
   bool get isNullable => true;
 
@@ -2669,7 +2685,7 @@ class DynamicMirrorImpl extends SpecialTypeMirrorImpl {
   bool isAssignableTo(TypeMirror other) => true;
 }
 
-class VoidMirrorImpl extends SpecialTypeMirrorImpl {
+class VoidMirrorImpl extends SpecialTypeMirrorImpl<void> {
   @override
   bool get isNullable => true;
 
@@ -2702,7 +2718,7 @@ class VoidMirrorImpl extends SpecialTypeMirrorImpl {
       other is DynamicMirrorImpl || other is VoidMirrorImpl;
 }
 
-class NeverMirrorImpl extends SpecialTypeMirrorImpl {
+class NeverMirrorImpl extends SpecialTypeMirrorImpl<Never> {
   final bool hasQuestionMark;
 
   NeverMirrorImpl({this.hasQuestionMark = false});
@@ -2761,8 +2777,8 @@ abstract class ReflectableImpl extends ReflectableBase
   }
 
   @override
-  InstanceMirror reflect(Object reflectee) {
-    return _InstanceMirrorImpl(reflectee, this);
+  InstanceMirror reflect<T extends Object>(T reflectee) {
+    return _InstanceMirrorImpl<T>(reflectee, this);
   }
 
   bool get _hasTypeCapability {

packages/reflectable_builder/lib/src/builder_implementation.dart

@@ -860,6 +860,49 @@ class _ReflectorDomain {
     return 'const $prefix${_reflector.name}()';
   }
 
+  /// Returns code for generic type arguments to use in mirror declarations.
+  ///
+  /// Generates a string like `<PrefixClassName>` for generic type parameters
+  /// in mirror constructors. Returns empty string if the type cannot be
+  /// represented (e.g., private classes, mixin applications, or non-interface
+  /// types).
+  Future<String> _typeGenericCode(
+    _ImportCollector importCollector, {
+    DartType? type,
+    InterfaceElement? element,
+  }) async {
+    if (type == null && element == null) {
+      return '';
+    }
+
+    if (type != null && type is! InterfaceType) {
+      return '';
+    }
+
+    InterfaceElement classElement =
+        (type as InterfaceType?)?.element ?? element!;
+
+    // MixinApplications cannot be used as type arguments
+    if (classElement is MixinApplication) {
+      return '';
+    }
+
+    if (classElement.isPrivate) {
+      return '';
+    }
+
+    String prefix = importCollector._getPrefix(classElement.library);
+    if (_isPrivateName(classElement.name)) {
+      await _severe(
+        'Cannot access private name `${classElement.name}`',
+        classElement,
+      );
+      return '';
+    }
+
+    return '<$prefix${classElement.name}>';
+  }
+
   /// Generate the code which will create a `ReflectorData` instance
   /// containing the mirrors and other reflection data which is needed for
   /// `_reflector` to behave correctly.
@@ -1706,7 +1749,7 @@ class _ReflectorDomain {
     }
 
     if (interfaceElement.typeParameters.isEmpty) {
-      return "r.NonGenericClassMirrorImpl(r'${classDomain._simpleName}', "
+      return "r.NonGenericClassMirrorImpl${await _typeGenericCode(importCollector, element: classDomain._interfaceElement)}(r'${classDomain._simpleName}', "
           "r'${_qualifiedName(interfaceElement)}', $descriptor, $classIndex, "
           '${await _constConstructionCode(importCollector)}, '
           '$declarationsCode, $instanceMembersCode, $staticMembersCode, '
@@ -1792,7 +1835,7 @@ class _ReflectorDomain {
         typedefs,
       );
 
-      return "r.GenericClassMirrorImpl(r'${classDomain._simpleName}', "
+      return "r.GenericClassMirrorImpl${await _typeGenericCode(importCollector, element: classDomain._interfaceElement)}(r'${classDomain._simpleName}', "
           "r'${_qualifiedName(interfaceElement)}', $descriptor, $classIndex, "
           '${await _constConstructionCode(importCollector)}, '
           '$declarationsCode, $instanceMembersCode, $staticMembersCode, '
@@ -1889,7 +1932,7 @@ class _ReflectorDomain {
               _generatedLibraryId,
             )
           : null;
-      return "r.MethodMirrorImpl(r'${element.name}', $descriptor, "
+      return "r.MethodMirrorImpl${await _typeGenericCode(importCollector, type: element.returnType)}(r'${element.name}', $descriptor, "
           '$ownerIndex, $returnTypeIndex, $reflectedReturnTypeIndex, '
           '$dynamicReflectedReturnTypeIndex, '
           '$reflectedTypeArgumentsOfReturnType, $parameterIndicesCode, '
@@ -1950,7 +1993,7 @@ class _ReflectorDomain {
       // it is a `List<Object>`, which has no other natural encoding.
       metadataCode = null;
     }
-    return "r.VariableMirrorImpl(r'${element.name}', $descriptor, "
+    return "r.VariableMirrorImpl${await _typeGenericCode(importCollector, type: element.type)}(r'${element.name}', $descriptor, "
         '$ownerIndex, ${await _constConstructionCode(importCollector)}, '
         '$classMirrorIndex, $reflectedTypeIndex, '
         '$dynamicReflectedTypeIndex, $reflectedTypeArguments, '
@@ -2011,7 +2054,7 @@ class _ReflectorDomain {
       // it is a `List<Object>`, which has no other natural encoding.
       metadataCode = null;
     }
-    return "r.VariableMirrorImpl(r'${element.name}', $descriptor, "
+    return "r.VariableMirrorImpl${await _typeGenericCode(importCollector, type: element.type)}(r'${element.name}', $descriptor, "
         '$ownerIndex, ${await _constConstructionCode(importCollector)}, '
         '$classMirrorIndex, $reflectedTypeIndex, '
         '$dynamicReflectedTypeIndex, $reflectedTypeArguments, $metadataCode)';
@@ -2664,7 +2707,7 @@ class _ReflectorDomain {
         ? '#${element.name}'
         : 'null';
 
-    return "r.ParameterMirrorImpl(r'${element.name}', $descriptor, "
+    return "r.ParameterMirrorImpl${await _typeGenericCode(importCollector, type: element.type)}(r'${element.name}', $descriptor, "
         '$ownerIndex, ${await _constConstructionCode(importCollector)}, '
         '$classMirrorIndex, $reflectedTypeIndex, $dynamicReflectedTypeIndex, '
         '$reflectedTypeArguments, $metadataCode, $defaultValueCode, '