Detect and reject illegal recursive types (non-contractive types).

runtime/vm/object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 1282 matching lines @@
 
   // Check the 'more specific' relationship, considering only a subvector of
   // length 'len' starting at 'from_index'.
   bool IsMoreSpecificThan(const TypeArguments& other,
                           intptr_t from_index,
                           intptr_t len,
                           Error* bound_error) const {
     return TypeTest(kIsMoreSpecificThan, other, from_index, len, bound_error);
   }
 
-  // Check if the vectors are equal.
+  // Check if the vectors are equal (they may be null).
   bool Equals(const TypeArguments& other) const {
-    return IsEquivalent(other);
+    return IsSubvectorEquivalent(other, 0, IsNull() ? 0 : Length());
   }
 
   bool IsEquivalent(const TypeArguments& other,
-                    GrowableObjectArray* trail = NULL) const;
+                    GrowableObjectArray* trail = NULL) const {
+    return IsSubvectorEquivalent(other, 0, IsNull() ? 0 : Length(), trail);
+  }
+  bool IsSubvectorEquivalent(const TypeArguments& other,
+                             intptr_t from_index,
+                             intptr_t len,
+                             GrowableObjectArray* trail = NULL) const;
 
-  bool IsInstantiated(GrowableObjectArray* trail = NULL) const;
+  // Check if the vector is instantiated (it must not be null).
+  bool IsInstantiated(GrowableObjectArray* trail = NULL) const {
+    return IsSubvectorInstantiated(0, Length(), trail);
+  }
+  bool IsSubvectorInstantiated(intptr_t from_index,
+                               intptr_t len,
+                               GrowableObjectArray* trail = NULL) const;
   bool IsUninstantiatedIdentity() const;
   bool CanShareInstantiatorTypeArguments(const Class& instantiator_class) const;
 
-  // Returns true if all types of this vector are respectively, resolved,
+  // Return true if all types of this vector are respectively, resolved,
   // finalized, or bounded.
   bool IsResolved() const;
   bool IsFinalized() const;
   bool IsBounded() const;
 
+  // Return true if this vector contains a recursive type argument.
+  bool IsRecursive() const;
+
   // Clone this type argument vector and clone all unfinalized type arguments.
   // Finalized type arguments are shared.
   RawTypeArguments* CloneUnfinalized() const;
 
   // Canonicalize only if instantiated, otherwise returns 'this'.
   RawTypeArguments* Canonicalize(GrowableObjectArray* trail = NULL) const;
 
   // Return 'this' if this type argument vector is instantiated, i.e. if it does
   // not refer to type parameters. Otherwise, return a new type argument vector
   // where each reference to a type parameter is replaced with the corresponding
@@ skipping 2794 matching lines @@
   virtual RawClass* type_class() const;
   virtual RawUnresolvedClass* unresolved_class() const;
   virtual RawTypeArguments* arguments() const;
   virtual intptr_t token_pos() const;
   virtual bool IsInstantiated(GrowableObjectArray* trail = NULL) const;
   virtual bool Equals(const Instance& other) const {
     return IsEquivalent(other);
   }
   virtual bool IsEquivalent(const Instance& other,
                             GrowableObjectArray* trail = NULL) const;
+  virtual bool IsRecursive() const;
 
   // Instantiate this type using the given type argument vector.
   // Return a new type, or return 'this' if it is already instantiated.
   // If bound_error is not NULL, it may be set to reflect a bound error.
   virtual RawAbstractType* InstantiateFrom(
       const TypeArguments& instantiator_type_arguments,
       Error* bound_error,
       GrowableObjectArray* trail = NULL) const;
 
   // Return a clone of this unfinalized type or the type itself if it is
   // already finalized. Apply recursively to type arguments, i.e. finalized
   // type arguments of an unfinalized type are not cloned, but shared.
   virtual RawAbstractType* CloneUnfinalized() const;
 
   virtual RawInstance* CheckAndCanonicalize(const char** error_str) const {
     return Canonicalize();
   }
 
   // Return the canonical version of this type.
   virtual RawAbstractType* Canonicalize(
       GrowableObjectArray* trail = NULL) const;
 
+  // Return the object associated with the receiver in the trail or
+  // Object::null() if the receiver is not contained in the trail.
+  RawObject* OnlyBuddyInTrail(GrowableObjectArray* trail) const;
+
+  // If the trail is null, allocate a trail, add the pair <receiver, buddy> to
+  // the trail. The receiver may only be added once with its only buddy.
+  void AddOnlyBuddyToTrail(GrowableObjectArray** trail,
+                           const Object& buddy) const;
+
   // The name of this type, including the names of its type arguments, if any.
   virtual RawString* Name() const {
     return BuildName(kInternalName);
   }
 
   // The name of this type, including the names of its type arguments, if any.
   // Names of internal classes are mapped to their public interfaces.
   virtual RawString* UserVisibleName() const {
     return BuildName(kUserVisibleName);
   }
@@ skipping 113 matching lines @@
   virtual bool HasResolvedTypeClass() const;  // Own type class resolved.
   virtual RawClass* type_class() const;
   void set_type_class(const Object& value) const;
   virtual RawUnresolvedClass* unresolved_class() const;
   virtual RawTypeArguments* arguments() const;
   void set_arguments(const TypeArguments& value) const;
   virtual intptr_t token_pos() const { return raw_ptr()->token_pos_; }
   virtual bool IsInstantiated(GrowableObjectArray* trail = NULL) const;
   virtual bool IsEquivalent(const Instance& other,
                             GrowableObjectArray* trail = NULL) const;
+  virtual bool IsRecursive() const;
   virtual RawAbstractType* InstantiateFrom(
       const TypeArguments& instantiator_type_arguments,
       Error* malformed_error,
       GrowableObjectArray* trail = NULL) const;
   virtual RawAbstractType* CloneUnfinalized() const;
   virtual RawAbstractType* Canonicalize(
       GrowableObjectArray* trail = NULL) const;
 
   virtual intptr_t Hash() const;
 
@@ skipping 98 matching lines @@
   }
   virtual RawTypeArguments* arguments() const {
     return AbstractType::Handle(type()).arguments();
   }
   virtual intptr_t token_pos() const {
     return AbstractType::Handle(type()).token_pos();
   }
   virtual bool IsInstantiated(GrowableObjectArray* trail = NULL) const;
   virtual bool IsEquivalent(const Instance& other,
                             GrowableObjectArray* trail = NULL) const;
+  virtual bool IsRecursive() const { return true; }
   virtual RawAbstractType* InstantiateFrom(
       const TypeArguments& instantiator_type_arguments,
       Error* bound_error,
       GrowableObjectArray* trail = NULL) const;
   virtual RawAbstractType* Canonicalize(
       GrowableObjectArray* trail = NULL) const;
 
   virtual intptr_t Hash() const;
 
   // Return true if the receiver is contained in the trail.
   // Otherwise, if the trail is null, allocate a trail, then add the receiver to
   // the trail and return false.
   bool TestAndAddToTrail(GrowableObjectArray** trail) const;
 
   // Return true if the pair <receiver, buddy> is contained in the trail.
   // Otherwise, if the trail is null, allocate a trail, add the pair <receiver,
   // buddy> to the trail and return false.
   // The receiver may be added several times, each time with a different buddy.
   bool TestAndAddBuddyToTrail(GrowableObjectArray** trail,
                               const Object& buddy) const;
 
-  // Return the object associated with the receiver in the trail or
-  // Object::null() if the receiver is not contained in the trail.
-  RawObject* OnlyBuddyInTrail(GrowableObjectArray* trail) const;
-
-  // If the trail is null, allocate a trail, add the pair <receiver, buddy> to
-  // the trail. The receiver may only be added once with its only buddy.
-  void AddOnlyBuddyToTrail(GrowableObjectArray** trail,
-                           const Object& buddy) const;
-
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawTypeRef));
   }
 
   static RawTypeRef* New(const AbstractType& type);
 
  private:
   static RawTypeRef* New();
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(TypeRef, AbstractType);
@@ skipping 38 matching lines @@
   // bound cannot be checked yet and this is not an error.
   bool CheckBound(const AbstractType& bounded_type,
                   const AbstractType& upper_bound,
                   Error* bound_error) const;
   virtual intptr_t token_pos() const { return raw_ptr()->token_pos_; }
   virtual bool IsInstantiated(GrowableObjectArray* trail = NULL) const {
     return false;
   }
   virtual bool IsEquivalent(const Instance& other,
                             GrowableObjectArray* trail = NULL) const;
+  virtual bool IsRecursive() const { return false; }
   virtual RawAbstractType* InstantiateFrom(
       const TypeArguments& instantiator_type_arguments,
       Error* bound_error,
       GrowableObjectArray* trail = NULL) const;
   virtual RawAbstractType* CloneUnfinalized() const;
   virtual RawAbstractType* Canonicalize(
       GrowableObjectArray* trail = NULL) const {
     return raw();
   }
 
@@ skipping 63 matching lines @@
   }
   virtual bool IsInstantiated(GrowableObjectArray* trail = NULL) const {
     // It is not possible to encounter an instantiated bounded type with an
     // uninstantiated upper bound. Therefore, we do not need to check if the
     // bound is instantiated. Moreover, doing so could lead into cycles, as in
     // class C<T extends C<C>> { }.
     return AbstractType::Handle(type()).IsInstantiated();
   }
   virtual bool IsEquivalent(const Instance& other,
                             GrowableObjectArray* trail = NULL) const;
+  virtual bool IsRecursive() const;
   virtual RawAbstractType* InstantiateFrom(
       const TypeArguments& instantiator_type_arguments,
       Error* bound_error,
       GrowableObjectArray* trail = NULL) const;
   virtual RawAbstractType* CloneUnfinalized() const;
   virtual RawAbstractType* Canonicalize(
       GrowableObjectArray* trail = NULL) const {
     return raw();
   }
 
@@ skipping 2170 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_