Fix wrong canonicalization of signature class due to name collision (issue 6353).

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 1043 matching lines @@
 };
 
 
 class Function : public Object {
  public:
   RawString* name() const { return raw_ptr()->name_; }
   RawString* UserVisibleName() const;
   RawString* QualifiedUserVisibleName() const;
   virtual RawString* DictionaryName() const { return name(); }
 
-  // Build a string of the form '<T, R>(T, [b: B, c: C]) => R' representing the
-  // internal signature of the given function.
+  // Build a string of the form 'C<T, R>(T, {b: B, c: C}) => R' representing the
+  // internal signature of the given function. In this example, T and R are
+  // type parameters of class C, the owner of the function.
   RawString* Signature() const {
     const bool instantiate = false;
     return BuildSignature(instantiate, kInternalName, TypeArguments::Handle());
   }
 
-  // Build a string of the form '(A, [b: B, c: C]) => D' representing the
+  // Build a string of the form '(A, {b: B, c: C}) => D' representing the
   // signature of the given function, where all generic types (e.g. '<T, R>' in
-  // '<T, R>(T, [b: B, c: C]) => R') are instantiated using the given
-  // instantiator type argument vector (e.g. '<A, D>').
+  // 'C<T, R>(T, {b: B, c: C}) => R') are instantiated using the given
+  // instantiator type argument vector of a C instance (e.g. '<A, D>').
   RawString* InstantiatedSignatureFrom(
       const AbstractTypeArguments& instantiator,
       NameVisibility name_visibility) const {
     const bool instantiate = true;
     return BuildSignature(instantiate, name_visibility, instantiator);
   }
 
   // Returns true if the signature of this function is instantiated, i.e. if it
   // does not involve generic parameter types or generic result type.
   bool HasInstantiatedSignature() const;
@@ skipping 4692 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_