Strip Interface class of most of its logic, make it all about Module exports

src/interface.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERFACE_H_
 #define V8_INTERFACE_H_
 
-#include "src/ast-value-factory.h"
+#include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 
 
-// This class implements the following abstract grammar of interfaces
-// (i.e. module types):
-//   interface ::= UNDETERMINED | VALUE | CONST | MODULE(exports)
-//   exports ::= {name : interface, ...}
-// A frozen type is one that is fully determined. Unification does not
-// allow to turn non-const values into const, or adding additional exports to
-// frozen interfaces. Otherwise, unifying modules merges their exports.
-// Undetermined types are unification variables that can be unified freely.
-// There is a natural subsort lattice that reflects the increase of knowledge:
+class AstRawString;
+
+
+// This class represents the interface of a module: a set of exported names.
 //
-//            undetermined
-//           //     |    \\                                                    .
-//       value  (frozen)  module
-//      //   \\  /    \  //
-//  const   fr.value  fr.module
-//      \\    /
-//     fr.const
-//
-// where the bold lines are the only transitions allowed.
-
+// TODO(adamk): Rename this to ModuleRecord, ModuleDescriptor, or similar.
 class Interface : public ZoneObject {
  public:
   // ---------------------------------------------------------------------------
   // Factory methods.
 
-  static Interface* NewUnknown(Zone* zone) {
-    return new(zone) Interface(NONE);
-  }
-
-  static Interface* NewValue();
-
-  static Interface* NewConst();
-
-  static Interface* NewModule(Zone* zone) {
-    return new(zone) Interface(MODULE);
-  }
+  static Interface* New(Zone* zone) { return new (zone) Interface(); }
 
   // ---------------------------------------------------------------------------
   // Mutators.
 
-  // Add a name to the list of exports. If it already exists, unify with
-  // interface, otherwise insert unless this is closed.
-  void Add(const AstRawString* name, Interface* interface, Zone* zone,
-           bool* ok) {
-    DoAdd(name, name->hash(), interface, zone, ok);
-  }
-
-  // Unify with another interface. If successful, both interface objects will
-  // represent the same type, and changes to one are reflected in the other.
-  void Unify(Interface* that, Zone* zone, bool* ok);
-
-  // Determine this interface to be a value interface.
-  void MakeValue(bool* ok) {
-    *ok = !IsModule();
-    if (*ok) Chase()->flags_ |= VALUE;
-  }
-
-  // Determine this interface to be an immutable interface.
-  void MakeConst(bool* ok) {
-    *ok = !IsModule() && (IsConst() || !IsFrozen());
-    if (*ok) Chase()->flags_ |= VALUE + CONST;
-  }
-
-  // Determine this interface to be a module interface.
-  void MakeModule(bool* ok) {
-    *ok = !IsValue();
-    if (*ok) Chase()->flags_ |= MODULE;
-  }
+  // Add a name to the list of exports. If it already exists, or this interface
+  // is frozen, that's an error.
+  void Add(const AstRawString* name, Zone* zone, bool* ok);
 
   // Do not allow any further refinements, directly or through unification.
-  void Freeze(bool* ok) {
-    *ok = IsValue() || IsModule();
-    if (*ok) Chase()->flags_ |= FROZEN;
-  }
+  void Freeze() { frozen_ = true; }
 
   // Assign an index.
   void Allocate(int index) {
-    DCHECK(IsModule() && IsFrozen() && Chase()->index_ == -1);
-    Chase()->index_ = index;
+    DCHECK(IsFrozen() && index_ == -1);
+    index_ = index;
   }
 
   // ---------------------------------------------------------------------------
   // Accessors.
 
-  // Check whether this is still a fully undetermined type.
-  bool IsUnknown() { return Chase()->flags_ == NONE; }
-
-  // Check whether this is a value type.
-  bool IsValue() { return Chase()->flags_ & VALUE; }
-
-  // Check whether this is a constant type.
-  bool IsConst() { return Chase()->flags_ & CONST; }
-
-  // Check whether this is a module type.
-  bool IsModule() { return Chase()->flags_ & MODULE; }
-
   // Check whether this is closed (i.e. fully determined).
-  bool IsFrozen() { return Chase()->flags_ & FROZEN; }
-
-  bool IsUnified(Interface* that) {
-    return Chase() == that->Chase()
-        || (this->IsValue() == that->IsValue() &&
-            this->IsConst() == that->IsConst());
-  }
+  bool IsFrozen() { return frozen_; }
 
   int Length() {
-    DCHECK(IsModule() && IsFrozen());
-    ZoneHashMap* exports = Chase()->exports_;
+    DCHECK(IsFrozen());
+    ZoneHashMap* exports = exports_;
     return exports ? exports->occupancy() : 0;
   }
 
   // The context slot in the hosting script context pointing to this module.
   int Index() {
-    DCHECK(IsModule() && IsFrozen());
-    return Chase()->index_;
+    DCHECK(IsFrozen());
+    return index_;
   }
 
-  // Look up an exported name. Returns NULL if not (yet) defined.
-  Interface* Lookup(Handle<String> name, Zone* zone);
-
   // ---------------------------------------------------------------------------
   // Iterators.
 
   // Use like:
   //   for (auto it = interface->iterator(); !it.done(); it.Advance()) {
   //     ... it.name() ... it.interface() ...
   //   }
   class Iterator {
    public:
     bool done() const { return entry_ == NULL; }
     const AstRawString* name() const {
       DCHECK(!done());
       return static_cast<const AstRawString*>(entry_->key);
     }
-    Interface* interface() const {
-      DCHECK(!done());
-      return static_cast<Interface*>(entry_->value);
-    }
     void Advance() { entry_ = exports_->Next(entry_); }
 
    private:
     friend class Interface;
     explicit Iterator(const ZoneHashMap* exports)
         : exports_(exports), entry_(exports ? exports->Start() : NULL) {}
 
     const ZoneHashMap* exports_;
     ZoneHashMap::Entry* entry_;
   };
 
   Iterator iterator() const { return Iterator(this->exports_); }
 
   // ---------------------------------------------------------------------------
   // Debugging.
 #ifdef DEBUG
   void Print(int n = 0);  // n = indentation; n < 0 => don't print recursively
 #endif
 
   // ---------------------------------------------------------------------------
   // Implementation.
  private:
-  struct Cache;
-
-  enum Flags {    // All flags are monotonic
-    NONE = 0,
-    VALUE = 1,    // This type describes a value
-    CONST = 2,    // This type describes a constant
-    MODULE = 4,   // This type describes a module
-    FROZEN = 8    // This type is fully determined
-  };
-
-  int flags_;
-  Interface* forward_;     // Unification link
+  bool frozen_;
   ZoneHashMap* exports_;   // Module exports and their types (allocated lazily)
   int index_;
 
-  explicit Interface(int flags)
-    : flags_(flags),
-      forward_(NULL),
-      exports_(NULL),
-      index_(-1) {
+  Interface() : frozen_(false), exports_(NULL), index_(-1) {
 #ifdef DEBUG
     if (FLAG_print_interface_details)
       PrintF("# Creating %p\n", static_cast<void*>(this));
 #endif
   }
-
-  Interface* Chase() {
-    Interface* result = this;
-    while (result->forward_ != NULL) result = result->forward_;
-    if (result != this) forward_ = result;  // On-the-fly path compression.
-    return result;
-  }
-
-  void DoAdd(const void* name, uint32_t hash, Interface* interface, Zone* zone,
-             bool* ok);
-  void DoUnify(Interface* that, bool* ok, Zone* zone);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_INTERFACE_H_