[modules] Explicitly keep track of module requests.

src/ast/modules.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_AST_MODULES_H_
 #define V8_AST_MODULES_H_
 
 #include "src/parsing/scanner.h"  // Only for Scanner::Location.
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 
 
 class AstRawString;
 class ModuleInfoEntry;
 
 class ModuleDescriptor : public ZoneObject {
  public:
   explicit ModuleDescriptor(Zone* zone)
-      : special_exports_(1, zone),
+      : module_requests_(zone),
+        special_exports_(1, zone),
         special_imports_(1, zone),
         regular_exports_(zone),
         regular_imports_(zone) {}
 
   // The following Add* methods are high-level convenience functions for use by
   // the parser.
 
   // import x from "foo.js";
   // import {x} from "foo.js";
   // import {x as y} from "foo.js";
@@ skipping 38 matching lines @@
   // Check if module is well-formed and report error if not.
   // Also canonicalize indirect exports.
   bool Validate(ModuleScope* module_scope,
                 PendingCompilationErrorHandler* error_handler, Zone* zone);
 
   struct Entry : public ZoneObject {
     const Scanner::Location location;
     const AstRawString* export_name;
     const AstRawString* local_name;
     const AstRawString* import_name;
-    const AstRawString* module_request;
+    int module_request;
 
     // TODO(neis): Remove local_name component?
     explicit Entry(Scanner::Location loc)
         : location(loc),
           export_name(nullptr),
           local_name(nullptr),
           import_name(nullptr),
-          module_request(nullptr) {}
+          module_request(-1) {}

[adamk, 2016/09/19 19:57:20]

Would be good to document somewhere that "-1" means "uninitialized" while "0"
means "this module". Maybe these could be constants?

[neis, 2016/09/19 21:13:46]

I added a comment.  Negative means no module request; non-negative is the
position and used as an index. 0 is not special.

 
     // (De-)serialization support.
     // Note that the location value is not preserved as it's only needed by the
     // parser.  (A Deserialize'd entry has an invalid location.)
     Handle<ModuleInfoEntry> Serialize(Isolate* isolate) const;
     static Entry* Deserialize(Isolate* isolate, AstValueFactory* avfactory,
                               Handle<ModuleInfoEntry> entry);
   };
 
+  // Module requests.
+  const ZoneMap<const AstRawString*, int>& module_requests() const {
+    return module_requests_;
+  }
+
   // Empty imports and namespace imports.
   const ZoneList<const Entry*>& special_imports() const {
     return special_imports_;
   }
 
   // All the remaining imports, indexed by local name.
   const ZoneMap<const AstRawString*, const Entry*>& regular_imports() const {
     return regular_imports_;
   }
 
   // Star exports and explicitly indirect exports.
   const ZoneList<const Entry*>& special_exports() const {
     return special_exports_;
   }
 
   // All the remaining exports, indexed by local name.
   const ZoneMultimap<const AstRawString*, Entry*>& regular_exports() const {
     return regular_exports_;
   }
 
   void AddRegularExport(Entry* entry) {
     DCHECK_NOT_NULL(entry->export_name);
     DCHECK_NOT_NULL(entry->local_name);
     DCHECK_NULL(entry->import_name);
+    DCHECK_LT(entry->module_request, 0);
     regular_exports_.insert(std::make_pair(entry->local_name, entry));
   }
 
   void AddSpecialExport(const Entry* entry, Zone* zone) {
-    DCHECK_NOT_NULL(entry->module_request);
+    DCHECK_LE(0, entry->module_request);
     special_exports_.Add(entry, zone);
   }
 
   void AddRegularImport(const Entry* entry) {
     DCHECK_NOT_NULL(entry->import_name);
     DCHECK_NOT_NULL(entry->local_name);
-    DCHECK_NOT_NULL(entry->module_request);
     DCHECK_NULL(entry->export_name);
+    DCHECK_LE(0, entry->module_request);
     regular_imports_.insert(std::make_pair(entry->local_name, entry));
     // We don't care if there's already an entry for this local name, as in that
     // case we will report an error when declaring the variable.
   }
 
   void AddSpecialImport(const Entry* entry, Zone* zone) {
-    DCHECK_NOT_NULL(entry->module_request);
     DCHECK_NULL(entry->export_name);
+    DCHECK_LE(0, entry->module_request);
     special_imports_.Add(entry, zone);
   }
 
  private:
   // TODO(neis): Use STL datastructure instead of ZoneList?
+  ZoneMap<const AstRawString*, int> module_requests_;
   ZoneList<const Entry*> special_exports_;
   ZoneList<const Entry*> special_imports_;
   ZoneMultimap<const AstRawString*, Entry*> regular_exports_;
   ZoneMap<const AstRawString*, const Entry*> regular_imports_;
 
   // If there are multiple export entries with the same export name, return the
   // last of them (in source order).  Otherwise return nullptr.
   const Entry* FindDuplicateExport(Zone* zone) const;
 
   // Find any implicitly indirect exports and make them explicit.
   //
   // An explicitly indirect export is an export entry arising from an export
   // statement of the following form:
   //   export {a as c} from "X";
   // An implicitly indirect export corresponds to
   //   export {b as c};
   // in the presence of an import statement of the form
   //   import {a as b} from "X";
   // This function finds such implicitly indirect export entries and rewrites
   // them by filling in the import name and module request, as well as nulling
   // out the local name.  Effectively, it turns
   //   import {a as b} from "X"; export {b as c};
   // into:
   //   import {a as b} from "X"; export {a as c} from "X";
   // (The import entry is never deleted.)
   void MakeIndirectExportsExplicit(Zone* zone);
+
+  int AddModuleRequest(const AstRawString* specifier) {
+    DCHECK_NOT_NULL(specifier);
+    auto it = module_requests_
+                  .insert(std::make_pair(specifier, module_requests_.size()))
+                  .first;
+    return it->second;
+  }
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_AST_MODULES_H_