Bug 930414 - Add ModuleObject and CompileModule() function r=shu

js/src/builtin/ModuleObject.cpp

@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "builtin/ModuleObject.h"
+
+#include "jsobjinlines.h"
+
+using namespace js;
+
+///////////////////////////////////////////////////////////////////////////
+// ModuleObject
+
+const Class ModuleObject::class_ = {
+    "Module",
+    JSCLASS_HAS_RESERVED_SLOTS(ModuleObject::SlotCount) |
+    JSCLASS_IS_ANONYMOUS |
+    JSCLASS_IMPLEMENTS_BARRIERS,
+    nullptr,        /* addProperty */
+    nullptr,        /* delProperty */
+    nullptr,        /* getProperty */
+    nullptr,        /* setProperty */
+    nullptr,        /* enumerate   */
+    nullptr,        /* resolve     */
+    nullptr,        /* mayResolve  */
+    nullptr,        /* convert     */
+    nullptr,        /* finalize    */
+    nullptr,        /* call        */
+    nullptr,        /* hasInstance */
+    nullptr,        /* construct   */
+    ModuleObject::trace
+};
+
+/* static */ ModuleObject*
+ModuleObject::create(ExclusiveContext* cx)
+{
+    return NewBuiltinClassInstance<ModuleObject>(cx, TenuredObject);
+}
+
+void
+ModuleObject::init(HandleScript script)
+{
+    initReservedSlot(ScriptSlot, PrivateValue(script));
+}
+
+JSScript*
+ModuleObject::script() const
+{
+    return static_cast<JSScript*>(getReservedSlot(ScriptSlot).toPrivate());
+}
+
+/* static */ void
+ModuleObject::trace(JSTracer* trc, JSObject* obj)
+{
+    ModuleObject& module = obj->as<ModuleObject>();
+    JSScript* script = module.script();
+    TraceManuallyBarrieredEdge(trc, &script, "Module script");
+    module.setReservedSlot(ScriptSlot, PrivateValue(script));
+}

js/src/builtin/ModuleObject.h

@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef builtin_ModuleObject_h
+#define builtin_ModuleObject_h
+
+#include "vm/NativeObject.h"
+
+namespace js {
+
+class ModuleObject : public NativeObject
+{
+  public:
+    enum
+    {
+        ScriptSlot = 0,
+        SlotCount
+    };
+
+    static const Class class_;
+
+    static ModuleObject* create(ExclusiveContext* cx);
+    void init(HandleScript script);
+
+    JSScript* script() const;
+
+  private:
+    static void trace(JSTracer* trc, JSObject* obj);
+};
+
+typedef Rooted<ModuleObject*> RootedModuleObject;
+typedef Handle<ModuleObject*> HandleModuleObject;
+
+} // namespace js
+
+#endif /* builtin_ModuleObject_h */

js/src/frontend/BytecodeCompiler.cpp

@@ -10,6 +10,7 @@
 #include "jsscript.h"
 
 #include "asmjs/AsmJSLink.h"
+#include "builtin/ModuleObject.h"
 #include "frontend/BytecodeEmitter.h"
 #include "frontend/FoldConstants.h"
 #include "frontend/NameFunctions.h"
@@ -57,6 +58,7 @@ class MOZ_STACK_CLASS BytecodeCompiler
     void setSourceArgumentsNotIncluded();
 
     JSScript* compileScript(HandleObject scopeChain, HandleScript evalCaller);
+    ModuleObject* compileModule();
     bool compileFunctionBody(MutableHandleFunction fun, Handle<PropertyNameVector> formals,
                              GeneratorKind generatorKind);
 
@@ -606,6 +608,50 @@ BytecodeCompiler::compileScript(HandleObject scopeChain, HandleScript evalCaller
     return script;
 }
 
+ModuleObject* BytecodeCompiler::compileModule()
+{
+    MOZ_ASSERT(!enclosingStaticScope);
+
+    if (!createSourceAndParser())
+        return nullptr;
+
+    if (!createScript())
+        return nullptr;
+
+    Rooted<ModuleObject*> module(cx, ModuleObject::create(cx));
+    if (!module)
+        return nullptr;
+
+    module->init(script);
+
+    ParseNode* pn = parser->standaloneModule(module);
+    if (!pn)
+        return nullptr;
+
+    if (!NameFunctions(cx, pn) ||
+        !maybeSetDisplayURL(parser->tokenStream) ||
+        !maybeSetSourceMap(parser->tokenStream))
+    {
+        return nullptr;
+    }
+
+    script->bindings = pn->pn_modulebox->bindings;
+
+    if (!createEmitter(pn->pn_modulebox) ||
+        !emitter->emitModuleScript(pn->pn_body))
+    {
+        return nullptr;
+    }
+
+    if (!maybeCompleteCompressSource())
+        return nullptr;
+
+    parser->handler.freeTree(pn);
+
+    MOZ_ASSERT_IF(cx->isJSContext(), !cx->asJSContext()->isExceptionPending());
+    return module;
+}
+
 bool
 BytecodeCompiler::compileFunctionBody(MutableHandleFunction fun,
                                       Handle<PropertyNameVector> formals,
@@ -721,6 +767,22 @@ frontend::CompileScript(ExclusiveContext* cx, LifoAlloc* alloc, HandleObject sco
     return compiler.compileScript(scopeChain, evalCaller);
 }
 
+ModuleObject*
+frontend::CompileModule(JSContext* cx, HandleObject obj,
+                        const ReadOnlyCompileOptions& optionsInput,
+                        SourceBufferHolder& srcBuf)
+{
+    MOZ_ASSERT(srcBuf.get());
+
+    CompileOptions options(cx, optionsInput);
+    options.maybeMakeStrictMode(true); // ES6 10.2.1 Module code is always strict mode code.
+    options.setIsRunOnce(true);
+
+    BytecodeCompiler compiler(cx, &cx->tempLifoAlloc(), options, srcBuf, nullptr,
+                              TraceLogger_ParserCompileModule);
+    return compiler.compileModule();
+}
+
 bool
 frontend::CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const char16_t* chars, size_t length)
 {

js/src/frontend/BytecodeCompiler.h

@@ -17,6 +17,7 @@ namespace js {
 
 class LazyScript;
 class LifoAlloc;
+class ModuleObject;
 class ScriptSourceObject;
 class ScopeObject;
 struct SourceCompressionTask;
@@ -30,6 +31,10 @@ CompileScript(ExclusiveContext* cx, LifoAlloc* alloc,
               SourceBufferHolder& srcBuf, JSString* source_ = nullptr,
               SourceCompressionTask* extraSct = nullptr);
 
+ModuleObject *
+CompileModule(JSContext *cx, HandleObject obj, const ReadOnlyCompileOptions &options,
+              SourceBufferHolder &srcBuf);
+
 bool
 CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const char16_t* chars, size_t length);
 

js/src/frontend/BytecodeEmitter.cpp

@@ -2212,6 +2212,10 @@ BytecodeEmitter::checkSideEffects(ParseNode* pn, bool* answer)
         *answer = false;
         return true;
 
+      case PNK_MODULE:
+        *answer = false;
+        return true;
+
       // Generator expressions have no side effects on their own.
       case PNK_GENEXP:
         MOZ_ASSERT(pn->isArity(PN_LIST));
@@ -3500,6 +3504,55 @@ BytecodeEmitter::emitFunctionScript(ParseNode* body)
     return true;
 }
 
+bool
+BytecodeEmitter::emitModuleScript(ParseNode* body)
+{
+    if (!updateLocalsToFrameSlots())
+        return false;
+
+    /*
+     * IonBuilder has assumptions about what may occur immediately after
+     * script->main (e.g., in the case of destructuring params). Thus, put the
+     * following ops into the range [script->code, script->main). Note:
+     * execution starts from script->code, so this has no semantic effect.
+     */
+
+    ModuleBox* modulebox = sc->asModuleBox();
+
+    // Link the module and the script to each other, so that StaticScopeIter
+    // may walk the scope chain of currently compiling scripts.
+    JSScript::linkToModuleFromEmitter(cx, script, modulebox);
+
+    if (!emitTree(body))
+        return false;
+
+    // Always end the script with a JSOP_RETRVAL. Some other parts of the codebase
+    // depend on this opcode, e.g. InterpreterRegs::setToEndOfScript.
+    if (!emit1(JSOP_RETRVAL))
+        return false;
+
+    // If all locals are aliased, the frame's block slots won't be used, so we
+    // can set numBlockScoped = 0. This is nice for generators as it ensures
+    // nfixed == 0, so we don't have to initialize any local slots when resuming
+    // a generator.
+    if (sc->allLocalsAliased())
+        script->bindings.setAllLocalsAliased();
+
+    if (!JSScript::fullyInitFromEmitter(cx, script, this))
+        return false;
+
+    /*
+     * Since modules are only run once. Mark the script so that initializers
+     * created within it may be given more precise types.
+     */
+    script->setTreatAsRunOnce();
+    MOZ_ASSERT(!script->hasRunOnce());
+
+    tellDebuggerAboutCompiledScript(cx);
+
+    return true;
+}
+
 bool
 BytecodeEmitter::maybeEmitVarDecl(JSOp prologueOp, ParseNode* pn, jsatomid* result)
 {

js/src/frontend/BytecodeEmitter.h

@@ -320,6 +320,9 @@ struct BytecodeEmitter
     // Emit function code for the tree rooted at body.
     bool emitFunctionScript(ParseNode* body);
 
+    // Emit module code for the tree rooted at body.
+    bool emitModuleScript(ParseNode* body);
+
     // If op is JOF_TYPESET (see the type barriers comment in TypeInference.h),
     // reserve a type set to store its result.
     void checkTypeSet(JSOp op);

js/src/frontend/FoldConstants.cpp

@@ -100,6 +100,10 @@ ContainsHoistedDeclaration(ExclusiveContext* cx, ParseNode* node, bool* result)
         *result = false;
         return true;
 
+      case PNK_MODULE:
+        *result = false;
+        return true;
+
       // Statements with no sub-components at all.
       case PNK_NOP: // induced by function f() {} function f() {}
       case PNK_DEBUGGER:
@@ -1114,6 +1118,17 @@ ComputeBinary(ParseNodeKind kind, double left, double right)
     return int32_t((kind == PNK_LSH) ? uint32_t(i) << j : i >> j);
 }
 
+static bool
+FoldModule(ExclusiveContext* cx, ParseNode* node, Parser<FullParseHandler>& parser)
+{
+    MOZ_ASSERT(node->isKind(PNK_MODULE));
+    MOZ_ASSERT(node->isArity(PN_CODE));
+
+    ParseNode*& moduleBody = node->pn_body;
+    MOZ_ASSERT(moduleBody);
+    return Fold(cx, &moduleBody, parser, false);
+}
+
 static bool
 FoldBinaryArithmetic(ExclusiveContext* cx, ParseNode* node, Parser<FullParseHandler>& parser,
                      bool inGenexpLambda)
@@ -1787,6 +1802,9 @@ Fold(ExclusiveContext* cx, ParseNode** pnp, Parser<FullParseHandler>& parser, bo
       case PNK_FUNCTION:
         return FoldFunction(cx, pn, parser, inGenexpLambda);
 
+      case PNK_MODULE:
+        return FoldModule(cx, pn, parser);
+
       case PNK_SUB:
       case PNK_STAR:
       case PNK_LSH:

js/src/frontend/FullParseHandler.h

@@ -635,7 +635,7 @@ class FullParseHandler
     inline void setLastFunctionArgumentDestructuring(ParseNode* funcpn, ParseNode* pn);
 
     ParseNode* newFunctionDefinition() {
-        return new_<CodeNode>(pos());
+        return new_<CodeNode>(PNK_FUNCTION, pos());
     }
     void setFunctionBody(ParseNode* pn, ParseNode* kid) {
         pn->pn_body = kid;
@@ -652,6 +652,14 @@ class FullParseHandler
         pn->pn_funbox->setDerivedClassConstructor();
     }
 
+    ParseNode* newModule() {
+        return new_<CodeNode>(PNK_MODULE, pos());
+    }
+    void setModuleBox(ParseNode* pn, ModuleBox* modulebox) {
+        MOZ_ASSERT(pn->isKind(PNK_MODULE));
+        pn->pn_modulebox = modulebox;
+    }
+
     ParseNode* newLexicalScope(ObjectBox* blockBox) {
         return new_<LexicalScopeNode>(blockBox, pos());
     }

js/src/frontend/NameFunctions.cpp

@@ -337,7 +337,7 @@ class NameResolver
         if (cur == nullptr)
             return true;
 
-        MOZ_ASSERT(cur->isKind(PNK_FUNCTION) == cur->isArity(PN_CODE));
+        MOZ_ASSERT((cur->isKind(PNK_FUNCTION) || cur->isKind(PNK_MODULE)) == cur->isArity(PN_CODE));
         if (cur->isKind(PNK_FUNCTION)) {
             RootedAtom prefix2(cx);
             if (!resolveFun(cur, prefix, &prefix2))
@@ -767,6 +767,7 @@ class NameResolver
             break;
 
           case PNK_FUNCTION:
+          case PNK_MODULE:
             MOZ_ASSERT(cur->isArity(PN_CODE));
             if (!resolve(cur->pn_body, prefix))
                 return false;

js/src/frontend/ParseNode.cpp

@@ -521,6 +521,7 @@ PushNodeChildren(ParseNode* pn, NodeStack* stack)
         return PushNameNodeChildren(pn, stack);
 
       case PNK_FUNCTION:
+      case PNK_MODULE:
         return PushCodeNodeChildren(pn, stack);
 
       case PNK_LIMIT: // invalid sentinel value
@@ -1151,6 +1152,13 @@ ObjectBox::asFunctionBox()
     return static_cast<FunctionBox*>(this);
 }
 
+ModuleBox*
+ObjectBox::asModuleBox()
+{
+    MOZ_ASSERT(isModuleBox());
+    return static_cast<ModuleBox*>(this);
+}
+
 void
 ObjectBox::trace(JSTracer* trc)
 {
@@ -1162,6 +1170,9 @@ ObjectBox::trace(JSTracer* trc)
             funbox->bindings.trace(trc);
             if (funbox->enclosingStaticScope_)
                 TraceRoot(trc, &funbox->enclosingStaticScope_, "funbox-enclosingStaticScope");
+        } else if (box->isModuleBox()) {
+            ModuleBox* modulebox = box->asModuleBox();
+            modulebox->bindings.trace(trc);
         }
         box = box->traceLink;
     }

js/src/frontend/ParseNode.h

@@ -19,6 +19,7 @@ struct ParseContext;
 
 class FullParseHandler;
 class FunctionBox;
+class ModuleBox;
 class ObjectBox;
 
 // A packed ScopeCoordinate for use in the frontend during bytecode
@@ -118,6 +119,7 @@ class PackedScopeCoordinate
     F(NULL) \
     F(THIS) \
     F(FUNCTION) \
+    F(MODULE) \
     F(IF) \
     F(SWITCH) \
     F(CASE) \
@@ -636,9 +638,10 @@ class ParseNode
         } unary;
         struct {                        /* name, labeled statement, etc. */
             union {
-                JSAtom*     atom;      /* lexical name or label atom */
-                ObjectBox*  objbox;    /* block or regexp object */
+                JSAtom*      atom;      /* lexical name or label atom */
+                ObjectBox*   objbox;    /* block or regexp object */
                 FunctionBox* funbox;    /* function object */
+                ModuleBox*   modulebox; /* module object */
             };
             union {
                 ParseNode*  expr;      /* module or function body, var
@@ -662,6 +665,7 @@ class ParseNode
     } pn_u;
 
 #define pn_modulebox    pn_u.name.modulebox
+#define pn_objbox       pn_u.name.objbox
 #define pn_funbox       pn_u.name.funbox
 #define pn_body         pn_u.name.expr
 #define pn_scopecoord   pn_u.name.scopeCoord
@@ -1072,15 +1076,17 @@ struct ListNode : public ParseNode
 
 struct CodeNode : public ParseNode
 {
-    explicit CodeNode(const TokenPos& pos)
-      : ParseNode(PNK_FUNCTION, JSOP_NOP, PN_CODE, pos)
+    CodeNode(ParseNodeKind kind, const TokenPos& pos)
+      : ParseNode(kind, JSOP_NOP, PN_CODE, pos)
     {
+        MOZ_ASSERT(kind == PNK_FUNCTION || kind == PNK_MODULE);
         MOZ_ASSERT(!pn_body);
-        MOZ_ASSERT(!pn_funbox);
+        MOZ_ASSERT(!pn_objbox);
         MOZ_ASSERT(pn_dflags == 0);
         pn_scopecoord.makeFree();
     }
 
+  public:
 #ifdef DEBUG
     void dump(int indent);
 #endif
@@ -1687,6 +1693,8 @@ class ObjectBox
     ObjectBox(JSObject* object, ObjectBox* traceLink);
     bool isFunctionBox() { return object->is<JSFunction>(); }
     FunctionBox* asFunctionBox();
+    bool isModuleBox() { return object->is<ModuleObject>(); }
+    ModuleBox* asModuleBox();
     void trace(JSTracer* trc);
 
   protected:

js/src/frontend/Parser.cpp

@@ -29,6 +29,7 @@
 #include "jstypes.h"
 
 #include "asmjs/AsmJSValidate.h"
+#include "builtin/ModuleObject.h"
 #include "frontend/BytecodeCompiler.h"
 #include "frontend/FoldConstants.h"
 #include "frontend/ParseMaps.h"
@@ -409,12 +410,9 @@ AppendPackedBindings(const ParseContext<ParseHandler>* pc, const DeclVector& vec
 
 template <typename ParseHandler>
 bool
-ParseContext<ParseHandler>::generateFunctionBindings(ExclusiveContext* cx, TokenStream& ts,
-                                                     LifoAlloc& alloc,
-                                                     MutableHandle<Bindings> bindings) const
+ParseContext<ParseHandler>::generateBindings(ExclusiveContext* cx, TokenStream& ts, LifoAlloc& alloc,
+                                             MutableHandle<Bindings> bindings) const
 {
-    MOZ_ASSERT(sc->isFunctionBox());
-    MOZ_ASSERT(args_.length() < ARGNO_LIMIT);
     MOZ_ASSERT(vars_.length() + bodyLevelLexicals_.length() < LOCALNO_LIMIT);
 
     /*
@@ -453,6 +451,28 @@ ParseContext<ParseHandler>::generateFunctionBindings(ExclusiveContext* cx, Token
                                               packedBindings);
 }
 
+template <typename ParseHandler>
+bool
+ParseContext<ParseHandler>::generateFunctionBindings(ExclusiveContext* cx, TokenStream& ts,
+                                                     LifoAlloc& alloc,
+                                                     MutableHandle<Bindings> bindings) const
+{
+    MOZ_ASSERT(sc->isFunctionBox());
+    MOZ_ASSERT(args_.length() < ARGNO_LIMIT);
+    return generateBindings(cx, ts, alloc, bindings);
+}
+
+template <typename ParseHandler>
+bool
+ParseContext<ParseHandler>::generateModuleBindings(ExclusiveContext* cx, TokenStream& ts,
+                                                   LifoAlloc& alloc,
+                                                   MutableHandle<Bindings> bindings) const
+{
+    MOZ_ASSERT(sc->isModuleBox());
+    MOZ_ASSERT(args_.length() == 0);
+    return generateBindings(cx, ts, alloc, bindings);
+}
+
 template <typename ParseHandler>
 bool
 Parser<ParseHandler>::reportHelper(ParseReportKind kind, bool strict, uint32_t offset,
@@ -688,6 +708,49 @@ Parser<ParseHandler>::newFunctionBox(Node fn, JSFunction* fun,
     return funbox;
 }
 
+template <typename ParseHandler>
+ModuleBox::ModuleBox(ExclusiveContext* cx, ObjectBox* traceListHead, ModuleObject* module,
+                     ParseContext<ParseHandler>* outerpc)
+  : ObjectBox(module, traceListHead),
+    SharedContext(cx, Directives(true), extraWarnings),
+    bindings()
+{}
+
+template <typename ParseHandler>
+ModuleBox*
+Parser<ParseHandler>::newModuleBox(Node pn, HandleModuleObject module)
+{
+    MOZ_ASSERT(module);
+
+    /*
+     * We use JSContext.tempLifoAlloc to allocate parsed objects and place them
+     * on a list in this Parser to ensure GC safety. Thus the tempLifoAlloc
+     * arenas containing the entries must be alive until we are done with
+     * scanning, parsing and code generation for the whole module.
+     */
+    ParseContext<ParseHandler>* outerpc = nullptr;
+    ModuleBox* modbox =
+        alloc.new_<ModuleBox>(context, traceListHead, module, outerpc);
+    if (!modbox) {
+        ReportOutOfMemory(context);
+        return nullptr;
+    }
+
+    traceListHead = modbox;
+    if (pn)
+        handler.setModuleBox(pn, modbox);
+
+    return modbox;
+}
+
+template <>
+ModuleBox*
+Parser<SyntaxParseHandler>::newModuleBox(Node pn, HandleModuleObject module)
+{
+    MOZ_ALWAYS_FALSE(abortIfSyntaxParser());
+    return nullptr;
+}
+
 template <typename ParseHandler>
 void
 Parser<ParseHandler>::trace(JSTracer* trc)
@@ -785,6 +848,57 @@ Parser<ParseHandler>::checkStrictBinding(PropertyName* name, Node pn)
     return true;
 }
 
+template <typename ParseHandler>
+typename ParseHandler::Node
+Parser<ParseHandler>::standaloneModule(HandleModuleObject module)
+{
+    MOZ_ASSERT(checkOptionsCalled);
+
+    Node mn = handler.newModule();
+    if (!mn)
+        return null();
+
+    ModuleBox* modulebox = newModuleBox(mn, module);
+    if (!modulebox)
+        return null();
+    handler.setModuleBox(mn, modulebox);
+
+    ParseContext<FullParseHandler> modulepc(this, pc, mn, modulebox, nullptr, 0);
+    if (!modulepc.init(*this))
+        return null();
+
+    ParseNode* pn = statements(YieldIsKeyword);
+    if (!pn)
+        return null();
+
+    MOZ_ASSERT(pn->isKind(PNK_STATEMENTLIST));
+    mn->pn_body = pn;
+
+    TokenKind tt;
+    if (!tokenStream.getToken(&tt, TokenStream::Operand))
+        return null();
+    MOZ_ASSERT(tt == TOK_EOF);
+
+    if (!FoldConstants(context, &pn, this))
+        return null();
+
+    Rooted<Bindings> bindings(context, modulebox->bindings);
+    if (!modulepc.generateModuleBindings(context, tokenStream, alloc, &bindings))
+        return null();
+    modulebox->bindings = bindings;
+
+    MOZ_ASSERT(mn->pn_modulebox == modulebox);
+    return mn;
+}
+
+template <>
+SyntaxParseHandler::Node
+Parser<SyntaxParseHandler>::standaloneModule(HandleModuleObject module)
+{
+    MOZ_ALWAYS_FALSE(abortIfSyntaxParser());
+    return SyntaxParseHandler::NodeFailure;
+}
+
 template <>
 ParseNode*
 Parser<FullParseHandler>::standaloneFunctionBody(HandleFunction fun,

js/src/frontend/Parser.h

@@ -22,7 +22,9 @@
 
 namespace js {
 
+class ModuleObject;
 class StaticFunctionBoxScopeObject;
+class StaticModuleBoxScopeObject;
 
 namespace frontend {
 
@@ -197,23 +199,32 @@ struct MOZ_STACK_CLASS ParseContext : public GenericParseContext
     void updateDecl(JSAtom* atom, Node newDecl);
 
     /*
-     * After a function body has been parsed, the parser generates the
-     * function's "bindings". Bindings are a data-structure, ultimately stored
-     * in the compiled JSScript, that serve three purposes:
+     * After a function body or module has been parsed, the parser generates the
+     * code's "bindings". Bindings are a data-structure, ultimately stored in
+     * the compiled JSScript, that serve three purposes:
      *  - After parsing, the ParseContext is destroyed and 'decls' along with
      *    it. Mostly, the emitter just uses the binding information stored in
      *    the use/def nodes, but the emitter occasionally needs 'bindings' for
      *    various scope-related queries.
      *  - Bindings provide the initial js::Shape to use when creating a dynamic
-     *    scope object (js::CallObject) for the function. This shape is used
-     *    during dynamic name lookup.
+     *    scope object (js::CallObject). This shape is used during dynamic name
+     *    lookup.
      *  - Sometimes a script's bindings are accessed at runtime to retrieve the
      *    contents of the lexical scope (e.g., from the debugger).
      */
+  private:
+    bool generateBindings(ExclusiveContext* cx, TokenStream& ts, LifoAlloc& alloc,
+                          MutableHandle<Bindings> bindings) const;
+
+  public:
     bool generateFunctionBindings(ExclusiveContext* cx, TokenStream& ts,
                                   LifoAlloc& alloc,
                                   MutableHandle<Bindings> bindings) const;
 
+    bool generateModuleBindings(ExclusiveContext* cx, TokenStream& ts,
+                                LifoAlloc& alloc,
+                                MutableHandle<Bindings> bindings) const;
+
   private:
     ParseContext**  parserPC;     /* this points to the Parser's active pc
                                        and holds either |this| or one of
@@ -300,8 +311,13 @@ struct MOZ_STACK_CLASS ParseContext : public GenericParseContext
     //   function f1() { function f2() { } }
     //   if (cond) { function f3() { if (cond) { function f4() { } } } }
     //
-    bool atBodyLevel() { return !innermostStmt(); }
-    bool atGlobalLevel() { return atBodyLevel() && !sc->isFunctionBox() && !innermostScopeStmt(); }
+    bool atBodyLevel() {
+        return !innermostStmt();
+    }
+
+    bool atGlobalLevel() {
+        return atBodyLevel() && !sc->isFunctionBox() && !innermostScopeStmt();
+    }
 
     // True if this is the ParseContext for the body of a function created by
     // the Function constructor.
@@ -490,6 +506,8 @@ class Parser : private JS::AutoGCRooter, public StrictModeGetter
         return newFunctionBox(fn, fun, outerpc, directives, generatorKind, enclosing);
     }
 
+    ModuleBox* newModuleBox(Node pn, HandleModuleObject module);
+
     /*
      * Create a new function object given a name (which is optional if this is
      * a function expression).
@@ -542,6 +560,8 @@ class Parser : private JS::AutoGCRooter, public StrictModeGetter
 
     bool maybeParseDirective(Node list, Node pn, bool* cont);
 
+    Node standaloneModule(Handle<ModuleObject*> module);
+
     // Parse a function, given only its body. Used for the Function and
     // Generator constructors.
     Node standaloneFunctionBody(HandleFunction fun, Handle<PropertyNameVector> formals,

js/src/frontend/SharedContext.h

@@ -13,6 +13,7 @@
 #include "jsscript.h"
 #include "jstypes.h"
 
+#include "builtin/ModuleObject.h"
 #include "frontend/ParseMaps.h"
 #include "frontend/ParseNode.h"
 #include "frontend/TokenStream.h"
@@ -215,8 +216,11 @@ class SharedContext
     void computeInWith(JSObject* staticScope);
 
     virtual ObjectBox* toObjectBox() { return nullptr; }
-    inline bool isFunctionBox() { return toObjectBox() && toObjectBox()->isFunctionBox(); }
+    bool isObjectBox() { return toObjectBox() != nullptr; }
+    bool isFunctionBox() { return isObjectBox() && toObjectBox()->isFunctionBox(); }
     inline FunctionBox* asFunctionBox();
+    bool isModuleBox() { return isObjectBox() && toObjectBox()->isModuleBox(); }
+    inline ModuleBox* asModuleBox();
 
     bool allowNewTarget()              const { return allowNewTarget_; }
     bool allowSuperProperty()          const { return allowSuperProperty_; }
@@ -368,6 +372,20 @@ class FunctionBox : public ObjectBox, public SharedContext
     }
 };
 
+class ModuleBox : public ObjectBox, public SharedContext
+{
+  public:
+    Bindings bindings;
+
+    template <typename ParseHandler>
+    ModuleBox(ExclusiveContext* cx, ObjectBox* traceListHead, ModuleObject* module,
+              ParseContext<ParseHandler>* pc);
+
+    ObjectBox* toObjectBox() override { return this; }
+    ModuleObject* module() const { return &object->as<ModuleObject>(); }
+    JSObject* staticScope() const override { return module(); }
+};
+
 inline FunctionBox*
 SharedContext::asFunctionBox()
 {
@@ -375,6 +393,13 @@ SharedContext::asFunctionBox()
     return static_cast<FunctionBox*>(this);
 }
 
+inline ModuleBox*
+SharedContext::asModuleBox()
+{
+    MOZ_ASSERT(isModuleBox());
+    return static_cast<ModuleBox*>(this);
+}
+
 
 // In generators, we treat all locals as aliased so that they get stored on the
 // heap.  This way there is less information to copy off the stack when

js/src/gc/Marking.cpp

@@ -361,6 +361,7 @@ AssertRootMarkingPhase(JSTracer* trc)
     D(GlobalObject*) \
     D(JSObject*) \
     D(JSFunction*) \
+    D(ModuleObject*)      \
     D(NestedScopeObject*) \
     D(PlainObject*) \
     D(SavedFrame*) \

js/src/jit-test/tests/modules/shell-parse.js

@@ -0,0 +1,4 @@
+// Exercise shell parseModule function.
+
+parseModule("");
+parseModule("const foo = 1;");

js/src/jsscript.cpp

@@ -2652,6 +2652,25 @@ JSScript::linkToFunctionFromEmitter(js::ExclusiveContext* cx, JS::Handle<JSScrip
         fun->setScript(script);
 }
 
+/* static */ void
+JSScript::linkToModuleFromEmitter(js::ExclusiveContext* cx, JS::Handle<JSScript*> script,
+                                    js::frontend::ModuleBox* modulebox)
+{
+    script->funHasExtensibleScope_ = false;
+    script->funNeedsDeclEnvObject_ = false;
+    script->needsHomeObject_ = false;
+    script->isDerivedClassConstructor_ = false;
+    script->funLength_ = 0;
+
+    script->isGeneratorExp_ = false;
+    script->setGeneratorKind(NotGenerator);
+
+    // Link the module and the script to each other, so that StaticScopeIter
+    // may walk the scope chain of currently compiling scripts.
+    RootedModuleObject module(cx, modulebox->module());
+    script->setModule(module);
+}
+
 /* static */ bool
 JSScript::fullyInitFromEmitter(ExclusiveContext* cx, HandleScript script, BytecodeEmitter* bce)
 {
@@ -3595,6 +3614,9 @@ JSScript::traceChildren(JSTracer* trc)
     if (functionNonDelazifying())
         TraceEdge(trc, &function_, "function");
 
+    if (module_)
+        TraceEdge(trc, &module_, "module");
+
     if (enclosingStaticScope_)
         TraceEdge(trc, &enclosingStaticScope_, "enclosingStaticScope");
 

js/src/jsscript.h

@@ -18,6 +18,7 @@
 #include "jsopcode.h"
 #include "jstypes.h"
 
+#include "builtin/ModuleObject.h"
 #include "gc/Barrier.h"
 #include "gc/Rooting.h"
 #include "jit/IonCode.h"
@@ -46,15 +47,16 @@ class BreakpointSite;
 class BindingIter;
 class Debugger;
 class LazyScript;
+class NestedScopeObject;
 class RegExpObject;
 struct SourceCompressionTask;
 class Shape;
-class NestedScopeObject;
 
 namespace frontend {
     struct BytecodeEmitter;
     class UpvarCookie;
     class FunctionBox;
+    class ModuleBox;
 } // namespace frontend
 
 namespace detail {
@@ -949,6 +951,7 @@ class JSScript : public js::gc::TenuredCell
     js::HeapPtrObject sourceObject_;
 
     js::HeapPtrFunction function_;
+    js::HeapPtr<js::ModuleObject*> module_;
     js::HeapPtrObject   enclosingStaticScope_;
 
     /*
@@ -1139,7 +1142,7 @@ class JSScript : public js::gc::TenuredCell
     // instead of private to suppress -Wunused-private-field compiler warnings.
   protected:
 #if JS_BITS_PER_WORD == 32
-    uint32_t padding;
+    // No padding currently required.
 #endif
 
     //
@@ -1167,6 +1170,8 @@ class JSScript : public js::gc::TenuredCell
                                      js::frontend::BytecodeEmitter* bce);
     static void linkToFunctionFromEmitter(js::ExclusiveContext* cx, JS::Handle<JSScript*> script,
                                           js::frontend::FunctionBox* funbox);
+    static void linkToModuleFromEmitter(js::ExclusiveContext* cx, JS::Handle<JSScript*> script,
+                                        js::frontend::ModuleBox* funbox);
     // Initialize a no-op script.
     static bool fullyInitTrivial(js::ExclusiveContext* cx, JS::Handle<JSScript*> script);
 
@@ -1547,6 +1552,11 @@ class JSScript : public js::gc::TenuredCell
      */
     inline void ensureNonLazyCanonicalFunction(JSContext* cx);
 
+    js::ModuleObject* module() const {
+        return module_;
+    }
+    inline void setModule(js::ModuleObject* module);
+
     JSFlatString* sourceData(JSContext* cx);
 
     static bool loadSource(JSContext* cx, js::ScriptSource* ss, bool* worked);

js/src/jsscriptinlines.h

@@ -67,10 +67,18 @@ JSScript::functionDelazifying() const
 inline void
 JSScript::setFunction(JSFunction* fun)
 {
+    MOZ_ASSERT(!function_ && !module_);
     MOZ_ASSERT(fun->isTenured());
     function_ = fun;
 }
 
+inline void
+JSScript::setModule(js::ModuleObject* module)
+{
+    MOZ_ASSERT(!function_ && !module_);
+    module_ = module;
+}
+
 inline void
 JSScript::ensureNonLazyCanonicalFunction(JSContext* cx)
 {

js/src/moz.build

@@ -147,6 +147,7 @@ UNIFIED_SOURCES += [
     'builtin/Eval.cpp',
     'builtin/Intl.cpp',
     'builtin/MapObject.cpp',
+    'builtin/ModuleObject.cpp',
     'builtin/Object.cpp',
     'builtin/Profilers.cpp',
     'builtin/Reflect.cpp',

js/src/shell/js.cpp

@@ -56,6 +56,7 @@
 #endif
 #include "jswrapper.h"
 
+#include "builtin/ModuleObject.h"
 #include "builtin/TestingFunctions.h"
 #include "frontend/Parser.h"
 #include "gc/GCInternals.h"
@@ -2067,7 +2068,12 @@ DisassembleToSprinter(JSContext* cx, unsigned argc, Value* vp, Sprinter* sprinte
     } else {
         for (unsigned i = 0; i < p.argc; i++) {
             RootedFunction fun(cx);
-            RootedScript script (cx, ValueToScript(cx, p.argv[i], fun.address()));
+            RootedScript script(cx);
+            RootedValue value(cx, p.argv[i]);
+            if (value.isObject() && value.toObject().is<ModuleObject>())
+                script = value.toObject().as<ModuleObject>().script();
+            else
+                script = ValueToScript(cx, value, fun.address());
             if (!script)
                 return false;
             if (!DisassembleScript(cx, script, fun, p.lines, p.recursive, sprinter))
@@ -3058,6 +3064,45 @@ Compile(JSContext* cx, unsigned argc, Value* vp)
     return ok;
 }
 
+static bool
+ParseModule(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() < 1) {
+        JS_ReportErrorNumber(cx, GetErrorMessage, nullptr,
+                             JSMSG_MORE_ARGS_NEEDED, "parseModule", "0", "s");
+        return false;
+    }
+    if (!args[0].isString()) {
+        JS_ReportError(cx, "expected string to compile, got %s",
+                       JS_TypeOfValue(cx, args[0]));
+        return false;
+    }
+
+    RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+    JSFlatString* scriptContents = args[0].toString()->ensureFlat(cx);
+    if (!scriptContents)
+        return false;
+
+    CompileOptions options(cx);
+    options.setFileAndLine("<string>", 1);
+
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    const char16_t* chars = stableChars.twoByteRange().start().get();
+    SourceBufferHolder srcBuf(chars, scriptContents->length(),
+                              SourceBufferHolder::NoOwnership);
+
+    RootedObject module(cx, frontend::CompileModule(cx, global, options, srcBuf));
+    if (!module)
+        return false;
+
+    args.rval().setObject(*module);
+    return true;
+}
+
 static bool
 Parse(JSContext* cx, unsigned argc, Value* vp)
 {
@@ -4606,6 +4651,10 @@ static const JSFunctionSpecWithHelp shell_functions[] = {
 "compile(code)",
 "  Compiles a string to bytecode, potentially throwing."),
 
+    JS_FN_HELP("parseModule", ParseModule, 1, 0,
+"parseModule(code)",
+"  Parses source text as a module and returns a Module object."),
+
     JS_FN_HELP("parse", Parse, 1, 0,
 "parse(code)",
 "  Parses a string, potentially throwing."),

js/src/vm/ScopeObject.h

@@ -21,6 +21,7 @@ namespace js {
 namespace frontend {
 struct Definition;
 class FunctionBox;
+class ModuleBox;
 }
 
 class StaticWithObject;
@@ -47,6 +48,9 @@ class StaticNonSyntacticScopeObjects;
  * JSFunction
  *   Scope for function bodies. e.g., |function f() { var x; let y; }|
  *
+ * ModuleObject
+ *   Scope for moddules.
+ *
  * StaticWithObject
  *   Scope for |with|. e.g., |with ({}) { ... }|
  *
@@ -63,8 +67,8 @@ class StaticNonSyntacticScopeObjects;
  *
  *   (function f() { var x; function g() { } })
  *
- * All static scope objects are ScopeObjects with the exception of
- * JSFunction. A JSFunction keeps its enclosing scope link on
+ * All static scope objects are ScopeObjects with the exception of JSFunction
+ * and ModuleObject, which keeps their enclosing scope link on
  * |JSScript::enclosingStaticScope()|.
  */
 template <AllowGC allowGC>
@@ -78,7 +82,8 @@ class StaticScopeIter
                obj->is<StaticWithObject>() ||
                obj->is<StaticEvalObject>() ||
                obj->is<StaticNonSyntacticScopeObjects>() ||
-               obj->is<JSFunction>();
+               obj->is<JSFunction>() ||
+               obj->is<ModuleObject>();
     }
 
   public:

js/src/vm/TraceLogging.cpp

@@ -672,6 +672,7 @@ TraceLoggerThreadState::init()
         enabledTextIds[TraceLogger_ParserCompileFunction] = true;
         enabledTextIds[TraceLogger_ParserCompileLazy] = true;
         enabledTextIds[TraceLogger_ParserCompileScript] = true;
+        enabledTextIds[TraceLogger_ParserCompileModule] = true;
         enabledTextIds[TraceLogger_IrregexpCompile] = true;
         enabledTextIds[TraceLogger_IrregexpExecute] = true;
         enabledTextIds[TraceLogger_Scripts] = true;

js/src/vm/TraceLoggingTypes.h

@@ -32,6 +32,7 @@
     _(ParserCompileFunction)                          \
     _(ParserCompileLazy)                              \
     _(ParserCompileScript)                            \
+    _(ParserCompileModule)                            \
     _(Scripts)                                        \
     _(VM)                                             \
                                                       \