Merge branch 'redwood' into releaseRELBASE_20200831

21 files changed, 385 insertions, 323 deletions

diff --git a/js/src/builtin/Module.js b/js/src/builtin/Module.js
index 64d62d216..355303d44 100644
--- a/js/src/builtin/Module.js
+++ b/js/src/builtin/Module.js
@@ -67,10 +67,16 @@ function ModuleGetExportedNames(exportStarSet = [])
 
 function ModuleSetStatus(module, newStatus)
 {
-    assert(newStatus >= MODULE_STATUS_ERRORED && newStatus <= MODULE_STATUS_EVALUATED,
+    assert(newStatus >= MODULE_STATUS_UNINSTANTIATED &&
+           newStatus <= MODULE_STATUS_EVALUATED_ERROR,
            "Bad new module status in ModuleSetStatus");
-    if (newStatus !== MODULE_STATUS_ERRORED)
-        assert(newStatus > module.status, "New module status inconsistent with current status");
+
+    // Note that under OOM conditions we can fail the module instantiation
+    // process even after modules have been marked as instantiated.
+    assert((module.status <= MODULE_STATUS_INSTANTIATED &&
+            newStatus === MODULE_STATUS_UNINSTANTIATED) ||
+           newStatus > module.status,
+           "New module status inconsistent with current status");
 
     UnsafeSetReservedSlot(module, MODULE_OBJECT_STATUS_SLOT, newStatus);
 }
@@ -80,20 +86,15 @@ function ModuleSetStatus(module, newStatus)
 // Returns an object describing the location of the resolved export or
 // indicating a failure.
 //
-// On success this returns: { resolved: true, module, bindingName }
-//
-// There are three failure cases:
+// On success this returns a resolved binding record: { module, bindingName }
 //
-//  - The resolution failure can be blamed on a particular module.
-//    Returns: { resolved: false, module, ambiguous: false }
+// There are two failure cases:
 //
-//  - No culprit can be determined and the resolution failure was due to star
-//    export ambiguity.
-//    Returns: { resolved: false, module: null, ambiguous: true }
+//  - If no definition was found or the request is found to be circular, *null*
+//    is returned.
 //
-//  - No culprit can be determined and the resolution failure was not due to
-//    star export ambiguity.
-//    Returns: { resolved: false, module: null, ambiguous: false }
+//  - If the request is found to be ambiguous, the string `"ambiguous"` is
+//    returned.
 //
 function ModuleResolveExport(exportName, resolveSet = [])
 {
@@ -106,53 +107,47 @@ function ModuleResolveExport(exportName, resolveSet = [])
     let module = this;
 
     // Step 2
-    assert(module.status !== MODULE_STATUS_ERRORED, "Bad module status in ResolveExport");
-    
-    // Step 3
     for (let i = 0; i < resolveSet.length; i++) {
         let r = resolveSet[i];
         if (r.module === module && r.exportName === exportName) {
             // This is a circular import request.
-            return {resolved: false, module: null, ambiguous: false};
+            return null;
         }
     }
 
-    // Step 4
+    // Step 3
     _DefineDataProperty(resolveSet, resolveSet.length, {module: module, exportName: exportName});
 
-    // Step 5
+    // Step 4
     let localExportEntries = module.localExportEntries;
     for (let i = 0; i < localExportEntries.length; i++) {
         let e = localExportEntries[i];
         if (exportName === e.exportName)
-            return {resolved: true, module, bindingName: e.localName};
+            return {module, bindingName: e.localName};
     }
 
-    // Step 6
+    // Step 5
     let indirectExportEntries = module.indirectExportEntries;
     for (let i = 0; i < indirectExportEntries.length; i++) {
         let e = indirectExportEntries[i];
         if (exportName === e.exportName) {
             let importedModule = CallModuleResolveHook(module, e.moduleRequest,
                                                        MODULE_STATUS_UNINSTANTIATED);
-            let resolution = callFunction(importedModule.resolveExport, importedModule, e.importName,
-                                          resolveSet);
-            if (!resolution.resolved && !resolution.module)
-                resolution.module = module;
-            return resolution;
+            return callFunction(importedModule.resolveExport, importedModule, e.importName,
+                                resolveSet);
         }
     }
 
-    // Step 7
+    // Step 6
     if (exportName === "default") {
         // A default export cannot be provided by an export *.
-        return {resolved: false, module: null, ambiguous: false};
+        return null;
     }
 
-    // Step 8
+    // Step 7
     let starResolution = null;
 
-    // Step 9
+    // Step 8
     let starExportEntries = module.starExportEntries;
     for (let i = 0; i < starExportEntries.length; i++) {
         let e = starExportEntries[i];
@@ -160,27 +155,31 @@ function ModuleResolveExport(exportName, resolveSet = [])
                                                    MODULE_STATUS_UNINSTANTIATED);
         let resolution = callFunction(importedModule.resolveExport, importedModule, exportName,
                                       resolveSet);
-        if (!resolution.resolved && (resolution.module || resolution.ambiguous))
+        if (resolution === "ambiguous")
             return resolution;
 
-        if (resolution.resolved) {
+        if (resolution !== null) {
             if (starResolution === null) {
                 starResolution = resolution;
             } else {
                 if (resolution.module !== starResolution.module ||
                     resolution.bindingName !== starResolution.bindingName)
                 {
-                    return {resolved: false, module: null, ambiguous: true};
+                    return "ambiguous";
                 }
             }
         }
     }
 
-    // Step 10
-    if (starResolution !== null)
-        return starResolution;
+    // Step 9
+    return starResolution;
+}
 
-    return {resolved: false, module: null, ambiguous: false};
+function IsResolvedBinding(resolution)
+{
+    assert(resolution === "ambiguous" || typeof resolution === "object",
+           "Bad module resolution result");
+    return typeof resolution === "object" && resolution !== null;
 }
 
 // 15.2.1.18 GetModuleNamespace(module)
@@ -189,12 +188,12 @@ function GetModuleNamespace(module)
     // Step 1
     assert(IsModule(module), "GetModuleNamespace called with non-module");
 
-    // Step 2
+    // Steps 2-3
     assert(module.status !== MODULE_STATUS_UNINSTANTIATED &&
-           module.status !== MODULE_STATUS_ERRORED,
+           module.status !== MODULE_STATUS_EVALUATED_ERROR,
            "Bad module status in GetModuleNamespace");
 
-    // Step 3
+    // Step 4
     let namespace = module.namespace;
 
     if (typeof namespace === "undefined") {
@@ -203,7 +202,7 @@ function GetModuleNamespace(module)
         for (let i = 0; i < exportedNames.length; i++) {
             let name = exportedNames[i];
             let resolution = callFunction(module.resolveExport, module, name);
-            if (resolution.resolved)
+            if (IsResolvedBinding(resolution))
                 _DefineDataProperty(unambiguousNames, unambiguousNames.length, name);
         }
         namespace = ModuleNamespaceCreate(module, unambiguousNames);
@@ -225,7 +224,7 @@ function ModuleNamespaceCreate(module, exports)
     for (let i = 0; i < exports.length; i++) {
         let name = exports[i];
         let binding = callFunction(module.resolveExport, module, name);
-        assert(binding.resolved, "Failed to resolve binding");
+        assert(IsResolvedBinding(binding), "Failed to resolve binding");
         AddModuleNamespaceBinding(ns, name, binding.module, binding.bindingName);
     }
 
@@ -236,31 +235,16 @@ function GetModuleEnvironment(module)
 {
     assert(IsModule(module), "Non-module passed to GetModuleEnvironment");
 
-    // Check for a previous failed attempt to instantiate this module. This can
-    // only happen due to a bug in the module loader.
-    if (module.status === MODULE_STATUS_ERRORED)
-        ThrowInternalError(JSMSG_MODULE_INSTANTIATE_FAILED, module.status);
+    assert(module.status >= MODULE_STATUS_INSTANTIATING,
+           "Attempt to access module environement before instantation");
 
     let env = UnsafeGetReservedSlot(module, MODULE_OBJECT_ENVIRONMENT_SLOT);
-    assert(env === undefined || IsModuleEnvironment(env),
+    assert(IsModuleEnvironment(env),
            "Module environment slot contains unexpected value");
 
     return env;
 }
 
-function RecordModuleError(module, error)
-{
-    // Set the module's status to 'errored' to indicate a failed module
-    // instantiation and record the exception. The environment slot is also
-    // reset to 'undefined'.
-
-    assert(IsObject(module) && IsModule(module), "Non-module passed to RecordModuleError");
-
-    ModuleSetStatus(module, MODULE_STATUS_ERRORED);
-    UnsafeSetReservedSlot(module, MODULE_OBJECT_ERROR_SLOT, error);
-    UnsafeSetReservedSlot(module, MODULE_OBJECT_ENVIRONMENT_SLOT, undefined);
-}
-
 function CountArrayValues(array, value)
 {
     let count = 0;
@@ -280,6 +264,16 @@ function ArrayContains(array, value)
     return false;
 }
 
+function HandleModuleInstantiationFailure(module)
+{
+    // Reset the module to the "uninstantiated" state. Don't reset the
+    // environment slot as the environment object will be required by any
+    // possible future instantiation attempt.
+    ModuleSetStatus(module, MODULE_STATUS_UNINSTANTIATED);
+    UnsafeSetReservedSlot(module, MODULE_OBJECT_DFS_INDEX_SLOT, undefined);
+    UnsafeSetReservedSlot(module, MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT, undefined);
+}
+
 // 15.2.1.16.4 ModuleInstantiate()
 function ModuleInstantiate()
 {
@@ -301,38 +295,30 @@ function ModuleInstantiate()
 
     // Steps 4-5
     try {
-        InnerModuleDeclarationInstantiation(module, stack, 0);
+        InnerModuleInstantiation(module, stack, 0);
     } catch (error) {
         for (let i = 0; i < stack.length; i++) {
             let m = stack[i];
 
-            assert(m.status === MODULE_STATUS_INSTANTIATING ||
-                   m.status === MODULE_STATUS_ERRORED,
-                   "Bad module status after failed instantiation");
-
-            RecordModuleError(m, error);
+            assert(m.status === MODULE_STATUS_INSTANTIATING,
+                   "Expected instantiating status during failed instantiation");
+            HandleModuleInstantiationFailure(m);
         }
 
-        if (stack.length === 0 &&
-            typeof(UnsafeGetReservedSlot(module, MODULE_OBJECT_ERROR_SLOT)) === "undefined")
-        {
-            // This can happen due to OOM when appending to the stack.
-            assert(error === "out of memory",
-                   "Stack must contain module unless we hit OOM");
-            RecordModuleError(module, error);
-        }
+        // Handle OOM when appending to the stack or over-recursion errors.
+        if (stack.length === 0)
+            HandleModuleInstantiationFailure(module);
 
-        assert(module.status === MODULE_STATUS_ERRORED,
-               "Bad module status after failed instantiation");
-        assert(SameValue(UnsafeGetReservedSlot(module, MODULE_OBJECT_ERROR_SLOT), error),
-               "Module has different error set after failed instantiation");
+        assert(module.status === MODULE_STATUS_UNINSTANTIATED,
+               "Expected uninstantiated status after failed instantiation");
 
         throw error;
     }
 
     // Step 6
-    assert(module.status == MODULE_STATUS_INSTANTIATED ||
-           module.status == MODULE_STATUS_EVALUATED,
+    assert(module.status === MODULE_STATUS_INSTANTIATED ||
+           module.status === MODULE_STATUS_EVALUATED ||
+           module.status === MODULE_STATUS_EVALUATED_ERROR,
            "Bad module status after successful instantiation");
 
     // Step 7
@@ -344,8 +330,8 @@ function ModuleInstantiate()
 }
 _SetCanonicalName(ModuleInstantiate, "ModuleInstantiate");
 
-// 15.2.1.16.4.1 InnerModuleDeclarationInstantiation(module, stack, index)
-function InnerModuleDeclarationInstantiation(module, stack, index)
+// 15.2.1.16.4.1 InnerModuleInstantiation(module, stack, index)
+function InnerModuleInstantiation(module, stack, index)
 {
     // Step 1
     // TODO: Support module records other than source text module records.
@@ -353,42 +339,40 @@ function InnerModuleDeclarationInstantiation(module, stack, index)
     // Step 2
     if (module.status === MODULE_STATUS_INSTANTIATING ||
         module.status === MODULE_STATUS_INSTANTIATED ||
-        module.status === MODULE_STATUS_EVALUATED)
+        module.status === MODULE_STATUS_EVALUATED ||
+        module.status === MODULE_STATUS_EVALUATED_ERROR)
     {
         return index;
     }
 
     // Step 3
-    if (module.status === MODULE_STATUS_ERRORED)
-        throw module.error;
-
-    // Step 4
     assert(module.status === MODULE_STATUS_UNINSTANTIATED,
           "Bad module status in ModuleDeclarationInstantiation");
 
-    // Steps 5
+    // Step 4
     ModuleSetStatus(module, MODULE_STATUS_INSTANTIATING);
 
-    // Step 6-8
+    // Steps 5-7
     UnsafeSetReservedSlot(module, MODULE_OBJECT_DFS_INDEX_SLOT, index);
     UnsafeSetReservedSlot(module, MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT, index);
     index++;
 
-    // Step 9
+    // Step 8
     _DefineDataProperty(stack, stack.length, module);
 
-    // Step 10
+    // Step 9
     let requestedModules = module.requestedModules;
     for (let i = 0; i < requestedModules.length; i++) {
         let required = requestedModules[i];
-        let requiredModule = CallModuleResolveHook(module, required, MODULE_STATUS_ERRORED);
+        let requiredModule = CallModuleResolveHook(module, required, MODULE_STATUS_UNINSTANTIATED);
 
-        index = InnerModuleDeclarationInstantiation(requiredModule, stack, index);
+        index = InnerModuleInstantiation(requiredModule, stack, index);
 
         assert(requiredModule.status === MODULE_STATUS_INSTANTIATING ||
                requiredModule.status === MODULE_STATUS_INSTANTIATED ||
-               requiredModule.status === MODULE_STATUS_EVALUATED,
-               "Bad required module status after InnerModuleDeclarationInstantiation");
+               requiredModule.status === MODULE_STATUS_EVALUATED ||
+               requiredModule.status === MODULE_STATUS_EVALUATED_ERROR,
+               "Bad required module status after InnerModuleInstantiation");
 
         assert((requiredModule.status === MODULE_STATUS_INSTANTIATING) ===
                ArrayContains(stack, requiredModule),
@@ -404,16 +388,16 @@ function InnerModuleDeclarationInstantiation(module, stack, index)
         }
     }
 
-    // Step 11
+    // Step 10
     ModuleDeclarationEnvironmentSetup(module);
 
-    // Steps 12-13
+    // Steps 11-12
     assert(CountArrayValues(stack, module) === 1,
            "Current module should appear exactly once in the stack");
     assert(module.dfsAncestorIndex <= module.dfsIndex,
            "Bad DFS ancestor index");
 
-    // Step 14
+    // Step 13
     if (module.dfsAncestorIndex === module.dfsIndex) {
         let requiredModule;
         do {
@@ -434,16 +418,14 @@ function ModuleDeclarationEnvironmentSetup(module)
     for (let i = 0; i < indirectExportEntries.length; i++) {
         let e = indirectExportEntries[i];
         let resolution = callFunction(module.resolveExport, module, e.exportName);
-        assert(resolution.resolved || resolution.module,
-               "Unexpected failure to resolve export in ModuleDeclarationEnvironmentSetup");
-        if (!resolution.resolved) {
-            return ResolutionError(resolution, "indirectExport", e.exportName,
-                                   e.lineNumber, e.columnNumber)
+        if (!IsResolvedBinding(resolution)) {
+            ThrowResolutionError(module, resolution, "indirectExport", e.exportName,
+                                 e.lineNumber, e.columnNumber);
         }
     }
 
     // Steps 5-6
-    CreateModuleEnvironment(module);
+    // Note that we have already created the environment by this point.
     let env = GetModuleEnvironment(module);
 
     // Step 8
@@ -458,12 +440,9 @@ function ModuleDeclarationEnvironmentSetup(module)
         } else {
             let resolution = callFunction(importedModule.resolveExport, importedModule,
                                           imp.importName);
-            if (!resolution.resolved && !resolution.module)
-                resolution.module = module;
-
-            if (!resolution.resolved) {
-                return ResolutionError(resolution, "import", imp.importName,
-                                       imp.lineNumber, imp.columnNumber);
+            if (!IsResolvedBinding(resolution)) {
+                ThrowResolutionError(module, resolution, "import", imp.importName,
+                                     imp.lineNumber, imp.columnNumber);
             }
 
             CreateImportBinding(env, imp.localName, resolution.module, resolution.bindingName);
@@ -473,38 +452,58 @@ function ModuleDeclarationEnvironmentSetup(module)
     InstantiateModuleFunctionDeclarations(module);
 }
 
-// 15.2.1.16.4.3 ResolutionError(module)
-function ResolutionError(resolution, kind, name, line, column)
+function ThrowResolutionError(module, resolution, kind, name, line, column)
 {
-    let module = resolution.module;
-    assert(module !== null,
-           "Null module passed to ResolutionError");
-
-    assert(module.status === MODULE_STATUS_UNINSTANTIATED ||
-           module.status === MODULE_STATUS_INSTANTIATING,
-           "Unexpected module status in ResolutionError");
+    assert(module.status === MODULE_STATUS_INSTANTIATING,
+           "Unexpected module status in ThrowResolutionError");
 
     assert(kind === "import" || kind === "indirectExport",
-           "Unexpected kind in ResolutionError");
+           "Unexpected kind in ThrowResolutionError");
 
     assert(line > 0,
            "Line number should be present for all imports and indirect exports");
 
+    let ambiguous = resolution === "ambiguous";
+
     let errorNumber;
-    if (kind === "import") {
-        errorNumber = resolution.ambiguous ? JSMSG_AMBIGUOUS_IMPORT
-                                           : JSMSG_MISSING_IMPORT;
-    } else {
-        errorNumber = resolution.ambiguous ? JSMSG_AMBIGUOUS_INDIRECT_EXPORT
-                                           : JSMSG_MISSING_INDIRECT_EXPORT;
-    }
+    if (kind === "import")
+        errorNumber = ambiguous ? JSMSG_AMBIGUOUS_IMPORT : JSMSG_MISSING_IMPORT;
+    else
+        errorNumber = ambiguous ? JSMSG_AMBIGUOUS_INDIRECT_EXPORT : JSMSG_MISSING_INDIRECT_EXPORT;
 
     let message = GetErrorMessage(errorNumber) + ": " + name;
     let error = CreateModuleSyntaxError(module, line, column, message);
-    RecordModuleError(module, error);
     throw error;
 }
 
+function GetModuleEvaluationError(module)
+{
+    assert(IsObject(module) && IsModule(module),
+           "Non-module passed to GetModuleEvaluationError");
+    assert(module.status === MODULE_STATUS_EVALUATED_ERROR,
+           "Bad module status in GetModuleEvaluationError");
+    return UnsafeGetReservedSlot(module, MODULE_OBJECT_EVALUATION_ERROR_SLOT);
+}
+
+function RecordModuleEvaluationError(module, error)
+{
+    // Set the module's EvaluationError slot to indicate a failed module
+    // evaluation.
+
+    assert(IsObject(module) && IsModule(module),
+           "Non-module passed to RecordModuleEvaluationError");
+
+    if (module.status === MODULE_STATUS_EVALUATED_ERROR) {
+        // It would be nice to assert that |error| is the same as the one we
+        // previously recorded, but that's not always true in the case of out of
+        // memory and over-recursion errors.
+        return;
+    }
+
+    ModuleSetStatus(module, MODULE_STATUS_EVALUATED_ERROR);
+    UnsafeSetReservedSlot(module, MODULE_OBJECT_EVALUATION_ERROR_SLOT, error);
+}
+
 // 15.2.1.16.5 ModuleEvaluate()
 function ModuleEvaluate()
 {
@@ -515,9 +514,9 @@ function ModuleEvaluate()
     let module = this;
 
     // Step 2
-    if (module.status !== MODULE_STATUS_ERRORED &&
-        module.status !== MODULE_STATUS_INSTANTIATED &&
-        module.status !== MODULE_STATUS_EVALUATED)
+    if (module.status !== MODULE_STATUS_INSTANTIATED &&
+        module.status !== MODULE_STATUS_EVALUATED &&
+        module.status !== MODULE_STATUS_EVALUATED_ERROR)
     {
         ThrowInternalError(JSMSG_BAD_MODULE_STATUS);
     }
@@ -535,27 +534,20 @@ function ModuleEvaluate()
             assert(m.status === MODULE_STATUS_EVALUATING,
                    "Bad module status after failed evaluation");
 
-            RecordModuleError(m, error);
+            RecordModuleEvaluationError(m, error);
         }
 
-        if (stack.length === 0 &&
-            typeof(UnsafeGetReservedSlot(module, MODULE_OBJECT_ERROR_SLOT)) === "undefined")
-        {
-            // This can happen due to OOM when appending to the stack.
-            assert(error === "out of memory",
-                  "Stack must contain module unless we hit OOM");
-            RecordModuleError(module, error);
-        }
+        // Handle OOM when appending to the stack or over-recursion errors.
+        if (stack.length === 0)
+            RecordModuleEvaluationError(module, error);
 
-        assert(module.status === MODULE_STATUS_ERRORED,
+        assert(module.status === MODULE_STATUS_EVALUATED_ERROR,
                "Bad module status after failed evaluation");
-        assert(SameValue(UnsafeGetReservedSlot(module, MODULE_OBJECT_ERROR_SLOT), error),
-               "Module has different error set after failed evaluation");
 
         throw error;
     }
 
-    assert(module.status == MODULE_STATUS_EVALUATED,
+    assert(module.status === MODULE_STATUS_EVALUATED,
            "Bad module status after successful evaluation");
     assert(stack.length === 0,
            "Stack should be empty after successful evaluation");
@@ -571,19 +563,19 @@ function InnerModuleEvaluation(module, stack, index)
     // TODO: Support module records other than source text module records.
 
     // Step 2
-    if (module.status === MODULE_STATUS_EVALUATING ||
-        module.status === MODULE_STATUS_EVALUATED)
-    {
+    if (module.status === MODULE_STATUS_EVALUATED_ERROR)
+        throw GetModuleEvaluationError(module);
+
+    if (module.status === MODULE_STATUS_EVALUATED)
         return index;
-    }
 
     // Step 3
-    if (module.status === MODULE_STATUS_ERRORED)
-        throw module.error;
+    if (module.status === MODULE_STATUS_EVALUATING)
+        return index;
 
     // Step 4
     assert(module.status === MODULE_STATUS_INSTANTIATED,
-          "Bad module status in ModuleEvaluation");
+          "Bad module status in InnerModuleEvaluation");
 
     // Step 5
     ModuleSetStatus(module, MODULE_STATUS_EVALUATING);
@@ -605,8 +597,8 @@ function InnerModuleEvaluation(module, stack, index)
 
         index = InnerModuleEvaluation(requiredModule, stack, index);
 
-        assert(requiredModule.status == MODULE_STATUS_EVALUATING ||
-               requiredModule.status == MODULE_STATUS_EVALUATED,
+        assert(requiredModule.status === MODULE_STATUS_EVALUATING ||
+               requiredModule.status === MODULE_STATUS_EVALUATED,
               "Bad module status after InnerModuleEvaluation");
 
         assert((requiredModule.status === MODULE_STATUS_EVALUATING) ===
diff --git a/js/src/builtin/ModuleObject.cpp b/js/src/builtin/ModuleObject.cpp
index 30e7120c0..728929e8c 100644
--- a/js/src/builtin/ModuleObject.cpp
+++ b/js/src/builtin/ModuleObject.cpp
@@ -18,10 +18,10 @@
 using namespace js;
 using namespace js::frontend;
 
-static_assert(MODULE_STATUS_ERRORED < MODULE_STATUS_UNINSTANTIATED &&
-              MODULE_STATUS_UNINSTANTIATED < MODULE_STATUS_INSTANTIATING &&
+static_assert(MODULE_STATUS_UNINSTANTIATED < MODULE_STATUS_INSTANTIATING &&
               MODULE_STATUS_INSTANTIATING < MODULE_STATUS_INSTANTIATED &&
-              MODULE_STATUS_INSTANTIATED < MODULE_STATUS_EVALUATED,
+              MODULE_STATUS_INSTANTIATED < MODULE_STATUS_EVALUATED &&
+              MODULE_STATUS_EVALUATED < MODULE_STATUS_EVALUATED_ERROR,
               "Module statuses are ordered incorrectly");
 
 template<typename T, Value ValueGetter(const T* obj)>
@@ -248,21 +248,13 @@ IndirectBindingMap::Binding::Binding(ModuleEnvironmentObject* environment, Shape
   : environment(environment), shape(shape)
 {}
 
-IndirectBindingMap::IndirectBindingMap(Zone* zone)
-  : map_(ZoneAllocPolicy(zone))
-{
-}
-
-bool
-IndirectBindingMap::init()
-{
-    return map_.init();
-}
-
 void
 IndirectBindingMap::trace(JSTracer* trc)
 {
-    for (Map::Enum e(map_); !e.empty(); e.popFront()) {
+    if (!map_)
+        return;
+
+    for (Map::Enum e(*map_); !e.empty(); e.popFront()) {
         Binding& b = e.front().value();
         TraceEdge(trc, &b.environment, "module bindings environment");
         TraceEdge(trc, &b.shape, "module bindings shape");
@@ -273,12 +265,25 @@ IndirectBindingMap::trace(JSTracer* trc)
 }
 
 bool
-IndirectBindingMap::putNew(JSContext* cx, HandleId name,
-                           HandleModuleEnvironmentObject environment, HandleId localName)
-{
+IndirectBindingMap::put(JSContext* cx, HandleId name,
+                        HandleModuleEnvironmentObject environment, HandleId localName)
+{
+    // This object might have been allocated on the background parsing thread in
+    // different zone to the final module. Lazily allocate the map so we don't
+    // have to switch its zone when merging compartments.
+    if (!map_) {
+        MOZ_ASSERT(!cx->zone()->usedByExclusiveThread);
+        map_.emplace(cx->zone());
+        if (!map_->init()) {
+            map_.reset();
+            ReportOutOfMemory(cx);
+            return false;
+        }
+    }
+
     RootedShape shape(cx, environment->lookup(cx, localName));
     MOZ_ASSERT(shape);
-    if (!map_.putNew(name, Binding(environment, shape))) {
+    if (!map_->put(name, Binding(environment, shape))) {
         ReportOutOfMemory(cx);
         return false;
     }
@@ -289,7 +294,10 @@ IndirectBindingMap::putNew(JSContext* cx, HandleId name,
 bool
 IndirectBindingMap::lookup(jsid name, ModuleEnvironmentObject** envOut, Shape** shapeOut) const
 {
-    auto ptr = map_.lookup(name);
+    if (!map_)
+        return false;
+
+    auto ptr = map_->lookup(name);
     if (!ptr)
         return false;
 
@@ -359,7 +367,7 @@ ModuleNamespaceObject::addBinding(JSContext* cx, HandleAtom exportedName,
     RootedModuleEnvironmentObject environment(cx, &targetModule->initialEnvironment());
     RootedId exportedNameId(cx, AtomToId(exportedName));
     RootedId localNameId(cx, AtomToId(localName));
-    return bindings->putNew(cx, exportedNameId, environment, localNameId);
+    return bindings->put(cx, exportedNameId, environment, localNameId);
 }
 
 const char ModuleNamespaceObject::ProxyHandler::family = 0;
@@ -625,10 +633,9 @@ ModuleObject::create(ExclusiveContext* cx)
     RootedModuleObject self(cx, &obj->as<ModuleObject>());
 
     Zone* zone = cx->zone();
-    IndirectBindingMap* bindings = zone->new_<IndirectBindingMap>(zone);
-    if (!bindings || !bindings->init()) {
+    IndirectBindingMap* bindings = zone->new_<IndirectBindingMap>();
+    if (!bindings) {
         ReportOutOfMemory(cx);
-        js_delete<IndirectBindingMap>(bindings);
         return nullptr;
     }
 
@@ -657,14 +664,24 @@ ModuleObject::finalize(js::FreeOp* fop, JSObject* obj)
         fop->delete_(funDecls);
 }
 
+ModuleEnvironmentObject&
+ModuleObject::initialEnvironment() const
+{
+    Value value = getReservedSlot(EnvironmentSlot);
+    return value.toObject().as<ModuleEnvironmentObject>();
+}
+
 ModuleEnvironmentObject*
 ModuleObject::environment() const
 {
-    Value value = getReservedSlot(EnvironmentSlot);
-    if (value.isUndefined())
+    MOZ_ASSERT(!hadEvaluationError());
+
+    // According to the spec the environment record is created during
+    // instantiation, but we create it earlier than that.
+    if (status() < MODULE_STATUS_INSTANTIATED)
         return nullptr;
 
-    return &value.toObject().as<ModuleEnvironmentObject>();
+    return &initialEnvironment();
 }
 
 bool
@@ -723,13 +740,13 @@ void
 ModuleObject::init(HandleScript script)
 {
     initReservedSlot(ScriptSlot, PrivateValue(script));
-    initReservedSlot(StatusSlot, Int32Value(MODULE_STATUS_ERRORED));
+    initReservedSlot(StatusSlot, Int32Value(MODULE_STATUS_UNINSTANTIATED));
 }
 
 void
 ModuleObject::setInitialEnvironment(HandleModuleEnvironmentObject initialEnvironment)
 {
-    initReservedSlot(InitialEnvironmentSlot, ObjectValue(*initialEnvironment));
+    initReservedSlot(EnvironmentSlot, ObjectValue(*initialEnvironment));
 }
 
 void
@@ -827,7 +844,8 @@ ModuleObject::script() const
 static inline void
 AssertValidModuleStatus(ModuleStatus status)
 {
-    MOZ_ASSERT(status >= MODULE_STATUS_ERRORED && status <= MODULE_STATUS_EVALUATED);
+    MOZ_ASSERT(status >= MODULE_STATUS_UNINSTANTIATED &&
+               status <= MODULE_STATUS_EVALUATED_ERROR);
 }
 
 ModuleStatus
@@ -838,11 +856,17 @@ ModuleObject::status() const
     return status;
 }
 
+bool
+ModuleObject::hadEvaluationError() const
+{
+    return status() == MODULE_STATUS_EVALUATED_ERROR;
+}
+
 Value
-ModuleObject::error() const
+ModuleObject::evaluationError() const
 {
-    MOZ_ASSERT(status() == MODULE_STATUS_ERRORED);
-    return getReservedSlot(ErrorSlot);
+    MOZ_ASSERT(hadEvaluationError());
+    return getReservedSlot(EvaluationErrorSlot);
 }
 
 Value
@@ -857,12 +881,6 @@ ModuleObject::setHostDefinedField(const JS::Value& value)
     setReservedSlot(HostDefinedSlot, value);
 }
 
-ModuleEnvironmentObject&
-ModuleObject::initialEnvironment() const
-{
-    return getReservedSlot(InitialEnvironmentSlot).toObject().as<ModuleEnvironmentObject>();
-}
-
 Scope*
 ModuleObject::enclosingScope() const
 {
@@ -888,16 +906,6 @@ ModuleObject::trace(JSTracer* trc, JSObject* obj)
         funDecls->trace(trc);
 }
 
-void
-ModuleObject::createEnvironment()
-{
-    // The environment has already been created, we just neet to set it in the
-    // right slot.
-    MOZ_ASSERT(!getReservedSlot(InitialEnvironmentSlot).isUndefined());
-    MOZ_ASSERT(getReservedSlot(EnvironmentSlot).isUndefined());
-    setReservedSlot(EnvironmentSlot, getReservedSlot(InitialEnvironmentSlot));
-}
-
 bool
 ModuleObject::noteFunctionDeclaration(ExclusiveContext* cx, HandleAtom name, HandleFunction fun)
 {
@@ -913,7 +921,10 @@ ModuleObject::noteFunctionDeclaration(ExclusiveContext* cx, HandleAtom name, Han
 /* static */ bool
 ModuleObject::instantiateFunctionDeclarations(JSContext* cx, HandleModuleObject self)
 {
+#ifdef DEBUG
+    MOZ_ASSERT(self->status() == MODULE_STATUS_INSTANTIATING);
     MOZ_ASSERT(IsFrozen(cx, self));
+#endif
 
     FunctionDeclarationVector* funDecls = self->functionDeclarations();
     if (!funDecls) {
@@ -944,7 +955,10 @@ ModuleObject::instantiateFunctionDeclarations(JSContext* cx, HandleModuleObject
 /* static */ bool
 ModuleObject::execute(JSContext* cx, HandleModuleObject self, MutableHandleValue rval)
 {
+#ifdef DEBUG
+    MOZ_ASSERT(self->status() == MODULE_STATUS_EVALUATING);
     MOZ_ASSERT(IsFrozen(cx, self));
+#endif
 
     RootedScript script(cx, self->script());
     RootedModuleEnvironmentObject scope(cx, self->environment());
@@ -967,10 +981,9 @@ ModuleObject::createNamespace(JSContext* cx, HandleModuleObject self, HandleObje
         return nullptr;
 
     Zone* zone = cx->zone();
-    IndirectBindingMap* bindings = zone->new_<IndirectBindingMap>(zone);
-    if (!bindings || !bindings->init()) {
+    IndirectBindingMap* bindings = zone->new_<IndirectBindingMap>();
+    if (!bindings) {
         ReportOutOfMemory(cx);
-        js_delete<IndirectBindingMap>(bindings);
         return nullptr;
     }
 
@@ -1005,7 +1018,7 @@ ModuleObject::Evaluate(JSContext* cx, HandleModuleObject self)
 
 DEFINE_GETTER_FUNCTIONS(ModuleObject, namespace_, NamespaceSlot)
 DEFINE_GETTER_FUNCTIONS(ModuleObject, status, StatusSlot)
-DEFINE_GETTER_FUNCTIONS(ModuleObject, error, ErrorSlot)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, evaluationError, EvaluationErrorSlot)
 DEFINE_GETTER_FUNCTIONS(ModuleObject, requestedModules, RequestedModulesSlot)
 DEFINE_GETTER_FUNCTIONS(ModuleObject, importEntries, ImportEntriesSlot)
 DEFINE_GETTER_FUNCTIONS(ModuleObject, localExportEntries, LocalExportEntriesSlot)
@@ -1020,7 +1033,7 @@ GlobalObject::initModuleProto(JSContext* cx, Handle<GlobalObject*> global)
     static const JSPropertySpec protoAccessors[] = {
         JS_PSG("namespace", ModuleObject_namespace_Getter, 0),
         JS_PSG("status", ModuleObject_statusGetter, 0),
-        JS_PSG("error", ModuleObject_errorGetter, 0),
+        JS_PSG("evaluationError", ModuleObject_evaluationErrorGetter, 0),
         JS_PSG("requestedModules", ModuleObject_requestedModulesGetter, 0),
         JS_PSG("importEntries", ModuleObject_importEntriesGetter, 0),
         JS_PSG("localExportEntries", ModuleObject_localExportEntriesGetter, 0),
diff --git a/js/src/builtin/ModuleObject.h b/js/src/builtin/ModuleObject.h
index be0315215..5e4e7f342 100644
--- a/js/src/builtin/ModuleObject.h
+++ b/js/src/builtin/ModuleObject.h
@@ -7,6 +7,8 @@
 #ifndef builtin_ModuleObject_h
 #define builtin_ModuleObject_h
 
+#include "mozilla/Maybe.h"
+
 #include "jsapi.h"
 #include "jsatom.h"
 
@@ -102,27 +104,27 @@ typedef Handle<ExportEntryObject*> HandleExportEntryObject;
 class IndirectBindingMap
 {
   public:
-    explicit IndirectBindingMap(Zone* zone);
-    bool init();
-
     void trace(JSTracer* trc);
 
-    bool putNew(JSContext* cx, HandleId name,
-                HandleModuleEnvironmentObject environment, HandleId localName);
+    bool put(JSContext* cx, HandleId name,
+             HandleModuleEnvironmentObject environment, HandleId localName);
 
     size_t count() const {
-        return map_.count();
+        return map_ ? map_->count() : 0;
     }
 
     bool has(jsid name) const {
-        return map_.has(name);
+        return map_ ? map_->has(name) : false;
     }
 
     bool lookup(jsid name, ModuleEnvironmentObject** envOut, Shape** shapeOut) const;
 
     template <typename Func>
     void forEachExportedName(Func func) const {
-        for (auto r = map_.all(); !r.empty(); r.popFront())
+        if (!map_)
+            return;
+
+        for (auto r = map_->all(); !r.empty(); r.popFront())
             func(r.front().key());
     }
 
@@ -136,7 +138,7 @@ class IndirectBindingMap
 
     typedef HashMap<jsid, Binding, DefaultHasher<jsid>, ZoneAllocPolicy> Map;
 
-    Map map_;
+    mozilla::Maybe<Map> map_;
 };
 
 class ModuleNamespaceObject : public ProxyObject
@@ -214,11 +216,10 @@ class ModuleObject : public NativeObject
     enum
     {
         ScriptSlot = 0,
-        InitialEnvironmentSlot,
         EnvironmentSlot,
         NamespaceSlot,
         StatusSlot,
-        ErrorSlot,
+        EvaluationErrorSlot,
         HostDefinedSlot,
         RequestedModulesSlot,
         ImportEntriesSlot,
@@ -238,8 +239,8 @@ class ModuleObject : public NativeObject
                   "EnvironmentSlot must match self-hosting define");
     static_assert(StatusSlot == MODULE_OBJECT_STATUS_SLOT,
                   "StatusSlot must match self-hosting define");
-    static_assert(ErrorSlot == MODULE_OBJECT_ERROR_SLOT,
-                  "ErrorSlot must match self-hosting define");
+    static_assert(EvaluationErrorSlot == MODULE_OBJECT_EVALUATION_ERROR_SLOT,
+                  "EvaluationErrorSlot must match self-hosting define");
     static_assert(DFSIndexSlot == MODULE_OBJECT_DFS_INDEX_SLOT,
                   "DFSIndexSlot must match self-hosting define");
     static_assert(DFSAncestorIndexSlot == MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT,
@@ -269,7 +270,8 @@ class ModuleObject : public NativeObject
     ModuleEnvironmentObject* environment() const;
     ModuleNamespaceObject* namespace_();
     ModuleStatus status() const;
-    Value error() const;
+    bool hadEvaluationError() const;
+    Value evaluationError() const;
     Value hostDefinedField() const;
     ArrayObject& requestedModules() const;
     ArrayObject& importEntries() const;
@@ -285,9 +287,6 @@ class ModuleObject : public NativeObject
 
     void setHostDefinedField(const JS::Value& value);
 
-    // For intrinsic_CreateModuleEnvironment.
-    void createEnvironment();
-
     // For BytecodeEmitter.
     bool noteFunctionDeclaration(ExclusiveContext* cx, HandleAtom name, HandleFunction fun);
 
diff --git a/js/src/builtin/SelfHostingDefines.h b/js/src/builtin/SelfHostingDefines.h
index a06c2aa62..a3ba36804 100644
--- a/js/src/builtin/SelfHostingDefines.h
+++ b/js/src/builtin/SelfHostingDefines.h
@@ -97,17 +97,17 @@
 #define REGEXP_STRING_ITERATOR_FLAGS_SLOT 2
 #define REGEXP_STRING_ITERATOR_DONE_SLOT 3
 
-#define MODULE_OBJECT_ENVIRONMENT_SLOT        2
-#define MODULE_OBJECT_STATUS_SLOT             4
-#define MODULE_OBJECT_ERROR_SLOT              5
-#define MODULE_OBJECT_DFS_INDEX_SLOT          16
-#define MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT 17
-
-#define MODULE_STATUS_ERRORED        0
-#define MODULE_STATUS_UNINSTANTIATED 1
-#define MODULE_STATUS_INSTANTIATING  2
-#define MODULE_STATUS_INSTANTIATED   3
-#define MODULE_STATUS_EVALUATING     4
-#define MODULE_STATUS_EVALUATED      5
+#define MODULE_OBJECT_ENVIRONMENT_SLOT        1
+#define MODULE_OBJECT_STATUS_SLOT             3
+#define MODULE_OBJECT_EVALUATION_ERROR_SLOT   4
+#define MODULE_OBJECT_DFS_INDEX_SLOT          15
+#define MODULE_OBJECT_DFS_ANCESTOR_INDEX_SLOT 16
+
+#define MODULE_STATUS_UNINSTANTIATED  0
+#define MODULE_STATUS_INSTANTIATING   1
+#define MODULE_STATUS_INSTANTIATED    2
+#define MODULE_STATUS_EVALUATING      3
+#define MODULE_STATUS_EVALUATED       4
+#define MODULE_STATUS_EVALUATED_ERROR 5
 
 #endif
diff --git a/js/src/builtin/TestingFunctions.cpp b/js/src/builtin/TestingFunctions.cpp
index 025620766..f589b8076 100644
--- a/js/src/builtin/TestingFunctions.cpp
+++ b/js/src/builtin/TestingFunctions.cpp
@@ -3566,8 +3566,6 @@ GetModuleEnvironment(JSContext* cx, HandleValue moduleValue)
     // before they have been instantiated.
     RootedModuleEnvironmentObject env(cx, &module->initialEnvironment());
     MOZ_ASSERT(env);
-    MOZ_ASSERT_IF(module->environment(), module->environment() == env);
-
     return env;
 }
 
@@ -3585,6 +3583,9 @@ GetModuleEnvironmentNames(JSContext* cx, unsigned argc, Value* vp)
         return false;
     }
 
+//-    if (module->status() == MODULE_STATUS_ERRORED) {
+//+    if (module->hadEvaluationError()) {
+
     RootedModuleEnvironmentObject env(cx, GetModuleEnvironment(cx, args[0]));
     Rooted<IdVector> ids(cx, IdVector(cx));
     if (!JS_Enumerate(cx, env, &ids))
@@ -3622,6 +3623,9 @@ GetModuleEnvironmentValue(JSContext* cx, unsigned argc, Value* vp)
         return false;
     }
 
+//-    if (module->status() == MODULE_STATUS_ERRORED) {
+//+    if (module->hadEvaluationError()) {
+
     RootedModuleEnvironmentObject env(cx, GetModuleEnvironment(cx, args[0]));
     RootedString name(cx, args[1].toString());
     RootedId id(cx);
diff --git a/js/src/gc/Marking.cpp b/js/src/gc/Marking.cpp
index 43e325394..b4db0297a 100644
--- a/js/src/gc/Marking.cpp
+++ b/js/src/gc/Marking.cpp
@@ -2267,6 +2267,8 @@ void
 js::gc::StoreBuffer::SlotsEdge::trace(TenuringTracer& mover) const
 {
     NativeObject* obj = object();
+    if(!IsCellPointerValid(obj))
+        return;
 
     // Beware JSObject::swap exchanging a native object for a non-native one.
     if (!obj->isNative())
@@ -2336,6 +2338,8 @@ js::gc::StoreBuffer::traceWholeCells(TenuringTracer& mover)
 {
     for (ArenaCellSet* cells = bufferWholeCell; cells; cells = cells->next) {
         Arena* arena = cells->arena;
+        if(!IsCellPointerValid(arena))
+            continue;
 
         MOZ_ASSERT(arena->bufferedCells == cells);
         arena->bufferedCells = &ArenaCellSet::Empty;
@@ -2364,6 +2368,7 @@ js::gc::StoreBuffer::CellPtrEdge::trace(TenuringTracer& mover) const
 {
     if (!*edge)
         return;
+    // XXX: We should check if the cell pointer is valid here too
 
     MOZ_ASSERT((*edge)->getTraceKind() == JS::TraceKind::Object);
     mover.traverse(reinterpret_cast<JSObject**>(edge));
diff --git a/js/src/jit-test/tests/modules/bug-1284486.js b/js/src/jit-test/tests/modules/bug-1284486.js
index 08286393a..6fbd67d9d 100644
--- a/js/src/jit-test/tests/modules/bug-1284486.js
+++ b/js/src/jit-test/tests/modules/bug-1284486.js
@@ -1,9 +1,8 @@
-// This tests that attempting to perform ModuleDeclarationInstantation a second
-// time after a failure re-throws the same error.
+// This tests that module instantiation can succeed when executed a second

+// time after a failure.
 //
 // The first attempt fails becuase module 'a' is not available. The second
-// attempt fails because of the previous failure (it would otherwise succeed as
-// 'a' is now available).
+// attempt succeeds as 'a' is now available.
 
 load(libdir + "dummyModuleResolveHook.js");
 
@@ -25,12 +24,9 @@ let a = moduleRepo['a'] = parseModule("export var a = 1; export var b = 2;");
 let d = moduleRepo['d'] = parseModule("import { a } from 'c'; a;");
 
 threw = false;
-let e2;
 try {
     d.declarationInstantiation();
 } catch (exc) {
     threw = true;
-    e2 = exc;
 }
-assertEq(threw, true);
-assertEq(e1, e2);
+assertEq(threw, false);
diff --git a/js/src/jit-test/tests/modules/bug-1420420-2.js b/js/src/jit-test/tests/modules/bug-1420420-2.js
new file mode 100644
index 000000000..0511e8126
--- /dev/null
+++ b/js/src/jit-test/tests/modules/bug-1420420-2.js
@@ -0,0 +1,19 @@
+// Test re-instantiation module after failure.
+
+load(libdir + "asserts.js");
+load(libdir + "dummyModuleResolveHook.js");
+
+moduleRepo["good"] = parseModule(`export let x`);
+
+moduleRepo["y1"] = parseModule(`export let y`);
+moduleRepo["y2"] = parseModule(`export let y`);
+moduleRepo["bad"] = parseModule(`export* from "y1"; export* from "y2";`);
+
+moduleRepo["a"] = parseModule(`import* as ns from "good"; import {y} from "bad";`);
+
+let b = moduleRepo["b"] = parseModule(`import "a";`);
+let c = moduleRepo["c"] = parseModule(`import "a";`);
+
+assertThrowsInstanceOf(() => b.declarationInstantiation(), SyntaxError);
+assertThrowsInstanceOf(() => c.declarationInstantiation(), SyntaxError);
+
diff --git a/js/src/jit-test/tests/modules/bug-1420420-3.js b/js/src/jit-test/tests/modules/bug-1420420-3.js
new file mode 100644
index 000000000..236c023b9
--- /dev/null
+++ b/js/src/jit-test/tests/modules/bug-1420420-3.js
@@ -0,0 +1,9 @@
+if (!('stackTest' in this))
+   quit();
+
+let a = parseModule(`throw new Error`);
+a.declarationInstantiation();
+stackTest(function() {
+    a.evaluation();
+});
+
diff --git a/js/src/jit-test/tests/modules/bug-1420420-4.js b/js/src/jit-test/tests/modules/bug-1420420-4.js
new file mode 100644
index 000000000..721c770bc
--- /dev/null
+++ b/js/src/jit-test/tests/modules/bug-1420420-4.js
@@ -0,0 +1,16 @@
+load(libdir + "asserts.js");
+load(libdir + "dummyModuleResolveHook.js");
+
+moduleRepo["a"] = parseModule(`throw undefined`);
+
+let b = moduleRepo["b"] = parseModule(`import "a";`);
+let c = moduleRepo["c"] = parseModule(`import "a";`);
+
+b.declarationInstantiation();
+c.declarationInstantiation();
+
+let count = 0;
+try { b.evaluation() } catch (e) { count++; }
+try { c.evaluation() } catch (e) { count++; }
+assertEq(count, 2);
+
diff --git a/js/src/jit-test/tests/modules/bug-1420420.js b/js/src/jit-test/tests/modules/bug-1420420.js
new file mode 100644
index 000000000..cd1101c76
--- /dev/null
+++ b/js/src/jit-test/tests/modules/bug-1420420.js
@@ -0,0 +1,19 @@
+// Test re-instantiation module after failure.
+
+load(libdir + "asserts.js");
+load(libdir + "dummyModuleResolveHook.js");
+
+moduleRepo["good"] = parseModule(`export let x`);
+
+moduleRepo["y1"] = parseModule(`export let y`);
+moduleRepo["y2"] = parseModule(`export let y`);
+moduleRepo["bad"] = parseModule(`export* from "y1"; export* from "y2";`);
+
+moduleRepo["a"] = parseModule(`import {x} from "good"; import {y} from "bad";`);
+
+let b = moduleRepo["b"] = parseModule(`import "a";`);
+let c = moduleRepo["c"] = parseModule(`import "a";`);
+
+assertThrowsInstanceOf(() => b.declarationInstantiation(), SyntaxError);
+assertThrowsInstanceOf(() => c.declarationInstantiation(), SyntaxError);
+
diff --git a/js/src/js.msg b/js/src/js.msg
index 9c508ebbd..587481864 100644
--- a/js/src/js.msg
+++ b/js/src/js.msg
@@ -579,7 +579,6 @@ MSG_DEF(JSMSG_MISSING_IMPORT,            0, JSEXN_SYNTAXERR, "import not found")
 MSG_DEF(JSMSG_AMBIGUOUS_IMPORT,          0, JSEXN_SYNTAXERR, "ambiguous import")
 MSG_DEF(JSMSG_MISSING_NAMESPACE_EXPORT,  0, JSEXN_SYNTAXERR, "export not found for namespace")
 MSG_DEF(JSMSG_MISSING_EXPORT,            1, JSEXN_SYNTAXERR, "local binding for export '{0}' not found")
-MSG_DEF(JSMSG_MODULE_INSTANTIATE_FAILED, 0, JSEXN_INTERNALERR, "attempt to re-instantiate module after failure")
 MSG_DEF(JSMSG_BAD_MODULE_STATUS,         0, JSEXN_INTERNALERR, "module record has unexpected status")
 
 // Promise
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index cf5880e03..69a3ba2ac 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -483,6 +483,11 @@ JS_DestroyContext(JSContext* cx)
     DestroyContext(cx);
 }
 
+JS_PUBLIC_API(JSRuntime*)
+JS_GetRuntime(JSContext* cx) {
+    return cx->runtime();
+}
+
 static JS_CurrentEmbedderTimeFunction currentEmbedderTimeFunction;
 
 JS_PUBLIC_API(void)
@@ -4662,21 +4667,16 @@ JS::Evaluate(JSContext* cx, const ReadOnlyCompileOptions& optionsArg,
     return ::Evaluate(cx, optionsArg, filename, rval);
 }
 
-JS_PUBLIC_API(JSFunction*)
-JS::GetModuleResolveHook(JSContext* cx)
+JS_PUBLIC_API(JS::ModuleResolveHook)
+JS::GetModuleResolveHook(JSRuntime* rt)
 {
-    AssertHeapIsIdle(cx);
-    CHECK_REQUEST(cx);
-    return cx->global()->moduleResolveHook();
+    return rt->moduleResolveHook;
 }
 
 JS_PUBLIC_API(void)
-JS::SetModuleResolveHook(JSContext* cx, HandleFunction func)
+JS::SetModuleResolveHook(JSRuntime* rt, JS::ModuleResolveHook func)
 {
-    AssertHeapIsIdle(cx);
-    CHECK_REQUEST(cx);
-    assertSameCompartment(cx, func);
-    cx->global()->setModuleResolveHook(func);
+    rt->moduleResolveHook = func;
 }
 
 JS_PUBLIC_API(bool)
@@ -4739,18 +4739,6 @@ JS::GetModuleScript(JSContext* cx, JS::HandleObject moduleArg)
     return moduleArg->as<ModuleObject>().script();
 }
 
-JS_PUBLIC_API(bool)
-JS::IsModuleErrored(JSObject* moduleArg)
-{
-    return moduleArg->as<ModuleObject>().status() == MODULE_STATUS_ERRORED;
-}
-
-JS_PUBLIC_API(JS::Value)
-JS::GetModuleError(JSObject* moduleArg)
-{
-    return moduleArg->as<ModuleObject>().error();
-}
-
 JS_PUBLIC_API(JSObject*)
 JS_New(JSContext* cx, HandleObject ctor, const JS::HandleValueArray& inputArgs)
 {
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 9c3bf8151..5cdfd958e 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -995,6 +995,9 @@ JS_NewContext(uint32_t maxbytes,
 extern JS_PUBLIC_API(void)
 JS_DestroyContext(JSContext* cx);
 
+extern JS_PUBLIC_API(JSRuntime*)
+JS_GetRuntime(JSContext* cx);
+
 typedef double (*JS_CurrentEmbedderTimeFunction)();
 
 /**
@@ -4322,17 +4325,19 @@ extern JS_PUBLIC_API(bool)
 Evaluate(JSContext* cx, const ReadOnlyCompileOptions& options,
          const char* filename, JS::MutableHandleValue rval);
 
+using ModuleResolveHook = JSObject* (*)(JSContext*, HandleObject, HandleString);
+
 /**
- * Get the HostResolveImportedModule hook for a global.
+ * Get the HostResolveImportedModule hook for the runtime.
  */
-extern JS_PUBLIC_API(JSFunction*)
-GetModuleResolveHook(JSContext* cx);
+extern JS_PUBLIC_API(ModuleResolveHook)
+GetModuleResolveHook(JSRuntime* rt);
 
 /**
- * Set the HostResolveImportedModule hook for a global to the given function.
+ * Set the HostResolveImportedModule hook for the runtime to the given function.
  */
 extern JS_PUBLIC_API(void)
-SetModuleResolveHook(JSContext* cx, JS::HandleFunction func);
+SetModuleResolveHook(JSRuntime* rt, ModuleResolveHook func);
 
 /**
  * Parse the given source buffer as a module in the scope of the current global
@@ -4395,12 +4400,6 @@ GetRequestedModules(JSContext* cx, JS::HandleObject moduleRecord);
 extern JS_PUBLIC_API(JSScript*)
 GetModuleScript(JSContext* cx, JS::HandleObject moduleRecord);
 
-extern JS_PUBLIC_API(bool)
-IsModuleErrored(JSObject* moduleRecord);
-
-extern JS_PUBLIC_API(JS::Value)
-GetModuleError(JSObject* moduleRecord);
-
 } /* namespace JS */
 
 extern JS_PUBLIC_API(bool)
diff --git a/js/src/moz.build b/js/src/moz.build
index c0cef9929..3e6402f71 100644
--- a/js/src/moz.build
+++ b/js/src/moz.build
@@ -687,8 +687,8 @@ if CONFIG['_MSC_VER']:
     elif CONFIG['CPU_ARCH'] == 'x86_64' and CONFIG['JS_HAS_CTYPES']:
         SOURCES['ctypes/CTypes.cpp'].no_pgo = True # Bug 810661
     # Prevent floating point errors caused by VC++ optimizations
-    # XXX We should add this to CXXFLAGS, too?
     CFLAGS += ['-fp:precise']
+    CXXFLAGS += ['-fp:precise']    
     # C4805 warns mixing bool with other integral types in computation.
     # But given the conversion from bool is specified, and this is a
     # pattern widely used in code in js/src, suppress this warning here.
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index 8cd821b31..bbf35459f 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -274,6 +274,7 @@ struct ShellContext
     JS::PersistentRooted<JobQueue> jobQueue;
     ExclusiveData<ShellAsyncTasks> asyncTasks;
     bool drainingJobQueue;
+    JS::PersistentRootedFunction moduleResolveHook;
 
     /*
      * Watchdog thread state.
@@ -439,7 +440,8 @@ ShellContext::ShellContext(JSContext* cx)
     exitCode(0),
     quitting(false),
     readLineBufPos(0),
-    spsProfilingStackSize(0)
+    spsProfilingStackSize(0),
+    moduleResolveHook(cx)
 {}
 
 static ShellContext*
@@ -4030,13 +4032,34 @@ SetModuleResolveHook(JSContext* cx, unsigned argc, Value* vp)
         return false;
     }
 
-    RootedFunction hook(cx, &args[0].toObject().as<JSFunction>());
-    Rooted<GlobalObject*> global(cx, cx->global());
-    global->setModuleResolveHook(hook);
+    ShellContext* sc = GetShellContext(cx);
+    sc->moduleResolveHook = &args[0].toObject().as<JSFunction>();
+
     args.rval().setUndefined();
     return true;
 }
 
+static JSObject*
+CallModuleResolveHook(JSContext* cx, HandleObject module, HandleString specifier)
+{
+    ShellContext* sc = GetShellContext(cx);
+
+    JS::AutoValueArray<2> args(cx);
+    args[0].setObject(*module);
+    args[1].setString(specifier);
+
+    RootedValue result(cx);
+    if (!JS_CallFunction(cx, nullptr, sc->moduleResolveHook, args, &result))
+        return nullptr;
+
+    if (!result.isObject() || !result.toObject().is<ModuleObject>()) {
+         JS_ReportErrorASCII(cx, "Module resolve hook did not return Module object");
+         return nullptr;
+    }
+
+    return &result.toObject();
+}
+
 static bool
 GetModuleLoadPath(JSContext* cx, unsigned argc, Value* vp)
 {
@@ -7962,6 +7985,8 @@ main(int argc, char** argv, char** envp)
 
     js::SetPreserveWrapperCallback(cx, DummyPreserveWrapperCallback);
 
+    JS::SetModuleResolveHook(cx->runtime(), CallModuleResolveHook);
+
     result = Shell(cx, &op, envp);
 
 #ifdef DEBUG
diff --git a/js/src/vm/EnvironmentObject.cpp b/js/src/vm/EnvironmentObject.cpp
index 7834940f1..871ae3f19 100644
--- a/js/src/vm/EnvironmentObject.cpp
+++ b/js/src/vm/EnvironmentObject.cpp
@@ -491,7 +491,7 @@ ModuleEnvironmentObject::createImportBinding(JSContext* cx, HandleAtom importNam
     RootedId importNameId(cx, AtomToId(importName));
     RootedId localNameId(cx, AtomToId(localName));
     RootedModuleEnvironmentObject env(cx, &module->initialEnvironment());
-    if (!importBindings().putNew(cx, importNameId, env, localNameId)) {
+    if (!importBindings().put(cx, importNameId, env, localNameId)) {
         ReportOutOfMemory(cx);
         return false;
     }
diff --git a/js/src/vm/GlobalObject.h b/js/src/vm/GlobalObject.h
index 720f63e69..a9f07d495 100644
--- a/js/src/vm/GlobalObject.h
+++ b/js/src/vm/GlobalObject.h
@@ -119,7 +119,6 @@ class GlobalObject : public NativeObject
         DEBUGGERS,
         INTRINSICS,
         FOR_OF_PIC_CHAIN,
-        MODULE_RESOLVE_HOOK,
         WINDOW_PROXY,
         GLOBAL_THIS_RESOLVED,
 
@@ -879,19 +878,6 @@ class GlobalObject : public NativeObject
         setReservedSlot(WINDOW_PROXY, ObjectValue(*windowProxy));
     }
 
-    void setModuleResolveHook(HandleFunction hook) {
-        MOZ_ASSERT(hook);
-        setSlot(MODULE_RESOLVE_HOOK, ObjectValue(*hook));
-    }
-
-    JSFunction* moduleResolveHook() {
-        Value value = getSlotRef(MODULE_RESOLVE_HOOK);
-        if (value.isUndefined())
-            return nullptr;
-
-        return &value.toObject().as<JSFunction>();
-    }
-
     // Returns either this global's star-generator function prototype, or null
     // if that object was never created.  Dodgy; for use only in also-dodgy
     // GlobalHelperThreadState::mergeParseTaskCompartment().
diff --git a/js/src/vm/Runtime.cpp b/js/src/vm/Runtime.cpp
index 284a4f3d7..5e0246b85 100644
--- a/js/src/vm/Runtime.cpp
+++ b/js/src/vm/Runtime.cpp
@@ -241,8 +241,10 @@ JSRuntime::JSRuntime(JSRuntime* parentRuntime)
     lastAnimationTime(0),
     performanceMonitoring(thisFromCtor()),
     ionLazyLinkListSize_(0),
-    stackFormat_(parentRuntime ? js::StackFormat::Default
-                               : js::StackFormat::SpiderMonkey)
+    stackFormat_(parentRuntime ?
+                 js::StackFormat::Default :
+                 js::StackFormat::SpiderMonkey),
+    moduleResolveHook()
 {
     setGCStoreBufferPtr(&gc.storeBuffer);
 
diff --git a/js/src/vm/Runtime.h b/js/src/vm/Runtime.h
index e60371e38..247a2dc9d 100644
--- a/js/src/vm/Runtime.h
+++ b/js/src/vm/Runtime.h
@@ -1294,6 +1294,9 @@ struct JSRuntime : public JS::shadow::Runtime,
     // For inherited heap state accessors.
     friend class js::gc::AutoTraceSession;
     friend class JS::AutoEnterCycleCollection;
+
+    // The implementation-defined abstract operation HostResolveImportedModule.
+    JS::ModuleResolveHook moduleResolveHook;
 };
 
 namespace js {
diff --git a/js/src/vm/SelfHosting.cpp b/js/src/vm/SelfHosting.cpp
index 0dfeffc36..f324a0a67 100644
--- a/js/src/vm/SelfHosting.cpp
+++ b/js/src/vm/SelfHosting.cpp
@@ -2026,36 +2026,26 @@ intrinsic_HostResolveImportedModule(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
     MOZ_ASSERT(args.length() == 2);
-    MOZ_ASSERT(args[0].toObject().is<ModuleObject>());
-    MOZ_ASSERT(args[1].isString());
+    RootedModuleObject module(cx, &args[0].toObject().as<ModuleObject>());
+    RootedString specifier(cx, args[1].toString());
 
-    RootedFunction moduleResolveHook(cx, cx->global()->moduleResolveHook());
+    JS::ModuleResolveHook moduleResolveHook = cx->runtime()->moduleResolveHook;
     if (!moduleResolveHook) {
         JS_ReportErrorASCII(cx, "Module resolve hook not set");
         return false;
     }
 
-    RootedValue result(cx);
-    if (!JS_CallFunction(cx, nullptr, moduleResolveHook, args, &result))
+    RootedObject result(cx);
+    result = moduleResolveHook(cx, module, specifier);
+    if (!result)
         return false;
 
-    if (!result.isObject() || !result.toObject().is<ModuleObject>()) {
+    if (!result->is<ModuleObject>()) {
         JS_ReportErrorASCII(cx, "Module resolve hook did not return Module object");
         return false;
     }
 
-    args.rval().set(result);
-    return true;
-}
-
-static bool
-intrinsic_CreateModuleEnvironment(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-    MOZ_ASSERT(args.length() == 1);
-    RootedModuleObject module(cx, &args[0].toObject().as<ModuleObject>());
-    module->createEnvironment();
-    args.rval().setUndefined();
+    args.rval().setObject(*result);
     return true;
 }
 
@@ -2087,7 +2077,6 @@ intrinsic_CreateNamespaceBinding(JSContext* cx, unsigned argc, Value* vp)
     // the slot directly.
     RootedShape shape(cx, environment->lookup(cx, name));
     MOZ_ASSERT(shape);
-    MOZ_ASSERT(environment->getSlot(shape->slot()).isMagic(JS_UNINITIALIZED_LEXICAL));
     environment->setSlot(shape->slot(), args[2]);
     args.rval().setUndefined();
     return true;
@@ -2659,7 +2648,6 @@ static const JSFunctionSpec intrinsic_functions[] = {
           CallNonGenericSelfhostedMethod<Is<ModuleObject>>, 2, 0),
     JS_FN("HostResolveImportedModule", intrinsic_HostResolveImportedModule, 2, 0),
     JS_FN("IsModuleEnvironment", intrinsic_IsInstanceOfBuiltin<ModuleEnvironmentObject>, 1, 0),
-    JS_FN("CreateModuleEnvironment", intrinsic_CreateModuleEnvironment, 1, 0),
     JS_FN("CreateImportBinding", intrinsic_CreateImportBinding, 4, 0),
     JS_FN("CreateNamespaceBinding", intrinsic_CreateNamespaceBinding, 3, 0),
     JS_FN("InstantiateModuleFunctionDeclarations",