Support ES6's "new function" construct

This resolves #75.

Merged remote-tracking branch 'janek/js_function_new_1'

29 files changed, 900 insertions, 502 deletions

diff --git a/js/src/builtin/Intl.cpp b/js/src/builtin/Intl.cpp
index 990a4acdb..3a20c487b 100644
--- a/js/src/builtin/Intl.cpp
+++ b/js/src/builtin/Intl.cpp
@@ -765,42 +765,53 @@ static const JSFunctionSpec collator_methods[] = {
 };
 
 /**
- * Collator constructor.
- * Spec: ECMAScript Internationalization API Specification, 10.1
+ * 10.1.2 Intl.Collator([ locales [, options]])
+ *
+ * ES2017 Intl draft rev 94045d234762ad107a3d09bb6f7381a65f1a2f9b
  */
 static bool
 Collator(JSContext* cx, const CallArgs& args, bool construct)
 {
     RootedObject obj(cx);
 
+    // We're following ECMA-402 1st Edition when Collator is called because of
+    // backward compatibility issues.
+    // See https://github.com/tc39/ecma402/issues/57
     if (!construct) {
-        // 10.1.2.1 step 3
+        // ES Intl 1st ed., 10.1.2.1 step 3
         JSObject* intl = cx->global()->getOrCreateIntlObject(cx);
         if (!intl)
             return false;
         RootedValue self(cx, args.thisv());
         if (!self.isUndefined() && (!self.isObject() || self.toObject() != *intl)) {
-            // 10.1.2.1 step 4
+            // ES Intl 1st ed., 10.1.2.1 step 4
             obj = ToObject(cx, self);
             if (!obj)
                 return false;
 
-            // 10.1.2.1 step 5
+            // ES Intl 1st ed., 10.1.2.1 step 5
             bool extensible;
             if (!IsExtensible(cx, obj, &extensible))
                 return false;
             if (!extensible)
                 return Throw(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE);
         } else {
-            // 10.1.2.1 step 3.a
+            // ES Intl 1st ed., 10.1.2.1 step 3.a
             construct = true;
         }
     }
     if (construct) {
-        // 10.1.3.1 paragraph 2
-        RootedObject proto(cx, cx->global()->getOrCreateCollatorPrototype(cx));
-        if (!proto)
+        // Steps 2-5 (Inlined 9.1.14, OrdinaryCreateFromConstructor).
+        RootedObject proto(cx);
+        if (args.isConstructing() && !GetPrototypeFromCallableConstructor(cx, args, &proto))
             return false;
+
+        if (!proto) {
+            proto = cx->global()->getOrCreateCollatorPrototype(cx);
+            if (!proto)
+                return false;
+        }
+
         obj = NewObjectWithGivenProto(cx, &CollatorClass, proto);
         if (!obj)
             return false;
@@ -808,15 +819,13 @@ Collator(JSContext* cx, const CallArgs& args, bool construct)
         obj->as<NativeObject>().setReservedSlot(UCOLLATOR_SLOT, PrivateValue(nullptr));
     }
 
-    // 10.1.2.1 steps 1 and 2; 10.1.3.1 steps 1 and 2
     RootedValue locales(cx, args.length() > 0 ? args[0] : UndefinedValue());
     RootedValue options(cx, args.length() > 1 ? args[1] : UndefinedValue());
 
-    // 10.1.2.1 step 6; 10.1.3.1 step 3
+    // Step 6.
     if (!IntlInitialize(cx, obj, cx->names().InitializeCollator, locales, options))
         return false;
 
-    // 10.1.2.1 steps 3.a and 7
     args.rval().setObject(*obj);
     return true;
 }
@@ -833,6 +842,7 @@ js::intl_Collator(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
     MOZ_ASSERT(args.length() == 2);
+    MOZ_ASSERT(!args.isConstructing());
     // intl_Collator is an intrinsic for self-hosted JavaScript, so it cannot
     // be used with "new", but it still has to be treated as a constructor.
     return Collator(cx, args, true);
@@ -1257,42 +1267,53 @@ static const JSFunctionSpec numberFormat_methods[] = {
 };
 
 /**
- * NumberFormat constructor.
- * Spec: ECMAScript Internationalization API Specification, 11.1
+ * 11.2.1 Intl.NumberFormat([ locales [, options]])
+ *
+ * ES2017 Intl draft rev 94045d234762ad107a3d09bb6f7381a65f1a2f9b
  */
 static bool
 NumberFormat(JSContext* cx, const CallArgs& args, bool construct)
 {
     RootedObject obj(cx);
 
+    // We're following ECMA-402 1st Edition when NumberFormat is called
+    // because of backward compatibility issues.
+    // See https://github.com/tc39/ecma402/issues/57
     if (!construct) {
-        // 11.1.2.1 step 3
+        // ES Intl 1st ed., 11.1.2.1 step 3
         JSObject* intl = cx->global()->getOrCreateIntlObject(cx);
         if (!intl)
             return false;
         RootedValue self(cx, args.thisv());
         if (!self.isUndefined() && (!self.isObject() || self.toObject() != *intl)) {
-            // 11.1.2.1 step 4
+            // ES Intl 1st ed., 11.1.2.1 step 4
             obj = ToObject(cx, self);
             if (!obj)
                 return false;
 
-            // 11.1.2.1 step 5
+            // ES Intl 1st ed., 11.1.2.1 step 5
             bool extensible;
             if (!IsExtensible(cx, obj, &extensible))
                 return false;
             if (!extensible)
                 return Throw(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE);
         } else {
-            // 11.1.2.1 step 3.a
+            // ES Intl 1st ed., 11.1.2.1 step 3.a
             construct = true;
         }
     }
     if (construct) {
-        // 11.1.3.1 paragraph 2
-        RootedObject proto(cx, cx->global()->getOrCreateNumberFormatPrototype(cx));
-        if (!proto)
+        // Step 2 (Inlined 9.1.14, OrdinaryCreateFromConstructor).
+        RootedObject proto(cx);
+        if (args.isConstructing() && !GetPrototypeFromCallableConstructor(cx, args, &proto))
             return false;
+
+        if (!proto) {
+            proto = cx->global()->getOrCreateNumberFormatPrototype(cx);
+            if (!proto)
+                return false;
+        }
+
         obj = NewObjectWithGivenProto(cx, &NumberFormatClass, proto);
         if (!obj)
             return false;
@@ -1300,15 +1321,13 @@ NumberFormat(JSContext* cx, const CallArgs& args, bool construct)
         obj->as<NativeObject>().setReservedSlot(UNUMBER_FORMAT_SLOT, PrivateValue(nullptr));
     }
 
-    // 11.1.2.1 steps 1 and 2; 11.1.3.1 steps 1 and 2
     RootedValue locales(cx, args.length() > 0 ? args[0] : UndefinedValue());
     RootedValue options(cx, args.length() > 1 ? args[1] : UndefinedValue());
 
-    // 11.1.2.1 step 6; 11.1.3.1 step 3
+    // Step 3.
     if (!IntlInitialize(cx, obj, cx->names().InitializeNumberFormat, locales, options))
         return false;
 
-    // 11.1.2.1 steps 3.a and 7
     args.rval().setObject(*obj);
     return true;
 }
@@ -1325,6 +1344,7 @@ js::intl_NumberFormat(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
     MOZ_ASSERT(args.length() == 2);
+    MOZ_ASSERT(!args.isConstructing());
     // intl_NumberFormat is an intrinsic for self-hosted JavaScript, so it
     // cannot be used with "new", but it still has to be treated as a
     // constructor.
@@ -1725,42 +1745,53 @@ static const JSFunctionSpec dateTimeFormat_methods[] = {
 };
 
 /**
- * DateTimeFormat constructor.
- * Spec: ECMAScript Internationalization API Specification, 12.1
+ * 12.2.1 Intl.DateTimeFormat([ locales [, options]])
+ *
+ * ES2017 Intl draft rev 94045d234762ad107a3d09bb6f7381a65f1a2f9b
  */
 static bool
 DateTimeFormat(JSContext* cx, const CallArgs& args, bool construct)
 {
     RootedObject obj(cx);
 
+    // We're following ECMA-402 1st Edition when DateTimeFormat is called
+    // because of backward compatibility issues.
+    // See https://github.com/tc39/ecma402/issues/57
     if (!construct) {
-        // 12.1.2.1 step 3
+        // ES Intl 1st ed., 12.1.2.1 step 3
         JSObject* intl = cx->global()->getOrCreateIntlObject(cx);
         if (!intl)
             return false;
         RootedValue self(cx, args.thisv());
         if (!self.isUndefined() && (!self.isObject() || self.toObject() != *intl)) {
-            // 12.1.2.1 step 4
+            // ES Intl 1st ed., 12.1.2.1 step 4
             obj = ToObject(cx, self);
             if (!obj)
                 return false;
 
-            // 12.1.2.1 step 5
+            // ES Intl 1st ed., 12.1.2.1 step 5
             bool extensible;
             if (!IsExtensible(cx, obj, &extensible))
                 return false;
             if (!extensible)
                 return Throw(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE);
         } else {
-            // 12.1.2.1 step 3.a
+            // ES Intl 1st ed., 12.1.2.1 step 3.a
             construct = true;
         }
     }
     if (construct) {
-        // 12.1.3.1 paragraph 2
-        RootedObject proto(cx, cx->global()->getOrCreateDateTimeFormatPrototype(cx));
-        if (!proto)
+        // Step 2 (Inlined 9.1.14, OrdinaryCreateFromConstructor).
+        RootedObject proto(cx);
+        if (args.isConstructing() && !GetPrototypeFromCallableConstructor(cx, args, &proto))
             return false;
+
+        if (!proto) {
+            proto = cx->global()->getOrCreateDateTimeFormatPrototype(cx);
+            if (!proto)
+                return false;
+        }
+
         obj = NewObjectWithGivenProto(cx, &DateTimeFormatClass, proto);
         if (!obj)
             return false;
@@ -1768,15 +1799,13 @@ DateTimeFormat(JSContext* cx, const CallArgs& args, bool construct)
         obj->as<NativeObject>().setReservedSlot(UDATE_FORMAT_SLOT, PrivateValue(nullptr));
     }
 
-    // 12.1.2.1 steps 1 and 2; 12.1.3.1 steps 1 and 2
     RootedValue locales(cx, args.length() > 0 ? args[0] : UndefinedValue());
     RootedValue options(cx, args.length() > 1 ? args[1] : UndefinedValue());
 
-    // 12.1.2.1 step 6; 12.1.3.1 step 3
+    // Step 3.
     if (!IntlInitialize(cx, obj, cx->names().InitializeDateTimeFormat, locales, options))
         return false;
 
-    // 12.1.2.1 steps 3.a and 7
     args.rval().setObject(*obj);
     return true;
 }
@@ -1793,6 +1822,7 @@ js::intl_DateTimeFormat(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
     MOZ_ASSERT(args.length() == 2);
+    MOZ_ASSERT(!args.isConstructing());
     // intl_DateTimeFormat is an intrinsic for self-hosted JavaScript, so it
     // cannot be used with "new", but it still has to be treated as a
     // constructor.
diff --git a/js/src/frontend/BytecodeCompiler.cpp b/js/src/frontend/BytecodeCompiler.cpp
index d4c758b6c..3fbfdaa1a 100644
--- a/js/src/frontend/BytecodeCompiler.cpp
+++ b/js/src/frontend/BytecodeCompiler.cpp
@@ -7,6 +7,7 @@
 #include "frontend/BytecodeCompiler.h"
 
 #include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/Maybe.h"
 
 #include "jscntxt.h"
 #include "jsscript.h"
@@ -28,6 +29,7 @@
 using namespace js;
 using namespace js::frontend;
 using mozilla::Maybe;
+using mozilla::Nothing;
 
 class MOZ_STACK_CLASS AutoCompilationTraceLogger
 {
@@ -57,24 +59,24 @@ class MOZ_STACK_CLASS BytecodeCompiler
 
     // Call setters for optional arguments.
     void maybeSetSourceCompressor(SourceCompressionTask* sourceCompressor);
-    void setSourceArgumentsNotIncluded();
 
     JSScript* compileGlobalScript(ScopeKind scopeKind);
     JSScript* compileEvalScript(HandleObject environment, HandleScope enclosingScope);
     ModuleObject* compileModule();
-    bool compileFunctionBody(MutableHandleFunction fun, Handle<PropertyNameVector> formals,
-                             GeneratorKind generatorKind, FunctionAsyncKind asyncKind);
+    bool compileStandaloneFunction(MutableHandleFunction fun, GeneratorKind generatorKind,
+                                   FunctionAsyncKind asyncKind,
+                                   Maybe<uint32_t> parameterListEnd);
 
     ScriptSourceObject* sourceObjectPtr() const;
 
   private:
     JSScript* compileScript(HandleObject environment, SharedContext* sc);
     bool checkLength();
-    bool createScriptSource();
+    bool createScriptSource(Maybe<uint32_t> parameterListEnd);
     bool maybeCompressSource();
     bool canLazilyParse();
     bool createParser();
-    bool createSourceAndParser();
+    bool createSourceAndParser(Maybe<uint32_t> parameterListEnd = Nothing());
     bool createScript();
     bool emplaceEmitter(Maybe<BytecodeEmitter>& emitter, SharedContext* sharedContext);
     bool handleParseFailure(const Directives& newDirectives);
@@ -90,7 +92,6 @@ class MOZ_STACK_CLASS BytecodeCompiler
     SourceBufferHolder& sourceBuffer;
 
     RootedScope enclosingScope;
-    bool sourceArgumentsNotIncluded;
 
     RootedScriptSource sourceObject;
     ScriptSource* scriptSource;
@@ -130,7 +131,6 @@ BytecodeCompiler::BytecodeCompiler(ExclusiveContext* cx,
     options(options),
     sourceBuffer(sourceBuffer),
     enclosingScope(cx, enclosingScope),
-    sourceArgumentsNotIncluded(false),
     sourceObject(cx),
     scriptSource(nullptr),
     sourceCompressor(nullptr),
@@ -147,12 +147,6 @@ BytecodeCompiler::maybeSetSourceCompressor(SourceCompressionTask* sourceCompress
     this->sourceCompressor = sourceCompressor;
 }
 
-void
-BytecodeCompiler::setSourceArgumentsNotIncluded()
-{
-    sourceArgumentsNotIncluded = true;
-}
-
 bool
 BytecodeCompiler::checkLength()
 {
@@ -169,12 +163,12 @@ BytecodeCompiler::checkLength()
 }
 
 bool
-BytecodeCompiler::createScriptSource()
+BytecodeCompiler::createScriptSource(Maybe<uint32_t> parameterListEnd)
 {
     if (!checkLength())
         return false;
 
-    sourceObject = CreateScriptSourceObject(cx, options);
+    sourceObject = CreateScriptSourceObject(cx, options, parameterListEnd);
     if (!sourceObject)
         return false;
 
@@ -193,9 +187,7 @@ BytecodeCompiler::maybeCompressSource()
     if (!cx->compartment()->behaviors().discardSource()) {
         if (options.sourceIsLazy) {
             scriptSource->setSourceRetrievable();
-        } else if (!scriptSource->setSourceCopy(cx, sourceBuffer, sourceArgumentsNotIncluded,
-                                                sourceCompressor))
-        {
+        } else if (!scriptSource->setSourceCopy(cx, sourceBuffer, sourceCompressor)) {
             return false;
         }
     }
@@ -242,9 +234,9 @@ BytecodeCompiler::createParser()
 }
 
 bool
-BytecodeCompiler::createSourceAndParser()
+BytecodeCompiler::createSourceAndParser(Maybe<uint32_t> parameterListEnd /* = Nothing() */)
 {
-    return createScriptSource() &&
+    return createScriptSource(parameterListEnd) &&
            maybeCompressSource() &&
            createParser();
 }
@@ -432,18 +424,19 @@ BytecodeCompiler::compileModule()
     return module;
 }
 
+// Compile a standalone JS function, which might appear as the value of an
+// event handler attribute in an HTML <INPUT> tag, or in a Function()
+// constructor.
 bool
-BytecodeCompiler::compileFunctionBody(MutableHandleFunction fun,
-                                      Handle<PropertyNameVector> formals,
-                                      GeneratorKind generatorKind,
-                                      FunctionAsyncKind asyncKind)
+BytecodeCompiler::compileStandaloneFunction(MutableHandleFunction fun,
+                                            GeneratorKind generatorKind,
+                                            FunctionAsyncKind asyncKind,
+                                            Maybe<uint32_t> parameterListEnd)
 {
     MOZ_ASSERT(fun);
     MOZ_ASSERT(fun->isTenured());
 
-    fun->setArgCount(formals.length());
-
-    if (!createSourceAndParser())
+    if (!createSourceAndParser(parameterListEnd))
         return false;
 
     // Speculatively parse using the default directives implied by the context.
@@ -454,8 +447,8 @@ BytecodeCompiler::compileFunctionBody(MutableHandleFunction fun,
     ParseNode* fn;
     do {
         Directives newDirectives = directives;
-        fn = parser->standaloneFunctionBody(fun, enclosingScope, formals, generatorKind, asyncKind,
-                                            directives, &newDirectives);
+        fn = parser->standaloneFunction(fun, enclosingScope, parameterListEnd, generatorKind,
+                                        asyncKind, directives, &newDirectives);
         if (!fn && !handleParseFailure(newDirectives))
             return false;
     } while (!fn);
@@ -492,14 +485,15 @@ BytecodeCompiler::sourceObjectPtr() const
 }
 
 ScriptSourceObject*
-frontend::CreateScriptSourceObject(ExclusiveContext* cx, const ReadOnlyCompileOptions& options)
+frontend::CreateScriptSourceObject(ExclusiveContext* cx, const ReadOnlyCompileOptions& options,
+                                   Maybe<uint32_t> parameterListEnd /* = Nothing() */)
 {
     ScriptSource* ss = cx->new_<ScriptSource>();
     if (!ss)
         return nullptr;
     ScriptSourceHolder ssHolder(ss);
 
-    if (!ss->initFromOptions(cx, options))
+    if (!ss->initFromOptions(cx, options, parameterListEnd))
         return nullptr;
 
     RootedScriptSource sso(cx, ScriptSourceObject::create(cx, ss));
@@ -676,63 +670,44 @@ frontend::CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const cha
     return bce.emitFunctionScript(pn->pn_body);
 }
 
-// Compile a JS function body, which might appear as the value of an event
-// handler attribute in an HTML <INPUT> tag, or in a Function() constructor.
-static bool
-CompileFunctionBody(JSContext* cx, MutableHandleFunction fun, const ReadOnlyCompileOptions& options,
-                    Handle<PropertyNameVector> formals, SourceBufferHolder& srcBuf,
-                    HandleScope enclosingScope, GeneratorKind generatorKind,
-                    FunctionAsyncKind asyncKind)
+bool
+frontend::CompileStandaloneFunction(JSContext* cx, MutableHandleFunction fun,
+                                    const ReadOnlyCompileOptions& options,
+                                    JS::SourceBufferHolder& srcBuf,
+                                    Maybe<uint32_t> parameterListEnd,
+                                    HandleScope enclosingScope /* = nullptr */)
 {
-    MOZ_ASSERT(!options.isRunOnce);
-
-    // FIXME: make Function pass in two strings and parse them as arguments and
-    // ProgramElements respectively.
+    RootedScope scope(cx, enclosingScope);
+    if (!scope)
+        scope = &cx->global()->emptyGlobalScope();
 
-    BytecodeCompiler compiler(cx, cx->tempLifoAlloc(), options, srcBuf, enclosingScope,
+    BytecodeCompiler compiler(cx, cx->tempLifoAlloc(), options, srcBuf, scope,
                               TraceLogger_ParserCompileFunction);
-    compiler.setSourceArgumentsNotIncluded();
-    return compiler.compileFunctionBody(fun, formals, generatorKind, asyncKind);
+    return compiler.compileStandaloneFunction(fun, NotGenerator, SyncFunction, parameterListEnd);
 }
 
 bool
-frontend::CompileFunctionBody(JSContext* cx, MutableHandleFunction fun,
-                              const ReadOnlyCompileOptions& options,
-                              Handle<PropertyNameVector> formals, JS::SourceBufferHolder& srcBuf,
-                              HandleScope enclosingScope)
-{
-    return CompileFunctionBody(cx, fun, options, formals, srcBuf, enclosingScope, NotGenerator,
-                               SyncFunction);
-}
-
-bool
-frontend::CompileFunctionBody(JSContext* cx, MutableHandleFunction fun,
-                              const ReadOnlyCompileOptions& options,
-                              Handle<PropertyNameVector> formals, JS::SourceBufferHolder& srcBuf)
+frontend::CompileStandaloneGenerator(JSContext* cx, MutableHandleFunction fun,
+                                     const ReadOnlyCompileOptions& options,
+                                     JS::SourceBufferHolder& srcBuf,
+                                     Maybe<uint32_t> parameterListEnd)
 {
     RootedScope emptyGlobalScope(cx, &cx->global()->emptyGlobalScope());
-    return CompileFunctionBody(cx, fun, options, formals, srcBuf, emptyGlobalScope,
-                               NotGenerator, SyncFunction);
-}
 
-bool
-frontend::CompileStarGeneratorBody(JSContext* cx, MutableHandleFunction fun,
-                                   const ReadOnlyCompileOptions& options,
-                                   Handle<PropertyNameVector> formals,
-                                   JS::SourceBufferHolder& srcBuf)
-{
-    RootedScope emptyGlobalScope(cx, &cx->global()->emptyGlobalScope());
-    return CompileFunctionBody(cx, fun, options, formals, srcBuf, emptyGlobalScope,
-                               StarGenerator, SyncFunction);
+    BytecodeCompiler compiler(cx, cx->tempLifoAlloc(), options, srcBuf, emptyGlobalScope,
+                              TraceLogger_ParserCompileFunction);
+    return compiler.compileStandaloneFunction(fun, StarGenerator, SyncFunction, parameterListEnd);
 }
 
 bool
-frontend::CompileAsyncFunctionBody(JSContext* cx, MutableHandleFunction fun,
-                                   const ReadOnlyCompileOptions& options,
-                                   Handle<PropertyNameVector> formals,
-                                   JS::SourceBufferHolder& srcBuf)
+frontend::CompileStandaloneAsyncFunction(JSContext* cx, MutableHandleFunction fun,
+                                         const ReadOnlyCompileOptions& options,
+                                         JS::SourceBufferHolder& srcBuf,
+                                         Maybe<uint32_t> parameterListEnd)
 {
     RootedScope emptyGlobalScope(cx, &cx->global()->emptyGlobalScope());
-    return CompileFunctionBody(cx, fun, options, formals, srcBuf, emptyGlobalScope,
-                               StarGenerator, AsyncFunction);
+
+    BytecodeCompiler compiler(cx, cx->tempLifoAlloc(), options, srcBuf, emptyGlobalScope,
+                              TraceLogger_ParserCompileFunction);
+    return compiler.compileStandaloneFunction(fun, StarGenerator, AsyncFunction, parameterListEnd);
 }
diff --git a/js/src/frontend/BytecodeCompiler.h b/js/src/frontend/BytecodeCompiler.h
index 1d86f1160..72e967639 100644
--- a/js/src/frontend/BytecodeCompiler.h
+++ b/js/src/frontend/BytecodeCompiler.h
@@ -7,6 +7,8 @@
 #ifndef frontend_BytecodeCompiler_h
 #define frontend_BytecodeCompiler_h
 
+#include "mozilla/Maybe.h"
+
 #include "NamespaceImports.h"
 
 #include "vm/Scope.h"
@@ -51,22 +53,36 @@ CompileModule(ExclusiveContext* cx, const ReadOnlyCompileOptions& options,
 MOZ_MUST_USE bool
 CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const char16_t* chars, size_t length);
 
+//
+// Compile a single function. The source in srcBuf must match the ECMA-262
+// FunctionExpression production.
+//
+// If nonzero, parameterListEnd is the offset within srcBuf where the parameter
+// list is expected to end. During parsing, if we find that it ends anywhere
+// else, it's a SyntaxError. This is used to implement the Function constructor;
+// it's how we detect that these weird cases are SyntaxErrors:
+//
+//     Function("/*", "*/x) {")
+//     Function("x){ if (3", "return x;}")
+//
 MOZ_MUST_USE bool
-CompileFunctionBody(JSContext* cx, MutableHandleFunction fun,
-                    const ReadOnlyCompileOptions& options,
-                    Handle<PropertyNameVector> formals, JS::SourceBufferHolder& srcBuf,
-                    HandleScope enclosingScope);
+CompileStandaloneFunction(JSContext* cx, MutableHandleFunction fun,
+                          const ReadOnlyCompileOptions& options,
+                          JS::SourceBufferHolder& srcBuf,
+                          mozilla::Maybe<uint32_t> parameterListEnd,
+                          HandleScope enclosingScope = nullptr);
 
-// As above, but defaults to the global lexical scope as the enclosing scope.
 MOZ_MUST_USE bool
-CompileFunctionBody(JSContext* cx, MutableHandleFunction fun,
-                    const ReadOnlyCompileOptions& options,
-                    Handle<PropertyNameVector> formals, JS::SourceBufferHolder& srcBuf);
+CompileStandaloneGenerator(JSContext* cx, MutableHandleFunction fun,
+                           const ReadOnlyCompileOptions& options,
+                           JS::SourceBufferHolder& srcBuf,
+                           mozilla::Maybe<uint32_t> parameterListEnd);
 
 MOZ_MUST_USE bool
-CompileStarGeneratorBody(JSContext* cx, MutableHandleFunction fun,
-                         const ReadOnlyCompileOptions& options,
-                         Handle<PropertyNameVector> formals, JS::SourceBufferHolder& srcBuf);
+CompileStandaloneAsyncFunction(JSContext* cx, MutableHandleFunction fun,
+                               const ReadOnlyCompileOptions& options,
+                               JS::SourceBufferHolder& srcBuf,
+                               mozilla::Maybe<uint32_t> parameterListEnd);
 
 MOZ_MUST_USE bool
 CompileAsyncFunctionBody(JSContext* cx, MutableHandleFunction fun,
@@ -74,7 +90,8 @@ CompileAsyncFunctionBody(JSContext* cx, MutableHandleFunction fun,
                          Handle<PropertyNameVector> formals, JS::SourceBufferHolder& srcBuf);
 
 ScriptSourceObject*
-CreateScriptSourceObject(ExclusiveContext* cx, const ReadOnlyCompileOptions& options);
+CreateScriptSourceObject(ExclusiveContext* cx, const ReadOnlyCompileOptions& options,
+                         mozilla::Maybe<uint32_t> parameterListEnd = mozilla::Nothing());
 
 /*
  * True if str consists of an IdentifierStart character, followed by one or
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 49fef2bf9..f42546eb5 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -2245,13 +2245,13 @@ GetYieldHandling(GeneratorKind generatorKind, FunctionAsyncKind asyncKind)
 
 template <>
 ParseNode*
-Parser<FullParseHandler>::standaloneFunctionBody(HandleFunction fun,
-                                                 HandleScope enclosingScope,
-                                                 Handle<PropertyNameVector> formals,
-                                                 GeneratorKind generatorKind,
-                                                 FunctionAsyncKind asyncKind,
-                                                 Directives inheritedDirectives,
-                                                 Directives* newDirectives)
+Parser<FullParseHandler>::standaloneFunction(HandleFunction fun,
+                                             HandleScope enclosingScope,
+                                             Maybe<uint32_t> parameterListEnd,
+                                             GeneratorKind generatorKind,
+                                             FunctionAsyncKind asyncKind,
+                                             Directives inheritedDirectives,
+                                             Directives* newDirectives)
 {
     MOZ_ASSERT(checkOptionsCalled);
 
@@ -2274,25 +2274,14 @@ Parser<FullParseHandler>::standaloneFunctionBody(HandleFunction fun,
     if (!funpc.init())
         return null();
     funpc.setIsStandaloneFunctionBody();
-    funpc.functionScope().useAsVarScope(&funpc);
-
-    if (formals.length() >= ARGNO_LIMIT) {
-        report(ParseError, false, null(), JSMSG_TOO_MANY_FUN_ARGS);
-        return null();
-    }
-
-    bool duplicatedParam = false;
-    for (uint32_t i = 0; i < formals.length(); i++) {
-        if (!notePositionalFormalParameter(fn, formals[i], false, &duplicatedParam))
-            return null();
-    }
-    funbox->hasDuplicateParameters = duplicatedParam;
 
     YieldHandling yieldHandling = GetYieldHandling(generatorKind, asyncKind);
     AutoAwaitIsKeyword awaitIsKeyword(&tokenStream, asyncKind == AsyncFunction);
-    ParseNode* pn = functionBody(InAllowed, yieldHandling, Statement, StatementListBody);
-    if (!pn)
+    if (!functionFormalParametersAndBody(InAllowed, yieldHandling, fn, Statement,
+                                         parameterListEnd))
+    {
         return null();
+    }
 
     TokenKind tt;
     if (!tokenStream.getToken(&tt, TokenStream::Operand))
@@ -2303,15 +2292,7 @@ Parser<FullParseHandler>::standaloneFunctionBody(HandleFunction fun,
         return null();
     }
 
-    if (!FoldConstants(context, &pn, this))
-        return null();
-
-    fn->pn_pos.end = pos().end;
-
-    MOZ_ASSERT(fn->pn_body->isKind(PNK_PARAMSBODY));
-    fn->pn_body->append(pn);
-
-    if (!finishFunction())
+    if (!FoldConstants(context, &fn, this))
         return null();
 
     return fn;
@@ -3415,7 +3396,8 @@ template <typename ParseHandler>
 bool
 Parser<ParseHandler>::functionFormalParametersAndBody(InHandling inHandling,
                                                       YieldHandling yieldHandling,
-                                                      Node pn, FunctionSyntaxKind kind)
+                                                      Node pn, FunctionSyntaxKind kind,
+                                                      Maybe<uint32_t> parameterListEnd /* = Nothing() */)
 {
     // Given a properly initialized parse context, try to parse an actual
     // function without concern for conversion to strict mode, use of lazy
@@ -3447,6 +3429,13 @@ Parser<ParseHandler>::functionFormalParametersAndBody(InHandling inHandling,
         }
     }
 
+    // When parsing something for new Function() we have to make sure to
+    // only treat a certain part of the source as a parameter list.
+    if (parameterListEnd.isSome() && parameterListEnd.value() != pos().begin) {
+        report(ParseError, false, null(), JSMSG_UNEXPECTED_PARAMLIST_END);
+        return false;
+    }
+
     // Parse the function body.
     FunctionBodyType bodyType = StatementListBody;
     TokenKind tt;
@@ -3502,7 +3491,7 @@ Parser<ParseHandler>::functionFormalParametersAndBody(InHandling inHandling,
             report(ParseError, false, null(), JSMSG_CURLY_AFTER_BODY);
             return false;
         }
-        funbox->bufEnd = pos().begin + 1;
+        funbox->bufEnd = pos().end;
     } else {
 #if !JS_HAS_EXPR_CLOSURES
         MOZ_ASSERT(kind == Arrow);
diff --git a/js/src/frontend/Parser.h b/js/src/frontend/Parser.h
index 0ad4d56a0..b58b021cd 100644
--- a/js/src/frontend/Parser.h
+++ b/js/src/frontend/Parser.h
@@ -1020,12 +1020,12 @@ class Parser final : private JS::AutoGCRooter, public StrictModeGetter
     // Parse a module.
     Node moduleBody(ModuleSharedContext* modulesc);
 
-    // Parse a function, given only its body. Used for the Function and
-    // Generator constructors.
-    Node standaloneFunctionBody(HandleFunction fun, HandleScope enclosingScope,
-                                Handle<PropertyNameVector> formals,
-                                GeneratorKind generatorKind, FunctionAsyncKind asyncKind,
-                                Directives inheritedDirectives, Directives* newDirectives);
+    // Parse a function, used for the Function, GeneratorFunction, and
+    // AsyncFunction constructors.
+    Node standaloneFunction(HandleFunction fun, HandleScope enclosingScope,
+                            mozilla::Maybe<uint32_t> parameterListEnd,
+                            GeneratorKind generatorKind, FunctionAsyncKind asyncKind,
+                            Directives inheritedDirectives, Directives* newDirectives);
 
     // Parse a function, given only its arguments and body. Used for lazily
     // parsed functions.
@@ -1041,7 +1041,9 @@ class Parser final : private JS::AutoGCRooter, public StrictModeGetter
     // Parse a function's formal parameters and its body assuming its function
     // ParseContext is already on the stack.
     bool functionFormalParametersAndBody(InHandling inHandling, YieldHandling yieldHandling,
-                                         Node pn, FunctionSyntaxKind kind);
+                                         Node pn, FunctionSyntaxKind kind,
+                                         mozilla::Maybe<uint32_t> parameterListEnd = mozilla::Nothing());
+ 
 
     // Determine whether |yield| is a valid name in the current context, or
     // whether it's prohibited due to strictness, JS version, or occurrence
diff --git a/js/src/jit-test/tests/basic/destructuring-default.js b/js/src/jit-test/tests/basic/destructuring-default.js
index 168977e80..49a908b8a 100644
--- a/js/src/jit-test/tests/basic/destructuring-default.js
+++ b/js/src/jit-test/tests/basic/destructuring-default.js
@@ -84,10 +84,7 @@ function testArgumentFunction(pattern, input) {
     'return [a, b, c, d, e, f];'
   )(input);
 }
-// XXX: ES6 requires the `Function` constructor to accept arbitrary
-// `BindingElement`s as formal parameters. See Bug 1037939.
-// Once fixed, please update the assertions below.
-assertThrowsInstanceOf(() => testAll(testArgumentFunction), SyntaxError);
+testAll(testArgumentFunction);
 
 function testThrow(pattern, input) {
   return new Function('input',
diff --git a/js/src/jit-test/tests/basic/destructuring-rest.js b/js/src/jit-test/tests/basic/destructuring-rest.js
index f53f07e03..fcb7b79bb 100644
--- a/js/src/jit-test/tests/basic/destructuring-rest.js
+++ b/js/src/jit-test/tests/basic/destructuring-rest.js
@@ -132,10 +132,9 @@ function testArgumentFunction(pattern, input, binding) {
     'return ' + binding
   )(input);
 }
-// XXX: ES6 requires the `Function` constructor to accept arbitrary
-// `BindingElement`s as formal parameters. See Bug 1037939.
-// Once fixed, please update the assertions below.
-assertThrowsInstanceOf(() => testDeclaration(testArgumentFunction), SyntaxError);
+// ES6 requires the `Function` constructor to accept arbitrary
+// `BindingElement`s as formal parameters.
+testDeclaration(testArgumentFunction);
 
 function testThrow(pattern, input, binding) {
   binding = binding || 'rest';
diff --git a/js/src/jit-test/tests/debug/Script-gc-02.js b/js/src/jit-test/tests/debug/Script-gc-02.js
index 33d33dfc1..04dd4b220 100644
--- a/js/src/jit-test/tests/debug/Script-gc-02.js
+++ b/js/src/jit-test/tests/debug/Script-gc-02.js
@@ -10,5 +10,5 @@ assertEq(arr.length, 10);
 gc();
 
 for (var i = 0; i < arr.length; i++)
-    assertEq(arr[i].lineCount, 1);
+    assertEq(arr[i].lineCount, 3);
 
diff --git a/js/src/jit-test/tests/debug/Script-gc-03.js b/js/src/jit-test/tests/debug/Script-gc-03.js
index b2cb70232..30c3e8dbc 100644
--- a/js/src/jit-test/tests/debug/Script-gc-03.js
+++ b/js/src/jit-test/tests/debug/Script-gc-03.js
@@ -10,6 +10,6 @@ assertEq(arr.length, 100);
 gc(g);
 
 for (var i = 0; i < arr.length; i++)
-    assertEq(arr[i].lineCount, 1);
+    assertEq(arr[i].lineCount, 3);
 
 gc();
diff --git a/js/src/jit-test/tests/debug/Script-sourceStart-04.js b/js/src/jit-test/tests/debug/Script-sourceStart-04.js
index c12e669bf..2aa382b7b 100644
--- a/js/src/jit-test/tests/debug/Script-sourceStart-04.js
+++ b/js/src/jit-test/tests/debug/Script-sourceStart-04.js
@@ -20,6 +20,6 @@ function test(string, range) {
 }
 
 test("eval('2 * 3')", [0, 5]);
-test("new Function('2 * 3')", [0, 5]);
-test("new Function('x', 'x * x')", [0, 5]);
+test("new Function('2 * 3')", [0, 12]);
+test("new Function('x', 'x * x')", [0, 13]);
 assertEq(count, 6);
diff --git a/js/src/js.msg b/js/src/js.msg
index 2a818056f..8766bfbf5 100644
--- a/js/src/js.msg
+++ b/js/src/js.msg
@@ -329,6 +329,7 @@ MSG_DEF(JSMSG_TOO_MANY_LOCALS,         0, JSEXN_SYNTAXERR, "too many local varia
 MSG_DEF(JSMSG_TOO_MANY_YIELDS,         0, JSEXN_SYNTAXERR, "too many yield expressions")
 MSG_DEF(JSMSG_TOUGH_BREAK,             0, JSEXN_SYNTAXERR, "unlabeled break must be inside loop or switch")
 MSG_DEF(JSMSG_UNEXPECTED_TOKEN,        2, JSEXN_SYNTAXERR, "expected {0}, got {1}")
+MSG_DEF(JSMSG_UNEXPECTED_PARAMLIST_END,0, JSEXN_SYNTAXERR, "unexpected end of function parameter list")
 MSG_DEF(JSMSG_UNNAMED_CLASS_STMT,      0, JSEXN_SYNTAXERR, "class statement requires a name")
 MSG_DEF(JSMSG_UNNAMED_FUNCTION_STMT,   0, JSEXN_SYNTAXERR, "function statement requires a name")
 MSG_DEF(JSMSG_UNTERMINATED_COMMENT,    0, JSEXN_SYNTAXERR, "unterminated comment")
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index ee9c61059..e6fc1f98b 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -11,6 +11,7 @@
 #include "jsapi.h"
 
 #include "mozilla/FloatingPoint.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/Sprintf.h"
 
@@ -107,6 +108,7 @@ using namespace js::gc;
 using mozilla::Maybe;
 using mozilla::PodCopy;
 using mozilla::PodZero;
+using mozilla::Some;
 
 using JS::AutoGCRooter;
 using JS::ToInt32;
@@ -4232,15 +4234,15 @@ JS_GetFunctionScript(JSContext* cx, HandleFunction fun)
 }
 
 /*
- * enclosingScope is a static enclosing scope, if any (e.g. a WithScope).  If
- * the enclosing scope is the global scope, this must be null.
+ * enclosingScope is a scope, if any (e.g. a WithScope).  If the scope is the
+ * global scope, this must be null.
  *
- * enclosingDynamicScope is a dynamic scope to use, if it's not the global.
+ * enclosingEnv is an environment to use, if it's not the global.
  */
 static bool
 CompileFunction(JSContext* cx, const ReadOnlyCompileOptions& optionsArg,
-                const char* name, unsigned nargs, const char* const* argnames,
-                SourceBufferHolder& srcBuf,
+                const char* name,
+                SourceBufferHolder& srcBuf, uint32_t parameterListEnd,
                 HandleObject enclosingEnv, HandleScope enclosingScope,
                 MutableHandleFunction fun)
 {
@@ -4256,13 +4258,6 @@ CompileFunction(JSContext* cx, const ReadOnlyCompileOptions& optionsArg,
             return false;
     }
 
-    Rooted<PropertyNameVector> formals(cx, PropertyNameVector(cx));
-    for (unsigned i = 0; i < nargs; i++) {
-        RootedAtom argAtom(cx, Atomize(cx, argnames[i], strlen(argnames[i])));
-        if (!argAtom || !formals.append(argAtom->asPropertyName()))
-            return false;
-    }
-
     fun.set(NewScriptedFunction(cx, 0, JSFunction::INTERPRETED_NORMAL, funAtom,
                                 /* proto = */ nullptr,
                                 gc::AllocKind::FUNCTION, TenuredObject,
@@ -4275,7 +4270,45 @@ CompileFunction(JSContext* cx, const ReadOnlyCompileOptions& optionsArg,
     MOZ_ASSERT_IF(!IsGlobalLexicalEnvironment(enclosingEnv),
                   enclosingScope->hasOnChain(ScopeKind::NonSyntactic));
 
-    if (!frontend::CompileFunctionBody(cx, fun, optionsArg, formals, srcBuf, enclosingScope))
+    if (!frontend::CompileStandaloneFunction(cx, fun, optionsArg, srcBuf,
+                                             Some(parameterListEnd), enclosingScope))
+    {
+        return false;
+    }
+
+    return true;
+}
+
+static MOZ_MUST_USE bool
+BuildFunctionString(unsigned nargs, const char* const* argnames,
+                    const SourceBufferHolder& srcBuf, StringBuffer* out,
+                    uint32_t* parameterListEnd)
+{
+    MOZ_ASSERT(out);
+    MOZ_ASSERT(parameterListEnd);
+
+    if (!out->ensureTwoByteChars())
+        return false;
+    if (!out->append("("))
+        return false;
+    for (unsigned i = 0; i < nargs; i++) {
+        if (i != 0) {
+            if (!out->append(", "))
+                return false;
+        }
+        if (!out->append(argnames[i], strlen(argnames[i])))
+            return false;
+    }
+
+    // Remember the position of ")".
+    *parameterListEnd = out->length();
+    MOZ_ASSERT(FunctionConstructorMedialSigils[0] == ')');
+
+    if (!out->append(FunctionConstructorMedialSigils))
+        return false;
+    if (!out->append(srcBuf.get(), srcBuf.length()))
+        return false;
+    if (!out->append(FunctionConstructorFinalBrace))
         return false;
 
     return true;
@@ -4291,7 +4324,16 @@ JS::CompileFunction(JSContext* cx, AutoObjectVector& envChain,
     RootedScope scope(cx);
     if (!CreateNonSyntacticEnvironmentChain(cx, envChain, &env, &scope))
         return false;
-    return CompileFunction(cx, options, name, nargs, argnames, srcBuf, env, scope, fun);
+
+    uint32_t parameterListEnd;
+    StringBuffer funStr(cx);
+    if (!BuildFunctionString(nargs, argnames, srcBuf, &funStr, &parameterListEnd))
+        return false;
+
+    size_t newLen = funStr.length();
+    SourceBufferHolder newSrcBuf(funStr.stealChars(), newLen, SourceBufferHolder::GiveOwnership);
+
+    return CompileFunction(cx, options, name, newSrcBuf, parameterListEnd, env, scope, fun);
 }
 
 JS_PUBLIC_API(bool)
diff --git a/js/src/jsfun.cpp b/js/src/jsfun.cpp
index c952441ad..1e1b76d5d 100644
--- a/js/src/jsfun.cpp
+++ b/js/src/jsfun.cpp
@@ -12,6 +12,7 @@
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/Range.h"
 
@@ -60,8 +61,10 @@ using namespace js::gc;
 using namespace js::frontend;
 
 using mozilla::ArrayLength;
+using mozilla::Maybe;
 using mozilla::PodCopy;
 using mozilla::RangedPtr;
+using mozilla::Some;
 
 static bool
 fun_enumerate(JSContext* cx, HandleObject obj)
@@ -985,19 +988,19 @@ js::FindBody(JSContext* cx, HandleFunction fun, HandleLinearString src, size_t*
 }
 
 JSString*
-js::FunctionToString(JSContext* cx, HandleFunction fun, bool lambdaParen)
+js::FunctionToString(JSContext* cx, HandleFunction fun, bool prettyPrint)
 {
     if (fun->isInterpretedLazy() && !fun->getOrCreateScript(cx))
         return nullptr;
 
     if (IsAsmJSModule(fun))
-        return AsmJSModuleToString(cx, fun, !lambdaParen);
+        return AsmJSModuleToString(cx, fun, !prettyPrint);
     if (IsAsmJSFunction(fun))
         return AsmJSFunctionToString(cx, fun);
 
     if (IsWrappedAsyncFunction(fun)) {
         RootedFunction unwrapped(cx, GetUnwrappedAsyncFunction(fun));
-        return FunctionToString(cx, unwrapped, lambdaParen);
+        return FunctionToString(cx, unwrapped, prettyPrint);
     }
 
     StringBuffer out(cx);
@@ -1023,11 +1026,10 @@ js::FunctionToString(JSContext* cx, HandleFunction fun, bool lambdaParen)
 
     bool funIsMethodOrNonArrowLambda = (fun->isLambda() && !fun->isArrow()) || fun->isMethod() ||
                                         fun->isGetter() || fun->isSetter();
+    bool haveSource = fun->isInterpreted() && !fun->isSelfHostedBuiltin();
 
     // If we're not in pretty mode, put parentheses around lambda functions and methods.
-    if (fun->isInterpreted() && !lambdaParen && funIsMethodOrNonArrowLambda &&
-        !fun->isSelfHostedBuiltin())
-    {
+    if (haveSource && !prettyPrint && funIsMethodOrNonArrowLambda) {
         if (!out.append("("))
             return nullptr;
     }
@@ -1045,7 +1047,6 @@ js::FunctionToString(JSContext* cx, HandleFunction fun, bool lambdaParen)
             return nullptr;
     }
 
-    bool haveSource = fun->isInterpreted() && !fun->isSelfHostedBuiltin();
     if (haveSource && !script->scriptSource()->hasSourceData() &&
         !JSScript::loadSource(cx, script->scriptSource(), &haveSource))
     {
@@ -1056,54 +1057,10 @@ js::FunctionToString(JSContext* cx, HandleFunction fun, bool lambdaParen)
         if (!src)
             return nullptr;
 
-        // The source data for functions created by calling the Function
-        // constructor is only the function's body.  This depends on the fact,
-        // asserted below, that in Function("function f() {}"), the inner
-        // function's sourceStart points to the '(', not the 'f'.
-        bool funCon = !fun->isArrow() &&
-                      script->sourceStart() == 0 &&
-                      script->sourceEnd() == script->scriptSource()->length() &&
-                      script->scriptSource()->argumentsNotIncluded();
-
-        // Functions created with the constructor can't be arrow functions or
-        // expression closures.
-        MOZ_ASSERT_IF(funCon, !fun->isArrow());
-        MOZ_ASSERT_IF(funCon, !fun->isExprBody());
-        MOZ_ASSERT_IF(!funCon && !fun->isArrow(),
-                      src->length() > 0 && src->latin1OrTwoByteChar(0) == '(');
-
-        bool buildBody = funCon;
-        if (buildBody) {
-            // This function was created with the Function constructor. We don't
-            // have source for the arguments, so we have to generate that. Part
-            // of bug 755821 should be cobbling the arguments passed into the
-            // Function constructor into the source string.
-            if (!out.append("("))
-                return nullptr;
-
-            // Fish out the argument names.
-            MOZ_ASSERT(script->numArgs() == fun->nargs());
-
-            BindingIter bi(script);
-            for (unsigned i = 0; i < fun->nargs(); i++, bi++) {
-                MOZ_ASSERT(bi.argumentSlot() == i);
-                if (i && !out.append(", "))
-                    return nullptr;
-                if (i == unsigned(fun->nargs() - 1) && fun->hasRest() && !out.append("..."))
-                    return nullptr;
-                if (!out.append(bi.name()))
-                    return nullptr;
-            }
-            if (!out.append(") {\n"))
-                return nullptr;
-        }
         if (!out.append(src))
             return nullptr;
-        if (buildBody) {
-            if (!out.append("\n}"))
-                return nullptr;
-        }
-        if (!lambdaParen && funIsMethodOrNonArrowLambda) {
+
+        if (!prettyPrint && funIsMethodOrNonArrowLambda) {
             if (!out.append(")"))
                 return nullptr;
         }
@@ -1114,8 +1071,6 @@ js::FunctionToString(JSContext* cx, HandleFunction fun, bool lambdaParen)
         {
             return nullptr;
         }
-        if (!lambdaParen && fun->isLambda() && !fun->isArrow() && !out.append(")"))
-            return nullptr;
     } else {
         MOZ_ASSERT(!fun->isExprBody());
 
@@ -1657,17 +1612,6 @@ fun_isGenerator(JSContext* cx, unsigned argc, Value* vp)
     return true;
 }
 
-/*
- * Report "malformed formal parameter" iff no illegal char or similar scanner
- * error was already reported.
- */
-static bool
-OnBadFormal(JSContext* cx)
-{
-    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_FORMAL);
-    return false;
-}
-
 const JSFunctionSpec js::function_methods[] = {
 #if JS_HAS_TOSOURCE
     JS_FN(js_toSource_str,   fun_toSource,   0,0),
@@ -1681,13 +1625,12 @@ const JSFunctionSpec js::function_methods[] = {
     JS_FS_END
 };
 
+// ES 2017 draft rev 0f10dba4ad18de92d47d421f378233a2eae8f077 19.2.1.1.1.
 static bool
-FunctionConstructor(JSContext* cx, unsigned argc, Value* vp, GeneratorKind generatorKind,
+FunctionConstructor(JSContext* cx, const CallArgs& args, GeneratorKind generatorKind,
                     FunctionAsyncKind asyncKind)
 {
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    /* Block this call if security callbacks forbid it. */
+    // Block this call if security callbacks forbid it.
     Rooted<GlobalObject*> global(cx, &args.callee().global());
     if (!GlobalObject::isRuntimeCodeGenEnabled(cx, global)) {
         JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CSP_BLOCKED_FUNCTION);
@@ -1719,82 +1662,65 @@ FunctionConstructor(JSContext* cx, unsigned argc, Value* vp, GeneratorKind gener
         introducerFilename = maybeScript->scriptSource()->introducerFilename();
 
     CompileOptions options(cx);
+    // Use line 0 to make the function body starts from line 1.
     options.setMutedErrors(mutedErrors)
-           .setFileAndLine(filename, 1)
+           .setFileAndLine(filename, 0)
            .setNoScriptRval(false)
            .setIntroductionInfo(introducerFilename, introductionType, lineno, maybeScript, pcOffset);
 
-    Vector<char16_t> paramStr(cx);
-    RootedString bodyText(cx);
+    StringBuffer sb(cx);
 
-    if (args.length() == 0) {
-        bodyText = cx->names().empty;
-    } else {
-        // Collect the function-argument arguments into one string, separated
-        // by commas, then make a tokenstream from that string, and scan it to
-        // get the arguments.  We need to throw the full scanner at the
-        // problem because the argument string may contain comments, newlines,
-        // destructuring arguments, and similar manner of insanities.  ("I have
-        // a feeling we're not in simple-comma-separated-parameters land any
-        // more, Toto....")
-        //
-        // XXX It'd be better if the parser provided utility methods to parse
-        //     an argument list, and to parse a function body given a parameter
-        //     list.  But our parser provides no such pleasant interface now.
-        unsigned n = args.length() - 1;
+    if (!sb.append('('))
+        return false;
 
-        // Convert the parameters-related arguments to strings, and determine
-        // the length of the string containing the overall parameter list.
-        mozilla::CheckedInt<uint32_t> paramStrLen = 0;
+    if (args.length() > 1) {
         RootedString str(cx);
+
+        // Steps 5-6, 9.
+        unsigned n = args.length() - 1;
+
         for (unsigned i = 0; i < n; i++) {
+            // Steps 9.a-b, 9.d.i-ii.
             str = ToString<CanGC>(cx, args[i]);
             if (!str)
                 return false;
 
-            args[i].setString(str);
-            paramStrLen += str->length();
-        }
-
-        // Tack in space for any combining commas.
-        if (n > 0)
-            paramStrLen += n - 1;
+            // Steps 9.b, 9.d.iii.
+            if (!sb.append(str))
+                 return false;
 
-        // Check for integer and string-size overflow.
-        if (!paramStrLen.isValid() || paramStrLen.value() > JSString::MAX_LENGTH) {
-            ReportAllocationOverflow(cx);
-            return false;
+            if (i < args.length() - 2) {
+                // Step 9.d.iii.
+                if (!sb.append(", "))
+                    return false;
+            }
         }
+    }
 
-        uint32_t paramsLen = paramStrLen.value();
+    // Remember the position of ")".
+    Maybe<uint32_t> parameterListEnd = Some(uint32_t(sb.length()));
+    MOZ_ASSERT(FunctionConstructorMedialSigils[0] == ')');
 
-        // Fill a vector with the comma-joined arguments.  Careful!  This
-        // string is *not* null-terminated!
-        MOZ_ASSERT(paramStr.length() == 0);
-        if (!paramStr.growBy(paramsLen)) {
-            ReportOutOfMemory(cx);
-            return false;
-        }
-
-        char16_t* cp = paramStr.begin();
-        for (unsigned i = 0; i < n; i++) {
-            JSLinearString* argLinear = args[i].toString()->ensureLinear(cx);
-            if (!argLinear)
-                return false;
+    if (!sb.append(FunctionConstructorMedialSigils))
+        return false;
 
-            CopyChars(cp, *argLinear);
-            cp += argLinear->length();
+    if (args.length() > 0) {
+        // Steps 7-8, 10.
+        RootedString body(cx, ToString<CanGC>(cx, args[args.length() - 1]));
+        if (!body || !sb.append(body))
+             return false;
+     }
 
-            if (i + 1 < n)
-                *cp++ = ',';
-        }
+    if (!sb.append(FunctionConstructorFinalBrace))
+        return false;
 
-        MOZ_ASSERT(cp == paramStr.end());
+    // The parser only accepts two byte strings.
+    if (!sb.ensureTwoByteChars())
+        return false;
 
-        bodyText = ToString(cx, args[n]);
-        if (!bodyText)
-            return false;
-    }
+    RootedString functionText(cx, sb.finishString());
+    if (!functionText)
+        return false;
 
     /*
      * NB: (new Function) is not lexically closed by its caller, it's just an
@@ -1803,18 +1729,23 @@ FunctionConstructor(JSContext* cx, unsigned argc, Value* vp, GeneratorKind gener
      * and so would a call to f from another top-level's script or function.
      */
     RootedAtom anonymousAtom(cx, cx->names().anonymous);
+
+    // Step 24.
     RootedObject proto(cx);
-    if (isStarGenerator) {
-        // Unwrapped function of async function should use GeneratorFunction,
-        // while wrapped function isn't generator.
+    if (!isAsync) {
+        if (!GetPrototypeFromCallableConstructor(cx, args, &proto))
+            return false;
+    }
+
+    // Step 4.d, use %Generator% as the fallback prototype.
+    // Also use %Generator% for the unwrapped function of async functions.
+    if (!proto && isStarGenerator) {
         proto = GlobalObject::getOrCreateStarGeneratorFunctionPrototype(cx, global);
         if (!proto)
             return false;
-    } else {
-        if (!GetPrototypeFromCallableConstructor(cx, args, &proto))
-            return false;
     }
 
+    // Step 25-32 (reordered).
     RootedObject globalLexical(cx, &global->lexicalEnvironment());
     AllocKind allocKind = isAsync ? AllocKind::FUNCTION_EXTENDED : AllocKind::FUNCTION;
     RootedFunction fun(cx, NewFunctionWithProto(cx, nullptr, 0,
@@ -1827,81 +1758,11 @@ FunctionConstructor(JSContext* cx, unsigned argc, Value* vp, GeneratorKind gener
     if (!JSFunction::setTypeForScriptedFunction(cx, fun))
         return false;
 
+    // Steps 2.a-b, 3.a-b, 4.a-b, 11-23.
     AutoStableStringChars stableChars(cx);
-    if (!stableChars.initTwoByte(cx, bodyText))
+    if (!stableChars.initTwoByte(cx, functionText))
         return false;
 
-    bool hasRest = false;
-
-    Rooted<PropertyNameVector> formals(cx, PropertyNameVector(cx));
-    if (args.length() > 1) {
-        // Initialize a tokenstream to parse the new function's arguments.  No
-        // StrictModeGetter is needed because this TokenStream won't report any
-        // strict mode errors.  Strict mode errors that might be reported here
-        // (duplicate argument names, etc.) will be detected when we compile
-        // the function body.
-        //
-        // XXX Bug!  We have to parse the body first to determine strictness.
-        //     We have to know strictness to parse arguments correctly, in case
-        //     arguments contains a strict mode violation.  And we should be
-        //     using full-fledged arguments parsing here, in order to handle
-        //     destructuring and other exotic syntaxes.
-        AutoKeepAtoms keepAtoms(cx->perThreadData);
-        TokenStream ts(cx, options, paramStr.begin(), paramStr.length(),
-                       /* strictModeGetter = */ nullptr);
-        bool yieldIsValidName = ts.versionNumber() < JSVERSION_1_7 && !isStarGenerator;
-
-        // The argument string may be empty or contain no tokens.
-        TokenKind tt;
-        if (!ts.getToken(&tt))
-            return false;
-        if (tt != TOK_EOF) {
-            while (true) {
-                // Check that it's a name.
-                if (hasRest) {
-                    ts.reportError(JSMSG_PARAMETER_AFTER_REST);
-                    return false;
-                }
-
-                if (tt == TOK_YIELD && yieldIsValidName)
-                    tt = TOK_NAME;
-
-                if (tt != TOK_NAME) {
-                    if (tt == TOK_TRIPLEDOT) {
-                        hasRest = true;
-                        if (!ts.getToken(&tt))
-                            return false;
-                        if (tt == TOK_YIELD && yieldIsValidName)
-                            tt = TOK_NAME;
-                        if (tt != TOK_NAME) {
-                            ts.reportError(JSMSG_NO_REST_NAME);
-                            return false;
-                        }
-                    } else {
-                        return OnBadFormal(cx);
-                    }
-                }
-
-                if (!formals.append(ts.currentName()))
-                    return false;
-
-                // Get the next token.  Stop on end of stream.  Otherwise
-                // insist on a comma, get another name, and iterate.
-                if (!ts.getToken(&tt))
-                    return false;
-                if (tt == TOK_EOF)
-                    break;
-                if (tt != TOK_COMMA)
-                    return OnBadFormal(cx);
-                if (!ts.getToken(&tt))
-                    return false;
-            }
-        }
-    }
-
-    if (hasRest)
-        fun->setHasRest();
-
     mozilla::Range<const char16_t> chars = stableChars.twoByteRange();
     SourceBufferHolder::Ownership ownership = stableChars.maybeGiveOwnershipToCaller()
                                               ? SourceBufferHolder::GiveOwnership
@@ -1909,11 +1770,13 @@ FunctionConstructor(JSContext* cx, unsigned argc, Value* vp, GeneratorKind gener
     bool ok;
     SourceBufferHolder srcBuf(chars.begin().get(), chars.length(), ownership);
     if (isAsync)
-        ok = frontend::CompileAsyncFunctionBody(cx, &fun, options, formals, srcBuf);
+        ok = frontend::CompileStandaloneAsyncFunction(cx, &fun, options, srcBuf, parameterListEnd);
     else if (isStarGenerator)
-        ok = frontend::CompileStarGeneratorBody(cx, &fun, options, formals, srcBuf);
+        ok = frontend::CompileStandaloneGenerator(cx, &fun, options, srcBuf, parameterListEnd);
     else
-        ok = frontend::CompileFunctionBody(cx, &fun, options, formals, srcBuf);
+        ok = frontend::CompileStandaloneFunction(cx, &fun, options, srcBuf, parameterListEnd);
+
+    // Step 33.
     args.rval().setObject(*fun);
     return ok;
 }
@@ -1921,24 +1784,47 @@ FunctionConstructor(JSContext* cx, unsigned argc, Value* vp, GeneratorKind gener
 bool
 js::Function(JSContext* cx, unsigned argc, Value* vp)
 {
-    return FunctionConstructor(cx, argc, vp, NotGenerator, SyncFunction);
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return FunctionConstructor(cx, args, NotGenerator, SyncFunction);
 }
 
 bool
 js::Generator(JSContext* cx, unsigned argc, Value* vp)
 {
-    return FunctionConstructor(cx, argc, vp, StarGenerator, SyncFunction);
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return FunctionConstructor(cx, args, StarGenerator, SyncFunction);
 }
 
 bool
 js::AsyncFunctionConstructor(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
-    if (!FunctionConstructor(cx, argc, vp, StarGenerator, AsyncFunction))
+
+    // Save the callee before its reset in FunctionConstructor().
+    RootedObject newTarget(cx);
+    if (args.isConstructing())
+        newTarget = &args.newTarget().toObject();
+    else
+        newTarget = &args.callee();
+
+    if (!FunctionConstructor(cx, args, StarGenerator, AsyncFunction))
         return false;
 
+    // ES2017, draft rev 0f10dba4ad18de92d47d421f378233a2eae8f077
+    // 19.2.1.1.1 Runtime Semantics: CreateDynamicFunction, step 24.
+    RootedObject proto(cx);
+    if (!GetPrototypeFromConstructor(cx, newTarget, &proto))
+        return false;
+
+    // 19.2.1.1.1, step 4.d, use %AsyncFunctionPrototype% as the fallback.
+    if (!proto) {
+        proto = GlobalObject::getOrCreateAsyncFunctionPrototype(cx, cx->global());
+        if (!proto)
+            return false;
+    }
+
     RootedFunction unwrapped(cx, &args.rval().toObject().as<JSFunction>());
-    RootedObject wrapped(cx, WrapAsyncFunction(cx, unwrapped));
+    RootedObject wrapped(cx, WrapAsyncFunctionWithProto(cx, unwrapped, proto));
     if (!wrapped)
         return false;
 
diff --git a/js/src/jsfun.h b/js/src/jsfun.h
index ef4a603d0..88af5c22d 100644
--- a/js/src/jsfun.h
+++ b/js/src/jsfun.h
@@ -28,6 +28,9 @@ static const uint32_t JSSLOT_BOUND_FUNCTION_TARGET     = 2;
 static const uint32_t JSSLOT_BOUND_FUNCTION_THIS       = 3;
 static const uint32_t JSSLOT_BOUND_FUNCTION_ARGS       = 4;
 
+static const char FunctionConstructorMedialSigils[] = ") {\n";
+static const char FunctionConstructorFinalBrace[] = "\n}";
+
 class JSFunction : public js::NativeObject
 {
   public:
@@ -816,7 +819,7 @@ JSFunction::getExtendedSlot(size_t which) const
 
 namespace js {
 
-JSString* FunctionToString(JSContext* cx, HandleFunction fun, bool lambdaParen);
+JSString* FunctionToString(JSContext* cx, HandleFunction fun, bool prettyPring);
 
 template<XDRMode mode>
 bool
diff --git a/js/src/jsscript.cpp b/js/src/jsscript.cpp
index 10821f26a..b568b4b30 100644
--- a/js/src/jsscript.cpp
+++ b/js/src/jsscript.cpp
@@ -1689,6 +1689,16 @@ ScriptSource::substringDontDeflate(JSContext* cx, size_t start, size_t stop)
     return NewStringCopyNDontDeflate<CanGC>(cx, chars, len);
 }
 
+JSFlatString*
+ScriptSource::functionBodyString(JSContext* cx)
+{
+    MOZ_ASSERT(isFunctionBody());
+
+    size_t start = parameterListEnd_ + (sizeof(FunctionConstructorMedialSigils) - 1);
+    size_t stop = length() - (sizeof(FunctionConstructorFinalBrace) - 1);
+    return substring(cx, start, stop);
+}
+
 MOZ_MUST_USE bool
 ScriptSource::setSource(ExclusiveContext* cx,
                         mozilla::UniquePtr<char16_t[], JS::FreePolicy>&& source,
@@ -1740,10 +1750,9 @@ ScriptSource::setCompressedSource(SharedImmutableString&& raw, size_t uncompress
 
 bool
 ScriptSource::setSourceCopy(ExclusiveContext* cx, SourceBufferHolder& srcBuf,
-                            bool argumentsNotIncluded, SourceCompressionTask* task)
+                            SourceCompressionTask* task)
 {
     MOZ_ASSERT(!hasSourceData());
-    argumentsNotIncluded_ = argumentsNotIncluded;
 
     auto& cache = cx->zone()->runtimeFromAnyThread()->sharedImmutableStrings();
     auto deduped = cache.getOrCreate(srcBuf.get(), srcBuf.length(), [&]() {
@@ -1940,16 +1949,6 @@ ScriptSource::performXDR(XDRState<mode>* xdr)
         if (!xdr->codeUint32(&compressedLength))
             return false;
 
-        {
-            uint8_t argumentsNotIncluded;
-            if (mode == XDR_ENCODE)
-                argumentsNotIncluded = argumentsNotIncluded_;
-            if (!xdr->codeUint8(&argumentsNotIncluded))
-                return false;
-            if (mode == XDR_DECODE)
-                argumentsNotIncluded_ = argumentsNotIncluded;
-        }
-
         size_t byteLen = compressedLength ? compressedLength : (len * sizeof(char16_t));
         if (mode == XDR_DECODE) {
             uint8_t* p = xdr->cx()->template pod_malloc<uint8_t>(Max<size_t>(byteLen, 1));
@@ -2074,7 +2073,8 @@ FormatIntroducedFilename(ExclusiveContext* cx, const char* filename, unsigned li
 }
 
 bool
-ScriptSource::initFromOptions(ExclusiveContext* cx, const ReadOnlyCompileOptions& options)
+ScriptSource::initFromOptions(ExclusiveContext* cx, const ReadOnlyCompileOptions& options,
+                              Maybe<uint32_t> parameterListEnd)
 {
     MOZ_ASSERT(!filename_);
     MOZ_ASSERT(!introducerFilename_);
@@ -2083,6 +2083,7 @@ ScriptSource::initFromOptions(ExclusiveContext* cx, const ReadOnlyCompileOptions
 
     introductionType_ = options.introductionType;
     setIntroductionOffset(options.introductionOffset);
+    parameterListEnd_ = parameterListEnd.isSome() ? parameterListEnd.value() : 0;
 
     if (options.hasIntroductionInfo) {
         MOZ_ASSERT(options.introductionType != nullptr);
diff --git a/js/src/jsscript.h b/js/src/jsscript.h
index bc8bda83d..ffd4b1e2e 100644
--- a/js/src/jsscript.h
+++ b/js/src/jsscript.h
@@ -10,6 +10,7 @@
 #define jsscript_h
 
 #include "mozilla/Atomics.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/Variant.h"
@@ -399,6 +400,11 @@ class ScriptSource
     // scripts.
     uint32_t introductionOffset_;
 
+    // If this source is for Function constructor, the position of ")" after
+    // parameter list in the source.  This is used to get function body.
+    // 0 for other cases.
+    uint32_t parameterListEnd_;
+
     // If this ScriptSource was generated by a code-introduction mechanism such
     // as |eval| or |new Function|, the debugger needs access to the "raw"
     // filename of the top-level script that contains the eval-ing code.  To
@@ -428,7 +434,6 @@ class ScriptSource
     // demand. If sourceRetrievable_ and hasSourceData() are false, it is not
     // possible to get source at all.
     bool sourceRetrievable_:1;
-    bool argumentsNotIncluded_:1;
     bool hasIntroductionOffset_:1;
 
     const char16_t* chunkChars(JSContext* cx, UncompressedSourceCache::AutoHoldEntry& holder,
@@ -443,10 +448,10 @@ class ScriptSource
         sourceMapURL_(nullptr),
         mutedErrors_(false),
         introductionOffset_(0),
+        parameterListEnd_(0),
         introducerFilename_(nullptr),
         introductionType_(nullptr),
         sourceRetrievable_(false),
-        argumentsNotIncluded_(false),
         hasIntroductionOffset_(false)
     {
     }
@@ -461,10 +466,10 @@ class ScriptSource
         if (--refs == 0)
             js_delete(this);
     }
-    bool initFromOptions(ExclusiveContext* cx, const ReadOnlyCompileOptions& options);
+    bool initFromOptions(ExclusiveContext* cx, const ReadOnlyCompileOptions& options,
+                         mozilla::Maybe<uint32_t> parameterListEnd = mozilla::Nothing());
     bool setSourceCopy(ExclusiveContext* cx,
                        JS::SourceBufferHolder& srcBuf,
-                       bool argumentsNotIncluded,
                        SourceCompressionTask* tok);
     void setSourceRetrievable() { sourceRetrievable_ = true; }
     bool sourceRetrievable() const { return sourceRetrievable_; }
@@ -492,11 +497,6 @@ class ScriptSource
         return data.match(LengthMatcher());
     }
 
-    bool argumentsNotIncluded() const {
-        MOZ_ASSERT(hasSourceData());
-        return argumentsNotIncluded_;
-    }
-
     // Return a string containing the chars starting at |begin| and ending at
     // |begin + len|.
     const char16_t* chars(JSContext* cx, UncompressedSourceCache::AutoHoldEntry& asp,
@@ -504,6 +504,12 @@ class ScriptSource
 
     JSFlatString* substring(JSContext* cx, size_t start, size_t stop);
     JSFlatString* substringDontDeflate(JSContext* cx, size_t start, size_t stop);
+
+    bool isFunctionBody() {
+        return parameterListEnd_ != 0;
+    }
+    JSFlatString* functionBodyString(JSContext* cx);
+
     void addSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf,
                                 JS::ScriptSourceInfo* info) const;
 
@@ -567,6 +573,10 @@ class ScriptSource
         introductionOffset_ = offset;
         hasIntroductionOffset_ = true;
     }
+
+    uint32_t parameterListEnd() const {
+        return parameterListEnd_;
+    }
 };
 
 class ScriptSourceHolder
diff --git a/js/src/tests/Intl/Collator/construct-newtarget.js b/js/src/tests/Intl/Collator/construct-newtarget.js
new file mode 100644
index 000000000..5db1abf37
--- /dev/null
+++ b/js/src/tests/Intl/Collator/construct-newtarget.js
@@ -0,0 +1,81 @@
+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+
+/* 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/. */
+
+
+// Test subclassing %Intl.Collator% works correctly.
+class MyCollator extends Intl.Collator {}
+
+var obj = new MyCollator();
+assertEq(obj instanceof MyCollator, true);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), MyCollator.prototype);
+
+obj = Reflect.construct(MyCollator, []);
+assertEq(obj instanceof MyCollator, true);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), MyCollator.prototype);
+
+obj = Reflect.construct(MyCollator, [], MyCollator);
+assertEq(obj instanceof MyCollator, true);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), MyCollator.prototype);
+
+obj = Reflect.construct(MyCollator, [], Intl.Collator);
+assertEq(obj instanceof MyCollator, false);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), Intl.Collator.prototype);
+
+
+// Set a different constructor as NewTarget.
+obj = Reflect.construct(MyCollator, [], Array);
+assertEq(obj instanceof MyCollator, false);
+assertEq(obj instanceof Intl.Collator, false);
+assertEq(obj instanceof Array, true);
+assertEq(Object.getPrototypeOf(obj), Array.prototype);
+
+obj = Reflect.construct(Intl.Collator, [], Array);
+assertEq(obj instanceof Intl.Collator, false);
+assertEq(obj instanceof Array, true);
+assertEq(Object.getPrototypeOf(obj), Array.prototype);
+
+
+// The prototype defaults to %CollatorPrototype% if null.
+function NewTargetNullPrototype() {}
+NewTargetNullPrototype.prototype = null;
+
+obj = Reflect.construct(Intl.Collator, [], NewTargetNullPrototype);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), Intl.Collator.prototype);
+
+obj = Reflect.construct(MyCollator, [], NewTargetNullPrototype);
+assertEq(obj instanceof MyCollator, false);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), Intl.Collator.prototype);
+
+
+// "prototype" property is retrieved exactly once.
+var trapLog = [], getLog = [];
+var ProxiedConstructor = new Proxy(Intl.Collator, new Proxy({
+    get(target, propertyKey, receiver) {
+        getLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}, {
+    get(target, propertyKey, receiver) {
+        trapLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}));
+
+obj = Reflect.construct(Intl.Collator, [], ProxiedConstructor);
+assertEqArray(trapLog, ["get"]);
+assertEqArray(getLog, ["prototype"]);
+assertEq(obj instanceof Intl.Collator, true);
+assertEq(Object.getPrototypeOf(obj), Intl.Collator.prototype);
+
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/tests/Intl/DateTimeFormat/construct-newtarget.js b/js/src/tests/Intl/DateTimeFormat/construct-newtarget.js
new file mode 100644
index 000000000..bbc08c79a
--- /dev/null
+++ b/js/src/tests/Intl/DateTimeFormat/construct-newtarget.js
@@ -0,0 +1,81 @@
+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+
+/* 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/. */
+
+
+// Test subclassing %Intl.DateTimeFormat% works correctly.
+class MyDateTimeFormat extends Intl.DateTimeFormat {}
+
+var obj = new MyDateTimeFormat();
+assertEq(obj instanceof MyDateTimeFormat, true);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), MyDateTimeFormat.prototype);
+
+obj = Reflect.construct(MyDateTimeFormat, []);
+assertEq(obj instanceof MyDateTimeFormat, true);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), MyDateTimeFormat.prototype);
+
+obj = Reflect.construct(MyDateTimeFormat, [], MyDateTimeFormat);
+assertEq(obj instanceof MyDateTimeFormat, true);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), MyDateTimeFormat.prototype);
+
+obj = Reflect.construct(MyDateTimeFormat, [], Intl.DateTimeFormat);
+assertEq(obj instanceof MyDateTimeFormat, false);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.DateTimeFormat.prototype);
+
+
+// Set a different constructor as NewTarget.
+obj = Reflect.construct(MyDateTimeFormat, [], Array);
+assertEq(obj instanceof MyDateTimeFormat, false);
+assertEq(obj instanceof Intl.DateTimeFormat, false);
+assertEq(obj instanceof Array, true);
+assertEq(Object.getPrototypeOf(obj), Array.prototype);
+
+obj = Reflect.construct(Intl.DateTimeFormat, [], Array);
+assertEq(obj instanceof Intl.DateTimeFormat, false);
+assertEq(obj instanceof Array, true);
+assertEq(Object.getPrototypeOf(obj), Array.prototype);
+
+
+// The prototype defaults to %DateTimeFormatPrototype% if null.
+function NewTargetNullPrototype() {}
+NewTargetNullPrototype.prototype = null;
+
+obj = Reflect.construct(Intl.DateTimeFormat, [], NewTargetNullPrototype);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.DateTimeFormat.prototype);
+
+obj = Reflect.construct(MyDateTimeFormat, [], NewTargetNullPrototype);
+assertEq(obj instanceof MyDateTimeFormat, false);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.DateTimeFormat.prototype);
+
+
+// "prototype" property is retrieved exactly once.
+var trapLog = [], getLog = [];
+var ProxiedConstructor = new Proxy(Intl.DateTimeFormat, new Proxy({
+    get(target, propertyKey, receiver) {
+        getLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}, {
+    get(target, propertyKey, receiver) {
+        trapLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}));
+
+obj = Reflect.construct(Intl.DateTimeFormat, [], ProxiedConstructor);
+assertEqArray(trapLog, ["get"]);
+assertEqArray(getLog, ["prototype"]);
+assertEq(obj instanceof Intl.DateTimeFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.DateTimeFormat.prototype);
+
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/tests/Intl/NumberFormat/construct-newtarget.js b/js/src/tests/Intl/NumberFormat/construct-newtarget.js
new file mode 100644
index 000000000..0053b2737
--- /dev/null
+++ b/js/src/tests/Intl/NumberFormat/construct-newtarget.js
@@ -0,0 +1,81 @@
+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+
+/* 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/. */
+
+
+// Test subclassing %Intl.NumberFormat% works correctly.
+class MyNumberFormat extends Intl.NumberFormat {}
+
+var obj = new MyNumberFormat();
+assertEq(obj instanceof MyNumberFormat, true);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), MyNumberFormat.prototype);
+
+obj = Reflect.construct(MyNumberFormat, []);
+assertEq(obj instanceof MyNumberFormat, true);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), MyNumberFormat.prototype);
+
+obj = Reflect.construct(MyNumberFormat, [], MyNumberFormat);
+assertEq(obj instanceof MyNumberFormat, true);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), MyNumberFormat.prototype);
+
+obj = Reflect.construct(MyNumberFormat, [], Intl.NumberFormat);
+assertEq(obj instanceof MyNumberFormat, false);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.NumberFormat.prototype);
+
+
+// Set a different constructor as NewTarget.
+obj = Reflect.construct(MyNumberFormat, [], Array);
+assertEq(obj instanceof MyNumberFormat, false);
+assertEq(obj instanceof Intl.NumberFormat, false);
+assertEq(obj instanceof Array, true);
+assertEq(Object.getPrototypeOf(obj), Array.prototype);
+
+obj = Reflect.construct(Intl.NumberFormat, [], Array);
+assertEq(obj instanceof Intl.NumberFormat, false);
+assertEq(obj instanceof Array, true);
+assertEq(Object.getPrototypeOf(obj), Array.prototype);
+
+
+// The prototype defaults to %NumberFormatPrototype% if null.
+function NewTargetNullPrototype() {}
+NewTargetNullPrototype.prototype = null;
+
+obj = Reflect.construct(Intl.NumberFormat, [], NewTargetNullPrototype);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.NumberFormat.prototype);
+
+obj = Reflect.construct(MyNumberFormat, [], NewTargetNullPrototype);
+assertEq(obj instanceof MyNumberFormat, false);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.NumberFormat.prototype);
+
+
+// "prototype" property is retrieved exactly once.
+var trapLog = [], getLog = [];
+var ProxiedConstructor = new Proxy(Intl.NumberFormat, new Proxy({
+    get(target, propertyKey, receiver) {
+        getLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}, {
+    get(target, propertyKey, receiver) {
+        trapLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}));
+
+obj = Reflect.construct(Intl.NumberFormat, [], ProxiedConstructor);
+assertEqArray(trapLog, ["get"]);
+assertEqArray(getLog, ["prototype"]);
+assertEq(obj instanceof Intl.NumberFormat, true);
+assertEq(Object.getPrototypeOf(obj), Intl.NumberFormat.prototype);
+
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/tests/ecma_2017/AsyncFunctions/construct-newtarget.js b/js/src/tests/ecma_2017/AsyncFunctions/construct-newtarget.js
new file mode 100644
index 000000000..7d75d0c93
--- /dev/null
+++ b/js/src/tests/ecma_2017/AsyncFunctions/construct-newtarget.js
@@ -0,0 +1,79 @@
+/* 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/. */
+
+const AsyncFunction = async function(){}.constructor;
+
+
+// Test subclassing %AsyncFunction% works correctly.
+class MyAsync extends AsyncFunction {}
+
+var fn = new MyAsync();
+assertEq(fn instanceof MyAsync, true);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), MyAsync.prototype);
+
+fn = Reflect.construct(MyAsync, []);
+assertEq(fn instanceof MyAsync, true);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), MyAsync.prototype);
+
+fn = Reflect.construct(MyAsync, [], MyAsync);
+assertEq(fn instanceof MyAsync, true);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), MyAsync.prototype);
+
+fn = Reflect.construct(MyAsync, [], AsyncFunction);
+assertEq(fn instanceof MyAsync, false);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), AsyncFunction.prototype);
+
+
+// Set a different constructor as NewTarget.
+fn = Reflect.construct(MyAsync, [], Array);
+assertEq(fn instanceof MyAsync, false);
+assertEq(fn instanceof AsyncFunction, false);
+assertEq(Object.getPrototypeOf(fn), Array.prototype);
+
+fn = Reflect.construct(AsyncFunction, [], Array);
+assertEq(fn instanceof AsyncFunction, false);
+assertEq(Object.getPrototypeOf(fn), Array.prototype);
+
+
+// The prototype defaults to %AsyncFunctionPrototype% if null.
+function NewTargetNullPrototype() {}
+NewTargetNullPrototype.prototype = null;
+
+fn = Reflect.construct(AsyncFunction, [], NewTargetNullPrototype);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), AsyncFunction.prototype);
+
+fn = Reflect.construct(MyAsync, [], NewTargetNullPrototype);
+assertEq(fn instanceof MyAsync, false);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), AsyncFunction.prototype);
+
+
+// "prototype" property is retrieved exactly once.
+var trapLog = [], getLog = [];
+var ProxiedConstructor = new Proxy(AsyncFunction, new Proxy({
+    get(target, propertyKey, receiver) {
+        getLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}, {
+    get(target, propertyKey, receiver) {
+        trapLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}));
+
+fn = Reflect.construct(AsyncFunction, [], ProxiedConstructor);
+assertEqArray(trapLog, ["get"]);
+assertEqArray(getLog, ["prototype"]);
+assertEq(fn instanceof AsyncFunction, true);
+assertEq(Object.getPrototypeOf(fn), AsyncFunction.prototype);
+
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/tests/ecma_2017/AsyncFunctions/subclass.js b/js/src/tests/ecma_2017/AsyncFunctions/subclass.js
new file mode 100644
index 000000000..da20ab19b
--- /dev/null
+++ b/js/src/tests/ecma_2017/AsyncFunctions/subclass.js
@@ -0,0 +1,31 @@
+// |reftest| skip-if(!xulRuntime.shell) -- needs drainJobQueue
+/* 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/. */
+
+const AsyncFunction = async function(){}.constructor;
+
+class MyAsync extends AsyncFunction {}
+
+// MyGen inherits from %AsyncFunction%.
+assertEq(Object.getPrototypeOf(MyAsync), AsyncFunction);
+
+// MyGen.prototype inherits from %AsyncFunctionPrototype%.
+assertEq(Object.getPrototypeOf(MyAsync.prototype), AsyncFunction.prototype);
+
+var fn = new MyAsync("return await 'ok';");
+
+// fn inherits from MyAsync.prototype.
+assertEq(Object.getPrototypeOf(fn), MyAsync.prototype);
+
+// Ensure the new async function can be executed.
+var promise = fn();
+
+// promise inherits from %Promise.prototype%.
+assertEq(Object.getPrototypeOf(promise), Promise.prototype);
+
+// Computes the expected result.
+assertEventuallyEq(promise, "ok");
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/tests/ecma_6/Function/invalid-parameter-list.js b/js/src/tests/ecma_6/Function/invalid-parameter-list.js
new file mode 100644
index 000000000..8aae89ef1
--- /dev/null
+++ b/js/src/tests/ecma_6/Function/invalid-parameter-list.js
@@ -0,0 +1,27 @@
+// This constructor behaves like `Function` without checking
+// if the parameter list end is at the expected position.
+// We use this to make sure that the tests we use are otherwise
+// syntactically correct.
+function DumpFunction(...args) {
+    let code = "function anonymous(";
+    code += args.slice(0, -1).join(", ");
+    code += ") {\n";
+    code += args[args.length -1];
+    code += "\n}";
+    eval(code);
+}
+
+const tests = [
+    ["/*", "*/) {"],
+    ["//", ") {"],
+    ["a = `", "` ) {"],
+    [") { var x = function (", "} "],
+    ["x = function (", "}) {"]
+];
+
+for (const test of tests) {
+    DumpFunction(...test);
+    assertThrowsInstanceOf(() => new Function(...test), SyntaxError);
+}
+
+reportCompare(0, 0, 'ok');
diff --git a/js/src/tests/ecma_6/Generators/construct-newtarget.js b/js/src/tests/ecma_6/Generators/construct-newtarget.js
new file mode 100644
index 000000000..f2087852b
--- /dev/null
+++ b/js/src/tests/ecma_6/Generators/construct-newtarget.js
@@ -0,0 +1,79 @@
+/* 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/. */
+
+const GeneratorFunction = function*(){}.constructor;
+
+
+// Test subclassing %GeneratorFunction% works correctly.
+class MyGenerator extends GeneratorFunction {}
+
+var fn = new MyGenerator();
+assertEq(fn instanceof MyGenerator, true);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), MyGenerator.prototype);
+
+fn = Reflect.construct(MyGenerator, []);
+assertEq(fn instanceof MyGenerator, true);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), MyGenerator.prototype);
+
+fn = Reflect.construct(MyGenerator, [], MyGenerator);
+assertEq(fn instanceof MyGenerator, true);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), MyGenerator.prototype);
+
+fn = Reflect.construct(MyGenerator, [], GeneratorFunction);
+assertEq(fn instanceof MyGenerator, false);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);
+
+
+// Set a different constructor as NewTarget.
+fn = Reflect.construct(MyGenerator, [], Array);
+assertEq(fn instanceof MyGenerator, false);
+assertEq(fn instanceof GeneratorFunction, false);
+assertEq(Object.getPrototypeOf(fn), Array.prototype);
+
+fn = Reflect.construct(GeneratorFunction, [], Array);
+assertEq(fn instanceof GeneratorFunction, false);
+assertEq(Object.getPrototypeOf(fn), Array.prototype);
+
+
+// The prototype defaults to %GeneratorFunctionPrototype% if null.
+function NewTargetNullPrototype() {}
+NewTargetNullPrototype.prototype = null;
+
+fn = Reflect.construct(GeneratorFunction, [], NewTargetNullPrototype);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);
+
+fn = Reflect.construct(MyGenerator, [], NewTargetNullPrototype);
+assertEq(fn instanceof MyGenerator, false);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);
+
+
+// "prototype" property is retrieved exactly once.
+var trapLog = [], getLog = [];
+var ProxiedConstructor = new Proxy(GeneratorFunction, new Proxy({
+    get(target, propertyKey, receiver) {
+        getLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}, {
+    get(target, propertyKey, receiver) {
+        trapLog.push(propertyKey);
+        return Reflect.get(target, propertyKey, receiver);
+    }
+}));
+
+fn = Reflect.construct(GeneratorFunction, [], ProxiedConstructor);
+assertEqArray(trapLog, ["get"]);
+assertEqArray(getLog, ["prototype"]);
+assertEq(fn instanceof GeneratorFunction, true);
+assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);
+
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/tests/ecma_6/Generators/subclass.js b/js/src/tests/ecma_6/Generators/subclass.js
new file mode 100644
index 000000000..f93f4df4d
--- /dev/null
+++ b/js/src/tests/ecma_6/Generators/subclass.js
@@ -0,0 +1,33 @@
+/* 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/. */
+
+const GeneratorFunction = function*(){}.constructor;
+
+class MyGen extends GeneratorFunction {}
+
+// MyGen inherits from %GeneratorFunction%.
+assertEq(Object.getPrototypeOf(MyGen), GeneratorFunction);
+
+// MyGen.prototype inherits from %Generator%.
+assertEq(Object.getPrototypeOf(MyGen.prototype), GeneratorFunction.prototype);
+
+var fn = new MyGen("yield* [1, 2, 3]");
+
+// fn inherits from MyGen.prototype.
+assertEq(Object.getPrototypeOf(fn), MyGen.prototype);
+
+// fn.prototype inherits from %GeneratorPrototype%.
+assertEq(Object.getPrototypeOf(fn.prototype), GeneratorFunction.prototype.prototype);
+
+// Ensure the new generator function can be executed.
+var it = fn();
+
+// it inherits from fn.prototype.
+assertEq(Object.getPrototypeOf(it), fn.prototype);
+
+// Computes the expected result.
+assertEqArray([...it], [1, 2, 3]);
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0);
diff --git a/js/src/vm/AsyncFunction.cpp b/js/src/vm/AsyncFunction.cpp
index bd0b4f32a..1e0c7d7c2 100644
--- a/js/src/vm/AsyncFunction.cpp
+++ b/js/src/vm/AsyncFunction.cpp
@@ -107,18 +107,15 @@ WrappedAsyncFunction(JSContext* cx, unsigned argc, Value* vp)
 //  the async function's body, replacing `await` with `yield`.  `wrapped` is a
 // function that is visible to the outside, and handles yielded values.
 JSObject*
-js::WrapAsyncFunction(JSContext* cx, HandleFunction unwrapped)
+js::WrapAsyncFunctionWithProto(JSContext* cx, HandleFunction unwrapped, HandleObject proto)
 {
     MOZ_ASSERT(unwrapped->isStarGenerator());
+    MOZ_ASSERT(proto, "We need an explicit prototype to avoid the default"
+                      "%FunctionPrototype% fallback in NewFunctionWithProto().");
 
     // Create a new function with AsyncFunctionPrototype, reusing the name and
     // the length of `unwrapped`.
 
-    // Step 1.
-    RootedObject proto(cx, GlobalObject::getOrCreateAsyncFunctionPrototype(cx, cx->global()));
-    if (!proto)
-        return nullptr;
-
     RootedAtom funName(cx, unwrapped->name());
     uint16_t length;
     if (!unwrapped->getLength(cx, &length))
@@ -141,6 +138,16 @@ js::WrapAsyncFunction(JSContext* cx, HandleFunction unwrapped)
     return wrapped;
 }
 
+JSObject*
+js::WrapAsyncFunction(JSContext* cx, HandleFunction unwrapped)
+{
+    RootedObject proto(cx, GlobalObject::getOrCreateAsyncFunctionPrototype(cx, cx->global()));
+    if (!proto)
+        return nullptr;
+
+    return WrapAsyncFunctionWithProto(cx, unwrapped, proto);
+}
+
 enum class ResumeKind {
     Normal,
     Throw
diff --git a/js/src/vm/AsyncFunction.h b/js/src/vm/AsyncFunction.h
index ddf81a177..d7f2c1311 100644
--- a/js/src/vm/AsyncFunction.h
+++ b/js/src/vm/AsyncFunction.h
@@ -22,6 +22,9 @@ bool
 IsWrappedAsyncFunction(JSFunction* fun);
 
 JSObject*
+WrapAsyncFunctionWithProto(JSContext* cx, HandleFunction unwrapped, HandleObject proto);
+
+JSObject*
 WrapAsyncFunction(JSContext* cx, HandleFunction unwrapped);
 
 MOZ_MUST_USE bool
diff --git a/js/src/vm/Debugger.cpp b/js/src/vm/Debugger.cpp
index b6bc7d62a..4d181545f 100644
--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -6890,8 +6890,13 @@ class DebuggerSourceGetTextMatcher
         bool hasSourceData = ss->hasSourceData();
         if (!ss->hasSourceData() && !JSScript::loadSource(cx_, ss, &hasSourceData))
             return nullptr;
-        return hasSourceData ? ss->substring(cx_, 0, ss->length())
-                             : NewStringCopyZ<CanGC>(cx_, "[no source]");
+        if (!hasSourceData)
+            return NewStringCopyZ<CanGC>(cx_, "[no source]");
+
+        if (ss->isFunctionBody())
+            return ss->functionBodyString(cx_);
+
+        return ss->substring(cx_, 0, ss->length());
     }
 
     ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
diff --git a/js/src/wasm/AsmJS.cpp b/js/src/wasm/AsmJS.cpp
index 34f5a8c0d..4dbc9b387 100644
--- a/js/src/wasm/AsmJS.cpp
+++ b/js/src/wasm/AsmJS.cpp
@@ -21,6 +21,7 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/Compression.h"
 #include "mozilla/MathAlgorithms.h"
+#include "mozilla/Maybe.h"
 
 #include "jsmath.h"
 #include "jsprf.h"
@@ -8033,21 +8034,6 @@ TryInstantiate(JSContext* cx, CallArgs args, Module& module, const AsmJSMetadata
     return true;
 }
 
-static MOZ_MUST_USE bool
-MaybeAppendUTF8Name(JSContext* cx, const char* utf8Chars, MutableHandle<PropertyNameVector> names)
-{
-    if (!utf8Chars)
-        return true;
-
-    UTF8Chars utf8(utf8Chars, strlen(utf8Chars));
-
-    JSAtom* atom = AtomizeUTF8Chars(cx, utf8Chars, strlen(utf8Chars));
-    if (!atom)
-        return false;
-
-    return names.append(atom->asPropertyName());
-}
-
 static bool
 HandleInstantiationFailure(JSContext* cx, CallArgs args, const AsmJSMetadata& metadata)
 {
@@ -8068,8 +8054,8 @@ HandleInstantiationFailure(JSContext* cx, CallArgs args, const AsmJSMetadata& me
         return false;
     }
 
-    uint32_t begin = metadata.srcBodyStart;  // starts right after 'use asm'
-    uint32_t end = metadata.srcEndBeforeCurly();
+    uint32_t begin = metadata.srcStart;
+    uint32_t end = metadata.srcEndAfterCurly();
     Rooted<JSFlatString*> src(cx, source->substringDontDeflate(cx, begin, end));
     if (!src)
         return false;
@@ -8080,18 +8066,11 @@ HandleInstantiationFailure(JSContext* cx, CallArgs args, const AsmJSMetadata& me
     if (!fun)
         return false;
 
-    Rooted<PropertyNameVector> formals(cx, PropertyNameVector(cx));
-    if (!MaybeAppendUTF8Name(cx, metadata.globalArgumentName.get(), &formals))
-        return false;
-    if (!MaybeAppendUTF8Name(cx, metadata.importArgumentName.get(), &formals))
-        return false;
-    if (!MaybeAppendUTF8Name(cx, metadata.bufferArgumentName.get(), &formals))
-        return false;
-
     CompileOptions options(cx);
     options.setMutedErrors(source->mutedErrors())
            .setFile(source->filename())
            .setNoScriptRval(false);
+    options.asmJSOption = AsmJSOption::Disabled;
 
     // The exported function inherits an implicit strict context if the module
     // also inherited it somehow.
@@ -8106,8 +8085,8 @@ HandleInstantiationFailure(JSContext* cx, CallArgs args, const AsmJSMetadata& me
     SourceBufferHolder::Ownership ownership = stableChars.maybeGiveOwnershipToCaller()
                                               ? SourceBufferHolder::GiveOwnership
                                               : SourceBufferHolder::NoOwnership;
-    SourceBufferHolder srcBuf(chars, end - begin, ownership);
-    if (!frontend::CompileFunctionBody(cx, &fun, options, formals, srcBuf))
+    SourceBufferHolder srcBuf(chars, stableChars.twoByteRange().length(), ownership);
+    if (!frontend::CompileStandaloneFunction(cx, &fun, options, srcBuf, Nothing()))
         return false;
 
     // Call the function we just recompiled.
@@ -8849,23 +8828,6 @@ js::IsAsmJSModuleLoadedFromCache(JSContext* cx, unsigned argc, Value* vp)
 /*****************************************************************************/
 // asm.js toString/toSource support
 
-static MOZ_MUST_USE bool
-MaybeAppendUTF8Chars(JSContext* cx, const char* sep, const char* utf8Chars, StringBuffer* sb)
-{
-    if (!utf8Chars)
-        return true;
-
-    UTF8Chars utf8(utf8Chars, strlen(utf8Chars));
-
-    size_t length;
-    UniqueTwoByteChars twoByteChars(UTF8CharsToNewTwoByteCharsZ(cx, utf8, &length).get());
-    if (!twoByteChars)
-        return false;
-
-    return sb->append(sep, strlen(sep)) &&
-           sb->append(twoByteChars.get(), length);
-}
-
 JSString*
 js::AsmJSModuleToString(JSContext* cx, HandleFunction fun, bool addParenToLambda)
 {
@@ -8895,33 +8857,12 @@ js::AsmJSModuleToString(JSContext* cx, HandleFunction fun, bool addParenToLambda
         if (!out.append("() {\n    [sourceless code]\n}"))
             return nullptr;
     } else {
-        // Whether the function has been created with a Function ctor
-        bool funCtor = begin == 0 && end == source->length() && source->argumentsNotIncluded();
-        if (funCtor) {
-            // Functions created with the function constructor don't have arguments in their source.
-            if (!out.append("("))
-                return nullptr;
-
-            if (!MaybeAppendUTF8Chars(cx, "", metadata.globalArgumentName.get(), &out))
-                return nullptr;
-            if (!MaybeAppendUTF8Chars(cx, ", ", metadata.importArgumentName.get(), &out))
-                return nullptr;
-            if (!MaybeAppendUTF8Chars(cx, ", ", metadata.bufferArgumentName.get(), &out))
-                return nullptr;
-
-            if (!out.append(") {\n"))
-                return nullptr;
-        }
-
         Rooted<JSFlatString*> src(cx, source->substring(cx, begin, end));
         if (!src)
             return nullptr;
 
         if (!out.append(src))
             return nullptr;
-
-        if (funCtor && !out.append("\n}"))
-            return nullptr;
     }
 
     if (addParenToLambda && fun->isLambda() && !out.append(")"))
@@ -8959,10 +8900,6 @@ js::AsmJSFunctionToString(JSContext* cx, HandleFunction fun)
         if (!out.append("() {\n    [sourceless code]\n}"))
             return nullptr;
     } else {
-        // asm.js functions cannot have been created with a Function constructor
-        // as they belong within a module.
-        MOZ_ASSERT(!(begin == 0 && end == source->length() && source->argumentsNotIncluded()));
-
         Rooted<JSFlatString*> src(cx, source->substring(cx, begin, end));
         if (!src)
             return nullptr;
diff --git a/js/xpconnect/loader/mozJSSubScriptLoader.cpp b/js/xpconnect/loader/mozJSSubScriptLoader.cpp
index 824e9ab9e..9c8908ea4 100644
--- a/js/xpconnect/loader/mozJSSubScriptLoader.cpp
+++ b/js/xpconnect/loader/mozJSSubScriptLoader.cpp
@@ -130,7 +130,9 @@ PrepareScript(nsIURI* uri,
               MutableHandleFunction function)
 {
     JS::CompileOptions options(cx);
-    options.setFileAndLine(uriStr, 1)
+    // Use line 0 to make the function body starts from line 1 when
+    // |reuseGlobal == true|.
+    options.setFileAndLine(uriStr, reuseGlobal ? 0 : 1)
            .setVersion(JSVERSION_LATEST);
     if (!charset.IsVoid()) {
         char16_t* scriptBuf = nullptr;