Add support for the function `name` property.

This resolves #78.

Merged remote-tracking branch 'janek/js_function_name_1'

10 files changed, 221 insertions, 61 deletions

diff --git a/js/src/frontend/BytecodeCompiler.cpp b/js/src/frontend/BytecodeCompiler.cpp
index 3fbfdaa1a..76afe80b1 100644
--- a/js/src/frontend/BytecodeCompiler.cpp
+++ b/js/src/frontend/BytecodeCompiler.cpp
@@ -336,10 +336,10 @@ BytecodeCompiler::compileScript(HandleObject environment, SharedContext* sc)
                 if (!deoptimizeArgumentsInEnclosingScripts(cx->asJSContext(), environment))
                     return nullptr;
             }
-            if (!NameFunctions(cx, pn))
-                return nullptr;
             if (!emitter->emitScript(pn))
                 return nullptr;
+            if (!NameFunctions(cx, pn))
+                return nullptr;
             parser->handler.freeTree(pn);
 
             break;
@@ -397,15 +397,15 @@ BytecodeCompiler::compileModule()
     if (!pn)
         return nullptr;
 
-    if (!NameFunctions(cx, pn))
-        return nullptr;
-
     Maybe<BytecodeEmitter> emitter;
     if (!emplaceEmitter(emitter, &modulesc))
         return nullptr;
     if (!emitter->emitScript(pn->pn_body))
         return nullptr;
 
+    if (!NameFunctions(cx, pn))
+        return nullptr;
+
     parser->handler.freeTree(pn);
 
     if (!builder.initModule())
@@ -453,9 +453,6 @@ BytecodeCompiler::compileStandaloneFunction(MutableHandleFunction fun,
             return false;
     } while (!fn);
 
-    if (!NameFunctions(cx, fn))
-        return false;
-
     if (fn->pn_funbox->function()->isInterpreted()) {
         MOZ_ASSERT(fun == fn->pn_funbox->function());
 
@@ -472,6 +469,9 @@ BytecodeCompiler::compileStandaloneFunction(MutableHandleFunction fun,
         MOZ_ASSERT(IsAsmJSModule(fun));
     }
 
+    if (!NameFunctions(cx, fn))
+        return false;
+
     if (!maybeCompleteCompressSource())
         return false;
 
@@ -646,9 +646,6 @@ frontend::CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const cha
     if (!pn)
         return false;
 
-    if (!NameFunctions(cx, pn))
-        return false;
-
     RootedScriptSource sourceObject(cx, lazy->sourceObject());
     MOZ_ASSERT(sourceObject);
 
@@ -667,7 +664,13 @@ frontend::CompileLazyFunction(JSContext* cx, Handle<LazyScript*> lazy, const cha
     if (!bce.init())
         return false;
 
-    return bce.emitFunctionScript(pn->pn_body);
+    if (!bce.emitFunctionScript(pn->pn_body))
+        return false;
+
+    if (!NameFunctions(cx, pn))
+        return false;
+
+    return true;
 }
 
 bool
diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index 1e9d8f224..acf734794 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -1053,7 +1053,7 @@ BytecodeEmitter::EmitterScope::enterFunction(BytecodeEmitter* bce, FunctionBox*
             if (p) {
                 MOZ_ASSERT(bi.kind() == BindingKind::FormalParameter);
                 MOZ_ASSERT(!funbox->hasDestructuringArgs);
-                MOZ_ASSERT(!funbox->function()->hasRest());
+                MOZ_ASSERT(!funbox->hasRest());
                 p->value() = loc;
                 continue;
             }
@@ -4070,7 +4070,7 @@ BytecodeEmitter::isRunOnceLambda()
     FunctionBox* funbox = sc->asFunctionBox();
     return !funbox->argumentsHasLocalBinding() &&
            !funbox->isGenerator() &&
-           !funbox->function()->name();
+           !funbox->function()->explicitName();
 }
 
 bool
@@ -4463,7 +4463,7 @@ BytecodeEmitter::emitDestructuringLHS(ParseNode* target, DestructuringFlavor fla
 }
 
 bool
-BytecodeEmitter::emitConditionallyExecutedDestructuringLHS(ParseNode* target, DestructuringFlavor flav)
+BytecodeEmitter::emitDestructuringLHSInBranch(ParseNode* target, DestructuringFlavor flav)
 {
     TDZCheckCache tdzCache(this);
     return emitDestructuringLHS(target, flav);
@@ -4491,7 +4491,7 @@ BytecodeEmitter::emitIteratorNext(ParseNode* pn, bool allowSelfHosted)
 }
 
 bool
-BytecodeEmitter::emitDefault(ParseNode* defaultExpr)
+BytecodeEmitter::emitDefault(ParseNode* defaultExpr, ParseNode* pattern)
 {
     if (!emit1(JSOP_DUP))                                 // VALUE VALUE
         return false;
@@ -4507,13 +4507,77 @@ BytecodeEmitter::emitDefault(ParseNode* defaultExpr)
         return false;
     if (!emit1(JSOP_POP))                                 // .
         return false;
-    if (!emitConditionallyExecutedTree(defaultExpr))      // DEFAULTVALUE
+    if (!emitInitializerInBranch(defaultExpr, pattern))   // DEFAULTVALUE
         return false;
     if (!emitJumpTargetAndPatch(jump))
         return false;
     return true;
 }
 
+bool
+BytecodeEmitter::setOrEmitSetFunName(ParseNode* maybeFun, HandleAtom name,
+                                     FunctionPrefixKind prefixKind)
+{
+    if (maybeFun->isKind(PNK_FUNCTION)) {
+        // Function doesn't have 'name' property at this point.
+        // Set function's name at compile time.
+        RootedFunction fun(cx, maybeFun->pn_funbox->function());
+
+        // Single node can be emitted multiple times if it appears in
+        // array destructuring default.  If function already has a name,
+        // just return.
+        if (fun->hasCompileTimeName()) {
+#ifdef DEBUG
+            RootedAtom funName(cx, NameToFunctionName(cx, name, prefixKind));
+            if (!funName)
+                return false;
+            MOZ_ASSERT(funName == maybeFun->pn_funbox->function()->compileTimeName());
+#endif
+            return true;
+        }
+
+        RootedAtom funName(cx, NameToFunctionName(cx, name, prefixKind));
+        if (!funName)
+            return false;
+        fun->setCompileTimeName(name);
+        return true;
+    }
+
+    uint32_t nameIndex;
+    if (!makeAtomIndex(name, &nameIndex))
+        return false;
+    if (!emitIndexOp(JSOP_STRING, nameIndex))   // FUN NAME
+        return false;
+    uint8_t kind = uint8_t(prefixKind);
+    if (!emit2(JSOP_SETFUNNAME, kind))          // FUN
+        return false;
+    return true;
+}
+
+bool
+BytecodeEmitter::emitInitializer(ParseNode* initializer, ParseNode* pattern)
+{
+    if (!emitTree(initializer))
+        return false;
+
+    if (!pattern->isInParens() && pattern->isKind(PNK_NAME) &&
+        initializer->isDirectRHSAnonFunction())
+    {
+        RootedAtom name(cx, pattern->name());
+        if (!setOrEmitSetFunName(initializer, name, FunctionPrefixKind::None))
+            return false;
+    }
+
+    return true;
+}
+
+bool
+BytecodeEmitter::emitInitializerInBranch(ParseNode* initializer, ParseNode* pattern)
+{
+    TDZCheckCache tdzCache(this);
+    return emitInitializer(initializer, pattern);
+}
+
 class MOZ_STACK_CLASS IfThenElseEmitter
 {
     BytecodeEmitter* bce_;
@@ -4765,7 +4829,7 @@ BytecodeEmitter::emitDestructuringOpsArray(ParseNode* pattern, DestructuringFlav
                     return false;
                 if (!emitUint32Operand(JSOP_NEWARRAY, 0))         // ... OBJ? ARRAY
                     return false;
-                if (!emitConditionallyExecutedDestructuringLHS(member, flav)) // ... OBJ?
+                if (!emitDestructuringLHSInBranch(member, flav))  // ... OBJ?
                     return false;
 
                 if (!ifThenElse.emitElse())                       // ... OBJ? ITER
@@ -4782,7 +4846,7 @@ BytecodeEmitter::emitDestructuringOpsArray(ParseNode* pattern, DestructuringFlav
                 return false;
             if (!emit1(JSOP_POP))                                 // ... OBJ? ARRAY
                 return false;
-            if (!emitConditionallyExecutedDestructuringLHS(member, flav)) // ... OBJ?
+            if (!emitDestructuringLHSInBranch(member, flav))      // ... OBJ?
                 return false;
 
             if (!isHead) {
@@ -4834,7 +4898,7 @@ BytecodeEmitter::emitDestructuringOpsArray(ParseNode* pattern, DestructuringFlav
         if (pndefault) {
             // Emit only pndefault tree here, as undefined check in emitDefault
             // should always be true.
-            if (!emitConditionallyExecutedTree(pndefault))        // ... OBJ? ITER VALUE
+            if (!emitInitializerInBranch(pndefault, subpattern))  // ... OBJ? ITER VALUE
                 return false;
         } else {
             if (!isElision) {
@@ -4845,7 +4909,7 @@ BytecodeEmitter::emitDestructuringOpsArray(ParseNode* pattern, DestructuringFlav
             }
         }
         if (!isElision) {
-            if (!emitConditionallyExecutedDestructuringLHS(subpattern, flav)) // ... OBJ? ITER
+            if (!emitDestructuringLHSInBranch(subpattern, flav))  // ... OBJ? ITER
                 return false;
         } else if (pndefault) {
             if (!emit1(JSOP_POP))                                 // ... OBJ? ITER
@@ -4872,12 +4936,12 @@ BytecodeEmitter::emitDestructuringOpsArray(ParseNode* pattern, DestructuringFlav
             return false;
 
         if (pndefault) {
-            if (!emitDefault(pndefault))                          // ... OBJ? ITER VALUE
+            if (!emitDefault(pndefault, subpattern))              // ... OBJ? ITER VALUE
                 return false;
         }
 
         if (!isElision) {
-            if (!emitConditionallyExecutedDestructuringLHS(subpattern, flav)) // ... OBJ? ITER
+            if (!emitDestructuringLHSInBranch(subpattern, flav))  // ... OBJ? ITER
                 return false;
         } else {
             if (!emit1(JSOP_POP))                                 // ... OBJ? ITER
@@ -4980,7 +5044,7 @@ BytecodeEmitter::emitDestructuringOpsObject(ParseNode* pattern, DestructuringFla
             return false;
 
         if (subpattern->isKind(PNK_ASSIGN)) {
-            if (!emitDefault(subpattern->pn_right))
+            if (!emitDefault(subpattern->pn_right, subpattern->pn_left))
                 return false;
             subpattern = subpattern->pn_left;
         }
@@ -5094,7 +5158,7 @@ BytecodeEmitter::emitSingleDeclaration(ParseNode* declList, ParseNode* decl,
     if (!initializer && declList->isKind(PNK_VAR))
         return true;
 
-    auto emitRhs = [initializer, declList](BytecodeEmitter* bce, const NameLocation&, bool) {
+    auto emitRhs = [initializer, declList, decl](BytecodeEmitter* bce, const NameLocation&, bool) {
         if (!initializer) {
             // Lexical declarations are initialized to undefined without an
             // initializer.
@@ -5105,7 +5169,7 @@ BytecodeEmitter::emitSingleDeclaration(ParseNode* declList, ParseNode* decl,
         }
 
         MOZ_ASSERT(initializer);
-        return bce->emitTree(initializer);
+        return bce->emitInitializer(initializer, decl);
     };
 
     if (!emitInitializeName(decl, emitRhs))
@@ -5164,6 +5228,12 @@ BytecodeEmitter::emitAssignment(ParseNode* lhs, JSOp op, ParseNode* rhs)
             if (!EmitAssignmentRhs(bce, rhs, emittedBindOp ? 2 : 1))
                 return false;
 
+            if (!lhs->isInParens() && op == JSOP_NOP && rhs && rhs->isDirectRHSAnonFunction()) {
+                RootedAtom name(bce->cx, lhs->name());
+                if (!bce->setOrEmitSetFunName(rhs, name, FunctionPrefixKind::None))
+                    return false;
+            }
+
             // Emit the compound assignment op if there is one.
             if (op != JSOP_NOP && !bce->emit1(op))
                 return false;
@@ -5788,7 +5858,7 @@ BytecodeEmitter::emitIf(ParseNode* pn)
 
   if_again:
     /* Emit code for the condition before pushing stmtInfo. */
-    if (!emitConditionallyExecutedTree(pn->pn_kid1))
+    if (!emitTreeInBranch(pn->pn_kid1))
         return false;
 
     ParseNode* elseNode = pn->pn_kid3;
@@ -5801,7 +5871,7 @@ BytecodeEmitter::emitIf(ParseNode* pn)
     }
 
     /* Emit code for the then part. */
-    if (!emitConditionallyExecutedTree(pn->pn_kid2))
+    if (!emitTreeInBranch(pn->pn_kid2))
         return false;
 
     if (elseNode) {
@@ -5814,7 +5884,7 @@ BytecodeEmitter::emitIf(ParseNode* pn)
         }
 
         /* Emit code for the else part. */
-        if (!emitConditionallyExecutedTree(elseNode))
+        if (!emitTreeInBranch(elseNode))
             return false;
     }
 
@@ -6283,8 +6353,8 @@ BytecodeEmitter::emitForIn(ParseNode* forInLoop, EmitterScope* headLexicalEmitte
                 if (!updateSourceCoordNotes(decl->pn_pos.begin))
                     return false;
 
-                auto emitRhs = [initializer](BytecodeEmitter* bce, const NameLocation&, bool) {
-                    return bce->emitTree(initializer);
+                auto emitRhs = [decl, initializer](BytecodeEmitter* bce, const NameLocation&, bool) {
+                    return bce->emitInitializer(initializer, decl);
                 };
 
                 if (!emitInitializeName(decl, emitRhs))
@@ -6504,7 +6574,7 @@ BytecodeEmitter::emitCStyleFor(ParseNode* pn, EmitterScope* headLexicalEmitterSc
     if (jmp.offset == -1 && !emitLoopEntry(forBody, jmp))
         return false;
 
-    if (!emitConditionallyExecutedTree(forBody))
+    if (!emitTreeInBranch(forBody))
         return false;
 
     // Set loop and enclosing "update" offsets, for continue.  Note that we
@@ -6903,7 +6973,7 @@ BytecodeEmitter::emitFunction(ParseNode* pn, bool needsProto)
 {
     FunctionBox* funbox = pn->pn_funbox;
     RootedFunction fun(cx, funbox->function());
-    RootedAtom name(cx, fun->name());
+    RootedAtom name(cx, fun->explicitName());
     MOZ_ASSERT_IF(fun->isInterpretedLazy(), fun->lazyScript());
     MOZ_ASSERT_IF(pn->isOp(JSOP_FUNWITHPROTO), needsProto);
 
@@ -7284,7 +7354,7 @@ BytecodeEmitter::emitWhile(ParseNode* pn)
     if (!emitLoopHead(pn->pn_right, &top))
         return false;
 
-    if (!emitConditionallyExecutedTree(pn->pn_right))
+    if (!emitTreeInBranch(pn->pn_right))
         return false;
 
     if (!emitLoopEntry(pn->pn_left, jmp))
@@ -8017,7 +8087,7 @@ BytecodeEmitter::isRestParameter(ParseNode* pn, bool* result)
 
     FunctionBox* funbox = sc->asFunctionBox();
     RootedFunction fun(cx, funbox->function());
-    if (!fun->hasRest()) {
+    if (!funbox->hasRest()) {
         *result = false;
         return true;
     }
@@ -8449,13 +8519,13 @@ BytecodeEmitter::emitConditionalExpression(ConditionalExpression& conditional)
     if (!ifThenElse.emitCond())
         return false;
 
-    if (!emitConditionallyExecutedTree(&conditional.thenExpression()))
+    if (!emitTreeInBranch(&conditional.thenExpression()))
         return false;
 
     if (!ifThenElse.emitElse())
         return false;
 
-    if (!emitConditionallyExecutedTree(&conditional.elseExpression()))
+    if (!emitTreeInBranch(&conditional.elseExpression()))
         return false;
 
     if (!ifThenElse.emitEnd())
@@ -8532,6 +8602,10 @@ BytecodeEmitter::emitPropertyList(ParseNode* pn, MutableHandlePlainObject objp,
                    op == JSOP_INITPROP_GETTER ||
                    op == JSOP_INITPROP_SETTER);
 
+        FunctionPrefixKind prefixKind = op == JSOP_INITPROP_GETTER ? FunctionPrefixKind::Get
+                                        : op == JSOP_INITPROP_SETTER ? FunctionPrefixKind::Set
+                                        : FunctionPrefixKind::None;
+
         if (op == JSOP_INITPROP_GETTER || op == JSOP_INITPROP_SETTER)
             objp.set(nullptr);
 
@@ -8573,6 +8647,12 @@ BytecodeEmitter::emitPropertyList(ParseNode* pn, MutableHandlePlainObject objp,
               case JSOP_INITHIDDENPROP_SETTER:  op = JSOP_INITHIDDENELEM_SETTER; break;
               default: MOZ_CRASH("Invalid op");
             }
+            if (propdef->pn_right->isDirectRHSAnonFunction()) {
+                if (!emitDupAt(1))
+                    return false;
+                if (!emit2(JSOP_SETFUNNAME, uint8_t(prefixKind)))
+                    return false;
+            }
             if (!emit1(op))
                 return false;
         } else {
@@ -8597,6 +8677,11 @@ BytecodeEmitter::emitPropertyList(ParseNode* pn, MutableHandlePlainObject objp,
                     objp.set(nullptr);
             }
 
+            if (propdef->pn_right->isDirectRHSAnonFunction()) {
+                RootedAtom keyName(cx, key->pn_atom);
+                if (!setOrEmitSetFunName(propdef->pn_right, keyName, prefixKind))
+                    return false;
+            }
             if (!emitIndex32(op, index))
                 return false;
         }
@@ -8960,7 +9045,7 @@ BytecodeEmitter::emitFunctionFormalParameters(ParseNode* pn)
     EmitterScope* funScope = innermostEmitterScope;
 
     bool hasParameterExprs = funbox->hasParameterExprs;
-    bool hasRest = funbox->function()->hasRest();
+    bool hasRest = funbox->hasRest();
 
     uint16_t argSlot = 0;
     for (ParseNode* arg = pn->pn_head; arg != funBody; arg = arg->pn_next, argSlot++) {
@@ -9017,7 +9102,7 @@ BytecodeEmitter::emitFunctionFormalParameters(ParseNode* pn)
                 return false;
             if (!emit1(JSOP_POP))
                 return false;
-            if (!emitConditionallyExecutedTree(initializer))
+            if (!emitInitializerInBranch(initializer, bindingElement))
                 return false;
             if (!emitJumpTargetAndPatch(jump))
                 return false;
@@ -9728,7 +9813,7 @@ BytecodeEmitter::emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote)
 }
 
 bool
-BytecodeEmitter::emitConditionallyExecutedTree(ParseNode* pn)
+BytecodeEmitter::emitTreeInBranch(ParseNode* pn)
 {
     // Code that may be conditionally executed always need their own TDZ
     // cache.
diff --git a/js/src/frontend/BytecodeEmitter.h b/js/src/frontend/BytecodeEmitter.h
index 1bb4191ee..9a2ddb568 100644
--- a/js/src/frontend/BytecodeEmitter.h
+++ b/js/src/frontend/BytecodeEmitter.h
@@ -435,7 +435,7 @@ struct MOZ_STACK_CLASS BytecodeEmitter
     MOZ_MUST_USE bool emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote = EMIT_LINENOTE);
 
     // Emit code for the tree rooted at pn with its own TDZ cache.
-    MOZ_MUST_USE bool emitConditionallyExecutedTree(ParseNode* pn);
+    MOZ_MUST_USE bool emitTreeInBranch(ParseNode* pn);
 
     // Emit global, eval, or module code for tree rooted at body. Always
     // encompasses the entire source.
@@ -648,8 +648,7 @@ struct MOZ_STACK_CLASS BytecodeEmitter
     // the stack and emits code to destructure a single lhs expression (either a
     // name or a compound []/{} expression).
     MOZ_MUST_USE bool emitDestructuringLHS(ParseNode* target, DestructuringFlavor flav);
-    MOZ_MUST_USE bool emitConditionallyExecutedDestructuringLHS(ParseNode* target,
-                                                                DestructuringFlavor flav);
+    MOZ_MUST_USE bool emitDestructuringLHSInBranch(ParseNode* target, DestructuringFlavor flav);
 
     // emitDestructuringOps assumes the to-be-destructured value has been
     // pushed on the stack and emits code to destructure each part of a [] or
@@ -678,7 +677,16 @@ struct MOZ_STACK_CLASS BytecodeEmitter
 
     // Check if the value on top of the stack is "undefined". If so, replace
     // that value on the stack with the value defined by |defaultExpr|.
-    MOZ_MUST_USE bool emitDefault(ParseNode* defaultExpr);
+    // |pattern| is a lhs node of the default expression.  If it's an
+    // identifier and |defaultExpr| is an anonymous function, |SetFunctionName|
+    // is called at compile time.
+    MOZ_MUST_USE bool emitDefault(ParseNode* defaultExpr, ParseNode* pattern);
+
+    MOZ_MUST_USE bool setOrEmitSetFunName(ParseNode* maybeFun, HandleAtom name,
+                                          FunctionPrefixKind prefixKind);
+
+    MOZ_MUST_USE bool emitInitializer(ParseNode* initializer, ParseNode* pattern);
+    MOZ_MUST_USE bool emitInitializerInBranch(ParseNode* initializer, ParseNode* pattern);
 
     MOZ_MUST_USE bool emitCallSiteObject(ParseNode* pn);
     MOZ_MUST_USE bool emitTemplateString(ParseNode* pn);
diff --git a/js/src/frontend/FullParseHandler.h b/js/src/frontend/FullParseHandler.h
index add881900..0fd137796 100644
--- a/js/src/frontend/FullParseHandler.h
+++ b/js/src/frontend/FullParseHandler.h
@@ -665,6 +665,11 @@ class FullParseHandler
                                                                    ParseNode* pn);
     inline void setLastFunctionFormalParameterDestructuring(ParseNode* funcpn, ParseNode* pn);
 
+    void checkAndSetIsDirectRHSAnonFunction(ParseNode* pn) {
+        if (IsAnonymousFunctionDefinition(pn))
+            pn->setDirectRHSAnonFunction(true);
+    }
+
     ParseNode* newFunctionDefinition() {
         return new_<CodeNode>(PNK_FUNCTION, pos());
     }
@@ -942,6 +947,8 @@ FullParseHandler::setLastFunctionFormalParameterDefault(ParseNode* funcpn, Parse
     if (!pn)
         return false;
 
+    checkAndSetIsDirectRHSAnonFunction(defaultValue);
+
     funcpn->pn_body->pn_pos.end = pn->pn_pos.end;
     ParseNode* pnchild = funcpn->pn_body->pn_head;
     ParseNode* pnlast = funcpn->pn_body->last();
diff --git a/js/src/frontend/ParseNode-inl.h b/js/src/frontend/ParseNode-inl.h
index 395d09b5b..21bd83766 100644
--- a/js/src/frontend/ParseNode-inl.h
+++ b/js/src/frontend/ParseNode-inl.h
@@ -18,7 +18,7 @@ inline PropertyName*
 ParseNode::name() const
 {
     MOZ_ASSERT(isKind(PNK_FUNCTION) || isKind(PNK_NAME));
-    JSAtom* atom = isKind(PNK_FUNCTION) ? pn_funbox->function()->name() : pn_atom;
+    JSAtom* atom = isKind(PNK_FUNCTION) ? pn_funbox->function()->explicitName() : pn_atom;
     return atom->asPropertyName();
 }
 
diff --git a/js/src/frontend/ParseNode.cpp b/js/src/frontend/ParseNode.cpp
index f79baba9e..ece3a45df 100644
--- a/js/src/frontend/ParseNode.cpp
+++ b/js/src/frontend/ParseNode.cpp
@@ -902,3 +902,21 @@ FunctionBox::trace(JSTracer* trc)
     if (enclosingScope_)
         TraceRoot(trc, &enclosingScope_, "funbox-enclosingScope");
 }
+
+bool
+js::frontend::IsAnonymousFunctionDefinition(ParseNode* pn)
+{
+    // ES 2017 draft
+    // 12.15.2 (ArrowFunction, AsyncArrowFunction).
+    // 14.1.12 (FunctionExpression).
+    // 14.4.8 (GeneratorExpression).
+    // 14.6.8 (AsyncFunctionExpression)
+    if (pn->isKind(PNK_FUNCTION) && !pn->pn_funbox->function()->explicitName())
+        return true;
+
+    // 14.5.8 (ClassExpression)
+    if (pn->is<ClassNode>() && !pn->as<ClassNode>().names())
+        return true;
+
+    return false;
+}
diff --git a/js/src/frontend/ParseNode.h b/js/src/frontend/ParseNode.h
index d37aaaae0..ff26279af 100644
--- a/js/src/frontend/ParseNode.h
+++ b/js/src/frontend/ParseNode.h
@@ -450,6 +450,9 @@ class ParseNode
     uint8_t pn_op;      /* see JSOp enum and jsopcode.tbl */
     uint8_t pn_arity:4; /* see ParseNodeArity enum */
     bool pn_parens:1;   /* this expr was enclosed in parens */
+    bool pn_rhs_anon_fun:1;  /* this expr is anonymous function or class that
+                              * is a direct RHS of PNK_ASSIGN or PNK_COLON of
+                              * property, that needs SetFunctionName. */
 
     ParseNode(const ParseNode& other) = delete;
     void operator=(const ParseNode& other) = delete;
@@ -460,6 +463,7 @@ class ParseNode
         pn_op(op),
         pn_arity(arity),
         pn_parens(false),
+        pn_rhs_anon_fun(false),
         pn_pos(0, 0),
         pn_next(nullptr)
     {
@@ -472,6 +476,7 @@ class ParseNode
         pn_op(op),
         pn_arity(arity),
         pn_parens(false),
+        pn_rhs_anon_fun(false),
         pn_pos(pos),
         pn_next(nullptr)
     {
@@ -512,6 +517,13 @@ class ParseNode
     bool isLikelyIIFE() const              { return isInParens(); }
     void setInParens(bool enabled)         { pn_parens = enabled; }
 
+    bool isDirectRHSAnonFunction() const {
+        return pn_rhs_anon_fun;
+    }
+    void setDirectRHSAnonFunction(bool enabled) {
+        pn_rhs_anon_fun = enabled;
+    }
+
     TokenPos            pn_pos;         /* two 16-bit pairs here, for 64 bits */
     ParseNode*          pn_next;        /* intrinsic link in parent PN_LIST */
 
@@ -1444,6 +1456,9 @@ FunctionFormalParametersList(ParseNode* fn, unsigned* numFormals)
     return argsBody->pn_head;
 }
 
+bool
+IsAnonymousFunctionDefinition(ParseNode* pn);
+
 } /* namespace frontend */
 } /* namespace js */
 
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index f42546eb5..f4c02720a 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -326,10 +326,14 @@ ParseContext::init()
         if (fun->isNamedLambda()) {
             if (!namedLambdaScope_->init(this))
                 return false;
-            AddDeclaredNamePtr p = namedLambdaScope_->lookupDeclaredNameForAdd(fun->name());
+            AddDeclaredNamePtr p =
+                namedLambdaScope_->lookupDeclaredNameForAdd(fun->explicitName());
             MOZ_ASSERT(!p);
-            if (!namedLambdaScope_->addDeclaredName(this, p, fun->name(), DeclarationKind::Const))
+            if (!namedLambdaScope_->addDeclaredName(this, p, fun->explicitName(),
+                                                    DeclarationKind::Const))
+            {
                 return false;
+            }
         }
 
         if (!functionScope_->init(this))
@@ -367,7 +371,7 @@ ParseContext::removeInnerFunctionBoxesForAnnexB(JSAtom* name)
 {
     for (uint32_t i = 0; i < innerFunctionBoxesForAnnexB_->length(); i++) {
         if (FunctionBox* funbox = innerFunctionBoxesForAnnexB_[i]) {
-            if (funbox->function()->name() == name)
+            if (funbox->function()->explicitName() == name)
                 innerFunctionBoxesForAnnexB_[i] = nullptr;
         }
     }
@@ -465,6 +469,7 @@ FunctionBox::FunctionBox(ExclusiveContext* cx, LifoAlloc& alloc, ObjectBox* trac
     usesApply(false),
     usesThis(false),
     usesReturn(false),
+    hasRest_(false),
     funCxFlags()
 {
     // Functions created at parse time may be set singleton after parsing and
@@ -477,7 +482,6 @@ void
 FunctionBox::initFromLazyFunction()
 {
     JSFunction* fun = function();
-    length = fun->nargs() - fun->hasRest();
     if (fun->lazyScript()->isDerivedClassConstructor())
         setDerivedClassConstructor();
     if (fun->lazyScript()->needsHomeObject())
@@ -492,8 +496,6 @@ FunctionBox::initStandaloneFunction(Scope* enclosingScope)
     // Standalone functions are Function or Generator constructors and are
     // always scoped to the global.
     MOZ_ASSERT(enclosingScope->is<GlobalScope>());
-    JSFunction* fun = function();
-    length = fun->nargs() - fun->hasRest();
     enclosingScope_ = enclosingScope;
     allowNewTarget_ = true;
     thisBinding_ = ThisBinding::Function;
@@ -836,7 +838,7 @@ Parser<ParseHandler>::reportBadReturn(Node pn, ParseReportKind kind,
                                       unsigned errnum, unsigned anonerrnum)
 {
     JSAutoByteString name;
-    if (JSAtom* atom = pc->functionBox()->function()->name()) {
+    if (JSAtom* atom = pc->functionBox()->function()->explicitName()) {
         if (!AtomToPrintableString(context, atom, &name))
             return false;
     } else {
@@ -2214,6 +2216,8 @@ Parser<SyntaxParseHandler>::finishFunction()
         lazy->setStrict();
     lazy->setGeneratorKind(funbox->generatorKind());
     lazy->setAsyncKind(funbox->asyncKind());
+    if (funbox->hasRest())
+        lazy->setHasRest();
     if (funbox->isLikelyConstructorWrapper())
         lazy->setLikelyConstructorWrapper();
     if (funbox->isDerivedClassConstructor())
@@ -2757,7 +2761,7 @@ Parser<ParseHandler>::functionArguments(YieldHandling yieldHandling, FunctionSyn
                 }
 
                 hasRest = true;
-                funbox->function()->setHasRest();
+                funbox->setHasRest();
 
                 if (!tokenStream.getToken(&tt))
                     return false;
@@ -3477,8 +3481,8 @@ Parser<ParseHandler>::functionFormalParametersAndBody(InHandling inHandling,
     if (!body)
         return false;
 
-    if ((kind != Method && !IsConstructorKind(kind)) && fun->name()) {
-        RootedPropertyName propertyName(context, fun->name()->asPropertyName());
+    if ((kind != Method && !IsConstructorKind(kind)) && fun->explicitName()) {
+        RootedPropertyName propertyName(context, fun->explicitName()->asPropertyName());
         if (!checkStrictBinding(propertyName, handler.getPosition(pn)))
             return false;
     }
@@ -4337,6 +4341,8 @@ Parser<ParseHandler>::declarationPattern(Node decl, DeclarationKind declKind, To
     if (!init)
         return null();
 
+    handler.checkAndSetIsDirectRHSAnonFunction(init);
+
     if (forHeadKind) {
         // For for(;;) declarations, consistency with |for (;| parsing requires
         // that the ';' first be examined as Operand, even though absence of a
@@ -4366,6 +4372,8 @@ Parser<ParseHandler>::initializerInNameDeclaration(Node decl, Node binding,
     if (!initializer)
         return false;
 
+    handler.checkAndSetIsDirectRHSAnonFunction(initializer);
+
     if (forHeadKind) {
         if (initialDeclaration) {
             bool isForIn, isForOf;
@@ -5063,7 +5071,7 @@ Parser<FullParseHandler>::exportDeclaration()
         if (!kid)
             return null();
 
-        if (!checkExportedName(kid->pn_funbox->function()->name()))
+        if (!checkExportedName(kid->pn_funbox->function()->explicitName()))
             return null();
         break;
 
@@ -6670,8 +6678,6 @@ Parser<ParseHandler>::classDefinition(YieldHandling yieldHandling,
             return null();
         }
 
-        // FIXME: Implement ES6 function "name" property semantics
-        // (bug 883377).
         RootedAtom funName(context);
         switch (propType) {
           case PropertyType::GetterNoExpressionClosure:
@@ -6694,6 +6700,8 @@ Parser<ParseHandler>::classDefinition(YieldHandling yieldHandling,
         if (!fn)
             return null();
 
+        handler.checkAndSetIsDirectRHSAnonFunction(fn);
+
         JSOp op = JSOpFromPropertyType(propType);
         if (!handler.addClassMethodDefinition(classMethods, propName, fn, op, isStatic))
             return null();
@@ -7753,6 +7761,9 @@ Parser<ParseHandler>::assignExpr(InHandling inHandling, YieldHandling yieldHandl
             return null();
     }
 
+    if (kind == PNK_ASSIGN)
+        handler.checkAndSetIsDirectRHSAnonFunction(rhs);
+
     return handler.newAssignment(kind, lhs, rhs, op);
 }
 
@@ -9155,6 +9166,8 @@ Parser<ParseHandler>::objectLiteral(YieldHandling yieldHandling, PossibleError*
             if (!propExpr)
                 return null();
 
+            handler.checkAndSetIsDirectRHSAnonFunction(propExpr);
+
             if (foldConstants && !FoldConstants(context, &propExpr, this))
                 return null();
 
@@ -9268,6 +9281,8 @@ Parser<ParseHandler>::objectLiteral(YieldHandling yieldHandling, PossibleError*
                     return null();
             }
 
+            handler.checkAndSetIsDirectRHSAnonFunction(rhs);
+
             Node propExpr = handler.newAssignment(PNK_ASSIGN, lhs, rhs, JSOP_NOP);
             if (!propExpr)
                 return null();
@@ -9278,8 +9293,6 @@ Parser<ParseHandler>::objectLiteral(YieldHandling yieldHandling, PossibleError*
             if (!abortIfSyntaxParser())
                 return null();
         } else {
-            // FIXME: Implement ES6 function "name" property semantics
-            // (bug 883377).
             RootedAtom funName(context);
             if (!tokenStream.isCurrentTokenType(TOK_RB)) {
                 funName = propAtom;
@@ -9295,6 +9308,8 @@ Parser<ParseHandler>::objectLiteral(YieldHandling yieldHandling, PossibleError*
             if (!fn)
                 return null();
 
+            handler.checkAndSetIsDirectRHSAnonFunction(fn);
+
             JSOp op = JSOpFromPropertyType(propType);
             if (!handler.addObjectMethodDefinition(literal, propName, fn, op))
                 return null();
diff --git a/js/src/frontend/SharedContext.h b/js/src/frontend/SharedContext.h
index 39df47c20..a6ac542f6 100644
--- a/js/src/frontend/SharedContext.h
+++ b/js/src/frontend/SharedContext.h
@@ -471,6 +471,7 @@ class FunctionBox : public ObjectBox, public SharedContext
     bool            usesApply:1;            /* contains an f.apply() call */
     bool            usesThis:1;             /* contains 'this' */
     bool            usesReturn:1;           /* contains a 'return' statement */
+    bool            hasRest_:1;             /* has rest parameter */
 
     FunctionContextFlags funCxFlags;
 
@@ -539,6 +540,11 @@ class FunctionBox : public ObjectBox, public SharedContext
     bool isAsync() const { return asyncKind() == AsyncFunction; }
     bool isArrow() const { return function()->isArrow(); }
 
+    bool hasRest() const { return hasRest_; }
+    void setHasRest() {
+        hasRest_ = true;
+    }
+
     void setGeneratorKind(GeneratorKind kind) {
         // A generator kind can be set at initialization, or when "yield" is
         // first seen.  In both cases the transition can only happen from
@@ -567,7 +573,7 @@ class FunctionBox : public ObjectBox, public SharedContext
     void setHasInnerFunctions()            { funCxFlags.hasInnerFunctions         = true; }
 
     bool hasSimpleParameterList() const {
-        return !function()->hasRest() && !hasParameterExprs && !hasDestructuringArgs;
+        return !hasRest() && !hasParameterExprs && !hasDestructuringArgs;
     }
 
     bool hasMappedArgsObj() const {
diff --git a/js/src/frontend/SyntaxParseHandler.h b/js/src/frontend/SyntaxParseHandler.h
index 75c7e3333..b7f00605b 100644
--- a/js/src/frontend/SyntaxParseHandler.h
+++ b/js/src/frontend/SyntaxParseHandler.h
@@ -339,6 +339,9 @@ class SyntaxParseHandler
                                     Node catchGuard, Node catchBody) { return true; }
 
     MOZ_MUST_USE bool setLastFunctionFormalParameterDefault(Node funcpn, Node pn) { return true; }
+
+    void checkAndSetIsDirectRHSAnonFunction(Node pn) {}
+
     Node newFunctionDefinition() { return NodeFunctionDefinition; }
     bool setComprehensionLambdaBody(Node pn, Node body) { return true; }
     void setFunctionFormalParametersAndBody(Node pn, Node kid) {}