Bug 1357506 - Remove assert that constructorBox can only be set once when parsing classes. (r=Yoric)

Both asm.js and syntax parsing can abort and rewind parsing of an inner
function. The bookkeeping to make sure that a class's constructor
FunctionBox is only set once is not worth it -- duplicate constructor
definitions already throw an early error.

js/src/frontend/Parser.cpp

@@ -548,7 +548,7 @@ FunctionBox::initWithEnclosingParseContext(ParseContext* enclosing, FunctionSynt
         if (kind == ClassConstructor || kind == DerivedClassConstructor) {
             auto stmt = enclosing->findInnermostStatement<ParseContext::ClassStatement>();
             MOZ_ASSERT(stmt);
-            stmt->setConstructorBox(this);
+            stmt->constructorBox = this;
 
             if (kind == DerivedClassConstructor) {
                 setDerivedClassConstructor();
@@ -574,16 +574,6 @@ FunctionBox::initWithEnclosingParseContext(ParseContext* enclosing, FunctionSynt
     }
 }
 
-void
-FunctionBox::resetForAbortedSyntaxParse(ParseContext* enclosing, FunctionSyntaxKind kind)
-{
-    if (kind == ClassConstructor || kind == DerivedClassConstructor) {
-        auto stmt = enclosing->findInnermostStatement<ParseContext::ClassStatement>();
-        MOZ_ASSERT(stmt);
-        stmt->clearConstructorBoxForAbortedSyntaxParse(this);
-    }
-}
-
 void
 FunctionBox::initWithEnclosingScope(Scope* enclosingScope)
 {
@@ -3455,7 +3445,6 @@ Parser<FullParseHandler>::trySyntaxParseInnerFunction(ParseNode* pn, HandleFunct
                 // correctness.
                 parser->clearAbortedSyntaxParse();
                 usedNames.rewind(token);
-                funbox->resetForAbortedSyntaxParse(pc, kind);
                 MOZ_ASSERT_IF(!parser->context->helperThread(),
                               !parser->context->isExceptionPending());
                 break;
@@ -7168,7 +7157,7 @@ Parser<ParseHandler>::classDefinition(YieldHandling yieldHandling,
                 errorAt(nameOffset, JSMSG_BAD_METHOD_DEF);
                 return null();
             }
-            if (classStmt.constructorBox()) {
+            if (classStmt.constructorBox) {
                 errorAt(nameOffset, JSMSG_DUPLICATE_PROPERTY, "constructor");
                 return null();
             }
@@ -7215,7 +7204,7 @@ Parser<ParseHandler>::classDefinition(YieldHandling yieldHandling,
     // Amend the toStringEnd offset for the constructor now that we've
     // finished parsing the class.
     uint32_t classEndOffset = pos().end;
-    if (FunctionBox* ctorbox = classStmt.constructorBox()) {
+    if (FunctionBox* ctorbox = classStmt.constructorBox) {
         if (ctorbox->function()->isInterpretedLazy())
             ctorbox->function()->lazyScript()->setToStringEnd(classEndOffset);
         ctorbox->toStringEnd = classEndOffset;

js/src/frontend/Parser.h

@@ -87,29 +87,14 @@ class ParseContext : public Nestable<ParseContext>
         }
     };
 
-    class ClassStatement : public Statement
+    struct ClassStatement : public Statement
     {
-        FunctionBox* constructorBox_;
+        FunctionBox* constructorBox;
 
-      public:
         explicit ClassStatement(ParseContext* pc)
           : Statement(pc, StatementKind::Class),
-            constructorBox_(nullptr)
+            constructorBox(nullptr)
         { }
-
-        void clearConstructorBoxForAbortedSyntaxParse(FunctionBox* funbox) {
-            MOZ_ASSERT(constructorBox_ == funbox);
-            constructorBox_ = nullptr;
-        }
-
-        void setConstructorBox(FunctionBox* funbox) {
-            MOZ_ASSERT(!constructorBox_);
-            constructorBox_ = funbox;
-        }
-
-        FunctionBox* constructorBox() const {
-            return constructorBox_;
-        }
     };
 
     // The intra-function scope stack.

js/src/frontend/SharedContext.h

@@ -503,7 +503,6 @@ class FunctionBox : public ObjectBox, public SharedContext
     void initFromLazyFunction();
     void initStandaloneFunction(Scope* enclosingScope);
     void initWithEnclosingParseContext(ParseContext* enclosing, FunctionSyntaxKind kind);
-    void resetForAbortedSyntaxParse(ParseContext* enclosing, FunctionSyntaxKind kind);
 
     ObjectBox* toObjectBox() override { return this; }
     JSFunction* function() const { return &object->as<JSFunction>(); }

js/src/jit-test/tests/class/bug1357506.js

@@ -0,0 +1,8 @@
+// Test that constructors that abort due to asm.js do not assert due to the
+// parser keeping track of the FunctionBox corresponding to the constructor.
+
+class a {
+  constructor() {
+    "use asm";
+  }
+}