Remove strong mode support from Scope and Variable

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index c2b05b7c040ca6ed11f700d952a10947fb4e893c..b9ad06482f52dcb46b73111004220213cb39eb12 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -27,12 +27,10 @@ VariableMap::VariableMap(Zone* zone)
       zone_(zone) {}
 VariableMap::~VariableMap() {}
 
-
 Variable* VariableMap::Declare(Scope* scope, const AstRawString* name,
                                VariableMode mode, Variable::Kind kind,
                                InitializationFlag initialization_flag,
-                               MaybeAssignedFlag maybe_assigned_flag,
-                               int declaration_group_start) {
+                               MaybeAssignedFlag maybe_assigned_flag) {
   // AstRawStrings are unambiguous, i.e., the same string is always represented
   // by the same AstRawString*.
   // FIXME(marja): fix the type of Lookup.
@@ -42,14 +40,8 @@ Variable* VariableMap::Declare(Scope* scope, const AstRawString* name,
   if (p->value == NULL) {
     // The variable has not been declared yet -> insert it.
     DCHECK(p->key == name);
-    if (kind == Variable::CLASS) {
-      p->value = new (zone())
-          ClassVariable(scope, name, mode, initialization_flag,
-                        maybe_assigned_flag, declaration_group_start);
-    } else {
-      p->value = new (zone()) Variable(
-          scope, name, mode, kind, initialization_flag, maybe_assigned_flag);
-    }
+    p->value = new (zone()) Variable(scope, name, mode, kind,
+                                     initialization_flag, maybe_assigned_flag);
   }
   return reinterpret_cast<Variable*>(p->value);
 }
@@ -103,8 +95,7 @@ Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type,
       sloppy_block_function_map_(zone),
       already_resolved_(false),
       ast_value_factory_(ast_value_factory),
-      zone_(zone),
-      class_declaration_group_start_(-1) {
+      zone_(zone) {
   SetDefaults(scope_type, outer_scope, Handle<ScopeInfo>::null(),
               function_kind);
   // The outermost scope must be a script scope.
@@ -112,7 +103,6 @@ Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type,
   DCHECK(!HasIllegalRedeclaration());
 }
 
-
 Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
              Handle<ScopeInfo> scope_info, AstValueFactory* value_factory)
     : inner_scopes_(4, zone),
@@ -125,8 +115,7 @@ Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
       sloppy_block_function_map_(zone),
       already_resolved_(true),
       ast_value_factory_(value_factory),
-      zone_(zone),
-      class_declaration_group_start_(-1) {
+      zone_(zone) {
   SetDefaults(scope_type, NULL, scope_info);
   if (!scope_info.is_null()) {
     num_heap_slots_ = scope_info_->ContextLength();
@@ -137,7 +126,6 @@ Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
   AddInnerScope(inner_scope);
 }
 
-
 Scope::Scope(Zone* zone, Scope* inner_scope,
              const AstRawString* catch_variable_name,
              AstValueFactory* value_factory)
@@ -151,8 +139,7 @@ Scope::Scope(Zone* zone, Scope* inner_scope,
       sloppy_block_function_map_(zone),
       already_resolved_(true),
       ast_value_factory_(value_factory),
-      zone_(zone),
-      class_declaration_group_start_(-1) {
+      zone_(zone) {
   SetDefaults(CATCH_SCOPE, NULL, Handle<ScopeInfo>::null());
   AddInnerScope(inner_scope);
   ++num_var_or_const_;
@@ -528,11 +515,9 @@ Variable* Scope::DeclareParameter(
   return var;
 }
 
-
 Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
                               InitializationFlag init_flag, Variable::Kind kind,
-                              MaybeAssignedFlag maybe_assigned_flag,
-                              int declaration_group_start) {
+                              MaybeAssignedFlag maybe_assigned_flag) {
   DCHECK(!already_resolved());
   // This function handles VAR, LET, and CONST modes.  DYNAMIC variables are
   // introduces during variable allocation, and TEMPORARY variables are
@@ -540,7 +525,7 @@ Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
   DCHECK(IsDeclaredVariableMode(mode));
   ++num_var_or_const_;
   return variables_.Declare(this, name, mode, kind, init_flag,
-                            maybe_assigned_flag, declaration_group_start);
+                            maybe_assigned_flag);
 }
 
 
@@ -660,11 +645,9 @@ class VarAndOrder {
   int order_;
 };
 
-
-void Scope::CollectStackAndContextLocals(
-    ZoneList<Variable*>* stack_locals, ZoneList<Variable*>* context_locals,
-    ZoneList<Variable*>* context_globals,
-    ZoneList<Variable*>* strong_mode_free_variables) {
+void Scope::CollectStackAndContextLocals(ZoneList<Variable*>* stack_locals,
+                                         ZoneList<Variable*>* context_locals,
+                                         ZoneList<Variable*>* context_globals) {
   DCHECK(stack_locals != NULL);
   DCHECK(context_locals != NULL);
   DCHECK(context_globals != NULL);
@@ -691,11 +674,6 @@ void Scope::CollectStackAndContextLocals(
        p != NULL;
        p = variables_.Next(p)) {
     Variable* var = reinterpret_cast<Variable*>(p->value);
-    if (strong_mode_free_variables && var->has_strong_mode_reference() &&
-        var->mode() == DYNAMIC_GLOBAL) {
-      strong_mode_free_variables->Add(var, zone());
-    }
-
     if (var->is_used()) {
       vars.Add(VarAndOrder(var, p->order), zone());
     }
@@ -1017,9 +995,7 @@ void Scope::Print(int n) {
   if (HasTrivialOuterContext()) {
     Indent(n1, "// scope has trivial outer context\n");
   }
-  if (is_strong(language_mode())) {
-    Indent(n1, "// strong mode scope\n");
-  } else if (is_strict(language_mode())) {
+  if (is_strict(language_mode())) {
     Indent(n1, "// strict mode scope\n");
   }
   if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");
@@ -1204,10 +1180,6 @@ bool Scope::ResolveVariable(ParseInfo* info, VariableProxy* proxy,
 
   switch (binding_kind) {
     case BOUND:
-      // We found a variable binding.
-      if (is_strong(language_mode())) {
-        if (!CheckStrongModeDeclaration(proxy, var)) return false;
-      }
       break;
 
     case BOUND_EVAL_SHADOWED:
@@ -1245,126 +1217,12 @@ bool Scope::ResolveVariable(ParseInfo* info, VariableProxy* proxy,
   DCHECK(var != NULL);
   if (proxy->is_assigned()) var->set_maybe_assigned();
 
-  if (is_strong(language_mode())) {
-    // Record that the variable is referred to from strong mode. Also, record
-    // the position.
-    var->RecordStrongModeReference(proxy->position(), proxy->end_position());
-  }
-
   proxy->BindTo(var);
 
   return true;
 }
 
 
-bool Scope::CheckStrongModeDeclaration(VariableProxy* proxy, Variable* var) {
-  // Check for declaration-after use (for variables) in strong mode. Note that
-  // we can only do this in the case where we have seen the declaration. And we
-  // always allow referencing functions (for now).
-
-  // This might happen during lazy compilation; we don't keep track of
-  // initializer positions for variables stored in ScopeInfo, so we cannot check
-  // bindings against them. TODO(marja, rossberg): remove this hack.
-  if (var->initializer_position() == RelocInfo::kNoPosition) return true;
-
-  // Allow referencing the class name from methods of that class, even though
-  // the initializer position for class names is only after the body.
-  Scope* scope = this;
-  while (scope) {
-    if (scope->ClassVariableForMethod() == var) return true;
-    scope = scope->outer_scope();
-  }
-
-  // Allow references from methods to classes declared later, if we detect no
-  // problematic dependency cycles. Note that we can be inside multiple methods
-  // at the same time, and it's enough if we find one where the reference is
-  // allowed.
-  if (var->is_class() &&
-      var->AsClassVariable()->declaration_group_start() >= 0) {
-    for (scope = this; scope && scope != var->scope();
-         scope = scope->outer_scope()) {
-      ClassVariable* class_var = scope->ClassVariableForMethod();
-      // A method is referring to some other class, possibly declared
-      // later. Referring to a class declared earlier is always OK and covered
-      // by the code outside this if. Here we only need to allow special cases
-      // for referring to a class which is declared later.
-
-      // Referring to a class C declared later is OK under the following
-      // circumstances:
-
-      // 1. The class declarations are in a consecutive group with no other
-      // declarations or statements in between, and
-
-      // 2. There is no dependency cycle where the first edge is an
-      // initialization time dependency (computed property name or extends
-      // clause) from C to something that depends on this class directly or
-      // transitively.
-      if (class_var &&
-          class_var->declaration_group_start() ==
-              var->AsClassVariable()->declaration_group_start()) {
-        return true;
-      }
-
-      // TODO(marja,rossberg): implement the dependency cycle detection. Here we
-      // undershoot the target and allow referring to any class in the same
-      // consectuive declaration group.
-
-      // The cycle detection can work roughly like this: 1) detect init-time
-      // references here (they are free variables which are inside the class
-      // scope but not inside a method scope - no parser changes needed to
-      // detect them) 2) if we encounter an init-time reference here, allow it,
-      // but record it for a later dependency cycle check 3) also record
-      // non-init-time references here 4) after scope analysis is done, analyse
-      // the dependency cycles: an illegal cycle is one starting with an
-      // init-time reference and leading back to the starting point with either
-      // non-init-time and init-time references.
-    }
-  }
-
-  // If both the use and the declaration are inside an eval scope (possibly
-  // indirectly), or one of them is, we need to check whether they are inside
-  // the same eval scope or different ones.
-
-  // TODO(marja,rossberg): Detect errors across different evals (depends on the
-  // future of eval in strong mode).
-  const Scope* eval_for_use = NearestOuterEvalScope();
-  const Scope* eval_for_declaration = var->scope()->NearestOuterEvalScope();
-
-  if (proxy->position() != RelocInfo::kNoPosition &&
-      proxy->position() < var->initializer_position() && !var->is_function() &&
-      eval_for_use == eval_for_declaration) {
-    DCHECK(proxy->end_position() != RelocInfo::kNoPosition);
-    ReportMessage(proxy->position(), proxy->end_position(),
-                  MessageTemplate::kStrongUseBeforeDeclaration,
-                  proxy->raw_name());
-    return false;
-  }
-  return true;
-}
-
-
-ClassVariable* Scope::ClassVariableForMethod() const {
-  // TODO(marja, rossberg): This fails to find a class variable in the following
-  // cases:
-  // let A = class { ... }
-  // It needs to be investigated whether this causes any practical problems.
-  if (!is_function_scope()) return nullptr;
-  if (IsInObjectLiteral(function_kind_)) return nullptr;
-  if (!IsConciseMethod(function_kind_) && !IsClassConstructor(function_kind_) &&
-      !IsAccessorFunction(function_kind_)) {
-    return nullptr;
-  }
-  DCHECK_NOT_NULL(outer_scope_);
-  // The class scope contains at most one variable, the class name.
-  DCHECK(outer_scope_->variables_.occupancy() <= 1);
-  if (outer_scope_->variables_.occupancy() == 0) return nullptr;
-  VariableMap::Entry* p = outer_scope_->variables_.Start();
-  Variable* var = reinterpret_cast<Variable*>(p->value);
-  if (!var->is_class()) return nullptr;
-  return var->AsClassVariable();
-}
-
-
 bool Scope::ResolveVariablesRecursively(ParseInfo* info,
                                         AstNodeFactory* factory) {
   DCHECK(info->script_scope()->is_script_scope());