[strong] Declaration-after-use errors.

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index 35449643cec2dce0742737c35b33e9b559b9ab0f..0c2eadb3fdbdbaa87797f567913b2994e85a7391 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -34,6 +34,7 @@ Variable* VariableMap::Declare(Scope* scope, const AstRawString* name,
                                VariableMode mode, bool is_valid_lhs,
                                Variable::Kind kind,
                                InitializationFlag initialization_flag,
+                               int position,
                                MaybeAssignedFlag maybe_assigned_flag) {
   // AstRawStrings are unambiguous, i.e., the same string is always represented
   // by the same AstRawString*.
@@ -43,8 +44,9 @@ 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);
-    p->value = new (zone()) Variable(scope, name, mode, is_valid_lhs, kind,
-                                     initialization_flag, maybe_assigned_flag);
+    p->value = new (zone())
+        Variable(scope, name, mode, is_valid_lhs, kind, initialization_flag,
+                 position, maybe_assigned_flag);
   }
   return reinterpret_cast<Variable*>(p->value);
 }
@@ -263,7 +265,12 @@ bool Scope::Analyze(CompilationInfo* info) {
   // Allocate the variables.
   {
     AstNodeFactory ast_node_factory(info->ast_value_factory());
-    if (!top->AllocateVariables(info, &ast_node_factory)) return false;
+    if (!top->AllocateVariables(info, &ast_node_factory)) {
+      DCHECK(top->pending_error_handler_.has_pending_error());
+      top->pending_error_handler_.ThrowPendingError(info->isolate(),
+                                                    info->script());
+      return false;
+    }
   }
 
 #ifdef DEBUG
@@ -402,8 +409,9 @@ Variable* Scope::LookupLocal(const AstRawString* name) {
     maybe_assigned_flag = kMaybeAssigned;
   }
 
-  Variable* var = variables_.Declare(this, name, mode, true, Variable::NORMAL,
-                                     init_flag, maybe_assigned_flag);
+  Variable* var =
+      variables_.Declare(this, name, mode, true, Variable::NORMAL, init_flag,
+                         RelocInfo::kNoPosition, maybe_assigned_flag);
   var->AllocateTo(location, index);
   return var;
 }
@@ -418,9 +426,9 @@ Variable* Scope::LookupFunctionVar(const AstRawString* name,
     VariableMode mode;
     int index = scope_info_->FunctionContextSlotIndex(*(name->string()), &mode);
     if (index < 0) return NULL;
-    Variable* var = new(zone()) Variable(
-        this, name, mode, true /* is valid LHS */,
-        Variable::NORMAL, kCreatedInitialized);
+    Variable* var = new (zone())
+        Variable(this, name, mode, true /* is valid LHS */, Variable::FUNCTION,
+                 kCreatedInitialized, RelocInfo::kNoPosition);
     VariableProxy* proxy = factory->NewVariableProxy(var);
     VariableDeclaration* declaration = factory->NewVariableDeclaration(
         proxy, mode, this, RelocInfo::kNoPosition);
@@ -461,7 +469,8 @@ Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
 
 
 Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
-                              InitializationFlag init_flag,
+                              InitializationFlag init_flag, int position,
+                              bool is_function,
                               MaybeAssignedFlag maybe_assigned_flag) {
   DCHECK(!already_resolved());
   // This function handles VAR, LET, and CONST modes.  DYNAMIC variables are
@@ -469,8 +478,9 @@ Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
   // explicitly, and TEMPORARY variables are allocated via NewTemporary().
   DCHECK(IsDeclaredVariableMode(mode));
   ++num_var_or_const_;
-  return variables_.Declare(this, name, mode, true, Variable::NORMAL, init_flag,
-                            maybe_assigned_flag);
+  return variables_.Declare(this, name, mode, true,
+                            is_function ? Variable::FUNCTION : Variable::NORMAL,
+                            init_flag, position, maybe_assigned_flag);
 }
 
 
@@ -499,12 +509,9 @@ void Scope::RemoveUnresolved(VariableProxy* var) {
 
 Variable* Scope::NewInternal(const AstRawString* name) {
   DCHECK(!already_resolved());
-  Variable* var = new(zone()) Variable(this,
-                                       name,
-                                       INTERNAL,
-                                       false,
-                                       Variable::NORMAL,
-                                       kCreatedInitialized);
+  Variable* var =
+      new (zone()) Variable(this, name, INTERNAL, false, Variable::NORMAL,
+                            kCreatedInitialized, RelocInfo::kNoPosition);
   internals_.Add(var, zone());
   return var;
 }
@@ -512,12 +519,9 @@ Variable* Scope::NewInternal(const AstRawString* name) {
 
 Variable* Scope::NewTemporary(const AstRawString* name) {
   DCHECK(!already_resolved());
-  Variable* var = new(zone()) Variable(this,
-                                       name,
-                                       TEMPORARY,
-                                       true,
-                                       Variable::NORMAL,
-                                       kCreatedInitialized);
+  Variable* var =
+      new (zone()) Variable(this, name, TEMPORARY, true, Variable::NORMAL,
+                            kCreatedInitialized, RelocInfo::kNoPosition);
   temps_.Add(var, zone());
   return var;
 }
@@ -768,6 +772,20 @@ void Scope::GetNestedScopeChain(Isolate* isolate,
 }
 
 
+void Scope::ReportMessage(int start_position, int end_position,
+                          const char* message, const AstRawString* arg) {
+  // Propagate the error to the topmost scope targeted by this scope analysis
+  // phase.
+  Scope* top = this;
+  while (!top->is_script_scope() && !top->outer_scope()->already_resolved()) {
+    top = top->outer_scope();
+  }
+
+  top->pending_error_handler_.ReportMessageAt(start_position, end_position,
+                                              message, arg, kReferenceError);
+}
+
+
 #ifdef DEBUG
 static const char* Header(ScopeType scope_type) {
   switch (scope_type) {
@@ -1050,6 +1068,27 @@ bool Scope::ResolveVariable(CompilationInfo* info, VariableProxy* proxy,
   switch (binding_kind) {
     case BOUND:
       // We found a variable binding.
+      if (is_strong(language_mode())) {
+        // 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).
+
+        // 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.

[rossberg, 2015/02/23 13:45:26]

Can you add a TODO regarding different evals? I suppose each direct eval scope
somehow would need to know its call position in the outer program text... Hm,
tricky... I think we want to disallow direct eval in strong mode anyway, but
that still leaves toplevel bindings.

[marja, 2015/02/24 13:29:34]

Added a todo.

So one error case is:

This throws:
"use strong"; eval("let x = 1;"); eval("x;")

But this doesn't:
"use strong"; eval("let x = 1;"); eval("if (false) { x; }");

But won't we need the context analysis for that anyway?

+        const Scope* eval_for_use = NearestOuterEvalScope();
+        const Scope* eval_for_declaration =
+            var->scope()->NearestOuterEvalScope();
+
+        if (proxy->position() != RelocInfo::kNoPosition &&
+            proxy->position() < var->position() && !var->is_function() &&

[rossberg, 2015/02/23 13:45:26]

I don't believe this is good enough. Consider:

  let x = x+1

Here, proxy->pos > var->pos, but it's an error nonetheless.

We already have var->initializer_position, which marks the position where a var
is known to be bound (and is used by codegen to eliminate unnecessary hole
checks for lexical bindings, see e.g. full-codegen-ia32.cc:1474). In the above
case that would point at the _end_ of the binding's RHS (but before the next
binding, if there are multiple comma-separated ones).

However, you probably need to set that position properly for a couple more
declaration forms now (previously it only mattered for lexical ones). Also, I
just saw that it seems wrong in ParseClassDeclaration.

[marja, 2015/02/24 13:29:35]

Fixed this to use initializer_position(), undid the position addition to
Variable, fixed a couple of places where the initializer position was set, added
test cases.

+            eval_for_use == eval_for_declaration) {
+          DCHECK(proxy->end_position() != RelocInfo::kNoPosition);
+          ReportMessage(proxy->position(), proxy->end_position(),
+                        "strong_use_before_declaration", proxy->raw_name());
+          return false;
+        }
+      }
       break;
 
     case BOUND_EVAL_SHADOWED: