Add errors for declarations which conflict with catch parameters.

src/parsing/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 3045 matching lines @@
         Expect(Token::LBRACE, CHECK_OK);
         while (peek() != Token::RBRACE) {
           Statement* stat = ParseStatementListItem(CHECK_OK);
           if (stat && !stat->IsEmpty()) {
             catch_block->statements()->Add(stat, zone());
           }
         }
         Consume(Token::RBRACE);
       }
       block_scope->set_end_position(scanner()->location().end_pos);
+      if (is_simple) {
+        // Check for `catch(e) { let e; }` and similar errors.
+        // The BindingPattern case is handled elsewhere, because
+        // the names created by destructuring being lexical.
+        Variable* var = block_scope->LookupLocal(name);
+        if (var != nullptr && IsLexicalVariableMode(var->mode())) {
+          auto position = pattern->position();
+          Scanner::Location location =
+              position == RelocInfo::kNoPosition
+                  ? Scanner::Location::invalid()
+                  : Scanner::Location(position, position + 1);
+          ParserTraits::ReportMessageAt(
+              location, MessageTemplate::kVarRedeclaration, name);
+          *ok = false;
+          return NULL;
+        }
+      }
       block_scope = block_scope->FinalizeBlockScope();
       catch_block->set_scope(block_scope);
     }
 
     catch_scope->set_end_position(scanner()->location().end_pos);
     tok = peek();
   }
 
   Block* finally_block = NULL;
   DCHECK(tok == Token::FINALLY || catch_block != NULL);
@@ skipping 485 matching lines @@
     body_scope = body_scope->FinalizeBlockScope();
     block->set_scope(body_scope);
     return block;
   }
 }
 
 Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
                                      bool* ok) {
   int stmt_pos = peek_position();
   Statement* init = NULL;
-  ZoneList<const AstRawString*> lexical_bindings(1, zone());
+  ZoneList<const AstRawString*> bound_names(1, zone());
+  bool bound_names_are_lexical = false;
 
   // Create an in-between scope for let-bound iteration variables.
   Scope* for_scope = NewScope(scope_, BLOCK_SCOPE);
 
   BlockState block_state(&scope_, for_scope);
   Expect(Token::FOR, CHECK_OK);
   Expect(Token::LPAREN, CHECK_OK);
   for_scope->set_start_position(scanner()->location().beg_pos);
   for_scope->set_is_hidden();
   DeclarationParsingResult parsing_result;
@@ skipping 30 matching lines @@
           }
           ParserTraits::ReportMessageAt(
               parsing_result.first_initializer_loc,
               MessageTemplate::kForInOfLoopInitializer,
               ForEachStatement::VisitModeString(mode));
           *ok = false;
           return nullptr;
         }
 
         Block* init_block = nullptr;
+        bound_names_are_lexical =
+            IsLexicalVariableMode(parsing_result.descriptor.mode);
 
         // special case for legacy for (var/const x =.... in)

[Dan Ehrenberg, 2016/06/29 20:24:32]

It's only var at this point, right? Could you change the unrelated comment which
happens to be adjacent to your change?

[bakkot, 2016/06/29 21:10:13]

Done, and in a few other places.

-        if (!IsLexicalVariableMode(parsing_result.descriptor.mode) &&
-            decl.pattern->IsVariableProxy() && decl.initializer != nullptr) {
+        if (!bound_names_are_lexical && decl.pattern->IsVariableProxy() &&
+            decl.initializer != nullptr) {
           DCHECK(!allow_harmony_for_in());
           ++use_counts_[v8::Isolate::kForInInitializer];
           const AstRawString* name =
               decl.pattern->AsVariableProxy()->raw_name();
           VariableProxy* single_var = scope_->NewUnresolved(
               factory(), name, Variable::NORMAL, each_beg_pos, each_end_pos);
           init_block = factory()->NewBlock(
               nullptr, 2, true, parsing_result.descriptor.declaration_pos);
           init_block->statements()->Add(
               factory()->NewExpressionStatement(
@@ skipping 55 matching lines @@
           auto each_initialization_block =
               factory()->NewBlock(nullptr, 1, true, RelocInfo::kNoPosition);
           {
             auto descriptor = parsing_result.descriptor;
             descriptor.declaration_pos = RelocInfo::kNoPosition;
             descriptor.initialization_pos = RelocInfo::kNoPosition;
             decl.initializer = factory()->NewVariableProxy(temp);
 
             PatternRewriter::DeclareAndInitializeVariables(
                 each_initialization_block, &descriptor, &decl,
-                IsLexicalVariableMode(descriptor.mode) ? &lexical_bindings
-                                                       : nullptr,
+                bound_names_are_lexical ||
+                        (mode == ForEachStatement::ITERATE &&
+                         parsing_result.descriptor.mode == VariableMode::VAR)

[Dan Ehrenberg, 2016/06/29 20:24:32]

Minor cleanup suggestion: since it occurs multiple times, make a boolean
variable for this special case.

[bakkot, 2016/06/29 21:10:13]

Done.

+                    ? &bound_names
+                    : nullptr,
                 CHECK_OK);
+
+            // Annex B.3.5 prohibits the form
+            // `try {} catch(e) { for (var e of {}); }`
+            // So if we are parsing a statement like `for (var ... of ...)`
+            // we need to walk up the scope chain and look for catch scopes
+            // which have a simple binding, then compare their binding against
+            // all of the names declared in the init of the for-of we're
+            // parsing.
+            if (mode == ForEachStatement::ITERATE &&
+                parsing_result.descriptor.mode == VariableMode::VAR) {
+              Scope* catch_scope = scope_;
+              while (catch_scope != nullptr &&
+                     !catch_scope->is_declaration_scope()) {
+                if (catch_scope->is_catch_scope()) {
+                  auto name = catch_scope->catch_variable_name();
+                  if (name !=
+                      ast_value_factory()
+                          ->dot_catch_string()) {  // i.e. is a simple binding
+                    if (bound_names.Contains(name)) {
+                      ParserTraits::ReportMessageAt(
+                          parsing_result.bindings_loc,
+                          MessageTemplate::kVarRedeclaration, name);
+                      *ok = false;
+                      return nullptr;
+                    }
+                  }
+                }
+                catch_scope = catch_scope->outer_scope();
+              }
+            }
           }
 
           body_block->statements()->Add(each_initialization_block, zone());
           body_block->statements()->Add(body, zone());
           VariableProxy* temp_proxy =
               factory()->NewVariableProxy(temp, each_beg_pos, each_end_pos);
           InitializeForEachStatement(loop, temp_proxy, enumerable, body_block,
                                      each_keyword_position);
         }
         body_scope->set_end_position(scanner()->location().end_pos);
         body_scope = body_scope->FinalizeBlockScope();
         body_block->set_scope(body_scope);
 
         // Create a TDZ for any lexically-bound names.
-        if (IsLexicalVariableMode(parsing_result.descriptor.mode)) {
+        if (bound_names_are_lexical) {
           DCHECK_NULL(init_block);
 
           init_block =
               factory()->NewBlock(nullptr, 1, false, RelocInfo::kNoPosition);
 
-          for (int i = 0; i < lexical_bindings.length(); ++i) {
+          for (int i = 0; i < bound_names.length(); ++i) {
             // TODO(adamk): This needs to be some sort of special
             // INTERNAL variable that's invisible to the debugger
             // but visible to everything else.
-            VariableProxy* tdz_proxy =
-                NewUnresolved(lexical_bindings[i], LET);
+            VariableProxy* tdz_proxy = NewUnresolved(bound_names[i], LET);
             Declaration* tdz_decl = factory()->NewVariableDeclaration(
                 tdz_proxy, LET, scope_, RelocInfo::kNoPosition);
             Variable* tdz_var = Declare(
                 tdz_decl, DeclarationDescriptor::NORMAL, true, CHECK_OK);
             tdz_var->set_initializer_position(position());
           }
         }
 
         Statement* final_loop = loop->IsForOfStatement()
             ? FinalizeForOfStatement(
                 loop->AsForOfStatement(), RelocInfo::kNoPosition)
             : loop;
 
         for_scope->set_end_position(scanner()->location().end_pos);
         for_scope = for_scope->FinalizeBlockScope();
         // Parsed for-in loop w/ variable declarations.
         if (init_block != nullptr) {
           init_block->statements()->Add(final_loop, zone());
           init_block->set_scope(for_scope);
           return init_block;
         } else {
           DCHECK_NULL(for_scope);
           return final_loop;
         }
       } else {
+        bound_names_are_lexical =
+            IsLexicalVariableMode(parsing_result.descriptor.mode);
         init = parsing_result.BuildInitializationBlock(
-            IsLexicalVariableMode(parsing_result.descriptor.mode)
-                ? &lexical_bindings
-                : nullptr,
-            CHECK_OK);
+            bound_names_are_lexical ? &bound_names : nullptr, CHECK_OK);
       }
     } else {
       int lhs_beg_pos = peek_position();
       ExpressionClassifier classifier(this);
       Expression* expression = ParseExpression(false, &classifier, CHECK_OK);
       int lhs_end_pos = scanner()->location().end_pos;
       ForEachStatement::VisitMode mode = ForEachStatement::ENUMERATE;
 
       bool is_for_each = CheckInOrOf(&mode, ok);
       if (!*ok) return nullptr;
@@ skipping 59 matching lines @@
   // Parsed initializer at this point.
   Expect(Token::SEMICOLON, CHECK_OK);
 
   Expression* cond = NULL;
   Statement* next = NULL;
   Statement* body = NULL;
 
   // If there are let bindings, then condition and the next statement of the
   // for loop must be parsed in a new scope.
   Scope* inner_scope = scope_;
-  if (lexical_bindings.length() > 0) {
+  if (bound_names_are_lexical && bound_names.length() > 0) {
     inner_scope = NewScope(for_scope, BLOCK_SCOPE);
     inner_scope->set_start_position(scanner()->location().beg_pos);
   }
   {
     BlockState block_state(&scope_, inner_scope);
 
     if (peek() != Token::SEMICOLON) {
       cond = ParseExpression(true, CHECK_OK);
     }
     Expect(Token::SEMICOLON, CHECK_OK);
 
     if (peek() != Token::RPAREN) {
       Expression* exp = ParseExpression(true, CHECK_OK);
       next = factory()->NewExpressionStatement(exp, exp->position());
     }
     Expect(Token::RPAREN, CHECK_OK);
 
     body = ParseScopedStatement(NULL, true, CHECK_OK);
   }
 
   Statement* result = NULL;
-  if (lexical_bindings.length() > 0) {
+  if (bound_names_are_lexical && bound_names.length() > 0) {
     BlockState block_state(&scope_, for_scope);
     result = DesugarLexicalBindingsInForStatement(
-        inner_scope, parsing_result.descriptor.mode, &lexical_bindings, loop,
-        init, cond, next, body, CHECK_OK);
+        inner_scope, parsing_result.descriptor.mode, &bound_names, loop, init,
+        cond, next, body, CHECK_OK);
     for_scope->set_end_position(scanner()->location().end_pos);
   } else {
     for_scope->set_end_position(scanner()->location().end_pos);
     for_scope = for_scope->FinalizeBlockScope();
     if (for_scope) {
       // Rewrite a for statement of the form
       //   for (const x = i; c; n) b
       //
       // into
       //
@@ skipping 3113 matching lines @@
                         try_block, target);
     final_loop = target;
   }
 
   return final_loop;
 }
 
 
 }  // namespace internal
 }  // namespace v8