[debugger] fix switch block source positions.

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 <memory>
 
 #include "src/api.h"
 #include "src/ast/ast-expression-rewriter.h"
@@ skipping 1647 matching lines @@
   switch_block->statements()->Add(
       factory()->NewExpressionStatement(
           factory()->NewUndefinedLiteral(kNoSourcePosition), kNoSourcePosition),
       zone());
 
   Expression* tag_read = factory()->NewVariableProxy(tag_variable);
   switch_statement->Initialize(tag_read, cases);
   Block* cases_block = factory()->NewBlock(NULL, 1, false, kNoSourcePosition);
   cases_block->statements()->Add(switch_statement, zone());
   cases_block->set_scope(scope);
+  DCHECK_IMPLIES(scope != nullptr,
+                 switch_statement->position() >= scope->start_position());
+  DCHECK_IMPLIES(scope != nullptr,
+                 switch_statement->position() < scope->end_position());
   switch_block->statements()->Add(cases_block, zone());
   return switch_block;
 }
 
 void Parser::RewriteCatchPattern(CatchInfo* catch_info, bool* ok) {
   if (catch_info->name == nullptr) {
     DCHECK_NOT_NULL(catch_info->pattern);
     catch_info->name = ast_value_factory()->dot_catch_string();
   }
   Variable* catch_variable =
@@ skipping 3355 matching lines @@
 
   return final_loop;
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8