Ensure hole checks take place in switch statement scopes

src/scopes.h

 // 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.
 
 #ifndef V8_SCOPES_H_
 #define V8_SCOPES_H_
 
 #include "src/ast.h"
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone.h"
@@ skipping 207 matching lines @@
   void RecordSuperPropertyUsage() { scope_uses_super_property_ = true; }
 
   // Set the language mode flag (unless disabled by a global flag).
   void SetLanguageMode(LanguageMode language_mode) {
     language_mode_ = language_mode;
   }
 
   // Set the ASM module flag.
   void SetAsmModule() { asm_module_ = true; }
 
+  // Inform the scope that the scope may execute declarations nonlinearly.
+  // Currently, the only nonlinear scope is a switch statement. The name is
+  // more general in case something else comes up with similar control flow,
+  // for example the ability to break out of something which does not have
+  // its own lexical scope.
+  // The bit does not need to be stored on the ScopeInfo because none of
+  // the three compilers will perform hole check elimination on a variable
+  // located in VariableLocation::CONTEXT. So, direct eval and closures
+  // will not expose holes.
+  void SetNonlinear() { scope_nonlinear_ = true; }
+
   // Position in the source where this scope begins and ends.
   //
   // * For the scope of a with statement
   //     with (obj) stmt
   //   start position: start position of first token of 'stmt'
   //   end position: end position of last token of 'stmt'
   // * For the scope of a block
   //     { stmts }
   //   start position: start position of '{'
   //   end position: end position of '}'
@@ skipping 64 matching lines @@
   bool inside_with() const { return scope_inside_with_; }
   // Does this scope contain a with statement.
   bool contains_with() const { return scope_contains_with_; }
 
   // Does this scope access "arguments".
   bool uses_arguments() const { return scope_uses_arguments_; }
   // Does any inner scope access "arguments".
   bool inner_uses_arguments() const { return inner_scope_uses_arguments_; }
   // Does this scope access "super" property (super.foo).
   bool uses_super_property() const { return scope_uses_super_property_; }
+  // Does this scope have the potential to execute declarations non-linearly?
+  bool is_nonlinear() const { return scope_nonlinear_; }
 
   // Whether this needs to be represented by a runtime context.
   bool NeedsContext() const { return num_heap_slots() > 0; }
 
   bool NeedsHomeObject() const {
     return scope_uses_super_property_ ||
            (scope_calls_eval_ && (IsConciseMethod(function_kind()) ||
                                   IsAccessorFunction(function_kind()) ||
                                   IsConstructor(function_kind())));
   }
@@ skipping 280 matching lines @@
   // the 'eval' call site this scope is the declaration scope.
   bool scope_calls_eval_;
   // This scope uses "arguments".
   bool scope_uses_arguments_;
   // This scope uses "super" property ('super.foo').
   bool scope_uses_super_property_;
   // This scope contains an "use asm" annotation.
   bool asm_module_;
   // This scope's outer context is an asm module.
   bool asm_function_;
+  // This scope's declarations might not be executed in order (e.g., switch).
+  bool scope_nonlinear_;
   // The language mode of this scope.
   LanguageMode language_mode_;
   // Source positions.
   int start_position_;
   int end_position_;
 
   // Computed via PropagateScopeInfo.
   bool outer_scope_calls_sloppy_eval_;
   bool inner_scope_calls_eval_;
   bool inner_scope_uses_arguments_;
@@ skipping 156 matching lines @@
   PendingCompilationErrorHandler pending_error_handler_;
 
   // For tracking which classes are declared consecutively. Needed for strong
   // mode.
   int class_declaration_group_start_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_