Ensure hole checks take place in switch statement scopes

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 97606a745bf563dc9e152071edb69e2f4a2dd85d..d30a95cda05584b8ec427ca3e39691a9ffb40dea 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -224,6 +224,13 @@ class Scope: public ZoneObject {
   // 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.
+  void SetNonlinear() { scope_nonlinear_ = true; }

[Michael Starzinger, 2015/08/26 11:30:30]

Isn't it necessary to serialize this flag into the ScopeInfo? Adding Andreas
whose scoping foo is clearly superior to mine.

[rossberg, 2015/08/26 12:07:58]

Indeed, AFAICS this flag needs to be de/serialized in scopeinfos, otherwise
lazily compiled local functions inside switch blocks will still miss hole
checks. A test for that case would be good, too.

[Dan Ehrenberg, 2015/08/27 01:40:49]

Well, that issue won't hit fullcodegen, as hole checks are only eliminated
within a particular block scope. Would it hurt any other compiler? I can't
figure out how to trigger it in TF.

+
   // Position in the source where this scope begins and ends.
   //
   // * For the scope of a with statement
@@ -308,6 +315,8 @@ class Scope: public ZoneObject {
   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; }
@@ -601,6 +610,8 @@ class Scope: public ZoneObject {
   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.