Make Error.prototype.toString spec compliant; and fix various side-effect-free error printing metho…

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index 1eda493d6e5d7880e709824e659c4958319a2cca..cf5dd29b66ed448d6c59891996749a08eed92eb2 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -1154,7 +1154,13 @@ bool Scope::ResolveVariable(ParseInfo* info, VariableProxy* proxy,
     //  - Variables must not be allocated to the global scope.
     CHECK_NOT_NULL(outer_scope());
     //  - Variables must be bound locally or unallocated.
-    CHECK_EQ(BOUND, binding_kind);
+    if (BOUND != binding_kind) {
+      // The following variable name may be minified. If so, disable
+      // minification in js2c.py for better output.
+      Handle<String> name = proxy->raw_name()->string();
+      V8_Fatal(__FILE__, __LINE__, "Unbound variable: '%s' in native script.",
+               name->ToCString().get());
+    }
     VariableLocation location = var->location();
     CHECK(location == VariableLocation::LOCAL ||
           location == VariableLocation::CONTEXT ||