Clean up dead code after spread desugaring

src/interpreter/bytecode-generator.cc

 // Copyright 2015 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/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-register-allocator.h"
 #include "src/interpreter/control-flow-builders.h"
@@ skipping 1179 matching lines @@
                                 expr->ComputeFlags(true));
   Register index, literal;
 
   // Evaluate all the non-constant subexpressions and store them into the
   // newly cloned array.
   bool literal_in_accumulator = true;
   for (int array_index = 0; array_index < expr->values()->length();
        array_index++) {
     Expression* subexpr = expr->values()->at(array_index);
     if (CompileTimeValue::IsCompileTimeValue(subexpr)) continue;
-    if (subexpr->IsSpread()) {
-      // TODO(rmcilroy): Deal with spread expressions.
-      UNIMPLEMENTED();
-    }
+    DCHECK(!subexpr->IsSpread());
 
     if (literal_in_accumulator) {
       index = register_allocator()->NewRegister();
       literal = register_allocator()->NewRegister();
       builder()->StoreAccumulatorInRegister(literal);
       literal_in_accumulator = false;
     }
 
     FeedbackVectorSlot slot = expr->LiteralFeedbackSlot();
     builder()
@@ skipping 1002 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8