Clean up dead code after spread desugaring

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index 9698773dda5693dc1b7c36b50d0388e15a05373e..6e9b454e8cf19171a712e7774bf3af96af8ddfda 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -1197,10 +1197,7 @@ void BytecodeGenerator::VisitArrayLiteral(ArrayLiteral* expr) {
        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();