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 959e15514976132c32a0292e367ba17ea3b23d5e..ab97e38a34f95a710b3c1c578aea2a508c882fab 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -1156,10 +1156,7 @@ 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();