[interpreter] Remove BytecodeArrayBuilder::Illegal().

src/interpreter/bytecode-array-writer.cc

Index: src/interpreter/bytecode-array-writer.cc
diff --git a/src/interpreter/bytecode-array-writer.cc b/src/interpreter/bytecode-array-writer.cc
index 17d1aedfc698f25613581e61bf8fced5cd5080e0..029688ea58f4ec60e489c45743983a781fcf649b 100644
--- a/src/interpreter/bytecode-array-writer.cc
+++ b/src/interpreter/bytecode-array-writer.cc
@@ -41,6 +41,8 @@ void BytecodeArrayWriter::UpdateSourcePositionTable(
 }
 
 void BytecodeArrayWriter::EmitBytecode(const BytecodeNode* const node) {
+  DCHECK_NE(node->bytecode(), Bytecode::kIllegal);
+
   OperandScale operand_scale = node->operand_scale();
   if (operand_scale != OperandScale::kSingle) {
     Bytecode prefix = Bytecodes::OperandScaleToPrefixBytecode(operand_scale);