ProtoReservedFieldTraitValue must be of exactly one type (#249)

* ProtoReservedFieldTraitValue must be of exactly one type

* add header

Author: benoitlouy

modules/core/src/alloy/proto/ProtoReservedFieldsTraitValue.java

@@ -18,6 +18,9 @@
 import software.amazon.smithy.model.node.*;
 import software.amazon.smithy.utils.SmithyBuilder;
 
+import java.util.stream.Stream;
+import java.util.Objects;
+
 public final class ProtoReservedFieldsTraitValue {
 
 	public static final String NUMBER = "number";
@@ -29,6 +32,13 @@ public final class ProtoReservedFieldsTraitValue {
 	public final Range range;
 
 	public ProtoReservedFieldsTraitValue(Builder builder) {
+		if (Stream.of(
+					builder.number,
+					builder.name,
+					builder.range
+				).filter(Objects::nonNull).count() != 1) {
+			throw new IllegalArgumentException("ProtoReservedFieldsTraitValue must be of exactly one type");
+		}
 		this.number = builder.number;
 		this.name = builder.name;
 		this.range = builder.range;

modules/core/test/src/alloy/proto/ProtoReservedFieldsTraitValueSpec.scala

@@ -0,0 +1,25 @@
+/* Copyright 2022 Disney Streaming
+ *
+ * Licensed under the Tomorrow Open Source Technology License, Version 1.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://disneystreaming.github.io/TOST-1.0.txt
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package alloy.proto
+
+final class ProtoReservedFieldsTraitValueSpec extends munit.FunSuite {
+
+  test("cannot instantiate invalid ProtoReservedFieldsTraitValue") {
+    intercept[IllegalArgumentException](
+      ProtoReservedFieldsTraitValue.builder().build()
+    )
+  }
+}