[ClientCore] Introduce Union type

sdk/clientcore/core/checkstyle-suppressions.xml

@@ -19,6 +19,7 @@
   <suppress files="io.clientcore.core.implementation.util.ImplUtils.java" checks="MissingJavadocTypeCheck" />
   <suppress files="io.clientcore.core.implementation.instrumentation.Slf4jLoggerShim.java" checks="com.azure.tools.checkstyle.checks.EnforceFinalFieldsCheck" />
   <suppress files="io.clientcore.core.implementation.util.EnvironmentConfiguration.java" checks="com.azure.tools.checkstyle.checks.EnforceFinalFieldsCheck" />
+  <suppress files="io.clientcore.core.util.Union.java" checks="com.azure.tools.checkstyle.checks.EnforceFinalFieldsCheck" />
   <suppress files="io.clientcore.core.implementation.ReflectionSerializable.java" checks="com.azure.tools.checkstyle.checks.JavadocThrowsChecks" />
   <suppress files="io.clientcore.core.implementation.http.serializer.HttpResponseBodyDecoder.java" checks="com.azure.tools.checkstyle.checks.JavadocThrowsChecks" />
   <suppress files="io.clientcore.core.http.client.DefaultHttpClientBuilder.java" checks="com.azure.tools.checkstyle.checks.ServiceClientBuilderCheck" />

sdk/clientcore/core/spotbugs-exclude.xml

@@ -35,7 +35,9 @@
       <Class name="io.clientcore.core.implementation.util.XmlSerializer" />
       <Class name="io.clientcore.core.serialization.xml.XmlReader" />
       <Class name="io.clientcore.core.shared.HttpClientTests" />
+      <Class name="io.clientcore.core.implementation.GenericParameterizedType" />
       <Class name="io.clientcore.core.util.SharedExecutorService" />
+      <Class name="io.clientcore.core.util.Union" />
       <Class name="io.clientcore.core.util.binarydata.FileBinaryData" />
       <Class name="io.clientcore.core.util.binarydata.InputStreamBinaryData" />
       <Class name="io.clientcore.core.util.binarydata.ListByteBufferBinaryData" />
@@ -280,6 +282,10 @@
     <Bug pattern="RV_RETURN_VALUE_IGNORED_BAD_PRACTICE" />
     <Class name="io.clientcore.core.http.client.implementation.InputStreamTimeoutResponseSubscriber" />
   </Match>
+  <Match>
+    <Bug pattern="RV_RETURN_VALUE_IGNORED_INFERRED" />
+    <Class name="io.clientcore.core.util.UnionTests" />
+  </Match>
   <Match>
     <Bug pattern="RV_RETURN_VALUE_IGNORED_NO_SIDE_EFFECT" />
     <Class name="io.clientcore.core.serialization.xml.XmlReaderCodesnippetsTests" />

sdk/clientcore/core/src/main/java/io/clientcore/core/implementation/GenericParameterizedType.java

@@ -0,0 +1,88 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package io.clientcore.core.implementation;
+
+import io.clientcore.core.instrumentation.logging.ClientLogger;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+/**
+ * A {@link ParameterizedType} implementation that allows for reference type arguments.
+ */
+public final class GenericParameterizedType implements ParameterizedType {
+    private static final ClientLogger LOGGER = new ClientLogger(GenericParameterizedType.class);
+
+    private final Class<?> raw;
+    private final Type[] args;
+    private String cachedToString;
+
+    /**
+     * Creates a new instance of {@link GenericParameterizedType}.
+     *
+     * @param raw The raw type.
+     * @param args The type arguments.
+     */
+    public GenericParameterizedType(Class<?> raw, Type... args) {
+        this.raw = raw;
+
+        if (args == null) {
+            throw LOGGER.logThrowableAsError(new IllegalArgumentException("args cannot be null"));
+        }
+
+        Type[] argsCopy = new Type[args.length];
+        for (int i = 0; i < args.length; i++) {
+            if (args[i] == null) {
+                throw LOGGER.logThrowableAsError(
+                    new IllegalArgumentException("args cannot contain null: null value in index " + i));
+            }
+            argsCopy[i] = args[i];
+        }
+        this.args = argsCopy;
+    }
+
+    @Override
+    public Type[] getActualTypeArguments() {
+        return args;
+    }
+
+    @Override
+    public Type getRawType() {
+        return raw;
+    }
+
+    @Override
+    public Type getOwnerType() {
+        return null;
+    }
+
+    @Override
+    public String toString() {
+        if (cachedToString == null) {
+            cachedToString = raw.getTypeName() + "<"
+                + Arrays.stream(args).map(Type::getTypeName).collect(Collectors.joining(", ")) + ">";
+        }
+        return cachedToString;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        GenericParameterizedType that = (GenericParameterizedType) o;
+        return Objects.equals(raw, that.raw) && Objects.deepEquals(args, that.args);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(raw, Arrays.hashCode(args));
+    }
+}