Avoid NullPointerException in --dumpGraphs & test & docs

build.sbt

@@ -989,6 +989,28 @@ lazy val `interpreter-dsl` = (project in file("lib/scala/interpreter-dsl"))
     )
   )
 
+lazy val `interpreter-dsl-test` =
+  (project in file("engine/interpreter-dsl-test"))
+    .configs(Test)
+    .settings(
+      version := "0.1",
+      frgaalJavaCompilerSetting,
+      Test / fork := true,
+      Test / javaOptions ++= Seq(
+        "-Dgraalvm.locatorDisabled=true",
+        s"--upgrade-module-path=${file("engine/runtime/build-cache/truffle-api.jar").absolutePath}"
+      ),
+      commands += WithDebugCommand.withDebug,
+      libraryDependencies ++= Seq(
+        "org.graalvm.truffle" % "truffle-api"           % graalVersion % "provided",
+        "org.graalvm.truffle" % "truffle-dsl-processor" % graalVersion % "provided",
+        "junit"               % "junit"                 % junitVersion % Test,
+        "com.novocode"        % "junit-interface"       % "0.11"       % Test exclude ("junit", "junit-dep")
+      )
+    )
+    .dependsOn(`interpreter-dsl`)
+    .dependsOn(`runtime`)
+
 // ============================================================================
 // === Sub-Projects ===========================================================
 // ============================================================================

engine/interpreter-dsl-test/src/test/java/org/enso/interpreter/dsl/test/InliningBuiltinsInNode.java

@@ -0,0 +1,13 @@
+package org.enso.interpreter.dsl.test;
+
+import com.oracle.truffle.api.nodes.Node;
+import org.enso.interpreter.dsl.BuiltinMethod;
+
+@BuiltinMethod(type = "InliningBuiltins", name = "in")
+final class InliningBuiltinsInNode extends Node {
+
+  long execute(long a, long b) {
+    return a + b;
+  }
+
+}

engine/interpreter-dsl-test/src/test/java/org/enso/interpreter/dsl/test/InliningBuiltinsOutNode.java

@@ -0,0 +1,16 @@
+package org.enso.interpreter.dsl.test;
+
+import com.oracle.truffle.api.frame.VirtualFrame;
+import com.oracle.truffle.api.nodes.Node;
+import org.enso.interpreter.dsl.BuiltinMethod;
+import org.junit.Assert;
+
+@BuiltinMethod(type = "InliningBuiltins", name = "out")
+final class InliningBuiltinsOutNode extends Node {
+
+  long execute(VirtualFrame frame, long a, long b) {
+    Assert.assertNotNull("VirtualFrame is always provided " + frame);
+    return a + b;
+  }
+
+}

engine/interpreter-dsl-test/src/test/java/org/enso/interpreter/dsl/test/InliningBuiltinsTest.java

@@ -0,0 +1,43 @@
+package org.enso.interpreter.dsl.test;
+
+import org.enso.interpreter.node.InlineableRootNode;
+import org.enso.interpreter.runtime.callable.function.Function;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+import org.junit.Test;
+
+public class InliningBuiltinsTest {
+
+  /** @see InliningBuiltinsInNode#execute(long, long) */
+  @Test
+  public void executeWithoutVirtualFrame() {
+    var fn = InliningBuiltinsInMethodGen.makeFunction(null);
+    if (fn.getCallTarget().getRootNode() instanceof InlineableRootNode root) {
+      var call = root.createDirectCallNode();
+      var clazz = call.getClass().getSuperclass();
+      assertEquals("InlinedCallNode", clazz.getSimpleName());
+      assertEquals("BuiltinRootNode", clazz.getEnclosingClass().getSimpleName());
+
+      var res = call.call(Function.ArgumentsHelper.buildArguments(null, null, new Object[] { null, 5L, 7L }));
+      assertEquals(12L, res);
+    } else {
+      fail("It is inlineable: " + fn.getCallTarget().getRootNode());
+    }
+  }
+
+  /** @see InliningBuiltinsOutNode#execute(com.oracle.truffle.api.frame.VirtualFrame, long, long) */
+  @Test
+  public void executeWithVirtualFrame() {
+    var fn = InliningBuiltinsOutMethodGen.makeFunction(null);
+    if (fn.getCallTarget().getRootNode() instanceof InlineableRootNode root) {
+      var call = root.createDirectCallNode();
+      var clazz = call.getClass().getSuperclass();
+      assertEquals("com.oracle.truffle.api.nodes.DirectCallNode", clazz.getName());
+
+      var res = call.call(Function.ArgumentsHelper.buildArguments(null, null, new Object[] { null, 3L, 9L }));
+      assertEquals(12L, res);
+    } else {
+      fail("It is inlineable: " + fn.getCallTarget().getRootNode());
+    }
+  }
+}

engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/BuiltinRootNode.java

@@ -90,7 +90,7 @@ public final boolean cloneCallTarget() {
 
     @Override
     public final CallTarget getClonedCallTarget() {
-      return null;
+      return getRootNode().getCallTarget();
     }
   }
 }

lib/scala/interpreter-dsl/src/main/java/org/enso/interpreter/dsl/BuiltinMethod.java

@@ -5,11 +5,17 @@
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
-/** An annotation denoting a node that should be wrapped for standard library export. */
+/**
+ * An annotation denoting a node that should be wrapped for standard library export. A subclass of
+ * {@code BuiltinRootNode} is generated with implementation of {@code
+ * InlineableRootNode#createDirectCallNode()} that either delegates to regular {@link
+ * DirectCallNode} (when the {@code execute} method requires {@code VirtualFrame} as one of its
+ * arguments) or provides a special implementation, if no {@code VirtualFrame} is needed.
+ */
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.SOURCE)
 public @interface BuiltinMethod {
-  /** @return the language-level type of {@code this} argument. */
+  /** @return the language-level type of {@code self} argument. */
   String type();
 
   /** @return the language-level name of this method. */