substitute() returns symbol for missing argument

com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/Substitute.java

 /*
- * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -57,6 +57,11 @@ public abstract class Substitute extends RBuiltinNode.Arg2 {
         casts.arg(1).defaultError(INVALID_ENVIRONMENT_SPECIFIED).allowNullAndMissing().mustBe(instanceOf(RAbstractListVector.class).or(instanceOf(REnvironment.class)));
     }
 
+    @Specialization
+    protected Object doSubstitute(VirtualFrame frame, @SuppressWarnings("unused") RMissing exprMissing, @SuppressWarnings("unused") RMissing envMissing) {
+        return RSymbol.MISSING;
+    }
+
     @Specialization
     protected Object doSubstitute(VirtualFrame frame, RPromise expr, @SuppressWarnings("unused") RMissing envMissing) {
         return doSubstituteWithEnv(expr, REnvironment.frameToEnvironment(frame.materialize()));

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/builtins/TestBuiltin_substitute.java

@@ -4,7 +4,7 @@
  * http://www.gnu.org/licenses/gpl-2.0.html
  *
  * Copyright (c) 2012-2014, Purdue University
- * Copyright (c) 2013, 2017, Oracle and/or its affiliates
+ * Copyright (c) 2013, 2018, Oracle and/or its affiliates
  *
  * All rights reserved.
  */
@@ -138,5 +138,7 @@ public class TestBuiltin_substitute extends TestBase {
         assertEval("{ foo <- function(...) bar(3+2); bar <- function(...) { ..1; substitute(..1); }; foo(1+2); }");
         assertEval("{ foo <- function(...) bar(3+2); bar <- function(...) { substitute(list(...)); }; foo(1+2); }");
         assertEval("{ foo <- function(...) bar(3+2); bar <- function(...) { list(...); substitute(list(...)); }; foo(1+2); }");
+
+        assertEval("typeof(substitue())");
     }
 }