Symbol#to_proc should return -1 arity to be compatible with MRI

* Even though it does required at least one argument and so -2 would be
  correct in terms of how many arguments are required.
* Fixes #1462.

Author: eregon

CHANGELOG.md

@@ -15,6 +15,7 @@ Compatibility:
 * Change to a new system for handling Ruby objects in C extensions which
   greatly increases compatibility with MRI.
 * Implemented `BigDecimal#to_r` (#1521).
+* `Symbol#to_proc` now returns `-1` like on MRI (#1462).
 
 # 1.0 RC 11, 15 January 2019
 

src/main/java/org/truffleruby/core/symbol/SymbolNodes.java

@@ -18,6 +18,7 @@
 import com.oracle.truffle.api.frame.MaterializedFrame;
 import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.object.DynamicObject;
+import com.oracle.truffle.api.profiles.BranchProfile;
 import com.oracle.truffle.api.source.SourceSection;
 import org.truffleruby.Layouts;
 import org.truffleruby.builtins.CoreClass;
@@ -27,6 +28,7 @@
 import org.truffleruby.core.proc.ProcOperations;
 import org.truffleruby.core.proc.ProcType;
 import org.truffleruby.core.string.StringNodes;
+import org.truffleruby.language.RubyNode;
 import org.truffleruby.language.RubyRootNode;
 import org.truffleruby.language.SourceIndexLength;
 import org.truffleruby.language.Visibility;
@@ -125,7 +127,7 @@ protected DynamicObject createProc(DeclarationContext declarationContext, Intern
             final SharedMethodInfo sharedMethodInfo = new SharedMethodInfo(
                     sourceSection,
                     method.getLexicalScope(),
-                    Arity.AT_LEAST_ONE,
+                    Arity.REST,
                     null,
                     Layouts.SYMBOL.getString(symbol),
                     0,
@@ -138,7 +140,7 @@ protected DynamicObject createProc(DeclarationContext declarationContext, Intern
             // binding as this simplifies the logic elsewhere in the runtime.
             final MaterializedFrame declarationFrame = Truffle.getRuntime().createMaterializedFrame(args, coreLibrary().getEmptyDescriptor());
             final RubyRootNode rootNode = new RubyRootNode(getContext(), sourceSection, new FrameDescriptor(nil()), sharedMethodInfo,
-                    Translator.sequence(sourceIndexLength, Arrays.asList(Translator.createCheckArityNode(Arity.AT_LEAST_ONE), new SymbolProcNode(Layouts.SYMBOL.getString(symbol)))));
+                    Translator.sequence(sourceIndexLength, Arrays.asList(new CheckReceiverArgumentNode(), new SymbolProcNode(Layouts.SYMBOL.getString(symbol)))));
 
             final CallTarget callTarget = Truffle.getRuntime().createCallTarget(rootNode);
 
@@ -168,6 +170,30 @@ protected DeclarationContext getDeclarationContext(VirtualFrame frame) {
         protected FrameDescriptor getDescriptor(VirtualFrame frame) {
             return frame.getFrameDescriptor();
         }
+
+        /** Not using CheckArityNode as the message is different and arity is reported as -1. */
+        private static class CheckReceiverArgumentNode extends RubyNode {
+
+            private final BranchProfile noReceiverProfile = BranchProfile.create();
+
+            @Override
+            public void doExecuteVoid(VirtualFrame frame) {
+                final int given = RubyArguments.getArgumentsCount(frame);
+
+                if (given == 0) {
+                    noReceiverProfile.enter();
+                    throw new RaiseException(getContext(), coreExceptions().argumentError("no receiver given", this));
+                }
+            }
+
+            @Override
+            public Object execute(VirtualFrame frame) {
+                doExecuteVoid(frame);
+                return nil();
+            }
+
+        }
+
     }
 
     @CoreMethod(names = "to_s")

src/main/java/org/truffleruby/language/methods/Arity.java

@@ -21,7 +21,7 @@ public class Arity {
     public static final String[] NO_KEYWORDS = new String[]{};
     public static final Arity NO_ARGUMENTS = new Arity(0, 0, false);
     public static final Arity ONE_REQUIRED = new Arity(1, 0, false);
-    public static final Arity AT_LEAST_ONE = new Arity(1, 0, true);
+    public static final Arity REST = new Arity(0, 0, true);
 
     private final int preRequired;
     private final int optional;