Fix arity of rb_define_method()-defined methods

Author: eregon

spec/tags/optional/capi/module_tags.txt

@@ -1334,7 +1334,7 @@ private RubySymbol defineMethod(RubyModule module, String name, RubyProc proc,
                 MaterializedFrame callerFrame) {
             final RootCallTarget callTargetForLambda = proc.callTargets.getCallTargetForLambda();
             final RubyLambdaRootNode rootNode = RubyLambdaRootNode.of(callTargetForLambda);
-            final SharedMethodInfo info = proc.getSharedMethodInfo().forDefineMethod(module, name);
+            final SharedMethodInfo info = proc.getSharedMethodInfo().forDefineMethod(module, name, proc);
             final RubyNode body = rootNode.copyBody();
             final RubyNode newBody = new CallMethodWithLambdaBody(isSingleContext() ? proc : null,
                     callTargetForLambda, body);

src/main/java/org/truffleruby/core/module/ModuleNodes.java

@@ -12,6 +12,7 @@
 import org.truffleruby.RubyLanguage;
 import org.truffleruby.core.klass.RubyClass;
 import org.truffleruby.core.module.RubyModule;
+import org.truffleruby.core.proc.RubyProc;
 import org.truffleruby.language.LexicalScope;
 import org.truffleruby.language.RubyDynamicObject;
 import org.truffleruby.language.RubyGuards;
@@ -60,16 +61,16 @@ public SharedMethodInfo(
         this.argumentDescriptors = argumentDescriptors;
     }
 
-    public SharedMethodInfo forDefineMethod(RubyModule declaringModule, String methodName) {
+    public SharedMethodInfo forDefineMethod(RubyModule declaringModule, String methodName, RubyProc proc) {
         return new SharedMethodInfo(
                 sourceSection,
                 staticLexicalScope,
-                arity,
+                proc.arity,
                 methodName,
                 0, // no longer a block
                 moduleAndMethodName(declaringModule, methodName),
                 null,
-                argumentDescriptors);
+                proc.argumentDescriptors);
     }
 
     public SharedMethodInfo convertMethodMissingToMethod(RubyModule declaringModule, String methodName) {