Fix Integer#div returning wrong type with a Rational divisor.

Co-authored-by: Simon LeVasseur <simon.levasseur@shopify.com>

Author: nirvdrum

CHANGELOG.md

@@ -18,6 +18,7 @@ Bug fixes:
 * Fix `Range#bsearch` and raise `TypeError` when range boundaries are non-numeric and block not passed (@andrykonchin).
 * Fix using the `--cpusampler` profiler when there are custom unblock functions for `rb_thread_call_without_gvl()` (#3013, @eregon).
 * Fix recursive raising `FrozenError` exception when redefined `#inspect` modifies an object (#3388, @andrykonchin).
+* Fix `Integer#div` returning the wrong object type when the divisor is a `Rational` (@simonlevasseur, @nirvdrum).
 
 Compatibility:
 

spec/ruby/core/integer/div_spec.rb

@@ -143,4 +143,12 @@
       -> { @bignum.div(-0) }.should raise_error(ZeroDivisionError)
     end
   end
+
+  context "rational" do
+    it "returns self divided by the given argument as an Integer" do
+      2.div(6/5r).should == 1
+      1.div(6/5r).should == 0
+      5.div(6/5r).should == 4
+    end
+  end
 end

src/main/java/org/truffleruby/core/numeric/IntegerNodes.java

@@ -49,6 +49,7 @@
 import org.truffleruby.language.NoImplicitCastsToLong;
 import org.truffleruby.language.NotProvided;
 import org.truffleruby.language.RubyBaseNode;
+import org.truffleruby.language.RubyGuards;
 import org.truffleruby.language.WarnNode;
 import org.truffleruby.language.control.RaiseException;
 import org.truffleruby.language.dispatch.DispatchNode;
@@ -495,15 +496,18 @@ public abstract static class IDivNode extends CoreMethodArrayArgumentsNode {
         @Specialization
         Object idiv(Object a, Object b,
                 @Cached InlinedConditionProfile zeroProfile,
-                @Cached FloatToIntegerNode floatToIntegerNode) {
+                @Cached FloatToIntegerNode floatToIntegerNode,
+                @Cached DispatchNode floorNode) {
             Object quotient = divNode.executeDiv(a, b);
             if (quotient instanceof Double) {
                 if (zeroProfile.profile(this, (double) b == 0.0)) {
                     throw new RaiseException(getContext(), coreExceptions().zeroDivisionError(this));
                 }
                 return floatToIntegerNode.execute(this, Math.floor((double) quotient));
-            } else {
+            } else if (RubyGuards.isRubyInteger(quotient)) {
                 return quotient;
+            } else {
+                return floorNode.call(quotient, "floor");
             }
         }