Fix Float#<=> when other responds to infinite?

Fixes `cmp` to support comparing infinity to rhs which responds to `infinite?`, and updates the spec to current upstream comparison spec.

spec/core/float/comparison_spec.rb

@@ -4,7 +4,7 @@
   it "returns -1, 0, 1 when self is less than, equal, or greater than other" do
     (1.5 <=> 5).should == -1
     (2.45 <=> 2.45).should == 0
-    #((bignum_value*1.1) <=> bignum_value).should == 1
+    ((bignum_value*1.1) <=> bignum_value).should == 1
   end
 
   it "returns nil when either argument is NaN" do
@@ -14,6 +14,9 @@
 
   it "returns nil when the given argument is not a Float" do
     (1.0 <=> "1").should be_nil
+    (1.0 <=> "1".freeze).should be_nil
+    (1.0 <=> :one).should be_nil
+    (1.0 <=> true).should be_nil
   end
 
   it "compares using #coerce when argument is not a Float" do
@@ -48,7 +51,7 @@ def coerce(other)
 
   # The 4 tests below are taken from matz's revision 23730 for Ruby trunk
   #
-  it "returns 1 when self is Infinity and other is a Bignum" do
+  it "returns 1 when self is Infinity and other is an Integer" do
     (infinity_value <=> Float::MAX.to_i*2).should == 1
   end
 
@@ -63,4 +66,43 @@ def coerce(other)
   it "returns 1 when self is negative and other is -Infinity" do
     (-Float::MAX.to_i*2 <=> -infinity_value).should == 1
   end
+
+  it "returns 0 when self is Infinity and other other is infinite?=1" do
+    obj = Object.new
+    def obj.infinite?
+      1
+    end
+    (infinity_value <=> obj).should == 0
+  end
+
+  it "returns 1 when self is Infinity and other is infinite?=-1" do
+    obj = Object.new
+    def obj.infinite?
+      -1
+    end
+    (infinity_value <=> obj).should == 1
+  end
+
+  it "returns 1 when self is Infinity and other is infinite?=nil (which means finite)" do
+    obj = Object.new
+    def obj.infinite?
+        nil
+    end
+    (infinity_value <=> obj).should == 1
+  end
+
+  it "returns 0 for -0.0 and 0.0" do
+    (-0.0 <=> 0.0).should == 0
+    (0.0 <=> -0.0).should == 0
+  end
+
+  it "returns 0 for -0.0 and 0" do
+    (-0.0 <=> 0).should == 0
+    (0 <=> -0.0).should == 0
+  end
+
+  it "returns 0 for 0.0 and 0" do
+    (0.0 <=> 0).should == 0
+    (0 <=> 0.0).should == 0
+  end
 end

src/float_object.cpp

@@ -136,11 +136,23 @@ Value FloatObject::to_s() const {
 }
 
 Value FloatObject::cmp(Env *env, Value rhs) {
-    if (is_infinity() && rhs->is_integer() && rhs->as_integer()->is_bignum()) {
-        if (is_positive_infinity())
-            return Value::integer(1);
-        else
+    if (is_infinity()) {
+        if (rhs->is_integer() && rhs->as_integer()->is_bignum()) {
+            if (is_positive_infinity()) return Value::integer(1);
             return Value::integer(-1);
+        }
+
+        auto is_infinite_symbol = "infinite?"_s;
+        if (rhs->respond_to(env, is_infinite_symbol)) {
+            auto rhs_infinite = rhs.send(env, is_infinite_symbol);
+            if (rhs_infinite->is_nil()) {
+                if (is_positive_infinity()) return Value::integer(1);
+                return Value::integer(-1);
+            }
+            auto rhs_infinite_int = rhs_infinite->as_integer()->to_nat_int_t();
+            int rhs_cmp = is_positive_infinity() ? (rhs_infinite_int > 0 ? 0 : 1) : (rhs_infinite_int < 0 ? 0 : -1);
+            return Value::integer(rhs_cmp);
+        }
     }
 
     Value lhs = this;