[Bug #18937] Coerce non-real non-Numeric into Complex at comparisons

complex.c

@@ -1124,15 +1124,23 @@ nucomp_cmp(VALUE self, VALUE other)
     if (!k_numeric_p(other)) {
         return rb_num_coerce_cmp(self, other, idCmp);
     }
-    if (nucomp_real_p(self)) {
-        if (RB_TYPE_P(other, T_COMPLEX) && nucomp_real_p(other)) {
+    if (!nucomp_real_p(self)) {
+        return Qnil;
+    }
+    if (RB_TYPE_P(other, T_COMPLEX)) {
+        if (nucomp_real_p(other)) {
             get_dat2(self, other);
             return rb_funcall(adat->real, idCmp, 1, bdat->real);
         }
-        else if (f_real_p(other)) {
-            get_dat1(self);
+    }
+    else {
+        get_dat1(self);
+        if (f_real_p(other)) {
             return rb_funcall(dat->real, idCmp, 1, other);
         }
+        else {
+            return rb_num_coerce_cmp(dat->real, other, idCmp);
+        }
     }
     return Qnil;
 }

test/ruby/test_complex.rb

@@ -568,19 +568,23 @@ class Complex_Test < Test::Unit::TestCase
   end
 
   class ObjectX
-    def +(x) Rational(1) end
+    def initialize(real = true, n = 1) @n = n; @real = real; end
+    def +(x) Rational(@n) end
     alias - +
     alias * +
     alias / +
     alias quo +
     alias ** +
-    def coerce(x) [x, Complex(1)] end
+    def coerce(x) [x, Complex(@n)] end
+    def real?; @real; end
   end
 
   def test_coerce2
     x = ObjectX.new
+    y = ObjectX.new(false)
     %w(+ - * / quo ** <=>).each do |op|
-      assert_kind_of(Numeric, Complex(1).__send__(op, x))
+      assert_kind_of(Numeric, Complex(1).__send__(op, x), op)
+      assert_kind_of(Numeric, Complex(1).__send__(op, y), op)
     end
   end