Special case Range#max for integer beginning and Float::Infinity end

Popular Ruby libraries such as Rails and Rubocop relying on the
previous behavior, even though it is technically a bug. The
correct behavior is probably raising RangeError, since that is what
an endless range raises.

Related to [Bug #17017]

1 files changed, 9 insertions, 0 deletions

diff --git a/range.c b/range.c
index 124d9faa51..6d507ea124 100644
--- a/range.c
+++ b/range.c
@@ -1255,6 +1255,15 @@ range_max(int argc, VALUE *argv, VALUE range)
             return rb_funcall(e, '-', 1, INT2FIX(1));
         }
         if (RB_INTEGER_TYPE_P(b) && !RB_INTEGER_TYPE_P(e)) {
+            if (RB_TYPE_P(e, T_FLOAT)) {
+                VALUE inf = rb_funcall(e, rb_intern("infinite?"), 0);
+                if (inf != Qnil) {
+                  /* For backwards compatibility, return end if the end
+                   * is Float::Infinity and the beginning is integer.
+                     If end is -Float::Infinity, return nil. */
+                  return(inf == INT2FIX(1) ? e : Qnil);
+                }
+            }
             e = rb_funcall(e, rb_intern("floor"), 0);
         }
         return e;