* numeric.c (do_coerce): Add a warning when an exception is raised

  or an invalid value is returned in #coerce called by
  numeric comparison operators and the exception
  thrown by the caller has no information on the failure.
  In the next release such exception should not be rescued or
  should be the cause of the caller exception. nil is accepted
  as the "no possible coercion" return value. See #7688.
* test/ruby/test_numeric.rb: Add corresponding test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46375 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 15 insertions, 1 deletions

diff --git a/numeric.c b/numeric.c
index 86de28eb6c..f61b1349a6 100644
--- a/numeric.c
+++ b/numeric.c
@@ -251,6 +251,12 @@ coerce_rescue(VALUE *x)
     return Qnil;		/* dummy */
 }
 
+static VALUE
+coerce_rescue_quiet(VALUE *x)
+{
+    return Qundef;
+}
+
 static int
 do_coerce(VALUE *x, VALUE *y, int err)
 {
@@ -266,10 +272,18 @@ do_coerce(VALUE *x, VALUE *y, int err)
 	return FALSE;
     }
 
-    ary = rb_rescue(coerce_body, (VALUE)a, err ? coerce_rescue : 0, (VALUE)a);
+    ary = rb_rescue(coerce_body, (VALUE)a, err ? coerce_rescue : coerce_rescue_quiet, (VALUE)a);
+    if (ary == Qundef) {
+	rb_warn("Numerical comparison operators will no more rescue exceptions of #coerce");
+	rb_warn("in the next release. Return nil in #coerce if the coercion is impossible.");
+	return FALSE;
+    }
     if (!RB_TYPE_P(ary, T_ARRAY) || RARRAY_LEN(ary) != 2) {
 	if (err) {
 	    rb_raise(rb_eTypeError, "coerce must return [x, y]");
+	} else if (!NIL_P(ary)) {
+	    rb_warn("Bad return value for #coerce, called by numerical comparison operators.");
+	    rb_warn("#coerce must return [x, y]. The next release will raise an error for this.");
 	}
 	return FALSE;
     }