Fix enumeration issue in ENV.{select, filter} when no block is given

Author: bjfish

CHANGELOG.md

@@ -55,6 +55,7 @@ Bug fixes:
 * Made `Kernel#caller_locations` accept a range argument, and return `nil` when appropriate.
 * Made `rb_respond_to` work with primitives (#1869, @chrisseaton).
 * Fixed issue with missing backtrace for `rescue $ERROR_INFO` (#1660).
+* Fixed enumeration issue in `ENV.{select, filter}`.
 
 Compatibility:
 

spec/tags/core/env/filter_tags.txt

@@ -240,7 +240,7 @@ def replace(other)
   end
 
   def select(&blk)
-    return to_enum { size } unless block_given?
+    return to_enum(:select) { size } unless block_given?
     to_hash.select(&blk)
   end
   alias_method :filter, :select