[GR-20432] Implement ENV.slice method.

PullRequest: truffleruby/1241

Author: eregon

CHANGELOG.md

@@ -89,6 +89,8 @@ Compatibility:
 * Implemented `-n` CLI option (#1532).
 * Cache the `Symbol` of method names in call nodes only when needed (#1872).
 * Implemented `rb_get_alloc_func` and related functions (#1874, @XrXr).
+* Implemented `rb_module_new`, `rb_define_class_id`, `rb_define_module_id`, (#1876, @chrisseaton).
+* Implemented `ENV.slice`.
 
 Performance:
 

spec/tags/core/env/slice_tags.txt

@@ -315,6 +315,17 @@ def rassoc(value)
     key ? [key, value] : nil
   end
 
+  def slice(*keys)
+    result = {}
+    keys.each do |k|
+      value = lookup(k)
+      unless value.nil?
+        result[k] = value
+      end
+    end
+    result
+  end
+
   def set_encoding(value)
     return unless value.kind_of? String
     if Encoding.default_internal && value.ascii_only?