From: nobu@...
Date: 2018-08-29T14:12:45+00:00
Subject: [ruby-core:88733] [Ruby trunk Bug#15027] When Struct#each method is overriden Struct#select and Struct#to_a use wrong collections

Issue #15027 has been updated by nobu (Nobuyoshi Nakada).


```diff
diff --git a/struct.c b/struct.c
index 7de46980aa..e4c875b5be 100644
--- a/struct.c
+++ b/struct.c
@@ -860,6 +860,9 @@ rb_struct_inspect(VALUE s)
 static VALUE
 rb_struct_to_a(VALUE s)
 {
+    if (!rb_method_basic_definition_p(CLASS_OF(s), idEach)) {
+        return rb_call_super(0, 0);
+    }
     return rb_ary_new4(RSTRUCT_LEN(s), RSTRUCT_CONST_PTR(s));
 }
 
@@ -1077,6 +1080,9 @@ rb_struct_select(int argc, VALUE *argv, VALUE s)
 
     rb_check_arity(argc, 0, 0);
     RETURN_SIZED_ENUMERATOR(s, 0, 0, struct_enum_size);
+    if (!rb_method_basic_definition_p(CLASS_OF(s), idEach)) {
+        return rb_call_super(argc, argv);
+    }
     result = rb_ary_new();
     for (i = 0; i < RSTRUCT_LEN(s); i++) {
 	if (RTEST(rb_yield(RSTRUCT_GET(s, i)))) {
```

----------------------------------------
Bug #15027: When Struct#each method is overriden Struct#select and Struct#to_a use wrong collections
https://bugs.ruby-lang.org/issues/15027#change-73788

* Author: bruno (Bruno Sutic)
* Status: Feedback
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.6.0dev
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
### Bug

Here's the code snippet that should reproduce the problem:

~~~ ruby
class Foo < Struct.new(:bar)
  def each(&block)
    [:baz, :qux].each(&block)
  end
end

foo = Foo.new(:foo)
foo.map(&:itself) # => [:baz, :qux]  # OK

foo.to_a # => [:foo]  # NOT OK, expected [:baz, :qux]
foo.select(&:itself) # => [:foo]  # NOT OK, expected [:baz, :qux]
~~~

As you can see, even tho we defined another collection for use by overriding `#each`, the `to_a` and `select` still use `Struct`'s original collection.

The problem seem to be with `Struct#to_a` and `Struct#select` methods from `struct.c` file that are defined unnecessarily.

### Proposed solution

The attached solution simply deletes `Struct#select` and `Struct#to_a`. A couple tests are added to show everything still works as before.

Please let me know if I can provide any more info and I'll be ready to do so.

---Files--------------------------------
struct_enumerable_fix.patch (2.8 KB)


-- 
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