Issue #12106 has been updated by Shyouhei Urabe.

Status changed from Open to Assigned
Assignee set to Nobuyoshi Nakada

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Bug #12106: Behavior of double splatting of hashes with non symbol key is different according to splatted hash position
https://bugs.ruby-lang.org/issues/12106#change-57495

* Author: Pablo Herrero
* Status: Assigned
* Priority: Normal
* Assignee: Nobuyoshi Nakada
* ruby -v: ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
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When doing double splatting with hash with non symbols keys you get different behaviors according to the position of the hash been splatted:

```ruby
{a: 3, **{b: 1}, **{'b' => 1}}     # Works fine
{a: 3, **{1 => 1}, **{b: 1}}       # Works fine
{3 => 3, **{b: 1}, **{'b' => 1}}   # Works fine
{**{}, a: 3, **{b: 1}, **{1 => 1}} # Works fine

{**{b: 1}, a: 3, **{1 => 1}}       # TypeError: wrong argument type Fixnum (expected Symbol)
{**{'b' => 1}, **{c: 4}}           # TypeError: wrong argument type Fixnum (expected Symbol)
{**{c: 4}, **{'b' => 1}}           # TypeError: wrong argument type Fixnum (expected Symbol)
{**{c: 4}, a: 3, **{'b' => 1}}     # TypeError: wrong argument type Fixnum (expected Symbol)
```

Same thing happens when you double splat inside a message send:


```ruby
puts(a: 3, **{b: 1}, **{'b' => 1})     # Works fine
puts(a: 3, **{1 => 1}, **{b: 1})       # Works fine
puts(3 => 3, **{b: 1}, **{'b' => 1})   # Works fine
puts(**{}, a: 3, **{b: 1}, **{1 => 1}) # Works fine

puts(**{b: 1}, a: 3, **{1 => 1})       # TypeError: wrong argument type Fixnum (expected Symbol)
puts(**{'b' => 1}, **{c: 4})           # TypeError: wrong argument type Fixnum (expected Symbol)
puts(**{c: 4}, **{'b' => 1})           # TypeError: wrong argument type Fixnum (expected Symbol)
puts(**{c: 4}, a: 3, **{'b' => 1})     # TypeError: wrong argument type Fixnum (expected Symbol)
```

What's basically going on is this: you can double splat hashes with no symbol keys all you want, only if the first value of the hash is a regular key (symbol or not) and not a splatted hash, or also a double splatted empty hash.


It feels strange that building the same hash in different orders yields so different behaviors. 
Anyhow, I personally feel it should be a bug if you cannot splat a hash with no symbol keys into another one, whichever are the remaining values of the hash.



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