[ruby-core:92250] [Ruby trunk Bug#15708] Implicit numbered argument decomposes an array

Issue #15708 has been updated by jeremyevans0 (Jeremy Evans).

File single-implicit-arg-no-destructure.diff added

Attached is a patch that will turn off destructuring if the only implicit block variable is `@1`:

```ruby
# equivalent to proc{|x| x}
proc{@1}.call([1,2])
# => [1, 2]

# equivalent to proc{|_,x| x}
proc{@2}.call([1,2])
# => 2

# equivalent to proc{|x,y| y; x}
proc{@2; @1}.call([1,2])
# => 1
```

I think this results in semantics that most people would expect, even if they don't like the implicit block argument syntax.

----------------------------------------
Bug #15708: Implicit numbered argument decomposes an array
https://bugs.ruby-lang.org/issues/15708#change-77584

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.7.0dev
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
In the following, `@1` refers to the entire item iterated:

```ruby
a = [1, 2, 3]
a.map{|x| x} # => [1, 2, 3]
a.map{@1} # => [1, 2, 3]
```

whereas in the following, `@1` refers to the first item achieved by decomposing the item iterated, behaving the same as `x` given by `|(x)|` rather than by `|x|`:

```ruby
a = [[1], [2], [3]]
a.map{|x| x} # => [[1], [2], [3]]
a.map{|(x)| x} # => [1, 2, 3]
a.map{@1} # => [1, 2, 3]
```

Is this intended?

---Files--------------------------------
single-implicit-arg-no-destructure.diff (471 Bytes)


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