Bug #15018: NODE_ARGSCAT is not parsed properly

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.6.0dev (2018-08-22 trunk 64505) [x86_64-linux]
• Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN

[chopraanmol1 (Anmol Chopra)]

Instead of wrapping following arguments in one list, current implementation creates multiple list wrapping only 2 elements.

e.g.
for

[*args,1,2,3,4,5,6]

Expected AST:

NODE_ARGSCAT---nd_head-->NODE_SPLAT(args)
|
|---nd_body-->NODE_ARRAY(1,2,3,4,5,6)

Current AST:

NODE_ARGSCAT---nd_head-->NODE_ARGSCAT--nd_head-->NODE_ARGSCAT--nd_head-->NODE_SPLAT(args)
|                          |                          |
|                          |                          |---nd_body-->NODE_ARRAY(1,2)
|                          |
|                          |---nd_body-->NODE_ARRAY(3,4)
|
|---nd_body-->NODE_ARRAY(5,6)

Current Implementation result into something like

args + [1,2] + [3,4] + [5,6]

instead of

args + [1,2,3,4,5,6]

Benchmark result
With patch:

                       user     system      total        real
argscat            0.556000   0.000000   0.556000 (  0.553981)
argscat_multiple   2.372000   0.000000   2.372000 (  2.373701)

Trunk:

                       user     system      total        real
argscat            1.656000   0.000000   1.656000 (  1.655868)
argscat_multiple   6.232000   0.000000   6.232000 (  6.234846)

Implementation:
https://github.com/ruby/ruby/pull/1940

[chopraanmol1 (Anmol Chopra)]

• Description updated (diff)

[mame (Yusuke Endoh)]

• Status changed from Open to Closed

Applied in changeset trunk|r64510.

---

parse.y (arg_append): support NODE_ARGSCAT case

Because of the lack of this case, [*ary,1,2,3,4,5,6] was parsed into
an inefficient AST like ary + [1,2] + [3,4] + [5,6].

A patch from Anmol Chopra [e-mail].
Fixes [Bug #15018].

[mame (Yusuke Endoh)]

Good catch! I've committed it. Thank you!