Bug #16293: Numbered parameter confirmation in Ruby 2.7

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN

[osyo (manga osyo)]

Overview

I want to make a final check on the behavior of Numbered parameter( No warning or Warning or Error).
There is a difference in DevelopersMeeting20190829Japan logs and behavior.

Ruby version

p RUBY_VERSION
# => "2.7.0"
p RUBY_DESCRIPTION
# => "ruby 2.7.0dev (2019-11-02T06:32:49Z trunk 772b0613c5) [x86_64-linux]"
p RUBY_RELEASE_DATE
# => "2019-11-02"
p RUBY_REVISION
# => "772b0613c583773cd2eda23bce8275926a351e79"

DevelopersMeeting20190829Japan logs

• local variables (parameters and assigned variable) → force warning (Don’t use) on Ruby 2.7 and syntax error on Ruby 3.
• method invocation
  • vcall: x = _0 # expect _0() outside block. → force warning on Ruby 2.7 and syntax error on Ruby 3.
  • vcall: 1.times{ _0 } → block parameter (incompatibility)
  • vcall: 1.times{|i| _0 } → force warning on Ruby 2.7 and syntax error on Ruby 3.
• method invocation (x = _0(), x = foo._0) → no warning
• method name (def _0(); end) → no warning

Proposal

def _1; end

# expected: warning: `_1' is used as numbered parameter
# actual: No warning
# reason: Because "`x = _0 # expect _0()` outside block. → force warning on Ruby 2.7 and syntax error on Ruby 3" is written in the log
x = _1

# expected: warning: `_1' is used as numbered parameter
#           and call to _1()
# actual: Error: numbered parameter outside block (SyntaxError)
# reason: Because hoge() method is called with `eval("hoge")`
eval("_1")

def _1; end

# expected: warning: `_1' is used as numbered parameter
#           and call to _1()
# actual: Error: ordinary parameter is defined
# reason: Because "`1.times{|i| _0 }` → force warning on Ruby 2.7 and syntax error on Ruby 3." is written in the log
proc { |i| _1 }.call 42

# expected: warning: `_1' is used as numbered parameter
# actual: No warning
# reason: Because define local variable _1 is warning
def hgoe(_1)
end

proc {
  # Warning
  _1 = 42
}

proc {
  _1
  # expected: warning: `_1' is used as numbered parameter
  # actual: No warning
  # reason: Because define local variable _1 is warning
  _1 = 42
}

:MEMO: Other behavior

• Other current behavior : https://gist.github.com/osyo-manga/f332ba1f31dbc3a437acd4d86d7986dc
• Is there any other syntax to change No warning Warning Error ?
• Considering compatibility, make it Warning instead of Error ?

Are there other edge cases for Numbered parameter?
Thank you :)

[hsbt (Hiroshi SHIBATA)]

I couldn't understand your request. Please summarize actual and expect behavior with your request.

[mame (Yusuke Endoh)]

It is difficult for me to analyze this ticket, too. Could you write your expectations and the actual results?

# expected: warning: `_1' is used as numbered parameter
# actual: no warning
def hgoe(_1)
end

def _1; end

# expected: warning: `_1' is used as numbered parameter
# actual: no warning
x = _1

It would be good to write the reason why you expect so. But firstly I need to understand what you expect.

[shevegen (Robert A. Heiler)]

The present behaviour:

def _1; end

seems correct and osyo's example of expecting a warning instead seems incorrect to me, unless
he meant it in in some other context. (It is indeed difficult to break the suggestion down
since it is so long. On a semi-related note, I know understand the ruby core team when it
encourages ruby users to explain what they want to see discussed at a developer meeting,
since they have to understand it first. I picture a round of question marks on the
faces ... ;))

[osyo (manga osyo)]

• Description updated (diff)

[osyo (manga osyo)]

Thank you all.
I updated text.

[nobu (Nobuyoshi Nakada)]

• Tracker changed from Feature to Bug
• Backport set to 2.5: UNKNOWN, 2.6: UNKNOWN

def _1; end

# expected: warning: `_1' is used as numbered parameter
# actual: No warning
# reason: Because "`x = _0 # expect _0()` outside block. → force warning on Ruby 2.7 and syntax error on Ruby 3" is written in the log
x = _1

The "outside block" warning is shown at assignment to a local variable looks like a numbered parameter.
There is no assignment.

# expected: warning: `_1' is used as numbered parameter
#           and call to _1()
# actual: Error: numbered parameter outside block (SyntaxError)
# reason: Because hoge() method is called with `eval("hoge")`
eval("_1")

This is a bug.
As numbered parameter looks like an ordinary variable now, the warning doesn't make sense.

def _1; end

# expected: warning: `_1' is used as numbered parameter
#           and call to _1()
# actual: Error: ordinary parameter is defined
# reason: Because "`1.times{|i| _0 }` → force warning on Ruby 2.7 and syntax error on Ruby 3." is written in the log
proc { |i| _1 }.call 42

The method is irrelevant, Ruby doesn't know if it is defined or not until calling it.
And _1 in a block is considered as a numbered parameter, it conflicts with |i|.

# expected: warning: `_1' is used as numbered parameter
# actual: No warning
# reason: Because define local variable _1 is warning
def hgoe(_1)
end

It is outside block.

proc {
  # Warning
  _1 = 42
}

proc {
  _1
  # expected: warning: `_1' is used as numbered parameter
  # actual: No warning
  # reason: Because define local variable _1 is warning
  _1 = 42
}

This is a bug.
It must be a syntax error.
It was a syntax error in old versions actually.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|82e840ad15bba42b399a21de746967a731240ec2.

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Numbered parameter cannot appear outside block now [Bug #16293]