From: eregontp@...
Date: 2019-11-02T12:56:05+00:00
Subject: [ruby-core:95653] [Ruby master Feature#16289] Reduce duplicated warnings for the change of Ruby 3 keyword arguments

Issue #16289 has been updated by Eregon (Benoit Daloze).


What's the performance with this patch for a call site that would warn?

```
$ chruby ruby-2.7.0-preview2
$ ruby -rbenchmark/ips -e 'def m(**kw); end; h = {a: 1}; Benchmark.ips { |x| x.report { m(h) } }' 2>/dev/null 
Warming up --------------------------------------
                        46.040k i/100ms
Calculating -------------------------------------
                        504.460k (� 7.0%) i/s -      2.532M in   5.050515s

$ chruby 2.6.2
$ ruby -rbenchmark/ips -e 'def m(**kw); end; h = {a: 1}; Benchmark.ips { |x| x.report { m(h) } }' 
Warming up --------------------------------------
                       322.637k i/100ms
Calculating -------------------------------------
                          5.925M (� 8.8%) i/s -     29.683M in   5.055851s
```

----------------------------------------
Feature #16289: Reduce duplicated warnings for the change of Ruby 3 keyword arguments
https://bugs.ruby-lang.org/issues/16289#change-82441

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
## Problem

Currently, the interpreter emits 200 lines of warnings against the following program.

```ruby
def foo(**opt); end
100.times { foo({kw:1}) }
```

```
$ ./miniruby -e 'def foo(**opt); end; 100.times { foo({kw:1}) }'
-e:1: warning: The last argument is used as the keyword parameter
-e:1: warning: for `foo' defined here
-e:1: warning: The last argument is used as the keyword parameter
-e:1: warning: for `foo' defined here
-e:1: warning: The last argument is used as the keyword parameter
-e:1: warning: for `foo' defined here
...
```

In theory, the warnings are not harmful because they don't stop or interfere the execution.  But in practice, I'm afraid if they are annoying because they flush all console logs away.
I think that the warning is not needed if the call is already warned.


## Proposal

How about limiting the count of warnings to at most once for each pair of caller and callee?

I've created [a pull request](https://github.com/ruby/ruby/pull/2458).  It records all pairs of caller position and callee iseq when emitting a warning, and suppress the warning if the same pair of caller and callee is already warned.

What do you think?



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