[ruby-core:95760] [Ruby master Bug#16334] Wrong line numbers for multiline method chains

[mame@ruby-lang.org]

Issue #16334 has been updated by mame (Yusuke Endoh).


A new line number counting mechanism was introduced at 2.6.  The patch would be too big to backport to 2.5.  @usa, what do you think?

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Bug #16334: Wrong line numbers for multiline method chains 
https://bugs.ruby-lang.org/issues/16334#change-82578

* Author: ViugiNick (Nickolay Viuginov)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
I faced a strange distribution of line numbers in bytecode for multiline expressions like this:
```
class Test
  def method1
    self
  end

  def method2
    self
  end

  def method3
    true
  end
end
def hello
  Test.new #bp here
      .method1 #bp here
      .method2 #bp here
      .method3 #bp here
end
```
2.3.7 bytecode:
```
== disasm: #<ISeq:hello@/home/viuignick/.RubyMine2019.2/config/scratches/scratch.rb>
0000 trace            8                                               (  14)
0002 trace            1                                               (  18)
0004 getinlinecache   11, <is:0>                                      (  15)
0007 getconstant      :Test
0009 setinlinecache   <is:0>
0011 opt_send_without_block <callinfo!mid:new, argc:0, ARGS_SIMPLE>, <callcache>(  16)
0014 opt_send_without_block <callinfo!mid:method1, argc:0, ARGS_SIMPLE>, <callcache>(  17)
0017 opt_send_without_block <callinfo!mid:method2, argc:0, ARGS_SIMPLE>, <callcache>(  18)
0020 opt_send_without_block <callinfo!mid:method3, argc:0, ARGS_SIMPLE>, <callcache>
0023 trace            16                                              (  19)
0025 leave                                                            (  18)
```
As you can see there is no trace line-event instuction for line №15, because of that debuggers will not stop there. Furthermore call of the method `new` is on the line #16(actually 15), method method1 is on the line 17(actually 16), method2 is on the line 18 (actually 19)

2.5.4 bytecode
```
0000 getinlinecache   7, <is:0>                                       (  15)[LiCa]
0003 getconstant      :Test
0005 setinlinecache   <is:0>
0007 opt_send_without_block <callinfo!mid:new, argc:0, ARGS_SIMPLE>, <callcache>(  16)
0010 opt_send_without_block <callinfo!mid:method1, argc:0, ARGS_SIMPLE>, <callcache>(  17)
0013 opt_send_without_block <callinfo!mid:method2, argc:0, ARGS_SIMPLE>, <callcache>(  18)
0016 opt_send_without_block <callinfo!mid:method3, argc:0, ARGS_SIMPLE>, <callcache>
0019 leave                                                            (  19)[Re]
```
The same situation to 2.5.*

for ruby versions > 2.5.0 work fine:
```
== disasm: #<ISeq:hello@/home/viuignick/.RubyMine2019.2/config/scratches/scratch.rb:14 (14,0)-(19,3)> (catch: FALSE)
0000 opt_getinlinecache           7, <is:0>                           (  15)[LiCa]
0003 getconstant                  :Test
0005 opt_setinlinecache           <is:0>
0007 opt_send_without_block       <callinfo!mid:new, argc:0, ARGS_SIMPLE>, <callcache>
0010 opt_send_without_block       <callinfo!mid:method1, argc:0, ARGS_SIMPLE>, <callcache>(  16)
0013 opt_send_without_block       <callinfo!mid:method2, argc:0, ARGS_SIMPLE>, <callcache>(  17)
0016 opt_send_without_block       <callinfo!mid:method3, argc:0, ARGS_SIMPLE>, <callcache>(  18)
0019 leave                                                            (  19)[Re]
```



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