From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2025-12-16T12:14:05+00:00
Subject: [ruby-core:124239] [Ruby Bug#21783] {Method,UnboundMethod,Proc}#source_location returns columns in bytes and not in characters

Issue #21783 has been updated by Eregon (Benoit Daloze).


Yes, it'd be useful for e.g. `assert_raise(SomeException) { ... }` in test-unit, `expect { ... }.to` in RSpec, `-> { ... }.should raise_error(...)` in MSpec, etc.

For example `-> { 13 - "10" }.should raise_error(ArgumentError)` in MSpec currently gives:
```
1)
Integer#- fixnum raises a TypeError when given a non-Integer ERROR
Expected ArgumentError
but got: TypeError (String can't be coerced into Integer)
/home/eregon/code/rubyspec/core/integer/minus_spec.rb:21:in 'Integer#-'
```
But it could show something like:
```
1)
Integer#- fixnum raises a TypeError when given a non-Integer ERROR
Expected ArgumentError
but got: TypeError (String can't be coerced into Integer)
For expression `13 - "10"`
/home/eregon/code/rubyspec/core/integer/minus_spec.rb:21:in 'Integer#-'
```


----------------------------------------
Bug #21783: {Method,UnboundMethod,Proc}#source_location returns columns in bytes and not in characters
https://bugs.ruby-lang.org/issues/21783#change-115725

* Author: Eregon (Benoit Daloze)
* Status: Open
* ruby -v: ruby 4.0.0dev (2025-12-14T07:11:02Z master 711d14992e) +PRISM [x86_64-linux]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
The documentation says:
```
= Proc.source_location

(from ruby core)
------------------------------------------------------------------------
  prc.source_location  -> [String, Integer, Integer, Integer, Integer]

------------------------------------------------------------------------

Returns the location where the Proc was defined. The returned Array
contains:
  (1) the Ruby source filename
  (2) the line number where the definition starts
  (3) the column number where the definition starts
  (4) the line number where the definition ends
  (5) the column number where the definitions ends

This method will return nil if the Proc was not defined in Ruby (i.e.
native).
```

So it talks about column numbers, so it should be a number of characters and not of bytes.

But currently it's a number of bytes:
```
$ ruby --parser=prism -ve 'def �t�; end; p method(:�t�).source_location'
ruby 4.0.0dev (2025-12-14T07:11:02Z master 711d14992e) +PRISM [x86_64-linux]
["-e", 1, 0, 1, 14]

$ ruby --parser=parse.y -ve 'def �t�; end; p method(:�t�).source_location'
ruby 4.0.0dev (2025-12-14T07:11:02Z master 711d14992e) [x86_64-linux]
["-e", 1, 0, 1, 14]
```

The last number should be 12 because `"def �t�; end".size` is 12 characters.

This is a Ruby-level API so I would never expect "byte columns" here, I think it's clear it should be a number of "editor columns" i.e. a number of characters.



-- 
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