From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2025-12-15T16:32:02+00:00
Subject: [ruby-core:124214] [Ruby Bug#21784] Proc#source_location start column seems strange for -> {}

Issue #21784 has been updated by Eregon (Benoit Daloze).


Interesting.
The arguments (parameters) between `->` and `{` are AFAIK integral part of the stabby lambda syntax, so I think it should be either:
* All cases start at the `{`:
  * consistent with non-stabby-lambda Procs
  * but does not include the arguments which is an critical part of the lambda declaration (and this is not an issue for non-stabby-lambda Procs as the arguments come after `{` like `{ |args|`)
* All cases start at the `->`
  * covers the whole expression
  * intuitive, I think most users would expect this one
  * Also enables e.g. `eval()`'ing the source string (in the right context)
  * Consistent with `for`

Starting at the arguments but skipping `->` and some spaces seems strange/inconsistent.

----------------------------------------
Bug #21784: Proc#source_location start column seems strange for -> {}
https://bugs.ruby-lang.org/issues/21784#change-115697

* 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
----------------------------------------
```
$ ruby -e 'p -> { a }.source_location' 
["-e", 1, 4, 1, 10]
```
So it considers the stabby lambda to be at:
```ruby
p -> { a }.source_location
    ^^^^^^
```
Note it starts at a whitespace after the `->`.
I think it should just include the `->`, i.e. return `["-e", 1, 2, 1, 10]`.
Or possibly start at the `{`, i.e. return `["-e", 1, 3, 1, 10]`.
But starting on a whitespace like here seems really strange, it looks like a bug.

It's the same result with `--parser=parse.y`, so I don't show it.

---

For context:
For Procs/block it looks like this:
```
$ ruby -e 'p proc { a }.source_location'
["-e", 1, 7, 1, 12]
```
```ruby
p proc { a }.source_location
       ^^^^^
```
This looks fine.
The block could of course be given to any other method so it won't always be `proc` in front.
Maybe it could include the method too (so it would return start column 2 here), I think either is fine.

For `for` blocks it looks like this:
```
$ ruby -e '                                                             
def self.each(&b); yield b; end;
for b in self
  42
end
p b.source_location'
["-e", 3, 0, 5, 3]
```
That is, it covers the entire `for` expression from `for` until `end`.
I think that's good and fine as-is.

For `def` methods it covers everything from `def` to `end` (or end of line for `def m = 42`), as expected.



-- 
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