adds a column number to dbg!()

[darklyspaced]

this would be very nice to have for a few reasons:

1. the rfc, when deciding not to add column numbers to macro, failed to acknowledge any potential ambiguous cases -- such as the one provided in dbg!: also print column #114910 -- which do exist
2. would be able to consistently and easily jump directly to the dbg!() regardless of the sutation
3. takes up, at a maximum, 3 characters of horizontal screen space

fixes #114910

[rustbot]

r? @cuviper

(rustbot has picked a reviewer for you, use r? to override)

[cuviper]

I think this needs API consideration, especially since it changes behavior that was explicitly chosen in an RFC.

@rustbot label -T-libs +T-libs-api
r? libs-api

[est31]

Having done a bunch of column number changes over the years, like #42938, #46762, #51980 or #79002, I am glad to see that my appreciation for column numbers is shared. 👍 from me! See those threads for discussion and arguments why column numbers are useful, especially the second and last linked PR.

[darklyspaced]

@m-ou-se have you gotten a chance to look over the API changes yet?

[m-ou-se]

Seems fine to me!

Since #106824, the impact of this is very minimal: the file name, line number and column number will all be 'inlined' into the stringl literal. dbg!() will expand to eprintln!("[{}:{}:{}]", file!(), line!(), column!()) which gets optimized into just eprintln!("[src/main.rs:2:4]"): as a single string literal. So the difference is just a few bytes more in the string literals, and nothing else.

@rfcbot merge

[rfcbot]

Team member @m-ou-se has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[joshtriplett]

👍 for column numbers anywhere we emit line numbers.

This could also affect someone's test cases, but the exact textual output of dbg! and similar have no stability guarantees, so relying on the output of dbg! in a test case is not a good idea.

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

[bors]

☔ The latest upstream changes (presumably #114571) made this pull request unmergeable. Please resolve the merge conflicts.

[est31]

@bors r+ rollup

[bors]

📌 Commit b05f211 has been approved by est31

It is now in the queue for this repository.

[matthiaskrgr]

@bors rollup=never
I suspect this will have at least some impact on binary size

[bors]

⌛ Testing commit b05f211 with merge 21fd484...

[rust-log-analyzer]

The job aarch64-gnu failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

 Documenting rustc_ast_passes v0.0.0 (/checkout/compiler/rustc_ast_passes)
[RUSTC-TIMING] rustc_ast_passes test:false 1.339
    Checking rustc_expand v0.0.0 (/checkout/compiler/rustc_expand)
 Documenting rustc_expand v0.0.0 (/checkout/compiler/rustc_expand)
##[error]The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.
##[group]Clock drift check
  local time: Sun Dec 17 00:02:05 UTC 2023
  local time: Sun Dec 17 00:02:05 UTC 2023
Session terminated, killing shell... ...killed.
##[error]The operation was canceled.
Cleaning up orphan processes

[bors]

💔 Test failed - checks-actions

[est31]

Seems like an unrelated issue (maybe the CI environment?).

[matthiaskrgr]

@bors retry

[bors]

⌛ Testing commit b05f211 with merge 43dcc9b...

[bors]

☀️ Test successful - checks-actions
Approved by: est31
Pushing 43dcc9b to master...

[rust-timer]

Finished benchmarking commit (43dcc9b): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.5%, 0.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.9%, -0.4%]	3
Improvements ✅ (secondary)	-1.8%	[-2.5%, -1.2%]	2
All ❌✅ (primary)	-0.3%	[-0.9%, 0.5%]	4

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.8%	[0.7%, 0.9%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-0.4%, 0.9%]	4

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 670.812s -> 670.368s (-0.07%)
Artifact size: 312.51 MiB -> 312.44 MiB (-0.02%)