lazily reevaluate nested goals

[lcnr]

It sure is a tragedy. Opening just so I have something to show for the last few weeks. This does not yet fix the perf regression in rayon. However, it does pass fuzzing and implements the simplest version of what I want this to be long term.

r? ghost

[lcnr]

let's see the perf cost of always building the search tree.

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit 5dc471c with merge 5a6edde…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 5a6edde (5a6edde1d282dc0c7083290f46e025a0848ae51c, parent: 8de4c7234dd9b97c9d76b58671343fdbbc9a433e)

[rust-log-analyzer]

The job mingw-check-tidy failed! Check out the build log: (web) (plain)

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

fmt: checked 6076 files
tidy check
Running eslint on rustdoc JS files
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_type_ir/src/search_graph/tree.rs:20: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
##[error]tidy error: /checkout/compiler/rustc_type_ir/src/search_graph/mod.rs:1218: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
##[error]tidy error: /checkout/compiler/rustc_type_ir/src/search_graph/mod.rs:1274: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
##[error]tidy error: /checkout/compiler/rustc_type_ir/src/search_graph/mod.rs:1424: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (25.1.1)
linting python files
All checks passed!
checking python file formatting
28 files already formatted
checking C++ file formatting
some tidy checks failed
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:22
  local time: Fri Jun 20 08:25:31 UTC 2025
  network time: Fri, 20 Jun 2025 08:25:32 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[rust-timer]

Finished benchmarking commit (5a6edde): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.3%, 0.3%]	3
Regressions ❌ (secondary)	0.7%	[0.3%, 1.2%]	17
Improvements ✅ (primary)	-1.2%	[-1.2%, -1.2%]	1
Improvements ✅ (secondary)	-0.4%	[-1.1%, -0.1%]	4
All ❌✅ (primary)	-0.1%	[-1.2%, 0.3%]	4

Max RSS (memory usage)

Results (primary 1.6%, secondary -0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	5.0%	[5.0%, 5.0%]	1
Regressions ❌ (secondary)	2.5%	[2.4%, 2.6%]	2
Improvements ✅ (primary)	-1.8%	[-1.8%, -1.8%]	1
Improvements ✅ (secondary)	-2.7%	[-2.8%, -2.6%]	2
All ❌✅ (primary)	1.6%	[-1.8%, 5.0%]	2

Cycles

Results (primary 1.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.8%	[1.8%, 1.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.8%	[1.8%, 1.8%]	1

Binary size

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

Bootstrap: 691.904s -> 693.336s (0.21%)
Artifact size: 372.02 MiB -> 372.05 MiB (0.01%)