Add relnotes for 1.90.0

[BoxyUwU]

r? @Mark-Simulacrum
cc @rust-lang/release
@rustbot ping relnotes-interest-group

[rustbot]

Hi relnotes-interest-group, this issue/PR could use some help in reviewing /
adjusting release notes. Could you take a look if available? Thanks <3

cc @alex-semenyuk @jieyouxu @joshtriplett @Kobzol @lcnr @traviscross

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[Mark-Simulacrum]

@bors r+ rollup p=1

Squashed changes.

[bors]

📌 Commit c92dee2 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit c92dee2 with merge a454fcc...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing a454fcc to master...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing f3fd3ef (parent) -> a454fcc (this PR)

Test differences

No test diffs found

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard a454fccb02df9d361f1201b747c01257f58a8b37 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. dist-aarch64-apple: 8056.8s -> 5759.0s (-28.5%)
2. dist-apple-various: 4674.6s -> 3597.6s (-23.0%)
3. test-various: 4383.7s -> 5026.7s (14.7%)
4. dist-x86_64-solaris: 6125.7s -> 5293.9s (-13.6%)
5. tidy: 176.1s -> 197.0s (11.9%)
6. x86_64-gnu-aux: 6355.6s -> 6875.3s (8.2%)
7. i686-msvc-2: 8321.5s -> 7660.7s (-7.9%)
8. aarch64-gnu-llvm-19-1: 3493.8s -> 3239.7s (-7.3%)
9. dist-arm-linux-gnueabi: 4686.2s -> 4995.3s (6.6%)
10. x86_64-msvc-ext3: 6303.7s -> 6638.2s (5.3%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain enhanced) (plain)

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

Prepare workflow directory
Prepare all required actions
Getting action download info
Download action repository 'actions/checkout@v5' (SHA:08c6903cd8c0fde910a37f88322edcfb5dd907a8)
Complete job name: DockerHub mirror
##[group]Run actions/checkout@v5
with:
  persist-credentials: false
  repository: rust-lang/rust
  token: ***
---
http.https://github.com/.extraheader
[command]/usr/bin/git config --local --unset-all http.https://github.com/.extraheader
[command]/usr/bin/git submodule foreach --recursive sh -c "git config --local --name-only --get-regexp 'http\.https\:\/\/github\.com\/\.extraheader' && git config --local --unset-all 'http.https://github.com/.extraheader' || :"
##[endgroup]
##[group]Run echo "***" | docker login ghcr.io -u rust-lang --password-stdin
echo "***" | docker login ghcr.io -u rust-lang --password-stdin
shell: /usr/bin/bash -e {0}
##[endgroup]
Error response from daemon: Get "https://ghcr.io/v2/": Get "https://ghcr.io/token?account=rust-lang&client_id=docker&offline_token=true&service=ghcr.io": net/http: request canceled (Client.Timeout exceeded while awaiting headers) (Client.Timeout exceeded while awaiting headers)
##[error]Process completed with exit code 1.
Post job cleanup.

[rust-timer]

Finished benchmarking commit (a454fcc): 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 (secondary 1.3%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.3%	[1.3%, 1.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 0.4%, secondary 7.5%)

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

	mean	range	count
Regressions ❌ (primary)	3.1%	[3.1%, 3.1%]	1
Regressions ❌ (secondary)	13.5%	[13.0%, 14.0%]	2
Improvements ✅ (primary)	-2.3%	[-2.3%, -2.3%]	1
Improvements ✅ (secondary)	-4.5%	[-4.5%, -4.5%]	1
All ❌✅ (primary)	0.4%	[-2.3%, 3.1%]	2

Binary size

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

Bootstrap: 473.025s -> 473.712s (0.15%)
Artifact size: 390.15 MiB -> 390.18 MiB (0.01%)