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%)