Backup of release/dev15.9.x tip before v4 reset to RTM (per user choi…

…ce A in S4)

Fix source-build: track Cryptography.Xml via Version.Details (#19839)

* Fix source-build: track System.Security.Cryptography.Xml via Version.Details

Move System.Security.Cryptography.Xml version management from hardcoded
eng/Versions.props to eng/Version.Details.xml + Version.Details.props,
following the same pattern as System.Diagnostics.DiagnosticSource and
other System.* runtime dependencies. This allows source-build to use
the live-built package instead of a prebuilt NuGet download.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Restore PrivateAssets=all on System.Security.Cryptography.Xml

Removing PrivateAssets=all caused transitive dependencies
(Microsoft.Bcl.Cryptography, System.Formats.Asn1, etc.) to flow into
fsc.fsproj on net472, triggering MSB3277 version conflicts with
System.ValueTuple from .NET Framework reference assemblies.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <copilot@github.com>

Replace PAT with WIF service connection for VS insertion (#19683)

Migrate from dn-bot-devdiv-build-rw-code-rw-release-rw PAT to the
dnceng-fsharp-vs-insertion-wif Entra WIF service connection for
authenticating to DevDiv when creating VS insertion PRs.

- Remove DotNet-VSTS-Infra-Access variable group reference
- Add AzureCLI@2 step to acquire bearer token via WIF SC
- Set InsertAccessToken as secret variable from WIF token

Resolves: https://dev.azure.com/dnceng/internal/_workitems/edit/10091

Co-authored-by: Tomas Grosup <Tomas.Grosup@gmail.com>
Co-authored-by: Adam Boniecki <20281641+abonie@users.noreply.github.com>

Fix seq try-with handler body executing twice (#19660) (#19661)

Guard disposeOriginal() against accessing a faulted Lazy<T> in
EnumerateTryWith. When source.GetEnumerator() throws, the Lazy
caches the exception and re-throws on every .Value access, causing
the disposal path to re-trigger moveExceptionHandler.

Add IsValueCreated check so disposal is skipped when no enumerator
was successfully created.

Fixes #19660

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Update VS image to windows.vs2026preview.scout.amd64 for release/dev1…

…8.0 (#19639)

Fix flaky async/task tests under CI load (#19632)

- AsyncType.CreateTask: increase waitASec timeout from 1s to 30s
  (thread pool saturation on loaded CI prevents scheduling trivial tasks)

- Tasks/TasksDynamic testNonBlocking: replace Thread.Sleep(100) race
  with ManualResetEventSlim gate for deterministic synchronization

- Tasks/TasksDynamic testExceptionThrownInFinally: wire up the
  already-declared-but-unused stepOutside SemaphoreSlim instead of
  Thread.Sleep(100) race (matching test2ndExceptionThrownInFinally pattern)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

[release/dev18.0] Update dependencies from dotnet/roslyn (#19524)

* Update dependencies from https://github.com/dotnet/roslyn build 20260330.2
On relative base path root
Microsoft.CodeAnalysis , Microsoft.CodeAnalysis.Compilers , Microsoft.CodeAnalysis.CSharp , Microsoft.CodeAnalysis.EditorFeatures , Microsoft.CodeAnalysis.EditorFeatures.Text , Microsoft.CodeAnalysis.ExternalAccess.FSharp , Microsoft.CodeAnalysis.Features , Microsoft.VisualStudio.LanguageServices From Version 5.0.0-2.26175.11 -> To Version 5.0.0-2.26180.2

* Update dependencies from https://github.com/dotnet/roslyn build 20260401.2
On relative base path root
Microsoft.CodeAnalysis , Microsoft.CodeAnalysis.Compilers , Microsoft.CodeAnalysis.CSharp , Microsoft.CodeAnalysis.EditorFeatures , Microsoft.CodeAnalysis.EditorFeatures.Text , Microsoft.CodeAnalysis.ExternalAccess.FSharp , Microsoft.CodeAnalysis.Features , Microsoft.VisualStudio.LanguageServices From Version 5.0.0-2.26175.11 -> To Version 5.0.0-2.26201.2

* Update dependencies from https://github.com/dotnet/roslyn build 20260402.6
On relative base path root
Microsoft.CodeAnalysis , Microsoft.CodeAnalysis.Compilers , Microsoft.CodeAnalysis.CSharp , Microsoft.CodeAnalysis.EditorFeatures , Microsoft.CodeAnalysis.EditorFeatures.Text , Microsoft.CodeAnalysis.ExternalAccess.FSharp , Microsoft.CodeAnalysis.Features , Microsoft.VisualStudio.LanguageServices From Version 5.0.0-2.26175.11 -> To Version 5.0.0-2.26202.6

* Fix CancellationPropagatesToTask test disposing running Task

Change 'use t' to 'let t' to avoid calling Dispose on a Task that
may still be running, which throws InvalidOperationException on .NET 10.

Replace 'waitASec t' (1-second timeout) with 't.Wait()' to wait for
cancellation to fully propagate, matching the pattern used by the
sibling CancellationPropagatesToGroup test.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Co-authored-by: dotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>
Co-authored-by: Tomas Grosup <tomasgrosup@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Tomas Grosup <Tomas.Grosup@gmail.com>

Add regression test: #3660, array of functions invocation correctness (…

…#19479)

* Add regression test for #3660: array of functions invocation without closure allocation

- Runtime correctness test: compiles and runs the indexed array function
  invocation pattern, verifying correct results
- IL verification test: compiles runAll as a library with optimizations and
  asserts no closure class (extending FSharpFunc) is emitted, ensuring the
  compiler does not generate needless allocations for fArr.[i] x

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Adam Boniecki <20281641+abonie@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Adam Boniecki <20281641+abonie@users.noreply.github.com>

Add regression test: #3660, array of functions invocation correctness (…

…#19479)

* Add regression test for #3660: array of functions invocation without closure allocation

- Runtime correctness test: compiles and runs the indexed array function
  invocation pattern, verifying correct results
- IL verification test: compiles runAll as a library with optimizations and
  asserts no closure class (extending FSharpFunc) is emitted, ensuring the
  compiler does not generate needless allocations for fArr.[i] x

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Adam Boniecki <20281641+abonie@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Adam Boniecki <20281641+abonie@users.noreply.github.com>

FCS: capture additional types during analysis (#19305)