Add release notes for SRTP nullness constraint fix

Copilot · T-Gro · Copilot · commit 475bb592b3b1 · 2025-08-13T09:27:25.000Z
Co-authored-by: T-Gro &lt;46543583+T-Gro@users.noreply.github.com&gt;
diff --git a/docs/release-notes/.FSharp.Compiler.Service/10.0.100.md b/docs/release-notes/.FSharp.Compiler.Service/10.0.100.md
@@ -18,6 +18,7 @@
 * Fix active pattern typechecking regression. ([Issue #18638](https://github.com/dotnet/fsharp/issues/18638), [PR #18642](https://github.com/dotnet/fsharp/pull/18642))
 * Fix nullness warnings when casting non-nullable values to `IEquatable<T>` to match C# behavior. ([Issue #18759](https://github.com/dotnet/fsharp/issues/18759))
 * Fix IsByRefLikeAttribute types being incorrectly suppressed in completion lists. Types like `Span<T>` and `ReadOnlySpan<T>` now appear correctly in IntelliSense.
+* Fix SRTP nullness constraint resolution for types imported from older assemblies. AmbivalentToNull types now use legacy F# nullness rules instead of always satisfying `'T : null` constraints. ([Issue #18390](https://github.com/dotnet/fsharp/issues/18390), [Issue #18344](https://github.com/dotnet/fsharp/issues/18344))
 
 ### Changed
 * Use `errorR` instead of `error` in `CheckDeclarations.fs` when possible. ([PR #18645](https://github.com/dotnet/fsharp/pull/18645))
