dotnet · danroth27 · Jun 29, 2026
@@ -0,0 +1,144 @@
+# F# in .NET 11 Preview 6 - Release Notes
+
+<!-- Verified against release-notes/11.0/preview/preview6/changes.json, the F# Preview 6 PR slice, and dotnet/fsharp PR metadata. No new public .NET reference APIs are named. -->
+
+Here's a summary of what's new in F# in this Preview 6 release:
+
+- [Array.init can inline initialization lambdas](#arrayinit-can-inline-initialization-lambdas)
+- [Interpolated strings parse next to equals signs](#interpolated-strings-parse-next-to-equals-signs)
+- [FSI --quiet keeps restore output off stdout](#fsi---quiet-keeps-restore-output-off-stdout)
+- [Signature-file diagnostics catch missing semantic attributes](#signature-file-diagnostics-catch-missing-semantic-attributes)
+- [Debug sequence points cover more F# expressions](#debug-sequence-points-cover-more-f-expressions)
+- [Bug fixes and other improvements](#bug-fixes-and-other-improvements)
+- [Community contributors](#community-contributors)
+
+## Array.init can inline initialization lambdas
+
+`Array.init` now carries the same inline-if-lambda behavior as the lower-level primitive it calls. When the initializer can be inlined, the compiler can avoid creating an extra closure for straightforward array initialization code ([dotnet/fsharp #19869](https://github.com/dotnet/fsharp/pull/19869)). Thank you [@kerams](https://github.com/kerams) for this contribution!
+
+```fsharp
+let squares = Array.init 10 (fun index -> index * index)
+```
+
+## Interpolated strings parse next to equals signs
+
+Interpolated strings can now appear immediately after `=` without a separating space. This fixes named arguments and expression forms that use regular, verbatim, triple-quoted, and multi-dollar interpolated strings ([dotnet/fsharp #19820](https://github.com/dotnet/fsharp/pull/19820), [dotnet/fsharp #19984](https://github.com/dotnet/fsharp/pull/19984)). Thank you [@edgarfgp](https://github.com/edgarfgp) for these contributions!
+
+```fsharp
+type C(?Name: string) =
+    member val Name = defaultArg Name "" with get, set
+
+let value = "Preview 6"
+
+let named = C(Name=$"Hello {value}")
+let verbatim =$@"{value}"
+let multiDollar =$$"""{{value}}"""
+```
+
+## FSI --quiet keeps restore output off stdout
+
+When F# Interactive runs with `--quiet`, NuGet restore output is now routed away from stdout. Scripts that intentionally write machine-readable output to stdout can use package references without restore chatter mixing into the stream ([dotnet/fsharp #19808](https://github.com/dotnet/fsharp/pull/19808)).
+
+```fsharp
+// script.fsx
+#r "nuget: Newtonsoft.Json, 13.0.3"
+
+printfn "ready"
+```
+
+```console
+dotnet fsi --quiet script.fsx > output.txt
+```
+
+## Signature-file diagnostics catch missing semantic attributes
+
+FS3888 now reports consumer-visible attributes that appear in an implementation file but are missing from the corresponding signature file. These attributes affect how downstream code type-checks against the `.fsi` contract, so the diagnostic helps keep the implementation and signature aligned. With the `ErrorOnMissingSignatureAttribute` preview language feature enabled, the diagnostic is an error ([dotnet/fsharp #19880](https://github.com/dotnet/fsharp/pull/19880)).
+
+```fsharp
+// Library.fsi
+module Library
+
+val parse: string -> int
+```
+
+```fsharp
+// Library.fs
+module Library
+
+[<NoDynamicInvocation>]
+let parse text = int text
+```
+
+## Debug sequence points cover more F# expressions
+
+The compiler now emits better sequence points for several common debugging scenarios. Breakpoints and stepping are improved for call arguments that need stack-empty debug points, `for` expressions and comprehensions, simple literal bindings, and `if` or `match` conditions ([dotnet/fsharp #19877](https://github.com/dotnet/fsharp/pull/19877), [dotnet/fsharp #19894](https://github.com/dotnet/fsharp/pull/19894), [dotnet/fsharp #19897](https://github.com/dotnet/fsharp/pull/19897), [dotnet/fsharp #19932](https://github.com/dotnet/fsharp/pull/19932)). Thank you [@auduchinok](https://github.com/auduchinok) for these contributions!
+
+```fsharp
+for item in items do
+    printfn "%A" item
+
+if shouldRun input then
+    run input
+else
+    skip input
+```
+
+<!-- Filtered features (significant engineering work, but too niche for release notes):
+  - ObsoleteDiagnosticInfo in compiler symbols: useful compiler-service metadata, but no broad end-user workflow was validated for this preview.
+  - ParallelCompilation property passing: important MSBuild plumbing, but it is build configuration correctness rather than a user-facing F# feature.
+  - Agentic workflow, state-machine, and dependency-update PRs: repository automation and infrastructure changes, not product release-note material.
+-->
+
+## Bug fixes and other improvements
+
+### Compiler correctness
+
+- `let _ = &expr` now compiles like an equivalent named binding instead of incorrectly reporting FS0421 ([dotnet/fsharp #19811](https://github.com/dotnet/fsharp/pull/19811)).
+- Single-case active pattern names and partial active pattern names now reject non-function bindings ([dotnet/fsharp #19763](https://github.com/dotnet/fsharp/pull/19763)).
+- SRTP calls constrained to `member get_Item` now resolve string indexers instead of hitting an internal compiler error ([dotnet/fsharp #19757](https://github.com/dotnet/fsharp/pull/19757)).
+- Null refinement in pattern matching now preserves type aliases when possible ([dotnet/fsharp #19745](https://github.com/dotnet/fsharp/pull/19745)).
+- Anonymous record type aliases with postfix type operators no longer produce a spurious parse error when the closing `|}` is column-aligned ([dotnet/fsharp #19762](https://github.com/dotnet/fsharp/pull/19762)).
+- Quotations no longer expose the compiler's empty-string match lowering in quoted ASTs ([dotnet/fsharp #19923](https://github.com/dotnet/fsharp/pull/19923)).
+- Inner recursive functions under `--realsig+` now regain the intended codegen shape, including static lifting and tail calls in cases that previously degraded ([dotnet/fsharp #19882](https://github.com/dotnet/fsharp/pull/19882)).
+- `use` bindings with `as` patterns or aliases no longer emit duplicate `Dispose` calls for the same value ([dotnet/fsharp #19858](https://github.com/dotnet/fsharp/pull/19858)).
+- Named arguments on indexer setters no longer cause an internal compiler error ([dotnet/fsharp #19851](https://github.com/dotnet/fsharp/pull/19851)).
+- Optimized Release builds no longer relocate protected base-field access into illegal IL that can throw `FieldAccessException` at runtime ([dotnet/fsharp #19964](https://github.com/dotnet/fsharp/pull/19964)).
+- Computation expressions such as `task { let! ... }` no longer report FS1110 when a generic IL extension method is in scope ([dotnet/fsharp #19938](https://github.com/dotnet/fsharp/pull/19938)).
+- Recursive self-reference ref cells are no longer classified as user-written mutable bindings ([dotnet/fsharp #19918](https://github.com/dotnet/fsharp/pull/19918)).
+
+### Diagnostics and tooling
+
+- Reference assembly MVIDs produced with `--refout` are now deterministic across builds ([dotnet/fsharp #19801](https://github.com/dotnet/fsharp/pull/19801)).
+- Type names in generic static member access expressions are colorized correctly when the type argument is qualified ([dotnet/fsharp #19800](https://github.com/dotnet/fsharp/pull/19800)).
+- XML documentation validation for get/set property pairs now accounts for parameters documented across both accessors ([dotnet/fsharp #19884](https://github.com/dotnet/fsharp/pull/19884)).
+- Editor diagnostics in Visual Studio are no longer duplicated by the F# analyzer workaround ([dotnet/fsharp #19812](https://github.com/dotnet/fsharp/pull/19812)).
+- FS3261 nullness diagnostics for dot access now pinpoint the receiver and name the member and binding involved ([dotnet/fsharp #19814](https://github.com/dotnet/fsharp/pull/19814)).
+- Namespace/type collisions now get a dedicated diagnostic instead of being reported as namespace/module collisions ([dotnet/fsharp #19802](https://github.com/dotnet/fsharp/pull/19802)).
+- Format specifier locations in computation expressions are no longer reported twice after desugaring ([dotnet/fsharp #19791](https://github.com/dotnet/fsharp/pull/19791)).
+- Wildcard patterns inside `member _.` bodies no longer resolve to the member's synthetic instance identifier in hover and symbol lookup ([dotnet/fsharp #19760](https://github.com/dotnet/fsharp/pull/19760)).
+- Empty-bodied computation expressions in pipelines now keep meaningful source ranges, so diagnostics can point to the right source location ([dotnet/fsharp #19849](https://github.com/dotnet/fsharp/pull/19849)).
+- QuickParse completion now handles indexed expressions before a dot, such as `a.[0].Data.` and `[1; 2].Length.` ([dotnet/fsharp #19934](https://github.com/dotnet/fsharp/pull/19934)).
+- QuickInfo and symbol-use results for overloaded `[<CustomOperation>]` keywords now report the overload chosen by F# overload resolution ([dotnet/fsharp #19865](https://github.com/dotnet/fsharp/pull/19865)).
+- Analysis now recovers after a language-version check error instead of leaving the rest of the file in a broken state ([dotnet/fsharp #19970](https://github.com/dotnet/fsharp/pull/19970)). Thank you [@auduchinok](https://github.com/auduchinok)!
+
+### FSI and scripting
+
+- FSI now pretty-prints anonymous records with `{| ... |}` delimiters and struct anonymous records with `struct {| ... |}` ([dotnet/fsharp #19919](https://github.com/dotnet/fsharp/pull/19919)).
+- Open-declaration insertion in `.fsx` scripts now places suggested `open` declarations after leading `#r` and `#load` directives ([dotnet/fsharp #19879](https://github.com/dotnet/fsharp/pull/19879)).
+
+## Community contributors
+
+Thank you contributors! ❤️
+
+- [@0101](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3A0101)
+- [@abonie](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3Aabonie)
+- [@auduchinok](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3Aauduchinok)
+- [@edgarfgp](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3Aedgarfgp)
+- [@kerams](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3Akerams)
+- [@majocha](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3Amajocha)
+- [@techiedesu](https://github.com/dotnet/fsharp/pulls?q=is%3Apr+is%3Amerged+author%3Atechiedesu)
+
+F# updates:
+
+- [F# release notes](https://fsharp.github.io/fsharp-compiler-docs/release-notes/About.html)
+- [dotnet/fsharp repository](https://github.com/dotnet/fsharp)