[F#] Add FS0410 compiler message (dotnet#49100)

* Add FS0410 compiler message

* Fix ms.date

* Fix text

* Update docs/fsharp/language-reference/compiler-messages/fs0410.md

Co-authored-by: Bill Wagner <[email protected]>

* Update docs/fsharp/language-reference/compiler-messages/fs0410.md

Co-authored-by: Bill Wagner <[email protected]>

* Update docs/fsharp/language-reference/compiler-messages/fs0410.md

Co-authored-by: Bill Wagner <[email protected]>

* Update docs/fsharp/language-reference/compiler-messages/toc.yml

Co-authored-by: Bill Wagner <[email protected]>

* Update docs/fsharp/language-reference/compiler-messages/fs0410.md

Co-authored-by: Bill Wagner <[email protected]>

---------

Co-authored-by: Bill Wagner <[email protected]>

Author: 64J0

docs/fsharp/language-reference/compiler-messages/fs0410.md

@@ -0,0 +1,27 @@
+---
+description: "Learn more about: FS0410: A type is less accessible than the value, member or type it is used in"
+title: "Compiler error FS0410"
+ms.date: 10/12/2025
+f1_keywords:
+  - "FS0410"
+helpviewer_keywords:
+  - "FS0410"
+---
+
+# FS0410: A type is less accessible than the value, member or type it is used in
+
+This message is given when you use a type that is less [accessible](../access-control.md) than the value, member or type it is used in.
+
+For example:
+
+[!code-fsharp[FS0410-less-accessible-type](~/samples/snippets/fsharp/compiler-messages/fs0410.fsx#L8-L11)]
+
+Notice that in this example, the type `Person` is `private`, but the function `_getName` is `public`. Also, the function `_getName` uses the type `Person` in its signature, which is not allowed since `Person` is less accessible than `_getName`.
+
+The example above causes the compiler to display the following message:
+
+```text
+FS0410: The type 'Person' is less accessible than the value, member or type 'val _getName: p: Person.Person -> string' it is used in.
+```
+
+A workaround would be changing the `Person` type to public accessibility, or the `_getName` function to private accessibility.

docs/fsharp/language-reference/compiler-messages/toc.yml

@@ -21,5 +21,7 @@
     href: ./fs0052.md
   - name: FS0067 - This type test or downcast will always hold
     href: ./fs0067.md
+  - name: FS0410 - A type is less accessible than the value, member or type it is used in
+    href: ./fs0410.md
   - name: FS0703 - Expected type parameter, not unit-of-measure parameter
     href: ./fs0703.md

samples/snippets/fsharp/compiler-messages/fs0410.fsx

@@ -0,0 +1,11 @@
+(*
+Compiler error: The type %s is less accessible than the value, member or type %s it is used in
+
+Notice that in this example, the type Person is private, but the function _getName is public by default.
+Also, the function _getName uses the type Person in its signature, which is not allowed since Person is
+less accessible than _getName.
+*)
+module Person =
+    type private Person = { Name: string; Email: string }
+
+    let _getName (p: Person) = p.Name