F# , add chapter on opening with global specifier (#40809)

* Update import-declarations-the-open-keyword.md Chapter on global keyword * better names * specifier not keyword * Update import-declarations-the-open-keyword.md Co-authored-by: Petr <psfinaki@users.noreply.github.com> * Update import-declarations-the-open-keyword.md Co-authored-by: Petr <psfinaki@users.noreply.github.com> * try fix md linting errors --------- Co-authored-by: Petr <psfinaki@users.noreply.github.com>
dotnet · May 10, 2024 · 3bcd650 · 3bcd650
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diff --git a/docs/fsharp/language-reference/import-declarations-the-open-keyword.md b/docs/fsharp/language-reference/import-declarations-the-open-keyword.md
@@ -63,6 +63,31 @@ open type M.DU
 printfn "%A" A
 ```
 
+## Open from root path only with `global` specifier
+
+Nested modules like
+
+```fsharp
+module A =
+    module B =
+        ...
+```
+
+can be opened via
+
+```fsharp
+open A // opens A
+open B // opens A.B
+```
+
+To open **only** fully qualified modules or namespaces prefix them with the `global` specifier:
+
+```fsharp
+open global.A   // works
+open global.B   // this now fails
+open global.A.B // works
+```
+
 ## Namespaces That Are Open by Default
 
 Some namespaces are so frequently used in F# code that they are opened implicitly without the need of an explicit import declaration. The following table shows the namespaces that are open by default.