Show Stdlib.Null and Stdlib.Nullable completions for Stdlib.null<'a> and Stdlib.nullable<'a> types, respectively (#7826)

* Add failing test for Stdlib.null<'a> and Stdlib.nullable<'a> completion

* Treat Primitive_js_extern.null and Primitive_js_extern.nullable as Stdlib_Null and Stdlib_Nullable for completion

* Add CHANGELOG

Author: mediremi

CHANGELOG.md

@@ -20,6 +20,7 @@
 
 #### :bug: Bug fix
 
+- Show `Stdlib.Null` and `Stdlib.Nullable` completions for `Stdlib.null<'a>` and `Stdlib.nullable<'a>` types, respectively. https://github.com/rescript-lang/rescript/pull/7826
 - Fix generation of interfaces for module types containing multiple type constraints. https://github.com/rescript-lang/rescript/pull/7825
 
 #### :memo: Documentation

analysis/src/TypeUtils.ml

@@ -1291,4 +1291,6 @@ let completionPathFromMaybeBuiltin path =
     | [mainModule; "t"] when String.starts_with ~prefix:"Stdlib_" mainModule ->
       (* Route Stdlib_X to Stdlib.X for proper completions without the Stdlib_ prefix *)
       Some (String.split_on_char '_' mainModule)
+    | ["Primitive_js_extern"; "null"] -> Some ["Stdlib"; "Null"]
+    | ["Primitive_js_extern"; "nullable"] -> Some ["Stdlib"; "Nullable"]
     | _ -> None)

tests/analysis_tests/tests/src/CompletionNullNullable.res

@@ -0,0 +1,9 @@
+let x: null<unit> = Stdlib_Null.null
+
+// x.
+//   ^com
+
+let y: nullable<unit> = null
+
+// y.
+//   ^com