Qualify extensions of nested interface modules and complete their payloads

Codex review on #9085: an extension two modules deep in an interface got
only the outer module in its path, because the signature walk didn't
extend the module path when entering a module, and completion inside the
payload of a qualified constructor such as `Sub.Toggle(...)` found no
constructor, because the payload position keeps only `Toggle`. Signature
modules now extend the path, and payload lookup also matches the last
part of a qualified constructor name.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kbf3gLMawVgtmiKy3TMBc3
Claude-Session: https://claude.ai/code/session_01Kr4cjoUi2f5VpMvE6wT9bo
Signed-off-by: Christoph Knittel <ck@cca.io>

Author: cknitt

analysis/src/process_cmt.ml

@@ -196,7 +196,7 @@ let rec for_type_signature_item ~(env : Shared_types.Env.t)
     let name = Ident.name ident in
     let declared =
       add_declared ~extent:md_loc
-        ~item:(for_type_module ~name ~env md_type)
+        ~item:(for_type_module ~name ~env:(env |> Env.add_module ~name) md_type)
         ~name:(Location.mkloc name md_loc)
         ~stamp:(Ident.binding_time ident) ~env md_attributes
         (Exported.add exported Exported.Module)

analysis/src/type_utils.ml

@@ -372,6 +372,17 @@ let with_completion_scope ~file ~module_path ~pos f =
   completion_scope := Some (file, module_path, pos);
   Fun.protect ~finally:(fun () -> completion_scope := previous) f
 
+(* Whether [c] is the constructor written [name] in a payload position, where
+   only the last part of a path such as [Sub.Flag] is kept. Extension
+   constructors are named by their module path, ordinary ones are not. *)
+let constructor_has_name (c : Constructor.t) name =
+  c.cname.txt = name
+  ||
+  match String.rindex_opt c.cname.txt '.' with
+  | Some i ->
+    String.sub c.cname.txt (i + 1) (String.length c.cname.txt - i - 1) = name
+  | None -> false
+
 (* The stamp under which [typ] is declared in [file]. *)
 let type_stamp (file : File.t) (typ : Type.t) =
   let found = ref None in
@@ -909,7 +920,7 @@ let rec resolve_nested ?type_arg_context ~env ~full ~state ~nested ?ctx
       match
         constructors
         |> List.find_opt (fun (c : Constructor.t) ->
-            c.cname.txt = constructor_name)
+            constructor_has_name c constructor_name)
       with
       | Some {args = Args args} -> (
         if Debug.verbose () then
@@ -1045,7 +1056,7 @@ let rec resolve_nested_pattern_path (typ : inner_type) ~env ~full ~state ~nested
         match
           constructors
           |> List.find_opt (fun (constructor : Constructor.t) ->
-              constructor.cname.txt = constructor_name)
+              constructor_has_name constructor constructor_name)
         with
         | Some {args = Args args} -> (
           let item_num, nested =

tests/analysis_tests/tests/src/CompletionExtensibleIface.res

@@ -5,4 +5,10 @@ module Sub = {
   type attr += Flag
 }
 
+module Outer = {
+  module Inner = {
+    type attr += Deep
+  }
+}
+
 let value: attr = Top

tests/analysis_tests/tests/src/CompletionExtensibleIface.resi

@@ -5,4 +5,10 @@ module Sub: {
   type attr += Flag
 }
 
+module Outer: {
+  module Inner: {
+    type attr += Deep
+  }
+}
+
 let value: attr

tests/analysis_tests/tests/src/CompletionExtensibleVariant.res

@@ -2,7 +2,7 @@ type attr = ..
 type attr += Str(string) | Num(int)
 
 module Sub = {
-  type attr += Flag
+  type attr += Flag | Toggle(bool)
   // Inside the declaring module the constructor is not qualified
   // let inside: attr = Fl
   //                      ^com
@@ -47,3 +47,7 @@ let a: A.t = A.FromA
 //                    ^com
 
 type attr += Later
+
+// Payload of a qualified extension constructor
+// let toggled: attr = Sub.Toggle(t
+//                                 ^com

tests/analysis_tests/tests/src/expected/CompletionExtensibleIfaceUse.res.txt

@@ -15,7 +15,7 @@ Path importe
   {
     "detail": "insert exhaustive switch for value",
     "filterText": "imported",
-    "insertText": "imported {\n   | CompletionExtensibleIface.Top => ${1:%todo}\n   | CompletionExtensibleIface.Sub.Flag => ${2:%todo}\n   | _ => ${3:%todo}\n   }",
+    "insertText": "imported {\n   | CompletionExtensibleIface.Top => ${1:%todo}\n   | CompletionExtensibleIface.Sub.Flag => ${2:%todo}\n   | CompletionExtensibleIface.Outer.Inner.Deep => ${3:%todo}\n   | _ => ${4:%todo}\n   }",
     "insertTextFormat": 2,
     "kind": 15,
     "label": "imported (exhaustive switch)",

tests/analysis_tests/tests/src/expected/CompletionExtensibleVariant.res.txt

@@ -99,6 +99,18 @@ Path value
     "kind": 4,
     "label": "Sub.Flag",
     "tags": []
+  },
+  {
+    "detail": "Sub.Toggle(bool)",
+    "documentation": {
+      "kind": "markdown",
+      "value": "```rescript\nSub.Toggle(bool)\n```\n\n```rescript\ntype attr = ..\n```"
+    },
+    "insertText": "Sub.Toggle(${1:_})",
+    "insertTextFormat": 2,
+    "kind": 4,
+    "label": "Sub.Toggle(_)",
+    "tags": []
   }
 ]
 
@@ -114,7 +126,7 @@ Path valu
   {
     "detail": "insert exhaustive switch for value",
     "filterText": "value",
-    "insertText": "value {\n   | Str(_) => ${1:%todo}\n   | Num(_) => ${2:%todo}\n   | Sub.Flag => ${3:%todo}\n   | _ => ${4:%todo}\n   }",
+    "insertText": "value {\n   | Str(_) => ${1:%todo}\n   | Num(_) => ${2:%todo}\n   | Sub.Flag => ${3:%todo}\n   | Sub.Toggle(_) => ${4:%todo}\n   | _ => ${5:%todo}\n   }",
     "insertTextFormat": 2,
     "kind": 15,
     "label": "value (exhaustive switch)",
@@ -206,3 +218,30 @@ ContextPath Value[La]
 Path La
 [ { "detail": "module Lazy", "kind": 9, "label": "Lazy", "tags": [] } ]
 
+Complete src/CompletionExtensibleVariant.res 51:35
+XXX Not found!
+Completable: Cexpression Type[attr]=t->variantPayload::Toggle($0)
+Package opens Stdlib.place holder Pervasives.JsxModules.place holder
+Resolved opens 1 Stdlib
+ContextPath Type[attr]
+Path attr
+[
+  {
+    "detail": "bool",
+    "kind": 4,
+    "label": "true",
+    "sortText": "A true",
+    "tags": []
+  },
+  {
+    "detail": "'a => Type.t",
+    "documentation": {
+      "kind": "markdown",
+      "value": "\n`typeof(value)` exposes JavaScript's `typeof` operator and returns a `Type.t` enum.\nIt helps you inspect values that come from JavaScript APIs.\n\n## Examples\n\n```rescript\ntypeof(1) == #number\ntypeof(\"a\") == #string\n```\n"
+    },
+    "kind": 12,
+    "label": "typeof",
+    "tags": []
+  }
+]
+

tests/analysis_tests/tests/src/expected/CompletionExtensibleVariantUse.res.txt

@@ -15,7 +15,7 @@ Path importe
   {
     "detail": "insert exhaustive switch for value",
     "filterText": "imported",
-    "insertText": "imported {\n   | CompletionExtensibleVariant.Str(_) => ${1:%todo}\n   | CompletionExtensibleVariant.Num(_) => ${2:%todo}\n   | CompletionExtensibleVariant.Sub.Flag => ${3:%todo}\n   | CompletionExtensibleVariant.Later => ${4:%todo}\n   | Local => ${5:%todo}\n   | _ => ${6:%todo}\n   }",
+    "insertText": "imported {\n   | CompletionExtensibleVariant.Str(_) => ${1:%todo}\n   | CompletionExtensibleVariant.Num(_) => ${2:%todo}\n   | CompletionExtensibleVariant.Sub.Flag => ${3:%todo}\n   | CompletionExtensibleVariant.Sub.Toggle(_) => ${4:%todo}\n   | CompletionExtensibleVariant.Later => ${5:%todo}\n   | Local => ${6:%todo}\n   | _ => ${7:%todo}\n   }",
     "insertTextFormat": 2,
     "kind": 15,
     "label": "imported (exhaustive switch)",