Perform type instantiation in field autocompletion

Fixes #349

Author: cristianoc

CHANGELOG.md

@@ -21,6 +21,7 @@
 
 #### :bug: Bug Fix
 
+- Fix issue where field autocomplete in records would not perform type instantiation https://github.com/rescript-lang/rescript-vscode/pull/561
 - Fix issue where hovering over a field in record construction would show the type without instantiating its type arguments https://github.com/rescript-lang/rescript-vscode/pull/560
 - Fix Incorrect semantic highlighting of `external` declarations https://github.com/rescript-lang/rescript-vscode/pull/517
 - Fix issue where doc comment with nested comments inside is not shown properly on hover https://github.com/rescript-lang/rescript-vscode/pull/526

analysis/src/CompletionBackEnd.ml

@@ -983,10 +983,10 @@ let findLocalCompletionsWithOpens ~pos ~(env : QueryEnv.t) ~prefix ~exact ~opens
 let rec extractRecordType ~env ~package (t : Types.type_expr) =
   match t.desc with
   | Tlink t1 | Tsubst t1 | Tpoly (t1, []) -> extractRecordType ~env ~package t1
-  | Tconstr (path, _, _) -> (
+  | Tconstr (path, args, _) -> (
     match References.digConstructor ~env ~package path with
     | Some (env, ({item = {kind = Record fields}} as typ)) ->
-      Some (env, fields, typ)
+      Some (env, fields, typ, args)
     | Some (env, {item = {decl = {type_manifest = Some t1}}}) ->
       extractRecordType ~env ~package t1
     | _ -> None)
@@ -1087,6 +1087,54 @@ let completionsGetTypeEnv = function
   | {Completion.kind = Field ({typ}, _); env} :: _ -> Some (typ, env)
   | _ -> None
 
+let instantiateType ~typeParams ~typeArgs (t : Types.type_expr) =
+  if typeParams = [] || typeArgs = [] then t
+  else
+    let rec applySub tp ta t =
+      match (tp, ta) with
+      | t1 :: tRest1, t2 :: tRest2 ->
+        if t1 = t then t2 else applySub tRest1 tRest2 t
+      | [], _ | _, [] -> assert false
+    in
+    let rec loop (t : Types.type_expr) =
+      match t.desc with
+      | Tlink t -> loop t
+      | Tvar _ -> applySub typeParams typeArgs t
+      | Tunivar _ -> t
+      | Tconstr (path, args, memo) ->
+        {t with desc = Tconstr (path, args |> List.map loop, memo)}
+      | Tsubst t -> loop t
+      | Tvariant rd -> {t with desc = Tvariant (rowDesc rd)}
+      | Tnil -> t
+      | Tarrow (lbl, t1, t2, c) ->
+        {t with desc = Tarrow (lbl, loop t1, loop t2, c)}
+      | Ttuple tl -> {t with desc = Ttuple (tl |> List.map loop)}
+      | Tobject (t, r) -> {t with desc = Tobject (loop t, r)}
+      | Tfield (n, k, t1, t2) -> {t with desc = Tfield (n, k, loop t1, loop t2)}
+      | Tpoly (t, []) -> loop t
+      | Tpoly (t, tl) -> {t with desc = Tpoly (loop t, tl |> List.map loop)}
+      | Tpackage (p, l, tl) ->
+        {t with desc = Tpackage (p, l, tl |> List.map loop)}
+    and rowDesc (rd : Types.row_desc) =
+      let row_fields =
+        rd.row_fields |> List.map (fun (l, rf) -> (l, rowField rf))
+      in
+      let row_more = loop rd.row_more in
+      let row_name =
+        match rd.row_name with
+        | None -> None
+        | Some (p, tl) -> Some (p, tl |> List.map loop)
+      in
+      {rd with row_fields; row_more; row_name}
+    and rowField (rf : Types.row_field) =
+      match rf with
+      | Rpresent None -> rf
+      | Rpresent (Some t) -> Rpresent (Some (loop t))
+      | Reither (b1, tl, b2, r) -> Reither (b1, tl |> List.map loop, b2, r)
+      | Rabsent -> Rabsent
+    in
+    loop t
+
 let rec getCompletionsForContextPath ~package ~opens ~rawOpens ~allFiles ~pos
     ~env ~exact ~scope (contextPath : Completable.contextPath) =
   match contextPath with
@@ -1163,9 +1211,14 @@ let rec getCompletionsForContextPath ~package ~opens ~rawOpens ~allFiles ~pos
     with
     | Some (typ, env) -> (
       match typ |> extractRecordType ~env ~package with
-      | Some (env, fields, typDecl) ->
+      | Some (env, fields, typDecl, typeArgs) ->
+        let typeParams = typDecl.item.decl.type_params in
         fields
         |> Utils.filterMap (fun field ->
+               let fieldTyp =
+                 field.typ |> instantiateType ~typeParams ~typeArgs
+               in
+               let field = {field with typ = fieldTyp} in
                if checkName field.fname.txt ~prefix:fieldName ~exact then
                  Some
                    (Completion.create ~name:field.fname.txt ~env

analysis/tests/src/Hover.res

@@ -166,8 +166,9 @@ module TypeSubstitutionRecords = {
   let x2: foobar = {content: {age: 42}, zzz: ""}
   //                  ^hov
 
-  // ^db+
-
   // x1.content.
   //            ^com
+
+  // x2.content.
+  //            ^com
 }

analysis/tests/src/expected/Hover.res.txt

@@ -110,19 +110,27 @@ Hover src/Hover.res 163:23
 Hover src/Hover.res 165:22
 {"contents": "```rescript\nfoobar\n```\n\n```rescript\ntype foobar = foo<bar>\n```"}
 
-
-Complete src/Hover.res 170:16
-posCursor:[170:16] posNoWhite:[170:15] Found expr:[170:5->170:16]
-Pexp_field [170:5->170:15] _:[172:0->170:16]
+Complete src/Hover.res 168:16
+posCursor:[168:16] posNoWhite:[168:15] Found expr:[168:5->168:16]
+Pexp_field [168:5->168:15] _:[173:0->168:16]
 Completable: Cpath Value[x1].content.""
-Ident!! Dep
-Ident!! JsLogger
-Ident!! A
-Ident!! B
-Ident!! Comp
-Raw ppens: 0 
-Package opens 
-Resolved opens 0 
-findLocalCompletionsWithOpens uri:Hover.res pos:170:16
-[]
+[{
+    "label": "age",
+    "kind": 5,
+    "tags": [],
+    "detail": "age: int\n\ntype bar = {age: int}",
+    "documentation": null
+  }]
+
+Complete src/Hover.res 171:16
+posCursor:[171:16] posNoWhite:[171:15] Found expr:[171:5->171:16]
+Pexp_field [171:5->171:15] _:[173:0->171:16]
+Completable: Cpath Value[x2].content.""
+[{
+    "label": "age",
+    "kind": 5,
+    "tags": [],
+    "detail": "age: int\n\ntype bar = {age: int}",
+    "documentation": null
+  }]