add TypeAtPos completion type and let it drive completion when something might've compiled already and has a type, but no explicit type annotation

Author: zth

analysis/src/CompletionBackEnd.ml

@@ -1113,6 +1113,14 @@ and getCompletionsForContextPath ~debug ~full ~opens ~rawOpens ~pos ~env ~exact
         [Completion.create "dummy" ~env ~kind:(kindFromInnerType typ)]
       | None -> [])
     | None -> [])
+  | CTypeAtPos loc -> (
+    match
+      References.getLocItem ~full ~pos:(Pos.ofLexing loc.loc_start) ~debug
+    with
+    | None -> []
+    | Some {locType = Typed (_, typExpr, _)} ->
+      [Completion.create "dummy" ~env ~kind:(Value typExpr)]
+    | _ -> [])
 
 let getOpens ~debug ~rawOpens ~package ~env =
   if debug && rawOpens <> [] then

analysis/src/CompletionFrontEnd.ml

@@ -591,6 +591,27 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
           (Completable.Cexpression
              {contextPath = ctxPath; prefix; nested = List.rev nested})
       | _ -> ())
+    | {pvb_pat = {ppat_desc = Ppat_var {loc}}; pvb_expr}
+      when locHasCursor pvb_expr.pexp_loc -> (
+      (* Expression without a type annotation. We can complete this if this
+         has compiled previously and there's a type available for the identifier itself.
+         This is nice because the type is assigned even if the assignment isn't complete.
+
+         E.g: let x = {name: "name", <com>}, when `x` has compiled. *)
+      match
+        pvb_expr
+        |> CompletionExpressions.traverseExpr ~exprPath:[] ~pos:posBeforeCursor
+             ~firstCharBeforeCursorNoWhite
+      with
+      | Some (prefix, nested) ->
+        (* This completion should be low prio, so let any deeper completion
+           hit first, and only set this TypeAtPos completion if nothing else
+           here hit. *)
+        Ast_iterator.default_iterator.value_binding iterator value_binding;
+        setResult
+          (Completable.Cexpression
+             {contextPath = CTypeAtPos loc; prefix; nested = List.rev nested})
+      | _ -> ())
     | {
      pvb_pat = {ppat_desc = Ppat_constraint (_pat, coreType); ppat_loc};
      pvb_expr;

analysis/src/SharedTypes.ml

@@ -592,6 +592,8 @@ module Completable = struct
       }
     | CJsxPropValue of {pathToComponent: string list; propName: string}
     | CPatternPath of {rootCtxPath: contextPath; nested: nestedPath list}
+    | CTypeAtPos of Location.t
+        (** A position holding something that might have a *compiled* type. *)
 
   type patternMode = Default | Destructuring
 
@@ -671,6 +673,7 @@ module Completable = struct
       ^ (nested
         |> List.map (fun nestedPath -> nestedPathToString nestedPath)
         |> String.concat "->")
+    | CTypeAtPos _loc -> "CTypeAtPos()"
 
   let toString = function
     | Cpath cp -> "Cpath " ^ contextPathToString cp

analysis/tests/src/RecordCompletion.res

@@ -22,3 +22,24 @@ let n = {R.name: ""}
 
 // n.R. xx
 //     ^com
+
+type optRecord = {
+  name: string,
+  age?: int,
+  online?: bool,
+}
+
+let optRecord = {
+  name: "Hello",
+  //             ^com
+}
+
+type someVariant = One(int, optRecord)
+
+let x = One(
+  1,
+  {
+    name: "What",
+    //            ^com
+  },
+)

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

@@ -12,5 +12,9 @@ posCursor:[9:56] posNoWhite:[9:55] Found expr:[9:13->9:66]
 JSX <SectionHeader:[9:13->9:26] > _children:9:26
 posCursor:[9:56] posNoWhite:[9:55] Found expr:__ghost__[9:10->9:67]
 Pexp_construct []:__ghost__[9:10->9:67] None
+Completable: Cexpression CTypeAtPos()=[]->variantPayload::::($1)
+Package opens Pervasives.JsxModules.place holder
+Resolved opens 1 pervasives
+ContextPath CTypeAtPos()
 null
 

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

@@ -50,8 +50,8 @@ Path Js.Array2.m
   }]
 
 Complete src/RecordCompletion.res 19:7
-posCursor:[19:7] posNoWhite:[19:6] Found expr:[19:3->19:7]
-Pexp_field [19:3->19:4] R.:[19:5->19:7]
+posCursor:[19:7] posNoWhite:[19:6] Found expr:[19:3->25:4]
+Pexp_field [19:3->19:4] R.:[19:5->25:4]
 Completable: Cpath Module[R].""
 Package opens Pervasives.JsxModules.place holder
 Resolved opens 1 pervasives
@@ -81,3 +81,46 @@ Path R.
     "documentation": null
   }]
 
+Complete src/RecordCompletion.res 32:17
+posCursor:[32:17] posNoWhite:[32:15] Found expr:[31:16->34:1]
+Completable: Cexpression CTypeAtPos()->recordBody
+Package opens Pervasives.JsxModules.place holder
+Resolved opens 1 pervasives
+ContextPath CTypeAtPos()
+[{
+    "label": "age",
+    "kind": 5,
+    "tags": [],
+    "detail": "age?: int\n\noptRecord",
+    "documentation": null
+  }, {
+    "label": "online",
+    "kind": 5,
+    "tags": [],
+    "detail": "online?: bool\n\noptRecord",
+    "documentation": null
+  }]
+
+Complete src/RecordCompletion.res 41:18
+posCursor:[41:18] posNoWhite:[41:16] Found expr:[38:8->44:1]
+Pexp_construct One:[38:8->38:11] [38:11->44:1]
+posCursor:[41:18] posNoWhite:[41:16] Found expr:[38:11->44:1]
+posCursor:[41:18] posNoWhite:[41:16] Found expr:[40:2->43:3]
+Completable: Cexpression CTypeAtPos()->variantPayload::One($1), recordBody
+Package opens Pervasives.JsxModules.place holder
+Resolved opens 1 pervasives
+ContextPath CTypeAtPos()
+[{
+    "label": "age",
+    "kind": 5,
+    "tags": [],
+    "detail": "age?: int\n\noptRecord",
+    "documentation": null
+  }, {
+    "label": "online",
+    "kind": 5,
+    "tags": [],
+    "detail": "online?: bool\n\noptRecord",
+    "documentation": null
+  }]
+