From c0544d121bbc48626970542741510229b462289c Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <ccrisccris@gmail.com>
Date: Sat, 13 Feb 2021 16:41:01 +0100
Subject: [PATCH] Fix type hint when hovering over labeled arguments of
 components.

This is a combination of `@react.component` PPX and compiler internals.
The PPX produces an object for the props, and the compiler generates a call to `Js_OO.unsafe_downgrade`.

The end result is that `~x` turns into `Js_OO.unsafe_downgrade(Props)#x`, which produces becomes 3 distinct values that appear to be at exactly the same source location: `Props`, `unsafe_downgrade`, and `x`.

Fixes https://github.com/rescript-lang/rescript-editor-support/issues/63
---
 Changes.md                                |  1 +
 src/rescript-editor-support/References.re | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/Changes.md b/Changes.md
index dd064637..d4f38838 100644
--- a/Changes.md
+++ b/Changes.md
@@ -2,6 +2,7 @@
 - Add support for autocomplete for `foo->`: the type of `foo` is used to determine the module to take completions from.
 - Add support for autocomplete for decorators such as `@module` and `@val`.
 - Fix issue for uncurried functions where the internal definition of `Js.Fn.arity` is shown on hover. (See https://github.com/rescript-lang/rescript-editor-support/issues/62).
+- Fix type hint when hovering over labeled arguments of components (See https://github.com/rescript-lang/rescript-editor-support/issues/63).
 
 ## Release 1.0.5 of rescript-vscode
 This [commit](https://github.com/rescript-lang/rescript-editor-support/commit/6bdd10f6af259edc5f9cbe5b9df06836de3ab865) is vendored in [rescript-vscode 1.0.5](https://github.com/rescript-lang/rescript-vscode/releases/tag/1.0.5).
diff --git a/src/rescript-editor-support/References.re b/src/rescript-editor-support/References.re
index 8322ab29..7e5019e5 100644
--- a/src/rescript-editor-support/References.re
+++ b/src/rescript-editor-support/References.re
@@ -29,6 +29,19 @@ let locsForPos = (~extra, pos) => {
 
 let locForPos = (~extra, pos) => {
   switch (locsForPos(~extra, pos)) {
+  | [
+      (loc1, Typed(_, LocalReference(_))),
+      (
+        loc2,
+        Typed(_, GlobalReference("Js_OO", Tip("unsafe_downgrade"), _)),
+      ),
+      (loc3, _) as l3,
+    ]
+      when loc1 == loc2 && loc2 == loc3 =>
+    // JSX and compiler combined:
+    // ~x becomes Js_OO.unsafe_downgrade(Props)#x
+    // heuristic for: [Props, unsafe_downgrade, x], give loc of `x`
+    Some(l3)
   | [(loc1, _), (loc2, _) as l, (loc3, _)]
       when loc1 == loc2 && loc2 == loc3 =>
     // JSX with at most one child