From 6d18764876a7347c0efcf7f7ccf0ae1dbe617713 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume.gomez@huawei.com>
Date: Wed, 14 Feb 2024 14:56:16 +0100
Subject: [PATCH] Extend documentation for `Ty::to_opt_closure_kind` method

---
 compiler/rustc_middle/src/ty/sty.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index a3d5f1f195510..10c6e88d6bc33 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -2362,6 +2362,19 @@ impl<'tcx> Ty<'tcx> {
     /// to represent the closure kind, because it has not yet been
     /// inferred. Once upvar inference (in `rustc_hir_analysis/src/check/upvar.rs`)
     /// is complete, that type variable will be unified.
+    ///
+    /// To be noted that you can use [`ClosureArgs::kind()`] or [`CoroutineClosureArgs::kind()`]
+    /// to get the same information, which you can get by calling [`GenericArgs::as_closure()`].
+    ///
+    /// Otherwise, this method can be used as follows:
+    ///
+    /// ```rust,ignore (snippet of compiler code)
+    /// let TyKind::Closure(def_id, [closure_fn_kind_ty, ..]) = closure_ty.kind()
+    ///     && let Some(closure_kind) = closure_fn_kind_ty.expect_ty().to_opt_closure_kind()
+    /// {
+    ///     // your code
+    /// }
+    /// ```
     pub fn to_opt_closure_kind(self) -> Option<ty::ClosureKind> {
         match self.kind() {
             Int(int_ty) => match int_ty {