From bf0da4418f061b74b0f3f9e2a2b1310385896355 Mon Sep 17 00:00:00 2001
From: jam1garner <8260240+jam1garner@users.noreply.github.com>
Date: Sun, 27 Jun 2021 00:28:07 -0400
Subject: [PATCH] Fix `future_prelude_collision` false positive

---
 .../rustc_typeck/src/check/method/prelude2021.rs |  7 +++++++
 .../future-prelude-collision-unneeded.rs         | 16 ++++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 src/test/ui/rust-2021/future-prelude-collision-unneeded.rs

diff --git a/compiler/rustc_typeck/src/check/method/prelude2021.rs b/compiler/rustc_typeck/src/check/method/prelude2021.rs
index 4c925a6f237..e8748dd062f 100644
--- a/compiler/rustc_typeck/src/check/method/prelude2021.rs
+++ b/compiler/rustc_typeck/src/check/method/prelude2021.rs
@@ -57,6 +57,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             {
                 return;
             }
+
+            // if it's an inherent `self` method (not `&self` or `&mut self`), it will take
+            // precedence over the `TryInto` impl, and thus won't break in 2021 edition
+            if pick.autoderefs == 0 && pick.autoref_or_ptr_adjustment.is_none() {
+                return;
+            }
+
             // Inherent impls only require not relying on autoref and autoderef in order to
             // ensure that the trait implementation won't be used
             self.tcx.struct_span_lint_hir(
diff --git a/src/test/ui/rust-2021/future-prelude-collision-unneeded.rs b/src/test/ui/rust-2021/future-prelude-collision-unneeded.rs
new file mode 100644
index 00000000000..a4a5b6667df
--- /dev/null
+++ b/src/test/ui/rust-2021/future-prelude-collision-unneeded.rs
@@ -0,0 +1,16 @@
+// edition:2018
+// check-pass
+#![allow(unused)]
+#![deny(future_prelude_collision)]
+
+struct S;
+
+impl S {
+    fn try_into(self) -> S { S }
+}
+
+// See https://github.com/rust-lang/rust/issues/86633
+fn main() {
+    let s = S;
+    let s2 = s.try_into();
+}