From fc0fb38b19809e6f134a3409863b445216ae9c61 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Mon, 30 Aug 2021 20:37:07 +0200
Subject: [PATCH] Add macro test for prelude collision suggestions.

---
 .../future-prelude-collision-macros.fixed     | 45 +++++++++++++++++++
 .../future-prelude-collision-macros.rs        | 45 +++++++++++++++++++
 .../future-prelude-collision-macros.stderr    | 25 +++++++++++
 3 files changed, 115 insertions(+)
 create mode 100644 src/test/ui/rust-2021/future-prelude-collision-macros.fixed
 create mode 100644 src/test/ui/rust-2021/future-prelude-collision-macros.rs
 create mode 100644 src/test/ui/rust-2021/future-prelude-collision-macros.stderr

diff --git a/src/test/ui/rust-2021/future-prelude-collision-macros.fixed b/src/test/ui/rust-2021/future-prelude-collision-macros.fixed
new file mode 100644
index 00000000000..a97dc176e1b
--- /dev/null
+++ b/src/test/ui/rust-2021/future-prelude-collision-macros.fixed
@@ -0,0 +1,45 @@
+// run-rustfix
+// edition:2018
+// check-pass
+#![warn(rust_2021_prelude_collisions)]
+#![allow(unreachable_code)]
+
+macro_rules! foo {
+    () => {{
+        123;
+        S
+    }};
+}
+
+trait MyTry<T> {
+    fn try_into(self, _: u8);
+}
+
+struct S;
+
+impl MyTry<i32> for S {
+    fn try_into(self, _: u8) {}
+}
+
+trait TryFromU8: Sized {
+    fn try_from(_: u8);
+}
+
+impl TryFromU8 for u32 {
+    fn try_from(_: u8) {}
+}
+
+macro_rules! bar {
+    () => {
+        u32
+    };
+}
+
+fn main() {
+    MyTry::try_into(foo!(), todo!());
+    //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+    //~| WARNING this is accepted in the current edition
+    <bar!() as TryFromU8>::try_from(0);
+    //~^ WARNING trait-associated function `try_from` will become ambiguous in Rust 2021
+    //~| WARNING this is accepted in the current edition
+}
diff --git a/src/test/ui/rust-2021/future-prelude-collision-macros.rs b/src/test/ui/rust-2021/future-prelude-collision-macros.rs
new file mode 100644
index 00000000000..82484b5b368
--- /dev/null
+++ b/src/test/ui/rust-2021/future-prelude-collision-macros.rs
@@ -0,0 +1,45 @@
+// run-rustfix
+// edition:2018
+// check-pass
+#![warn(rust_2021_prelude_collisions)]
+#![allow(unreachable_code)]
+
+macro_rules! foo {
+    () => {{
+        123;
+        S
+    }};
+}
+
+trait MyTry<T> {
+    fn try_into(self, _: u8);
+}
+
+struct S;
+
+impl MyTry<i32> for S {
+    fn try_into(self, _: u8) {}
+}
+
+trait TryFromU8: Sized {
+    fn try_from(_: u8);
+}
+
+impl TryFromU8 for u32 {
+    fn try_from(_: u8) {}
+}
+
+macro_rules! bar {
+    () => {
+        u32
+    };
+}
+
+fn main() {
+    foo!().try_into(todo!());
+    //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+    //~| WARNING this is accepted in the current edition
+    <bar!()>::try_from(0);
+    //~^ WARNING trait-associated function `try_from` will become ambiguous in Rust 2021
+    //~| WARNING this is accepted in the current edition
+}
diff --git a/src/test/ui/rust-2021/future-prelude-collision-macros.stderr b/src/test/ui/rust-2021/future-prelude-collision-macros.stderr
new file mode 100644
index 00000000000..4c3543ca782
--- /dev/null
+++ b/src/test/ui/rust-2021/future-prelude-collision-macros.stderr
@@ -0,0 +1,25 @@
+warning: trait method `try_into` will become ambiguous in Rust 2021
+  --> $DIR/future-prelude-collision-macros.rs:39:5
+   |
+LL |     foo!().try_into(todo!());
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: disambiguate the associated function: `MyTry::try_into(foo!(), todo!())`
+   |
+note: the lint level is defined here
+  --> $DIR/future-prelude-collision-macros.rs:4:9
+   |
+LL | #![warn(rust_2021_prelude_collisions)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/prelude.html>
+
+warning: trait-associated function `try_from` will become ambiguous in Rust 2021
+  --> $DIR/future-prelude-collision-macros.rs:42:5
+   |
+LL |     <bar!()>::try_from(0);
+   |     ^^^^^^^^^^^^^^^^^^ help: disambiguate the associated function: `<bar!() as TryFromU8>::try_from`
+   |
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/prelude.html>
+
+warning: 2 warnings emitted
+