From 80d730b52618d4dcc52dae25c0e3fceea12d4b33 Mon Sep 17 00:00:00 2001
From: SoniEx2 <endermoneymod@gmail.com>
Date: Mon, 23 Jan 2023 13:10:27 -0300
Subject: [PATCH] Add MCP 563 syntax

---
 compiler/rustc_feature/src/builtin_attrs.rs   |  2 +-
 compiler/rustc_span/src/symbol.rs             |  1 +
 .../dropck/mcp563-dropck-eyepatch-syntax.rs   | 26 +++++++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/dropck/mcp563-dropck-eyepatch-syntax.rs

diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index af56a0b245987..53319c748db73 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -540,7 +540,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
 
     gated!(fundamental, Normal, template!(Word), WarnFollowing, experimental!(fundamental)),
     gated!(
-        may_dangle, Normal, template!(Word), WarnFollowing, dropck_eyepatch,
+        may_dangle, Normal, template!(Word, List: "borrow"), WarnFollowing, dropck_eyepatch,
         "`may_dangle` has unstable semantics and may be removed in the future",
     ),
 
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 7597b8d126a9c..19f122d096436 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -425,6 +425,7 @@ symbols! {
         black_box,
         block,
         bool,
+        borrow,
         borrowck_graphviz_format,
         borrowck_graphviz_postflow,
         box_free,
diff --git a/tests/ui/dropck/mcp563-dropck-eyepatch-syntax.rs b/tests/ui/dropck/mcp563-dropck-eyepatch-syntax.rs
new file mode 100644
index 0000000000000..5ade731bc4760
--- /dev/null
+++ b/tests/ui/dropck/mcp563-dropck-eyepatch-syntax.rs
@@ -0,0 +1,26 @@
+#![feature(dropck_eyepatch)]
+
+// This test checks the `#[may_dangle]` attribute syntax.
+
+struct Foo<T>(*const T);
+
+// No error: "drops" bound
+unsafe impl<#[may_dangle] T> Drop for Foo<T> {
+    fn drop(&mut self) { }
+}
+
+struct Bar<T>(*const T);
+
+// No error: "borrows" bound
+unsafe impl<#[may_dangle(borrow)] T> Drop for Bar<T> {
+    fn drop(&mut self) { }
+}
+
+struct Baz<T>(*const T);
+
+// Error: invalid syntax
+unsafe impl<#[may_dangle(invalid)] T> Drop for Baz<T> {
+    fn drop(&mut self) { }
+}
+
+pub fn main() { }