From 4d33d41ef3a3a6f01ab7211b5fc6acbd758bf619 Mon Sep 17 00:00:00 2001
From: Jesus Rubio <jesusprubio@gmail.com>
Date: Mon, 8 Feb 2021 18:25:05 +0100
Subject: [PATCH] Add long explanation for E0547

---
 compiler/rustc_error_codes/src/error_codes.rs |  2 +-
 .../src/error_codes/E0547.md                  | 27 +++++++++++++++++++
 .../stability-attribute-sanity.stderr         |  2 +-
 3 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 compiler/rustc_error_codes/src/error_codes/E0547.md

diff --git a/compiler/rustc_error_codes/src/error_codes.rs b/compiler/rustc_error_codes/src/error_codes.rs
index 849ef18fb90..d01c162b0c8 100644
--- a/compiler/rustc_error_codes/src/error_codes.rs
+++ b/compiler/rustc_error_codes/src/error_codes.rs
@@ -287,6 +287,7 @@
 E0541: include_str!("./error_codes/E0541.md"),
 E0542: include_str!("./error_codes/E0542.md"),
 E0546: include_str!("./error_codes/E0546.md"),
+E0547: include_str!("./error_codes/E0547.md"),
 E0550: include_str!("./error_codes/E0550.md"),
 E0551: include_str!("./error_codes/E0551.md"),
 E0552: include_str!("./error_codes/E0552.md"),
@@ -606,7 +607,6 @@
     E0543, // missing 'reason'
     E0544, // multiple stability levels
     E0545, // incorrect 'issue'
-    E0547, // missing 'issue'
 //  E0548, // replaced with a generic attribute input check
     // rustc_deprecated attribute must be paired with either stable or unstable
     // attribute
diff --git a/compiler/rustc_error_codes/src/error_codes/E0547.md b/compiler/rustc_error_codes/src/error_codes/E0547.md
new file mode 100644
index 00000000000..7a719850040
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0547.md
@@ -0,0 +1,27 @@
+#![stable(since = "1.0.0", feature = "test")]
+#[unstable(feature = "_unstable_fn")] // invalid
+fn _unstable_fn() {}
+#[rustc_const_unstable(feature = "_unstable_const_fn")] // invalid
+fn _unstable_const_fn() {}
+```
+
+To fix the issue you need to provide the `issue` field.
+
+```
+#![feature(staged_api)]
+#![stable(since = "1.0.0", feature = "test")]
+#[unstable(feature = "_unstable_fn", issue = "none")] // ok!
+fn _unstable_fn() {}
+#[rustc_const_unstable(
+    feature = "_unstable_const_fn",
+    issue = "none"
+)] // ok!
+fn _unstable_const_fn() {}
+```
+
+See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix
+of the Book and the [Stability attributes][stability-attributes] section of the
+Rustc Dev Guide for more details.
+
+[how-rust-made-nightly]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html
+[stability-attributes]: https://rustc-dev-guide.rust-lang.org/stability.html
diff --git a/src/test/ui/stability-attribute/stability-attribute-sanity.stderr b/src/test/ui/stability-attribute/stability-attribute-sanity.stderr
index 151b96b8b5a..674139f4afc 100644
--- a/src/test/ui/stability-attribute/stability-attribute-sanity.stderr
+++ b/src/test/ui/stability-attribute/stability-attribute-sanity.stderr
@@ -116,5 +116,5 @@ LL | #[rustc_deprecated(since = "a", reason = "text")]
 
 error: aborting due to 19 previous errors
 
-Some errors have detailed explanations: E0539, E0541, E0542, E0546, E0550.
+Some errors have detailed explanations: E0539, E0541, E0542, E0546, E0547, E0550.
 For more information about an error, try `rustc --explain E0539`.