From a19952435bada35dbffd8b219211ecacfcaa6754 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 2 Sep 2023 13:09:52 -0700
Subject: [PATCH] Implement AsDisplay using GAT

---
 .github/workflows/ci.yml   |  2 +-
 Cargo.toml                 |  2 +-
 README.md                  |  2 +-
 impl/Cargo.toml            |  2 +-
 src/display.rs             | 30 +++++++++++++++++-------------
 tests/ui/no-display.stderr |  2 +-
 6 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b56868ec..cd685a24 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [nightly, beta, stable, 1.56.0]
+        rust: [nightly, beta, stable, 1.65.0]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v3
diff --git a/Cargo.toml b/Cargo.toml
index 0a8526cb..07d6ced9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,7 +9,7 @@ edition = "2021"
 keywords = ["error", "error-handling", "derive"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/thiserror"
-rust-version = "1.56"
+rust-version = "1.65"
 
 [dependencies]
 thiserror-impl = { version = "=1.0.47", path = "impl" }
diff --git a/README.md b/README.md
index 9de063c3..1bae0383 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ This library provides a convenient derive macro for the standard library's
 thiserror = "1.0"
 ```
 
-*Compiler support: requires rustc 1.56+*
+*Compiler support: requires rustc 1.65+*
 
 <br>
 
diff --git a/impl/Cargo.toml b/impl/Cargo.toml
index 091be615..4aaacae3 100644
--- a/impl/Cargo.toml
+++ b/impl/Cargo.toml
@@ -6,7 +6,7 @@ description = "Implementation detail of the `thiserror` crate"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/thiserror"
-rust-version = "1.56"
+rust-version = "1.65"
 
 [lib]
 proc-macro = true
diff --git a/src/display.rs b/src/display.rs
index 58d11e45..38ae9e86 100644
--- a/src/display.rs
+++ b/src/display.rs
@@ -2,37 +2,41 @@ use std::fmt::Display;
 use std::path::{self, Path, PathBuf};
 
 #[doc(hidden)]
-pub trait AsDisplay<'a> {
-    type Target: Display;
+pub trait AsDisplay {
+    type Target<'a>: Display
+    where
+        Self: 'a;
 
-    fn as_display(&'a self) -> Self::Target;
+    fn as_display<'a>(&'a self) -> Self::Target<'a>;
 }
 
-impl<'a, T> AsDisplay<'a> for &T
+impl<T> AsDisplay for &T
 where
-    T: Display + 'a,
+    T: Display,
 {
-    type Target = &'a T;
+    type Target<'a> = &'a T
+    where
+        Self: 'a;
 
-    fn as_display(&'a self) -> Self::Target {
+    fn as_display<'a>(&'a self) -> Self::Target<'a> {
         *self
     }
 }
 
-impl<'a> AsDisplay<'a> for Path {
-    type Target = path::Display<'a>;
+impl AsDisplay for Path {
+    type Target<'a> = path::Display<'a>;
 
     #[inline]
-    fn as_display(&'a self) -> Self::Target {
+    fn as_display<'a>(&'a self) -> Self::Target<'a> {
         self.display()
     }
 }
 
-impl<'a> AsDisplay<'a> for PathBuf {
-    type Target = path::Display<'a>;
+impl AsDisplay for PathBuf {
+    type Target<'a> = path::Display<'a>;
 
     #[inline]
-    fn as_display(&'a self) -> Self::Target {
+    fn as_display<'a>(&'a self) -> Self::Target<'a> {
         self.display()
     }
 }
diff --git a/tests/ui/no-display.stderr b/tests/ui/no-display.stderr
index 0f47c24b..26dc8429 100644
--- a/tests/ui/no-display.stderr
+++ b/tests/ui/no-display.stderr
@@ -9,7 +9,7 @@ error[E0599]: the method `as_display` exists for reference `&NoDisplay`, but its
   |
   = note: the following trait bounds were not satisfied:
           `NoDisplay: std::fmt::Display`
-          which is required by `&NoDisplay: AsDisplay<'_>`
+          which is required by `&NoDisplay: AsDisplay`
 note: the trait `std::fmt::Display` must be implemented
  --> $RUST/core/src/fmt/mod.rs
   |