From 9876f6bd9c2927633e6df21889a585469dc5fce6 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sat, 4 Jan 2020 00:28:15 +0100
Subject: [PATCH 1/2] Fix error code failure check in rustdoc test

---
 src/librustdoc/test.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index db66b7530b29d..ca5c09edfbb28 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -299,7 +299,6 @@ fn run_test(
             eprint!("{}", self.0);
         }
     }
-
     let out = str::from_utf8(&output.stderr).unwrap();
     let _bomb = Bomb(&out);
     match (output.status.success(), compile_fail) {
@@ -309,7 +308,7 @@ fn run_test(
         (true, false) => {}
         (false, true) => {
             if !error_codes.is_empty() {
-                error_codes.retain(|err| !out.contains(err));
+                error_codes.retain(|err| !out.contains(&format!("error[{}]: ", err)));
 
                 if !error_codes.is_empty() {
                     return Err(TestFailure::MissingErrorCodes(error_codes));

From 5b7d64e9473216dc8650ca5f910100389ab91726 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sat, 4 Jan 2020 01:41:25 +0100
Subject: [PATCH 2/2] Fix error codes explanation' code examples

---
 src/librustc_error_codes/error_codes/E0445.md |  4 +++
 src/librustc_error_codes/error_codes/E0446.md |  4 +++
 src/librustc_error_codes/error_codes/E0491.md | 36 ++++++++++---------
 3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/src/librustc_error_codes/error_codes/E0445.md b/src/librustc_error_codes/error_codes/E0445.md
index 9cc62b2ba6d0a..e6a28a9c2c460 100644
--- a/src/librustc_error_codes/error_codes/E0445.md
+++ b/src/librustc_error_codes/error_codes/E0445.md
@@ -12,6 +12,8 @@ trait Foo {
 pub trait Bar : Foo {} // error: private trait in public interface
 pub struct Bar2<T: Foo>(pub T); // same error
 pub fn foo<T: Foo> (t: T) {} // same error
+
+fn main() {}
 ```
 
 To solve this error, please ensure that the trait is also public. The trait
@@ -26,4 +28,6 @@ pub trait Foo { // we set the Foo trait public
 pub trait Bar : Foo {} // ok!
 pub struct Bar2<T: Foo>(pub T); // ok!
 pub fn foo<T: Foo> (t: T) {} // ok!
+
+fn main() {}
 ```
diff --git a/src/librustc_error_codes/error_codes/E0446.md b/src/librustc_error_codes/error_codes/E0446.md
index d0144478dbfe0..77a1834ece42f 100644
--- a/src/librustc_error_codes/error_codes/E0446.md
+++ b/src/librustc_error_codes/error_codes/E0446.md
@@ -12,6 +12,8 @@ mod Foo {
         Bar(0)
     }
 }
+
+fn main() {}
 ```
 
 To solve this error, please ensure that the type is also public. The type
@@ -27,4 +29,6 @@ mod Foo {
         Bar(0)
     }
 }
+
+fn main() {}
 ```
diff --git a/src/librustc_error_codes/error_codes/E0491.md b/src/librustc_error_codes/error_codes/E0491.md
index 1ccaf71257b8b..d45663f3a5347 100644
--- a/src/librustc_error_codes/error_codes/E0491.md
+++ b/src/librustc_error_codes/error_codes/E0491.md
@@ -3,30 +3,34 @@ A reference has a longer lifetime than the data it references.
 Erroneous code example:
 
 ```compile_fail,E0491
-trait SomeTrait<'a> {
-    type Output;
+struct Foo<'a> {
+    x: fn(&'a i32),
 }
 
-impl<'a, T> SomeTrait<'a> for T {
-    type Output = &'a T; // compile error E0491
+trait Trait<'a, 'b> {
+    type Out;
+}
+
+impl<'a, 'b> Trait<'a, 'b> for usize {
+    type Out = &'a Foo<'b>; // error!
 }
 ```
 
-Here, the problem is that a reference type like `&'a T` is only valid
-if all the data in T outlives the lifetime `'a`. But this impl as written
-is applicable to any lifetime `'a` and any type `T` -- we have no guarantee
-that `T` outlives `'a`. To fix this, you can add a where clause like
-`where T: 'a`.
+Here, the problem is that the compiler cannot be sure that the `'b` lifetime
+will live longer than `'a`, which should be mandatory in order to be sure that
+`Trait::Out` will always have a reference pointing to an existing type. So in
+this case, we just need to tell the compiler than `'b` must outlive `'a`:
 
 ```
-trait SomeTrait<'a> {
-    type Output;
+struct Foo<'a> {
+    x: fn(&'a i32),
+}
+
+trait Trait<'a, 'b> {
+    type Out;
 }
 
-impl<'a, T> SomeTrait<'a> for T
-where
-    T: 'a,
-{
-    type Output = &'a T; // compile error E0491
+impl<'a, 'b: 'a> Trait<'a, 'b> for usize { // we added the lifetime enforcement
+    type Out = &'a Foo<'b>; // it now works!
 }
 ```