diff --git a/src/librustc/error_codes.rs b/src/librustc/error_codes.rs
index f40b892a06bf..d5c2db5fb970 100644
--- a/src/librustc/error_codes.rs
+++ b/src/librustc/error_codes.rs
@@ -1896,6 +1896,51 @@ fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 {
 ```
 "##,
 
+E0623: r##"
+A lifetime didn't match what was expected.
+
+Erroneous code example:
+
+```compile_fail,E0623
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+fn bar<'short, 'long>(c: Foo<'short>, l: &'long isize) {
+    let _: Foo<'long> = c; // error!
+}
+```
+
+In this example, we tried to set a value with an incompatible lifetime to
+another one (`'long` is unrelated to `'short`). We can solve this issue in
+two different ways:
+
+Either we make `'short` live at least as long as `'long`:
+
+```
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+// we set 'short to live at least as long as 'long
+fn bar<'short: 'long, 'long>(c: Foo<'short>, l: &'long isize) {
+    let _: Foo<'long> = c; // ok!
+}
+```
+
+Or we use only one lifetime:
+
+```
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+fn bar<'short>(c: Foo<'short>, l: &'short isize) {
+    let _: Foo<'short> = c; // ok!
+}
+```
+"##,
+
 E0635: r##"
 The `#![feature]` attribute specified an unknown feature.
 
@@ -2329,7 +2374,6 @@ the future, [RFC 2091] prohibits their implementation without a follow-up RFC.
     E0488, // lifetime of variable does not enclose its declaration
     E0489, // type/lifetime parameter not in scope here
     E0490, // a value of type `..` is borrowed for too long
-    E0623, // lifetime mismatch where both parameters are anonymous regions
     E0628, // generators cannot have explicit parameters
     E0631, // type mismatch in closure arguments
     E0637, // "'_" is not a valid lifetime bound
diff --git a/src/test/ui/associated-type-bounds/implied-region-constraints.stderr b/src/test/ui/associated-type-bounds/implied-region-constraints.stderr
index 9968f3e8bac5..60c6e8a80fb6 100644
--- a/src/test/ui/associated-type-bounds/implied-region-constraints.stderr
+++ b/src/test/ui/associated-type-bounds/implied-region-constraints.stderr
@@ -18,3 +18,4 @@ LL |             let _failure_proves_not_implied_outlives_region_b: &'b T = &x;
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr b/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
index 63d662f44658..d5310c47fcf1 100644
--- a/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
+++ b/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
@@ -11,3 +11,4 @@ LL |     let z: I::A = if cond { x } else { y };
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/associated-types-subtyping-1.stderr b/src/test/ui/associated-types/associated-types-subtyping-1.stderr
index 660e5b3928ac..58ceec9040b9 100644
--- a/src/test/ui/associated-types/associated-types-subtyping-1.stderr
+++ b/src/test/ui/associated-types/associated-types-subtyping-1.stderr
@@ -18,3 +18,4 @@ LL |     let _c: <T as Trait<'a>>::Type = b;
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr b/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr
index dc9a549586ba..fa4c6adb5fff 100644
--- a/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr
+++ b/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr
@@ -22,3 +22,4 @@ LL |    (a, b)
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr b/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr
index 6accf8110ad1..5009e0868a7d 100644
--- a/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr
+++ b/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr
@@ -21,3 +21,4 @@ LL |    let b = bar(foo, x);
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr b/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
index ef036bd8fbaa..65d16440ac9b 100644
--- a/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
+++ b/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
@@ -11,3 +11,4 @@ LL |    let b = bar(f, y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/async-await/issues/issue-63388-1.stderr b/src/test/ui/async-await/issues/issue-63388-1.stderr
index 2917fa9ccb7f..8813183312dd 100644
--- a/src/test/ui/async-await/issues/issue-63388-1.stderr
+++ b/src/test/ui/async-await/issues/issue-63388-1.stderr
@@ -11,3 +11,4 @@ LL |         foo
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr b/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr
index f6d611517bc8..7b8f290d6c2f 100644
--- a/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr
+++ b/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr
@@ -9,3 +9,4 @@ LL | async fn async_ret_impl_trait1<'a, 'b>(a: &'a u8, b: &'b u8) -> impl Trait<
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr b/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr
index 4142fc488c0d..67b6f64eaa64 100644
--- a/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr
+++ b/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr
@@ -10,3 +10,4 @@ LL |     S { pointer: &mut *p.pointer }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/continue-after-missing-main.stderr b/src/test/ui/continue-after-missing-main.stderr
index 64d34cb6a194..439f9e5221f6 100644
--- a/src/test/ui/continue-after-missing-main.stderr
+++ b/src/test/ui/continue-after-missing-main.stderr
@@ -21,4 +21,5 @@ LL |     let _: AdaptedMatrixProvider<'original_data, MP> = tableau.provider().c
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0601`.
+Some errors have detailed explanations: E0601, E0623.
+For more information about an error, try `rustc --explain E0601`.
diff --git a/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr b/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr
index 2ffb94348616..a8341f62e1d1 100644
--- a/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr
+++ b/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr
@@ -77,4 +77,5 @@ LL | fn ty_param_wont_outlive_static<T:Debug>(x: T) -> impl Debug + 'static {
 
 error: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0310`.
+Some errors have detailed explanations: E0310, E0623.
+For more information about an error, try `rustc --explain E0310`.
diff --git a/src/test/ui/in-band-lifetimes/mismatched.stderr b/src/test/ui/in-band-lifetimes/mismatched.stderr
index ec1045d5fae3..db72c2069710 100644
--- a/src/test/ui/in-band-lifetimes/mismatched.stderr
+++ b/src/test/ui/in-band-lifetimes/mismatched.stderr
@@ -16,4 +16,5 @@ LL | fn foo2(x: &'a u32, y: &'b u32) -> &'a u32 { y }
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0621`.
+Some errors have detailed explanations: E0621, E0623.
+For more information about an error, try `rustc --explain E0621`.
diff --git a/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr b/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr
index bc302e91c1c5..15891c9e7a62 100644
--- a/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr
+++ b/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr
@@ -22,3 +22,4 @@ LL |         x
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/issues/issue-17728.stderr b/src/test/ui/issues/issue-17728.stderr
index 56dfb89456fe..945dfc26b206 100644
--- a/src/test/ui/issues/issue-17728.stderr
+++ b/src/test/ui/issues/issue-17728.stderr
@@ -29,4 +29,5 @@ LL | |     }
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr
index 56ca610019c4..e9f5fc311dfc 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr
@@ -11,3 +11,4 @@ LL |         if x > y { x } else { y }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr
index df34d18ee83a..0d506f2b9fcb 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr
@@ -11,3 +11,4 @@ LL |     x
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr
index 22e14df9edc0..98a23613c363 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr
@@ -11,3 +11,4 @@ LL |         if true { x } else { self }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr
index c0c75c7453d2..e505c9c0dc26 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr
index 57101cffe9b9..63b1c6db28f1 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr
@@ -9,3 +9,4 @@ LL |     x.push(z);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr
index cab30636280a..2f669efcf1eb 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr
@@ -8,3 +8,4 @@ LL |     let a: &mut Vec<Ref<i32>> = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr
index 384caca82489..258b6805acd5 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr
@@ -8,3 +8,4 @@ LL |     let a: &mut Vec<Ref<i32>> = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
index 9251c5e2446f..0aff80c6fbdd 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
@@ -8,3 +8,4 @@ LL |     *v = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr
index adda66899cbf..2e5ff6782d3b 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr
@@ -16,3 +16,4 @@ LL |     z.push((x,y));
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr
index 4341e8e663e1..8e41d7c54e68 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr
@@ -8,3 +8,4 @@ LL |     x.b = y.b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr
index b49ee0cfc703..d659c88f69ef 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr
@@ -8,3 +8,4 @@ LL |     x.a = x.b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr
index a13c7e63cd6d..374bbd93d087 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr
@@ -9,3 +9,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr
index 14faf6f460f5..94798d1ce2ab 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr
index e5696b74da9e..9f5a79ed333d 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr
index bbf5d2452bfb..2c87f8dbd2c2 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr
index f1bc1ca3aab0..60b92ed2b324 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr
@@ -10,3 +10,4 @@ LL |     y = x.b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr
index d8f6b8c49d30..a220c8ddb2be 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr
@@ -8,3 +8,4 @@ LL |     y.b = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
index 08ae2c9db52e..73472a8d0225 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
@@ -8,3 +8,4 @@ LL |     y.b = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr
index ff286d722aac..eb6e6f2e95e7 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr
@@ -8,3 +8,4 @@ LL |     x.b = y;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
index 3d16c2656835..199f880b3c48 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
@@ -10,3 +10,4 @@ LL |     x
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
index 10872d31ef20..838f43b37747 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
@@ -10,3 +10,4 @@ LL |         if true { x } else { self }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
index 99e6e8bc5aa9..d2cc3dba6a43 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
@@ -8,3 +8,4 @@ LL |   y.push(z);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
index 8ac221e333ad..e8b0208f092f 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
@@ -8,3 +8,4 @@ LL |         x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
index bfecb4d33931..2acc4eaf60f5 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
@@ -8,3 +8,4 @@ LL |   y.push(z);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr
index 053d577fa01e..b2784827672b 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr b/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr
index f825475b96b0..89579fb1df3d 100644
--- a/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr
+++ b/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr
@@ -27,4 +27,5 @@ LL | fn load2<'a>(ss: &MyBox<dyn SomeTrait + 'a>) -> MyBox<dyn SomeTrait + 'a> {
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr b/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr
index fd78f82d0f32..36c66451cfaf 100644
--- a/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr
+++ b/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr
@@ -27,4 +27,5 @@ LL |     let _: fn(&mut &isize, &mut &isize) = a;
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr b/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr
index 220c5493d19b..a366bd2e5c2d 100644
--- a/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr
+++ b/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr
@@ -38,4 +38,5 @@ LL |     let _: fn(&mut &isize, &mut &isize, &mut &isize) = a;
 
 error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr b/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr
index 4e88be1c1e8a..eb205a303dbd 100644
--- a/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr
+++ b/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr
@@ -9,3 +9,4 @@ LL |     a.bigger_region(b)
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr b/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr
index 6b1302b53940..de1073cd1d9d 100644
--- a/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr
+++ b/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr
@@ -9,3 +9,4 @@ LL |     f.method(b);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-creating-enums3.stderr b/src/test/ui/regions/regions-creating-enums3.stderr
index 763b62d945df..2fc1fc3f6812 100644
--- a/src/test/ui/regions/regions-creating-enums3.stderr
+++ b/src/test/ui/regions/regions-creating-enums3.stderr
@@ -10,3 +10,4 @@ LL |     Ast::Add(x, y)
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-free-region-ordering-callee.stderr b/src/test/ui/regions/regions-free-region-ordering-callee.stderr
index 49cf1dfc642d..4648bf046bc7 100644
--- a/src/test/ui/regions/regions-free-region-ordering-callee.stderr
+++ b/src/test/ui/regions/regions-free-region-ordering-callee.stderr
@@ -22,3 +22,4 @@ LL |     let z: &'b usize = &*x;
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr b/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr
index 9d6bae79ce5d..a33d3583552d 100644
--- a/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr
+++ b/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr
@@ -29,3 +29,4 @@ LL |     let z: Option<&'a &'b usize> = None;
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr b/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr
index 9374818960d3..f3a0358b90fb 100644
--- a/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr
+++ b/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr
@@ -12,3 +12,4 @@ LL |     let _: Contravariant<'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr b/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr
index cd0a18a892f2..c3e2075fbc37 100644
--- a/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr
+++ b/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr
@@ -11,3 +11,4 @@ LL |     let _: Covariant<'short> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr b/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr
index 0c3c342728c0..e260fccf8488 100644
--- a/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr
+++ b/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr
@@ -27,4 +27,5 @@ LL |     let _: fn(&mut &isize, &mut &isize) = a;
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr
index ead448df930f..aca3a1ed0572 100644
--- a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr
+++ b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr
@@ -10,3 +10,4 @@ LL |     &mut ***p
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr
index 064e89ee001c..a9916dbe4f5e 100644
--- a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr
+++ b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr
@@ -10,3 +10,4 @@ LL |     &mut **p
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr b/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr
index 6b3a488805f9..98f7a8136da9 100644
--- a/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr
+++ b/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr
@@ -9,3 +9,4 @@ LL |     let _: S<'long, 'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr b/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr
index 44199881444a..e7c106cbbe3d 100644
--- a/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr
+++ b/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr
@@ -12,3 +12,4 @@ LL |     let _: Contravariant<'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr b/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr
index 22ba8838893d..e5e5261ba993 100644
--- a/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr
+++ b/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr
@@ -11,3 +11,4 @@ LL |     let _: Covariant<'short> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr b/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr
index a779b485ea70..2a2d5d019a12 100644
--- a/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr
+++ b/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr
@@ -11,3 +11,4 @@ LL |     let _: Invariant<'short> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
index e3c261576e61..37297032632e 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
@@ -24,3 +24,4 @@ LL |     async fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
index 3296e14f806e..f3a7d1472017 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
@@ -24,3 +24,4 @@ LL |     fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/lt-ref-self-async.stderr b/src/test/ui/self/elision/lt-ref-self-async.stderr
index 6b668d9f1f65..235b71ccab3a 100644
--- a/src/test/ui/self/elision/lt-ref-self-async.stderr
+++ b/src/test/ui/self/elision/lt-ref-self-async.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/lt-ref-self.stderr b/src/test/ui/self/elision/lt-ref-self.stderr
index f73b3eddd382..afd07d38f2fe 100644
--- a/src/test/ui/self/elision/lt-ref-self.stderr
+++ b/src/test/ui/self/elision/lt-ref-self.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-self-async.stderr b/src/test/ui/self/elision/ref-mut-self-async.stderr
index 29fbec9fa7ae..a656808d46bc 100644
--- a/src/test/ui/self/elision/ref-mut-self-async.stderr
+++ b/src/test/ui/self/elision/ref-mut-self-async.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-self.stderr b/src/test/ui/self/elision/ref-mut-self.stderr
index 37984cd72fba..3d6ae4b3dd38 100644
--- a/src/test/ui/self/elision/ref-mut-self.stderr
+++ b/src/test/ui/self/elision/ref-mut-self.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-struct-async.stderr b/src/test/ui/self/elision/ref-mut-struct-async.stderr
index 46591bfc9580..2dc8cdb7d28e 100644
--- a/src/test/ui/self/elision/ref-mut-struct-async.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct-async.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-struct.stderr b/src/test/ui/self/elision/ref-mut-struct.stderr
index 2a4826905b94..3fec398bb987 100644
--- a/src/test/ui/self/elision/ref-mut-struct.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-self-async.stderr b/src/test/ui/self/elision/ref-self-async.stderr
index c255d1893637..bda958241b67 100644
--- a/src/test/ui/self/elision/ref-self-async.stderr
+++ b/src/test/ui/self/elision/ref-self-async.stderr
@@ -70,3 +70,4 @@ LL |         f
 
 error: aborting due to 7 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-self.stderr b/src/test/ui/self/elision/ref-self.stderr
index 611498f18da4..8343c8d349e1 100644
--- a/src/test/ui/self/elision/ref-self.stderr
+++ b/src/test/ui/self/elision/ref-self.stderr
@@ -70,3 +70,4 @@ LL |         f
 
 error: aborting due to 7 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-struct-async.stderr b/src/test/ui/self/elision/ref-struct-async.stderr
index c70facc931ec..49a2a00953d8 100644
--- a/src/test/ui/self/elision/ref-struct-async.stderr
+++ b/src/test/ui/self/elision/ref-struct-async.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-struct.stderr b/src/test/ui/self/elision/ref-struct.stderr
index 186e651c143b..5116488dd22b 100644
--- a/src/test/ui/self/elision/ref-struct.stderr
+++ b/src/test/ui/self/elision/ref-struct.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr b/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr
index 21fdfcaef862..76c14ccc14b4 100644
--- a/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr
+++ b/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr
@@ -8,3 +8,4 @@ LL | fn foo(x: &mut Vec<&'_ u8>, y: &'_ u8) { x.push(y); }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/variance/variance-cell-is-invariant.stderr b/src/test/ui/variance/variance-cell-is-invariant.stderr
index 91f6d7659ed4..6fcd6460fe30 100644
--- a/src/test/ui/variance/variance-cell-is-invariant.stderr
+++ b/src/test/ui/variance/variance-cell-is-invariant.stderr
@@ -12,3 +12,4 @@ LL |     let _: Foo<'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.