Auto merge of #103755 - Dylan-DPC:rollup-dl2hups, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #93582 (Allow `impl Fn() -> impl Trait` in return position)
 - #103560 (Point only to the identifiers in the typo suggestions of shadowed names instead of the entire struct)
 - #103588 (rustdoc: add missing URL redirect)
 - #103689 (Do fewer passes and generally be more efficient when filtering tests)
 - #103740 (rustdoc: remove unnecessary CSS `.search-results { padding-bottom }`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

22 files changed, 299 insertions, 93 deletions

diff --git a/src/doc/rustdoc/book.toml b/src/doc/rustdoc/book.toml
index 45405a11765..dfa68578500 100644
--- a/src/doc/rustdoc/book.toml
+++ b/src/doc/rustdoc/book.toml
@@ -6,5 +6,9 @@ title = "The rustdoc book"
 git-repository-url = "https://github.com/rust-lang/rust/tree/master/src/doc/rustdoc"
 
 [output.html.redirect]
+"/what-to-include.html" = "write-documentation/what-to-include.html"
 "/the-doc-attribute.html" = "write-documentation/the-doc-attribute.html"
+"/linking-to-items-by-name.html" = "write-documentation/linking-to-items-by-name.html"
 "/documentation-tests.html" = "write-documentation/documentation-tests.html"
+"/website-features.html" = "advanced-features.html#custom-search-engines"
+"/passes.html" = "deprecated-features.html#passes"
diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index 330bdb45465..118c6779cb1 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -869,7 +869,6 @@ so that we can apply CSS-filters to change the arrow color in themes */
 
 .search-results {
 	display: none;
-	padding-bottom: 2em;
 }
 
 .search-results.active {
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 8aa0abd369c..0bd0dbbeb70 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -1893,7 +1893,7 @@ fn disambiguator_error(
     diag_info.link_range = disambiguator_range;
     report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, msg, &diag_info, |diag, _sp| {
         let msg = format!(
-            "see {}/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators",
+            "see {}/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators",
             crate::DOC_RUST_LANG_ORG_CHANNEL
         );
         diag.note(&msg);
diff --git a/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr b/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr
index e7b4c43e790..19e541736bd 100644
--- a/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr
+++ b/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr
@@ -4,7 +4,7 @@ error: unknown disambiguator `foo`
 LL | //! Linking to [foo@banana] and [`bar@banana!()`].
    |                 ^^^
    |
-   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 note: the lint level is defined here
   --> $DIR/unknown-disambiguator.rs:2:9
    |
@@ -18,7 +18,7 @@ error: unknown disambiguator `bar`
 LL | //! Linking to [foo@banana] and [`bar@banana!()`].
    |                                   ^^^
    |
-   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `foo`
   --> $DIR/unknown-disambiguator.rs:10:34
@@ -26,7 +26,7 @@ error: unknown disambiguator `foo`
 LL | //! And with weird backticks: [``foo@hello``] [foo`@`hello].
    |                                  ^^^
    |
-   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `foo`
   --> $DIR/unknown-disambiguator.rs:10:48
@@ -34,7 +34,7 @@ error: unknown disambiguator `foo`
 LL | //! And with weird backticks: [``foo@hello``] [foo`@`hello].
    |                                                ^^^
    |
-   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator ``
   --> $DIR/unknown-disambiguator.rs:7:31
@@ -42,7 +42,7 @@ error: unknown disambiguator ``
 LL | //! And to [no disambiguator](@nectarine) and [another](@apricot!()).
    |                               ^
    |
-   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator ``
   --> $DIR/unknown-disambiguator.rs:7:57
@@ -50,7 +50,7 @@ error: unknown disambiguator ``
 LL | //! And to [no disambiguator](@nectarine) and [another](@apricot!()).
    |                                                         ^
    |
-   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/write-documentation/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.rs b/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.rs
new file mode 100644
index 00000000000..0db8088f7ee
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.rs
@@ -0,0 +1,6 @@
+fn f() -> impl Fn() -> impl Sized { || () }
+//~^ ERROR `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
+fn g() -> &'static dyn Fn() -> impl Sized { &|| () }
+//~^ ERROR `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
+
+fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr b/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr
new file mode 100644
index 00000000000..c485bc5c3ab
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr
@@ -0,0 +1,15 @@
+error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
+  --> $DIR/feature-gate-impl_trait_in_fn_trait_return.rs:1:24
+   |
+LL | fn f() -> impl Fn() -> impl Sized { || () }
+   |                        ^^^^^^^^^^
+
+error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
+  --> $DIR/feature-gate-impl_trait_in_fn_trait_return.rs:3:32
+   |
+LL | fn g() -> &'static dyn Fn() -> impl Sized { &|| () }
+   |                                ^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0562`.
diff --git a/src/test/ui/impl-trait/impl-fn-hrtb-bounds-2.rs b/src/test/ui/impl-trait/impl-fn-hrtb-bounds-2.rs
new file mode 100644
index 00000000000..b0aeded0ef7
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-hrtb-bounds-2.rs
@@ -0,0 +1,8 @@
+#![feature(impl_trait_in_fn_trait_return)]
+use std::fmt::Debug;
+
+fn a() -> impl Fn(&u8) -> impl Debug {
+    |x| x //~ ERROR hidden type for `impl Debug` captures lifetime that does not appear in bounds
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/impl-fn-hrtb-bounds-2.stderr b/src/test/ui/impl-trait/impl-fn-hrtb-bounds-2.stderr
new file mode 100644
index 00000000000..433b76b7afa
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-hrtb-bounds-2.stderr
@@ -0,0 +1,11 @@
+error[E0700]: hidden type for `impl Debug` captures lifetime that does not appear in bounds
+  --> $DIR/impl-fn-hrtb-bounds-2.rs:5:9
+   |
+LL |     |x| x
+   |     --- ^
+   |     |
+   |     hidden type `&u8` captures the anonymous lifetime #1 defined here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0700`.
diff --git a/src/test/ui/impl-trait/impl-fn-hrtb-bounds.rs b/src/test/ui/impl-trait/impl-fn-hrtb-bounds.rs
new file mode 100644
index 00000000000..527a4586fd7
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-hrtb-bounds.rs
@@ -0,0 +1,24 @@
+#![feature(impl_trait_in_fn_trait_return)]
+use std::fmt::Debug;
+
+fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
+    //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+    |x| x
+}
+
+fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
+    //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+    |x| x
+}
+
+fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
+    //~^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+    |x| x
+}
+
+fn d() -> impl Fn() -> (impl Debug + '_) {
+    //~^ ERROR missing lifetime specifier
+    || ()
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/impl-fn-hrtb-bounds.stderr b/src/test/ui/impl-trait/impl-fn-hrtb-bounds.stderr
new file mode 100644
index 00000000000..443ffeb55cd
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-hrtb-bounds.stderr
@@ -0,0 +1,51 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/impl-fn-hrtb-bounds.rs:19:38
+   |
+LL | fn d() -> impl Fn() -> (impl Debug + '_) {
+   |                                      ^^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+help: consider using the `'static` lifetime
+   |
+LL | fn d() -> impl Fn() -> (impl Debug + 'static) {
+   |                                      ~~~~~~~
+
+error: higher kinded lifetime bounds on nested opaque types are not supported yet
+  --> $DIR/impl-fn-hrtb-bounds.rs:4:41
+   |
+LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
+   |                                         ^^
+   |
+note: lifetime declared here
+  --> $DIR/impl-fn-hrtb-bounds.rs:4:19
+   |
+LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
+   |                   ^
+
+error: higher kinded lifetime bounds on nested opaque types are not supported yet
+  --> $DIR/impl-fn-hrtb-bounds.rs:9:52
+   |
+LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
+   |                                                    ^^
+   |
+note: lifetime declared here
+  --> $DIR/impl-fn-hrtb-bounds.rs:9:20
+   |
+LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
+   |                    ^^
+
+error: higher kinded lifetime bounds on nested opaque types are not supported yet
+  --> $DIR/impl-fn-hrtb-bounds.rs:14:52
+   |
+LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
+   |                                                    ^^
+   |
+note: lifetime declared here
+  --> $DIR/impl-fn-hrtb-bounds.rs:14:20
+   |
+LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
+   |                    ^^
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/impl-trait/impl-fn-parsing-ambiguities.rs b/src/test/ui/impl-trait/impl-fn-parsing-ambiguities.rs
new file mode 100644
index 00000000000..3e760710797
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-parsing-ambiguities.rs
@@ -0,0 +1,15 @@
+#![feature(impl_trait_in_fn_trait_return)]
+use std::fmt::Debug;
+
+fn a() -> impl Fn(&u8) -> impl Debug + '_ {
+    //~^ ERROR ambiguous `+` in a type
+    //~^^ ERROR higher kinded lifetime bounds on nested opaque types are not supported yet
+    |x| x
+}
+
+fn b() -> impl Fn() -> impl Debug + Send {
+    //~^ ERROR ambiguous `+` in a type
+    || ()
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/impl-fn-parsing-ambiguities.stderr b/src/test/ui/impl-trait/impl-fn-parsing-ambiguities.stderr
new file mode 100644
index 00000000000..cf6e5ef7bac
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-parsing-ambiguities.stderr
@@ -0,0 +1,26 @@
+error: ambiguous `+` in a type
+  --> $DIR/impl-fn-parsing-ambiguities.rs:4:27
+   |
+LL | fn a() -> impl Fn(&u8) -> impl Debug + '_ {
+   |                           ^^^^^^^^^^^^^^^ help: use parentheses to disambiguate: `(impl Debug + '_)`
+
+error: ambiguous `+` in a type
+  --> $DIR/impl-fn-parsing-ambiguities.rs:10:24
+   |
+LL | fn b() -> impl Fn() -> impl Debug + Send {
+   |                        ^^^^^^^^^^^^^^^^^ help: use parentheses to disambiguate: `(impl Debug + Send)`
+
+error: higher kinded lifetime bounds on nested opaque types are not supported yet
+  --> $DIR/impl-fn-parsing-ambiguities.rs:4:40
+   |
+LL | fn a() -> impl Fn(&u8) -> impl Debug + '_ {
+   |                                        ^^
+   |
+note: lifetime declared here
+  --> $DIR/impl-fn-parsing-ambiguities.rs:4:19
+   |
+LL | fn a() -> impl Fn(&u8) -> impl Debug + '_ {
+   |                   ^
+
+error: aborting due to 3 previous errors
+
diff --git a/src/test/ui/impl-trait/impl-fn-predefined-lifetimes.rs b/src/test/ui/impl-trait/impl-fn-predefined-lifetimes.rs
new file mode 100644
index 00000000000..15778662375
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-predefined-lifetimes.rs
@@ -0,0 +1,15 @@
+#![feature(impl_trait_in_fn_trait_return)]
+use std::fmt::Debug;
+
+fn a<'a>() -> impl Fn(&'a u8) -> (impl Debug + '_) {
+    //~^ ERROR cannot resolve opaque type
+
+    |x| x
+    //~^ ERROR concrete type differs from previous defining opaque type use
+}
+
+fn _b<'a>() -> impl Fn(&'a u8) -> (impl Debug + 'a) {
+    a()
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/impl-fn-predefined-lifetimes.stderr b/src/test/ui/impl-trait/impl-fn-predefined-lifetimes.stderr
new file mode 100644
index 00000000000..7747319c153
--- /dev/null
+++ b/src/test/ui/impl-trait/impl-fn-predefined-lifetimes.stderr
@@ -0,0 +1,24 @@
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/impl-fn-predefined-lifetimes.rs:7:9
+   |
+LL |     |x| x
+   |         ^ expected `impl Debug + '_`, got `&u8`
+   |
+note: previous use here
+  --> $DIR/impl-fn-predefined-lifetimes.rs:7:5
+   |
+LL |     |x| x
+   |     ^^^^^
+
+error[E0720]: cannot resolve opaque type
+  --> $DIR/impl-fn-predefined-lifetimes.rs:4:35
+   |
+LL | fn a<'a>() -> impl Fn(&'a u8) -> (impl Debug + '_) {
+   |                                   ^^^^^^^^^^^^^^^ recursive opaque type
+...
+LL |     |x| x
+   |     ----- returning here with type `[closure@$DIR/impl-fn-predefined-lifetimes.rs:7:5: 7:8]`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0720`.
diff --git a/src/test/ui/impl-trait/impl_fn_associativity.rs b/src/test/ui/impl-trait/impl_fn_associativity.rs
new file mode 100644
index 00000000000..71a8f9c7796
--- /dev/null
+++ b/src/test/ui/impl-trait/impl_fn_associativity.rs
@@ -0,0 +1,26 @@
+// run-pass
+#![feature(impl_trait_in_fn_trait_return)]
+use std::fmt::Debug;
+
+fn f_debug() -> impl Fn() -> impl Debug {
+    || ()
+}
+
+fn ff_debug() -> impl Fn() -> impl Fn() -> impl Debug {
+    || f_debug()
+}
+
+fn multi() -> impl Fn() -> (impl Debug + Send) {
+    || ()
+}
+
+fn main() {
+    // Check that `ff_debug` is `() -> (() -> Debug)` and not `(() -> ()) -> Debug`
+    let debug = ff_debug()()();
+    assert_eq!(format!("{:?}", debug), "()");
+
+    let x = multi()();
+    assert_eq!(format!("{:?}", x), "()");
+    fn assert_send(_: &impl Send) {}
+    assert_send(&x);
+}
diff --git a/src/test/ui/impl-trait/nested_impl_trait.rs b/src/test/ui/impl-trait/nested_impl_trait.rs
index 85c6f8c462c..e95fab3b650 100644
--- a/src/test/ui/impl-trait/nested_impl_trait.rs
+++ b/src/test/ui/impl-trait/nested_impl_trait.rs
@@ -1,3 +1,4 @@
+#![feature(impl_trait_in_fn_trait_return)]
 use std::fmt::Debug;
 
 fn fine(x: impl Into<u32>) -> impl Into<u32> { x }
@@ -25,8 +26,7 @@ fn allowed_in_assoc_type() -> impl Iterator<Item=impl Fn()> {
 }
 
 fn allowed_in_ret_type() -> impl Fn() -> impl Into<u32> {
-//~^ `impl Trait` only allowed in function and inherent method return types
-    || 5
+    || 5u8
 }
 
 fn main() {}
diff --git a/src/test/ui/impl-trait/nested_impl_trait.stderr b/src/test/ui/impl-trait/nested_impl_trait.stderr
index 3291cad6882..9a8f5a34068 100644
--- a/src/test/ui/impl-trait/nested_impl_trait.stderr
+++ b/src/test/ui/impl-trait/nested_impl_trait.stderr
@@ -1,5 +1,5 @@
 error[E0666]: nested `impl Trait` is not allowed
-  --> $DIR/nested_impl_trait.rs:5:56
+  --> $DIR/nested_impl_trait.rs:6:56
    |
 LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                              ----------^^^^^^^^^^-
@@ -8,7 +8,7 @@ LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                              outer `impl Trait`
 
 error[E0666]: nested `impl Trait` is not allowed
-  --> $DIR/nested_impl_trait.rs:9:42
+  --> $DIR/nested_impl_trait.rs:10:42
    |
 LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
    |                                ----------^^^^^^^^^^-
@@ -17,7 +17,7 @@ LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
    |                                outer `impl Trait`
 
 error[E0666]: nested `impl Trait` is not allowed
-  --> $DIR/nested_impl_trait.rs:13:37
+  --> $DIR/nested_impl_trait.rs:14:37
    |
 LL | fn bad_in_arg_position(_: impl Into<impl Debug>) { }
    |                           ----------^^^^^^^^^^-
@@ -26,7 +26,7 @@ LL | fn bad_in_arg_position(_: impl Into<impl Debug>) { }
    |                           outer `impl Trait`
 
 error[E0666]: nested `impl Trait` is not allowed
-  --> $DIR/nested_impl_trait.rs:18:44
+  --> $DIR/nested_impl_trait.rs:19:44
    |
 LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                  ----------^^^^^^^^^^-
@@ -35,19 +35,13 @@ LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                  outer `impl Trait`
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `fn` pointer return
-  --> $DIR/nested_impl_trait.rs:9:32
+  --> $DIR/nested_impl_trait.rs:10:32
    |
 LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
    |                                ^^^^^^^^^^^^^^^^^^^^^
 
-error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
-  --> $DIR/nested_impl_trait.rs:27:42
-   |
-LL | fn allowed_in_ret_type() -> impl Fn() -> impl Into<u32> {
-   |                                          ^^^^^^^^^^^^^^
-
 error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfied
-  --> $DIR/nested_impl_trait.rs:5:46
+  --> $DIR/nested_impl_trait.rs:6:46
    |
 LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                              ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Debug`
@@ -56,7 +50,7 @@ LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    = note: required for `impl Into<u32>` to implement `Into<impl Debug>`
 
 error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfied
-  --> $DIR/nested_impl_trait.rs:18:34
+  --> $DIR/nested_impl_trait.rs:19:34
    |
 LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                  ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Debug`
@@ -64,7 +58,7 @@ LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    = help: the trait `Into<U>` is implemented for `T`
    = note: required for `impl Into<u32>` to implement `Into<impl Debug>`
 
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
 Some errors have detailed explanations: E0277, E0562, E0666.
 For more information about an error, try `rustc --explain E0277`.
diff --git a/src/test/ui/impl-trait/where-allowed.rs b/src/test/ui/impl-trait/where-allowed.rs
index c1dd46c7ff7..ff63b04c268 100644
--- a/src/test/ui/impl-trait/where-allowed.rs
+++ b/src/test/ui/impl-trait/where-allowed.rs
@@ -1,5 +1,6 @@
 //! A simple test for testing many permutations of allowedness of
 //! impl Trait
+#![feature(impl_trait_in_fn_trait_return)]
 use std::fmt::Debug;
 
 // Allowed
@@ -39,9 +40,8 @@ fn in_dyn_Fn_return_in_parameters(_: &dyn Fn() -> impl Debug) { panic!() }
 fn in_dyn_Fn_parameter_in_return() -> &'static dyn Fn(impl Debug) { panic!() }
 //~^ ERROR `impl Trait` only allowed in function and inherent method return types
 
-// Disallowed
+// Allowed
 fn in_dyn_Fn_return_in_return() -> &'static dyn Fn() -> impl Debug { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method return types
 
 // Disallowed
 fn in_impl_Fn_parameter_in_parameters(_: &impl Fn(impl Debug)) { panic!() }
@@ -57,9 +57,8 @@ fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
 //~^ ERROR `impl Trait` only allowed in function and inherent method return types
 //~| ERROR nested `impl Trait` is not allowed
 
-// Disallowed
+// Allowed
 fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method return types
 
 // Disallowed
 fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
diff --git a/src/test/ui/impl-trait/where-allowed.stderr b/src/test/ui/impl-trait/where-allowed.stderr
index 2e7c7ca40dd..3ad0a9f9d5c 100644
--- a/src/test/ui/impl-trait/where-allowed.stderr
+++ b/src/test/ui/impl-trait/where-allowed.stderr
@@ -17,7 +17,7 @@ LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic
    |                                                 outer `impl Trait`
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:119:16
+  --> $DIR/where-allowed.rs:118:16
    |
 LL |     type Out = impl Debug;
    |                ^^^^^^^^^^
@@ -26,7 +26,7 @@ LL |     type Out = impl Debug;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:154:23
+  --> $DIR/where-allowed.rs:153:23
    |
 LL | type InTypeAlias<R> = impl Debug;
    |                       ^^^^^^^^^^
@@ -35,7 +35,7 @@ LL | type InTypeAlias<R> = impl Debug;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:157:39
+  --> $DIR/where-allowed.rs:156:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
@@ -44,53 +44,47 @@ LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `fn` pointer param
-  --> $DIR/where-allowed.rs:15:40
+  --> $DIR/where-allowed.rs:16:40
    |
 LL | fn in_fn_parameter_in_parameters(_: fn(impl Debug)) { panic!() }
    |                                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `fn` pointer return
-  --> $DIR/where-allowed.rs:19:42
+  --> $DIR/where-allowed.rs:20:42
    |
 LL | fn in_fn_return_in_parameters(_: fn() -> impl Debug) { panic!() }
    |                                          ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `fn` pointer param
-  --> $DIR/where-allowed.rs:23:38
+  --> $DIR/where-allowed.rs:24:38
    |
 LL | fn in_fn_parameter_in_return() -> fn(impl Debug) { panic!() }
    |                                      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `fn` pointer return
-  --> $DIR/where-allowed.rs:27:40
+  --> $DIR/where-allowed.rs:28:40
    |
 LL | fn in_fn_return_in_return() -> fn() -> impl Debug { panic!() }
    |                                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait param
-  --> $DIR/where-allowed.rs:31:49
+  --> $DIR/where-allowed.rs:32:49
    |
 LL | fn in_dyn_Fn_parameter_in_parameters(_: &dyn Fn(impl Debug)) { panic!() }
    |                                                 ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
-  --> $DIR/where-allowed.rs:35:51
+  --> $DIR/where-allowed.rs:36:51
    |
 LL | fn in_dyn_Fn_return_in_parameters(_: &dyn Fn() -> impl Debug) { panic!() }
    |                                                   ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait param
-  --> $DIR/where-allowed.rs:39:55
+  --> $DIR/where-allowed.rs:40:55
    |
 LL | fn in_dyn_Fn_parameter_in_return() -> &'static dyn Fn(impl Debug) { panic!() }
    |                                                       ^^^^^^^^^^
 
-error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
-  --> $DIR/where-allowed.rs:43:57
-   |
-LL | fn in_dyn_Fn_return_in_return() -> &'static dyn Fn() -> impl Debug { panic!() }
-   |                                                         ^^^^^^^^^^
-
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait param
   --> $DIR/where-allowed.rs:47:51
    |
@@ -109,56 +103,50 @@ error[E0562]: `impl Trait` only allowed in function and inherent method return t
 LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
    |                                                         ^^^^^^^^^^
 
-error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
-  --> $DIR/where-allowed.rs:61:59
-   |
-LL | fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
-   |                                                           ^^^^^^^^^^
-
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait param
-  --> $DIR/where-allowed.rs:65:38
+  --> $DIR/where-allowed.rs:64:38
    |
 LL | fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
    |                                      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
-  --> $DIR/where-allowed.rs:69:40
+  --> $DIR/where-allowed.rs:68:40
    |
 LL | fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
    |                                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:82:32
+  --> $DIR/where-allowed.rs:81:32
    |
 LL | struct InBraceStructField { x: impl Debug }
    |                                ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in path
-  --> $DIR/where-allowed.rs:86:41
+  --> $DIR/where-allowed.rs:85:41
    |
 LL | struct InAdtInBraceStructField { x: Vec<impl Debug> }
    |                                         ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:90:27
+  --> $DIR/where-allowed.rs:89:27
    |
 LL | struct InTupleStructField(impl Debug);
    |                           ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:95:25
+  --> $DIR/where-allowed.rs:94:25
    |
 LL |     InBraceVariant { x: impl Debug },
    |                         ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:97:20
+  --> $DIR/where-allowed.rs:96:20
    |
 LL |     InTupleVariant(impl Debug),
    |                    ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in trait method return
-  --> $DIR/where-allowed.rs:108:23
+  --> $DIR/where-allowed.rs:107:23
    |
 LL |     fn in_return() -> impl Debug;
    |                       ^^^^^^^^^^
@@ -167,7 +155,7 @@ LL |     fn in_return() -> impl Debug;
    = help: add `#![feature(return_position_impl_trait_in_trait)]` to the crate attributes to enable
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `impl` method return
-  --> $DIR/where-allowed.rs:125:34
+  --> $DIR/where-allowed.rs:124:34
    |
 LL |     fn in_trait_impl_return() -> impl Debug { () }
    |                                  ^^^^^^^^^^
@@ -176,127 +164,127 @@ LL |     fn in_trait_impl_return() -> impl Debug { () }
    = help: add `#![feature(return_position_impl_trait_in_trait)]` to the crate attributes to enable
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `extern fn` param
-  --> $DIR/where-allowed.rs:138:33
+  --> $DIR/where-allowed.rs:137:33
    |
 LL |     fn in_foreign_parameters(_: impl Debug);
    |                                 ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `extern fn` return
-  --> $DIR/where-allowed.rs:141:31
+  --> $DIR/where-allowed.rs:140:31
    |
 LL |     fn in_foreign_return() -> impl Debug;
    |                               ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `fn` pointer return
-  --> $DIR/where-allowed.rs:157:39
+  --> $DIR/where-allowed.rs:156:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in trait
-  --> $DIR/where-allowed.rs:162:16
+  --> $DIR/where-allowed.rs:161:16
    |
 LL | impl PartialEq<impl Debug> for () {
    |                ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:167:24
+  --> $DIR/where-allowed.rs:166:24
    |
 LL | impl PartialEq<()> for impl Debug {
    |                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:172:6
+  --> $DIR/where-allowed.rs:171:6
    |
 LL | impl impl Debug {
    |      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:178:24
+  --> $DIR/where-allowed.rs:177:24
    |
 LL | impl InInherentImplAdt<impl Debug> {
    |                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:184:11
+  --> $DIR/where-allowed.rs:183:11
    |
 LL |     where impl Debug: Debug
    |           ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:191:15
+  --> $DIR/where-allowed.rs:190:15
    |
 LL |     where Vec<impl Debug>: Debug
    |               ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in bound
-  --> $DIR/where-allowed.rs:198:24
+  --> $DIR/where-allowed.rs:197:24
    |
 LL |     where T: PartialEq<impl Debug>
    |                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait param
-  --> $DIR/where-allowed.rs:205:17
+  --> $DIR/where-allowed.rs:204:17
    |
 LL |     where T: Fn(impl Debug)
    |                 ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in `Fn` trait return
-  --> $DIR/where-allowed.rs:212:22
+  --> $DIR/where-allowed.rs:211:22
    |
 LL |     where T: Fn() -> impl Debug
    |                      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:218:40
+  --> $DIR/where-allowed.rs:217:40
    |
 LL | struct InStructGenericParamDefault<T = impl Debug>(T);
    |                                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:222:36
+  --> $DIR/where-allowed.rs:221:36
    |
 LL | enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
    |                                    ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:226:38
+  --> $DIR/where-allowed.rs:225:38
    |
 LL | trait InTraitGenericParamDefault<T = impl Debug> {}
    |                                      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:230:41
+  --> $DIR/where-allowed.rs:229:41
    |
 LL | type InTypeAliasGenericParamDefault<T = impl Debug> = T;
    |                                         ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:234:11
+  --> $DIR/where-allowed.rs:233:11
    |
 LL | impl <T = impl Debug> T {}
    |           ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in type
-  --> $DIR/where-allowed.rs:241:40
+  --> $DIR/where-allowed.rs:240:40
    |
 LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    |                                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in variable binding
-  --> $DIR/where-allowed.rs:247:29
+  --> $DIR/where-allowed.rs:246:29
    |
 LL |     let _in_local_variable: impl Fn() = || {};
    |                             ^^^^^^^^^
 
 error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in closure return
-  --> $DIR/where-allowed.rs:249:46
+  --> $DIR/where-allowed.rs:248:46
    |
 LL |     let _in_return_in_local_variable = || -> impl Fn() { || {} };
    |                                              ^^^^^^^^^
 
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/where-allowed.rs:234:7
+  --> $DIR/where-allowed.rs:233:7
    |
 LL | impl <T = impl Debug> T {}
    |       ^^^^^^^^^^^^^^
@@ -306,7 +294,7 @@ LL | impl <T = impl Debug> T {}
    = note: `#[deny(invalid_type_param_default)]` on by default
 
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/where-allowed.rs:241:36
+  --> $DIR/where-allowed.rs:240:36
    |
 LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    |                                    ^^^^^^^^^^^^^^
@@ -315,14 +303,14 @@ LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
 
 error[E0118]: no nominal type found for inherent implementation
-  --> $DIR/where-allowed.rs:234:23
+  --> $DIR/where-allowed.rs:233:23
    |
 LL | impl <T = impl Debug> T {}
    |                       ^ impl requires a nominal type
    |
    = note: either implement a trait on it or create a newtype to wrap it instead
 
-error: aborting due to 49 previous errors
+error: aborting due to 47 previous errors
 
 Some errors have detailed explanations: E0118, E0562, E0658, E0666.
 For more information about an error, try `rustc --explain E0118`.
diff --git a/src/test/ui/lexical-scopes.stderr b/src/test/ui/lexical-scopes.stderr
index 53598545223..f0eaa1a5c64 100644
--- a/src/test/ui/lexical-scopes.stderr
+++ b/src/test/ui/lexical-scopes.stderr
@@ -2,7 +2,7 @@ error[E0574]: expected struct, variant or union type, found type parameter `T`
   --> $DIR/lexical-scopes.rs:3:13
    |
 LL | struct T { i: i32 }
-   | ------------------- you might have meant to refer to this struct
+   |        - you might have meant to refer to this struct
 LL | fn f<T>() {
    |      - found this type parameter
 LL |     let t = T { i: 0 };
diff --git a/src/test/ui/resolve/point-at-type-parameter-shadowing-another-type.stderr b/src/test/ui/resolve/point-at-type-parameter-shadowing-another-type.stderr
index eb26cd9cabb..5790e425c0a 100644
--- a/src/test/ui/resolve/point-at-type-parameter-shadowing-another-type.stderr
+++ b/src/test/ui/resolve/point-at-type-parameter-shadowing-another-type.stderr
@@ -1,16 +1,14 @@
 error[E0574]: expected struct, variant or union type, found type parameter `Baz`
   --> $DIR/point-at-type-parameter-shadowing-another-type.rs:16:13
    |
-LL | / struct Baz {
-LL | |     num: usize,
-LL | | }
-   | |_- you might have meant to refer to this struct
-LL |
-LL |   impl<Baz> Foo<Baz> for Bar {
-   |        --- found this type parameter
+LL | struct Baz {
+   |        --- you might have meant to refer to this struct
 ...
-LL |               Baz { num } => num,
-   |               ^^^ not a struct, variant or union type
+LL | impl<Baz> Foo<Baz> for Bar {
+   |      --- found this type parameter
+...
+LL |             Baz { num } => num,
+   |             ^^^ not a struct, variant or union type
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/span/issue-35987.stderr b/src/test/ui/span/issue-35987.stderr
index d8fddc8007f..057d40ac0cb 100644
--- a/src/test/ui/span/issue-35987.stderr
+++ b/src/test/ui/span/issue-35987.stderr
@@ -1,6 +1,9 @@
 error[E0404]: expected trait, found type parameter `Add`
   --> $DIR/issue-35987.rs:5:21
    |
+LL | use std::ops::Add;
+   |               --- you might have meant to refer to this trait
+LL |
 LL | impl<T: Clone, Add> Add for Foo<T> {
    |                ---  ^^^ not a trait
    |                |