Auto merge of #60510 - Centril:rollup-gsndjbp, r=Centril

Rollup of 12 pull requests

Successful merges:

 - #59928 (Make deprecation lint `ambiguous_associated_items` deny-by-default)
 - #60220 (report fatal errors during doctest parsing)
 - #60373 (Tidy: ensure lang features are sorted by since)
 - #60388 (Disallow non-explicit elided lifetimes in async fn)
 - #60393 ( Do not suggest incorrect syntax on pattern type error due to borrow)
 - #60401 (Rename `RUST_LOG` to `RUSTC_LOG`)
 - #60409 (Require a trait in the bounds of existential types)
 - #60455 (Resolve match arm ty when arms diverge)
 - #60457 (Const prop refactoring)
 - #60467 (Avoid repeated interning of static strings.)
 - #60478 (minor compiler doc tweaks)
 - #60501 (Propagate mutability from arguments to local bindings in async fn)

Failed merges:

r? @ghost

43 files changed, 357 insertions, 71 deletions

diff --git a/src/test/run-make-fulldeps/libs-through-symlinks/Makefile b/src/test/run-make-fulldeps/libs-through-symlinks/Makefile
index 7c5ea7e402e..8be2e234fea 100644
--- a/src/test/run-make-fulldeps/libs-through-symlinks/Makefile
+++ b/src/test/run-make-fulldeps/libs-through-symlinks/Makefile
@@ -8,4 +8,4 @@ all:
 	mkdir -p $(TMPDIR)/outdir
 	$(RUSTC) foo.rs -o $(TMPDIR)/outdir/$(NAME)
 	ln -nsf outdir/$(NAME) $(TMPDIR)
-	RUST_LOG=rustc_metadata::loader $(RUSTC) bar.rs
+	RUSTC_LOG=rustc_metadata::loader $(RUSTC) bar.rs
diff --git a/src/test/run-pass/existential_type.rs b/src/test/run-pass/existential_type.rs
index dfb195ec830..b36435cf113 100644
--- a/src/test/run-pass/existential_type.rs
+++ b/src/test/run-pass/existential_type.rs
@@ -68,14 +68,14 @@ fn my_other_iter<U>(u: U) -> MyOtherIter<U> {
 }
 
 trait Trait {}
-existential type GenericBound<'a, T: Trait>: 'a;
+existential type GenericBound<'a, T: Trait>: Sized + 'a;
 
 fn generic_bound<'a, T: Trait + 'a>(t: T) -> GenericBound<'a, T> {
     t
 }
 
 mod pass_through {
-    pub existential type Passthrough<T>: 'static;
+    pub existential type Passthrough<T>: Sized + 'static;
 
     fn define_passthrough<T: 'static>(t: T) -> Passthrough<T> {
         t
diff --git a/src/test/run-pass/issues/issue-18075.rs b/src/test/run-pass/issues/issue-18075.rs
index dcd67d8d15a..ee6845c1278 100644
--- a/src/test/run-pass/issues/issue-18075.rs
+++ b/src/test/run-pass/issues/issue-18075.rs
@@ -1,5 +1,5 @@
 // run-pass
-// exec-env:RUST_LOG=rustc::middle=debug
+// exec-env:RUSTC_LOG=rustc::middle=debug
 
 fn main() {
     let b = 1isize;
diff --git a/src/test/run-pass/logging-only-prints-once.rs b/src/test/run-pass/logging-only-prints-once.rs
index 7b105600225..1a4c4d89e7d 100644
--- a/src/test/run-pass/logging-only-prints-once.rs
+++ b/src/test/run-pass/logging-only-prints-once.rs
@@ -1,6 +1,6 @@
 // ignore-windows
 // ignore-emscripten no threads support
-// exec-env:RUST_LOG=debug
+// exec-env:RUSTC_LOG=debug
 
 use std::cell::Cell;
 use std::fmt;
diff --git a/src/test/run-pass/logging_before_rt_started.rs b/src/test/run-pass/logging_before_rt_started.rs
index 0cba1080de2..69cfc54c465 100644
--- a/src/test/run-pass/logging_before_rt_started.rs
+++ b/src/test/run-pass/logging_before_rt_started.rs
@@ -1,4 +1,4 @@
-// exec-env:RUST_LOG=std::ptr
+// exec-env:RUSTC_LOG=std::ptr
 
 // In issue #9487, it was realized that std::ptr was invoking the logging
 // infrastructure, and when std::ptr was used during runtime initialization,
diff --git a/src/test/run-pass/rustc-rust-log.rs b/src/test/run-pass/rustc-rust-log.rs
index 4360a154015..b6642572418 100644
--- a/src/test/run-pass/rustc-rust-log.rs
+++ b/src/test/run-pass/rustc-rust-log.rs
@@ -8,6 +8,6 @@
 // dont-check-compiler-stderr
 // compile-flags: --error-format human
 
-// rustc-env:RUST_LOG=debug
+// rustc-env:RUSTC_LOG=debug
 
 fn main() {}
diff --git a/src/test/run-pass/threads-sendsync/spawning-with-debug.rs b/src/test/run-pass/threads-sendsync/spawning-with-debug.rs
index c78ae78dd1b..388d62aa710 100644
--- a/src/test/run-pass/threads-sendsync/spawning-with-debug.rs
+++ b/src/test/run-pass/threads-sendsync/spawning-with-debug.rs
@@ -2,7 +2,7 @@
 #![allow(unused_must_use)]
 #![allow(unused_mut)]
 // ignore-windows
-// exec-env:RUST_LOG=debug
+// exec-env:RUSTC_LOG=debug
 // ignore-emscripten no threads support
 
 // regression test for issue #10405, make sure we don't call println! too soon.
diff --git a/src/test/rustdoc-ui/failed-doctest-output.stdout b/src/test/rustdoc-ui/failed-doctest-output.stdout
index c9f59405ce0..7b1cd702731 100644
--- a/src/test/rustdoc-ui/failed-doctest-output.stdout
+++ b/src/test/rustdoc-ui/failed-doctest-output.stdout
@@ -15,7 +15,7 @@ error[E0425]: cannot find value `no` in this scope
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0425`.
-thread '$DIR/failed-doctest-output.rs - OtherStruct (line 17)' panicked at 'couldn't compile the test', src/librustdoc/test.rs:310:13
+thread '$DIR/failed-doctest-output.rs - OtherStruct (line 17)' panicked at 'couldn't compile the test', src/librustdoc/test.rs:319:13
 note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
 
 ---- $DIR/failed-doctest-output.rs - SomeStruct (line 11) stdout ----
@@ -24,7 +24,7 @@ thread '$DIR/failed-doctest-output.rs - SomeStruct (line 11)' panicked at 'test
 thread 'main' panicked at 'oh no', $DIR/failed-doctest-output.rs:3:1
 note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
 
-', src/librustdoc/test.rs:332:17
+', src/librustdoc/test.rs:341:17
 
 
 failures:
diff --git a/src/test/rustdoc-ui/unparseable-doc-test.rs b/src/test/rustdoc-ui/unparseable-doc-test.rs
new file mode 100644
index 00000000000..18d6b32bf40
--- /dev/null
+++ b/src/test/rustdoc-ui/unparseable-doc-test.rs
@@ -0,0 +1,10 @@
+// compile-flags: --test
+// normalize-stdout-test: "src/test/rustdoc-ui" -> "$$DIR"
+// failure-status: 101
+// rustc-env: RUST_BACKTRACE=0
+
+/// ```rust
+/// let x = 7;
+/// "unterminated
+/// ```
+pub fn foo() {}
diff --git a/src/test/rustdoc-ui/unparseable-doc-test.stdout b/src/test/rustdoc-ui/unparseable-doc-test.stdout
new file mode 100644
index 00000000000..7048ef2c589
--- /dev/null
+++ b/src/test/rustdoc-ui/unparseable-doc-test.stdout
@@ -0,0 +1,24 @@
+
+running 1 test
+test $DIR/unparseable-doc-test.rs - foo (line 6) ... FAILED
+
+failures:
+
+---- $DIR/unparseable-doc-test.rs - foo (line 6) stdout ----
+error: unterminated double quote string
+ --> $DIR/unparseable-doc-test.rs:8:1
+  |
+2 | "unterminated
+  | ^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+thread '$DIR/unparseable-doc-test.rs - foo (line 6)' panicked at 'couldn't compile the test', src/librustdoc/test.rs:319:13
+note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
+
+
+failures:
+    $DIR/unparseable-doc-test.rs - foo (line 6)
+
+test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
+
diff --git a/src/test/ui/async-await/mutable-arguments.rs b/src/test/ui/async-await/mutable-arguments.rs
new file mode 100644
index 00000000000..4d6dba74097
--- /dev/null
+++ b/src/test/ui/async-await/mutable-arguments.rs
@@ -0,0 +1,10 @@
+// edition:2018
+// run-pass
+
+#![feature(async_await)]
+
+async fn foo(n: u32, mut vec: Vec<u32>) {
+    vec.push(n);
+}
+
+fn main() {}
diff --git a/src/test/ui/async-fn-path-elision.rs b/src/test/ui/async-fn-path-elision.rs
new file mode 100644
index 00000000000..8db7631ef41
--- /dev/null
+++ b/src/test/ui/async-fn-path-elision.rs
@@ -0,0 +1,16 @@
+// edition:2018
+
+#![feature(async_await, await_macro)]
+#![allow(dead_code)]
+
+struct HasLifetime<'a>(&'a bool);
+
+async fn error(lt: HasLifetime) { //~ ERROR implicit elided lifetime not allowed here
+    if *lt.0 {}
+}
+
+fn no_error(lt: HasLifetime) {
+    if *lt.0 {}
+}
+
+fn main() {}
diff --git a/src/test/ui/async-fn-path-elision.stderr b/src/test/ui/async-fn-path-elision.stderr
new file mode 100644
index 00000000000..3b311baba01
--- /dev/null
+++ b/src/test/ui/async-fn-path-elision.stderr
@@ -0,0 +1,8 @@
+error[E0726]: implicit elided lifetime not allowed here
+  --> $DIR/async-fn-path-elision.rs:8:20
+   |
+LL | async fn error(lt: HasLifetime) {
+   |                    ^^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/consts/const-err.rs b/src/test/ui/consts/const-err.rs
index 8cc3dc7f587..7dfcda69058 100644
--- a/src/test/ui/consts/const-err.rs
+++ b/src/test/ui/consts/const-err.rs
@@ -13,4 +13,5 @@ const FOO: u8 = [5u8][1];
 fn main() {
     black_box((FOO, FOO));
     //~^ ERROR erroneous constant used
+    //~| ERROR erroneous constant
 }
diff --git a/src/test/ui/consts/const-err.stderr b/src/test/ui/consts/const-err.stderr
index 0ee9ecdef45..429e2ae7600 100644
--- a/src/test/ui/consts/const-err.stderr
+++ b/src/test/ui/consts/const-err.stderr
@@ -13,11 +13,17 @@ LL | #![warn(const_err)]
    |         ^^^^^^^^^
 
 error[E0080]: erroneous constant used
-  --> $DIR/const-err.rs:14:15
+  --> $DIR/const-err.rs:14:16
    |
 LL |     black_box((FOO, FOO));
-   |               ^^^^^^^^^^ referenced constant has errors
+   |                ^^^ referenced constant has errors
 
-error: aborting due to previous error
+error[E0080]: erroneous constant used
+  --> $DIR/const-err.rs:14:21
+   |
+LL |     black_box((FOO, FOO));
+   |                     ^^^ referenced constant has errors
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0080`.
diff --git a/src/test/ui/destructure-trait-ref.stderr b/src/test/ui/destructure-trait-ref.stderr
index 34dd213e2b3..bc3013b78b3 100644
--- a/src/test/ui/destructure-trait-ref.stderr
+++ b/src/test/ui/destructure-trait-ref.stderr
@@ -20,21 +20,25 @@ error[E0308]: mismatched types
   --> $DIR/destructure-trait-ref.rs:31:10
    |
 LL |     let &&x = &1isize as &T;
-   |          ^^ expected trait T, found reference
+   |          ^^
+   |          |
+   |          expected trait T, found reference
+   |          help: you can probably remove the explicit borrow: `x`
    |
    = note: expected type `dyn T`
               found type `&_`
-   = help: did you mean `x: &dyn T`?
 
 error[E0308]: mismatched types
   --> $DIR/destructure-trait-ref.rs:36:11
    |
 LL |     let &&&x = &(&1isize as &T);
-   |           ^^ expected trait T, found reference
+   |           ^^
+   |           |
+   |           expected trait T, found reference
+   |           help: you can probably remove the explicit borrow: `x`
    |
    = note: expected type `dyn T`
               found type `&_`
-   = help: did you mean `x: &dyn T`?
 
 error[E0308]: mismatched types
   --> $DIR/destructure-trait-ref.rs:41:13
diff --git a/src/test/ui/existential_types/existential-types-with-no-traits.rs b/src/test/ui/existential_types/existential-types-with-no-traits.rs
new file mode 100644
index 00000000000..46339c73b1f
--- /dev/null
+++ b/src/test/ui/existential_types/existential-types-with-no-traits.rs
@@ -0,0 +1,14 @@
+#![feature(existential_type)]
+
+existential type Foo: 'static;
+//~^ ERROR: at least one trait must be specified
+
+fn foo() -> Foo {
+    "foo"
+}
+
+fn bar() -> impl 'static { //~ ERROR: at least one trait must be specified
+    "foo"
+}
+
+fn main() {}
diff --git a/src/test/ui/existential_types/existential-types-with-no-traits.stderr b/src/test/ui/existential_types/existential-types-with-no-traits.stderr
new file mode 100644
index 00000000000..4b2fbc79d3b
--- /dev/null
+++ b/src/test/ui/existential_types/existential-types-with-no-traits.stderr
@@ -0,0 +1,14 @@
+error: at least one trait must be specified
+  --> $DIR/existential-types-with-no-traits.rs:3:23
+   |
+LL | existential type Foo: 'static;
+   |                       ^^^^^^^
+
+error: at least one trait must be specified
+  --> $DIR/existential-types-with-no-traits.rs:10:13
+   |
+LL | fn bar() -> impl 'static {
+   |             ^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/existential_types/generic_nondefining_use.rs b/src/test/ui/existential_types/generic_nondefining_use.rs
index 75af5d9570f..ffc965aca47 100644
--- a/src/test/ui/existential_types/generic_nondefining_use.rs
+++ b/src/test/ui/existential_types/generic_nondefining_use.rs
@@ -4,6 +4,8 @@ fn main() {}
 
 existential type Cmp<T>: 'static;
 //~^ ERROR could not find defining uses
+//~^^ ERROR: at least one trait must be specified
+
 
 // not a defining use, because it doesn't define *all* possible generics
 fn cmp() -> Cmp<u32> { //~ ERROR defining existential type use does not fully define
diff --git a/src/test/ui/existential_types/generic_nondefining_use.stderr b/src/test/ui/existential_types/generic_nondefining_use.stderr
index ef579260f06..d205d44c68c 100644
--- a/src/test/ui/existential_types/generic_nondefining_use.stderr
+++ b/src/test/ui/existential_types/generic_nondefining_use.stderr
@@ -1,5 +1,11 @@
+error: at least one trait must be specified
+  --> $DIR/generic_nondefining_use.rs:5:26
+   |
+LL | existential type Cmp<T>: 'static;
+   |                          ^^^^^^^
+
 error: defining existential type use does not fully define existential type
-  --> $DIR/generic_nondefining_use.rs:9:1
+  --> $DIR/generic_nondefining_use.rs:11:1
    |
 LL | / fn cmp() -> Cmp<u32> {
 LL | |     5u32
@@ -12,5 +18,5 @@ error: could not find defining uses
 LL | existential type Cmp<T>: 'static;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/existential_types/generic_not_used.rs b/src/test/ui/existential_types/generic_not_used.rs
index bfe7b8c4a1d..054e6f5f2ad 100644
--- a/src/test/ui/existential_types/generic_not_used.rs
+++ b/src/test/ui/existential_types/generic_not_used.rs
@@ -3,6 +3,7 @@
 fn main() {}
 
 existential type WrongGeneric<T: 'static>: 'static;
+//~^ ERROR: at least one trait must be specified
 
 fn wrong_generic<U: 'static, V: 'static>(_: U, v: V) -> WrongGeneric<U> {
 //~^ ERROR type parameter `V` is part of concrete type but not used in parameter list
diff --git a/src/test/ui/existential_types/generic_not_used.stderr b/src/test/ui/existential_types/generic_not_used.stderr
index 1ae4ab65929..d243233992b 100644
--- a/src/test/ui/existential_types/generic_not_used.stderr
+++ b/src/test/ui/existential_types/generic_not_used.stderr
@@ -1,5 +1,11 @@
+error: at least one trait must be specified
+  --> $DIR/generic_not_used.rs:5:44
+   |
+LL | existential type WrongGeneric<T: 'static>: 'static;
+   |                                            ^^^^^^^
+
 error: type parameter `V` is part of concrete type but not used in parameter list for existential type
-  --> $DIR/generic_not_used.rs:7:73
+  --> $DIR/generic_not_used.rs:8:73
    |
 LL |   fn wrong_generic<U: 'static, V: 'static>(_: U, v: V) -> WrongGeneric<U> {
    |  _________________________________________________________________________^
@@ -8,5 +14,5 @@ LL | |     v
 LL | | }
    | |_^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/existential_types/generic_type_does_not_live_long_enough.rs b/src/test/ui/existential_types/generic_type_does_not_live_long_enough.rs
index 02bb151ccb6..d9eedd6dca7 100644
--- a/src/test/ui/existential_types/generic_type_does_not_live_long_enough.rs
+++ b/src/test/ui/existential_types/generic_type_does_not_live_long_enough.rs
@@ -8,6 +8,7 @@ fn main() {
 
 existential type WrongGeneric<T>: 'static;
 //~^ ERROR the parameter type `T` may not live long enough
+//~^^ ERROR: at least one trait must be specified
 
 fn wrong_generic<T>(t: T) -> WrongGeneric<T> {
     t
diff --git a/src/test/ui/existential_types/generic_type_does_not_live_long_enough.stderr b/src/test/ui/existential_types/generic_type_does_not_live_long_enough.stderr
index 002acc41553..2f76eea4460 100644
--- a/src/test/ui/existential_types/generic_type_does_not_live_long_enough.stderr
+++ b/src/test/ui/existential_types/generic_type_does_not_live_long_enough.stderr
@@ -1,3 +1,9 @@
+error: at least one trait must be specified
+  --> $DIR/generic_type_does_not_live_long_enough.rs:9:35
+   |
+LL | existential type WrongGeneric<T>: 'static;
+   |                                   ^^^^^^^
+
 error[E0308]: mismatched types
   --> $DIR/generic_type_does_not_live_long_enough.rs:6:18
    |
@@ -22,7 +28,7 @@ note: ...so that the type `T` will meet its required lifetime bounds
 LL | existential type WrongGeneric<T>: 'static;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0308, E0310.
 For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/existential_types/generic_underconstrained.rs b/src/test/ui/existential_types/generic_underconstrained.rs
index 967faca067c..cc0db893c6a 100644
--- a/src/test/ui/existential_types/generic_underconstrained.rs
+++ b/src/test/ui/existential_types/generic_underconstrained.rs
@@ -4,6 +4,7 @@ fn main() {}
 
 trait Trait {}
 existential type Underconstrained<T: Trait>: 'static; //~ ERROR the trait bound `T: Trait`
+//~^ ERROR: at least one trait must be specified
 
 // no `Trait` bound
 fn underconstrain<T>(_: T) -> Underconstrained<T> {
diff --git a/src/test/ui/existential_types/generic_underconstrained.stderr b/src/test/ui/existential_types/generic_underconstrained.stderr
index 8551a939e8e..35083a53eb3 100644
--- a/src/test/ui/existential_types/generic_underconstrained.stderr
+++ b/src/test/ui/existential_types/generic_underconstrained.stderr
@@ -1,3 +1,9 @@
+error: at least one trait must be specified
+  --> $DIR/generic_underconstrained.rs:6:46
+   |
+LL | existential type Underconstrained<T: Trait>: 'static;
+   |                                              ^^^^^^^
+
 error[E0277]: the trait bound `T: Trait` is not satisfied
   --> $DIR/generic_underconstrained.rs:6:1
    |
@@ -7,6 +13,6 @@ LL | existential type Underconstrained<T: Trait>: 'static;
    = help: consider adding a `where T: Trait` bound
    = note: the return type of a function must have a statically known size
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/existential_types/generic_underconstrained2.rs b/src/test/ui/existential_types/generic_underconstrained2.rs
index 98d9da832cf..c6263eacd53 100644
--- a/src/test/ui/existential_types/generic_underconstrained2.rs
+++ b/src/test/ui/existential_types/generic_underconstrained2.rs
@@ -4,6 +4,7 @@ fn main() {}
 
 existential type Underconstrained<T: std::fmt::Debug>: 'static;
 //~^ ERROR `U` doesn't implement `std::fmt::Debug`
+//~^^ ERROR: at least one trait must be specified
 
 // not a defining use, because it doesn't define *all* possible generics
 fn underconstrained<U>(_: U) -> Underconstrained<U> {
@@ -12,6 +13,7 @@ fn underconstrained<U>(_: U) -> Underconstrained<U> {
 
 existential type Underconstrained2<T: std::fmt::Debug>: 'static;
 //~^ ERROR `V` doesn't implement `std::fmt::Debug`
+//~^^ ERROR: at least one trait must be specified
 
 // not a defining use, because it doesn't define *all* possible generics
 fn underconstrained2<U, V>(_: U, _: V) -> Underconstrained2<V> {
diff --git a/src/test/ui/existential_types/generic_underconstrained2.stderr b/src/test/ui/existential_types/generic_underconstrained2.stderr
index c7b6d6ade55..6ff783f33b9 100644
--- a/src/test/ui/existential_types/generic_underconstrained2.stderr
+++ b/src/test/ui/existential_types/generic_underconstrained2.stderr
@@ -1,3 +1,15 @@
+error: at least one trait must be specified
+  --> $DIR/generic_underconstrained2.rs:5:56
+   |
+LL | existential type Underconstrained<T: std::fmt::Debug>: 'static;
+   |                                                        ^^^^^^^
+
+error: at least one trait must be specified
+  --> $DIR/generic_underconstrained2.rs:14:57
+   |
+LL | existential type Underconstrained2<T: std::fmt::Debug>: 'static;
+   |                                                         ^^^^^^^
+
 error[E0277]: `U` doesn't implement `std::fmt::Debug`
   --> $DIR/generic_underconstrained2.rs:5:1
    |
@@ -9,7 +21,7 @@ LL | existential type Underconstrained<T: std::fmt::Debug>: 'static;
    = note: the return type of a function must have a statically known size
 
 error[E0277]: `V` doesn't implement `std::fmt::Debug`
-  --> $DIR/generic_underconstrained2.rs:13:1
+  --> $DIR/generic_underconstrained2.rs:14:1
    |
 LL | existential type Underconstrained2<T: std::fmt::Debug>: 'static;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `V` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
@@ -18,6 +30,6 @@ LL | existential type Underconstrained2<T: std::fmt::Debug>: 'static;
    = help: consider adding a `where V: std::fmt::Debug` bound
    = note: the return type of a function must have a statically known size
 
-error: aborting due to 2 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/existential_types/unused_generic_param.rs b/src/test/ui/existential_types/unused_generic_param.rs
index 7af65087881..5455b39f4cb 100644
--- a/src/test/ui/existential_types/unused_generic_param.rs
+++ b/src/test/ui/existential_types/unused_generic_param.rs
@@ -1,18 +1,17 @@
-// compile-pass
 #![feature(existential_type)]
 
 fn main() {
 }
 
-// test that unused generic parameters are ok
 existential type PartiallyDefined<T>: 'static;
+//~^ ERROR: at least one trait must be specified
 
 fn partially_defined<T: std::fmt::Debug>(_: T) -> PartiallyDefined<T> {
     4u32
 }
 
-// test that unused generic parameters are ok
 existential type PartiallyDefined2<T>: 'static;
+//~^ ERROR: at least one trait must be specified
 
 fn partially_defined2<T: std::fmt::Debug>(_: T) -> PartiallyDefined2<T> {
     4u32
diff --git a/src/test/ui/existential_types/unused_generic_param.stderr b/src/test/ui/existential_types/unused_generic_param.stderr
new file mode 100644
index 00000000000..9d628d069d3
--- /dev/null
+++ b/src/test/ui/existential_types/unused_generic_param.stderr
@@ -0,0 +1,14 @@
+error: at least one trait must be specified
+  --> $DIR/unused_generic_param.rs:6:39
+   |
+LL | existential type PartiallyDefined<T>: 'static;
+   |                                       ^^^^^^^
+
+error: at least one trait must be specified
+  --> $DIR/unused_generic_param.rs:13:40
+   |
+LL | existential type PartiallyDefined2<T>: 'static;
+   |                                        ^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/impl-header-lifetime-elision/path-elided.rs b/src/test/ui/impl-header-lifetime-elision/path-elided.rs
index 6532b0aebe7..40a52efc7f9 100644
--- a/src/test/ui/impl-header-lifetime-elision/path-elided.rs
+++ b/src/test/ui/impl-header-lifetime-elision/path-elided.rs
@@ -5,7 +5,7 @@ trait MyTrait { }
 struct Foo<'a> { x: &'a u32 }
 
 impl MyTrait for Foo {
-    //~^ ERROR missing lifetime specifier
+    //~^ ERROR implicit elided lifetime not allowed here
 }
 
 fn main() {}
diff --git a/src/test/ui/impl-header-lifetime-elision/path-elided.stderr b/src/test/ui/impl-header-lifetime-elision/path-elided.stderr
index c9287ffba96..6500a2a55f6 100644
--- a/src/test/ui/impl-header-lifetime-elision/path-elided.stderr
+++ b/src/test/ui/impl-header-lifetime-elision/path-elided.stderr
@@ -1,9 +1,8 @@
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
   --> $DIR/path-elided.rs:7:18
    |
 LL | impl MyTrait for Foo {
-   |                  ^^^ expected lifetime parameter
+   |                  ^^^- help: indicate the anonymous lifetime: `<'_>`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/impl-header-lifetime-elision/trait-elided.rs b/src/test/ui/impl-header-lifetime-elision/trait-elided.rs
index 3979eda740a..102d259b0c8 100644
--- a/src/test/ui/impl-header-lifetime-elision/trait-elided.rs
+++ b/src/test/ui/impl-header-lifetime-elision/trait-elided.rs
@@ -3,7 +3,7 @@
 trait MyTrait<'a> { }
 
 impl MyTrait for u32 {
-    //~^ ERROR missing lifetime specifier
+    //~^ ERROR implicit elided lifetime not allowed here
 }
 
 fn main() {}
diff --git a/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr b/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr
index b742db1c75c..ad97cb0abd6 100644
--- a/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr
+++ b/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr
@@ -1,9 +1,8 @@
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
   --> $DIR/trait-elided.rs:5:6
    |
 LL | impl MyTrait for u32 {
-   |      ^^^^^^^ expected lifetime parameter
+   |      ^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/issues/issue-10412.rs b/src/test/ui/issues/issue-10412.rs
index a0bc2fc2f3c..02058513685 100644
--- a/src/test/ui/issues/issue-10412.rs
+++ b/src/test/ui/issues/issue-10412.rs
@@ -5,7 +5,8 @@ trait Serializable<'self, T> { //~ ERROR lifetimes cannot use keyword names
 
 impl<'self> Serializable<str> for &'self str { //~ ERROR lifetimes cannot use keyword names
     //~^ ERROR lifetimes cannot use keyword names
-    //~| ERROR missing lifetime specifier
+    //~| ERROR implicit elided lifetime not allowed here
+    //~| ERROR the size for values of type `str` cannot be known at compilation time
     fn serialize(val : &'self str) -> Vec<u8> { //~ ERROR lifetimes cannot use keyword names
         vec![1]
     }
diff --git a/src/test/ui/issues/issue-10412.stderr b/src/test/ui/issues/issue-10412.stderr
index 48920813ae1..0793dd99b4d 100644
--- a/src/test/ui/issues/issue-10412.stderr
+++ b/src/test/ui/issues/issue-10412.stderr
@@ -29,23 +29,32 @@ LL | impl<'self> Serializable<str> for &'self str {
    |                                    ^^^^^
 
 error: lifetimes cannot use keyword names
-  --> $DIR/issue-10412.rs:9:25
+  --> $DIR/issue-10412.rs:10:25
    |
 LL |     fn serialize(val : &'self str) -> Vec<u8> {
    |                         ^^^^^
 
 error: lifetimes cannot use keyword names
-  --> $DIR/issue-10412.rs:12:37
+  --> $DIR/issue-10412.rs:13:37
    |
 LL |     fn deserialize(repr: &[u8]) -> &'self str {
    |                                     ^^^^^
 
-error[E0106]: missing lifetime specifier
+error[E0726]: implicit elided lifetime not allowed here
   --> $DIR/issue-10412.rs:6:13
    |
 LL | impl<'self> Serializable<str> for &'self str {
-   |             ^^^^^^^^^^^^^^^^^ expected lifetime parameter
+   |             ^^^^^^^^^^^^^^^^^ help: indicate the anonymous lifetime: `Serializable<'_, str>`
 
-error: aborting due to 8 previous errors
+error[E0277]: the size for values of type `str` cannot be known at compilation time
+  --> $DIR/issue-10412.rs:6:13
+   |
+LL | impl<'self> Serializable<str> for &'self str {
+   |             ^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `std::marker::Sized` is not implemented for `str`
+   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
+
+error: aborting due to 9 previous errors
 
-For more information about this error, try `rustc --explain E0106`.
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/match/match-type-err-first-arm.rs b/src/test/ui/match/match-type-err-first-arm.rs
index b4b84ef8f1c..8dfbf1019e9 100644
--- a/src/test/ui/match/match-type-err-first-arm.rs
+++ b/src/test/ui/match/match-type-err-first-arm.rs
@@ -3,8 +3,7 @@ fn main() {
     let _ = test_func2(1);
 }
 
-fn test_func1(n: i32) -> i32 {
-    //~^ NOTE expected `i32` because of return type
+fn test_func1(n: i32) -> i32 { //~ NOTE expected `i32` because of return type
     match n {
         12 => 'b',
         //~^ ERROR mismatched types
@@ -14,10 +13,8 @@ fn test_func1(n: i32) -> i32 {
 }
 
 fn test_func2(n: i32) -> i32 {
-    let x = match n {
-    //~^ NOTE `match` arms have incompatible types
-        12 => 'b',
-        //~^ NOTE this is found to be of type `char`
+    let x = match n { //~ NOTE `match` arms have incompatible types
+        12 => 'b', //~ NOTE this is found to be of type `char`
         _ => 42,
         //~^ ERROR match arms have incompatible types
         //~| NOTE expected char, found integer
@@ -27,8 +24,7 @@ fn test_func2(n: i32) -> i32 {
 }
 
 fn test_func3(n: i32) -> i32 {
-    let x = match n {
-    //~^ NOTE `match` arms have incompatible types
+    let x = match n { //~ NOTE `match` arms have incompatible types
         1 => 'b',
         2 => 'b',
         3 => 'b',
@@ -43,3 +39,15 @@ fn test_func3(n: i32) -> i32 {
     };
     x
 }
+
+fn test_func4() {
+    match Some(0u32) { //~ NOTE `match` arms have incompatible types
+        Some(x) => {
+            x //~ NOTE this is found to be of type `u32`
+        },
+        None => {}
+        //~^ ERROR match arms have incompatible types
+        //~| NOTE expected u32, found ()
+        //~| NOTE expected type `u32`
+    };
+}
diff --git a/src/test/ui/match/match-type-err-first-arm.stderr b/src/test/ui/match/match-type-err-first-arm.stderr
index a318e6cffb9..e0553fca683 100644
--- a/src/test/ui/match/match-type-err-first-arm.stderr
+++ b/src/test/ui/match/match-type-err-first-arm.stderr
@@ -1,24 +1,23 @@
 error[E0308]: mismatched types
-  --> $DIR/match-type-err-first-arm.rs:9:15
+  --> $DIR/match-type-err-first-arm.rs:8:15
    |
 LL | fn test_func1(n: i32) -> i32 {
    |                          --- expected `i32` because of return type
-...
+LL |     match n {
 LL |         12 => 'b',
    |               ^^^ expected i32, found char
 
 error[E0308]: match arms have incompatible types
-  --> $DIR/match-type-err-first-arm.rs:21:14
+  --> $DIR/match-type-err-first-arm.rs:18:14
    |
 LL |       let x = match n {
    |  _____________-
-LL | |
 LL | |         12 => 'b',
    | |               --- this is found to be of type `char`
-LL | |
 LL | |         _ => 42,
    | |              ^^ expected char, found integer
-...  |
+LL | |
+LL | |
 LL | |
 LL | |     };
    | |_____- `match` arms have incompatible types
@@ -27,13 +26,13 @@ LL | |     };
               found type `{integer}`
 
 error[E0308]: match arms have incompatible types
-  --> $DIR/match-type-err-first-arm.rs:39:14
+  --> $DIR/match-type-err-first-arm.rs:35:14
    |
 LL |       let x = match n {
    |  _____________-
-LL | |
 LL | |         1 => 'b',
 LL | |         2 => 'b',
+LL | |         3 => 'b',
 ...  |
 LL | |         6 => 'b',
    | |              --- this and all prior arms are found to be of type `char`
@@ -48,6 +47,24 @@ LL | |     };
    = note: expected type `char`
               found type `{integer}`
 
-error: aborting due to 3 previous errors
+error[E0308]: match arms have incompatible types
+  --> $DIR/match-type-err-first-arm.rs:48:17
+   |
+LL | /     match Some(0u32) {
+LL | |         Some(x) => {
+LL | |             x
+   | |             - this is found to be of type `u32`
+LL | |         },
+LL | |         None => {}
+   | |                 ^^ expected u32, found ()
+...  |
+LL | |
+LL | |     };
+   | |_____- `match` arms have incompatible types
+   |
+   = note: expected type `u32`
+              found type `()`
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/mismatched_types/issue-38371.stderr b/src/test/ui/mismatched_types/issue-38371.stderr
index 236f742db3f..a9347926bda 100644
--- a/src/test/ui/mismatched_types/issue-38371.stderr
+++ b/src/test/ui/mismatched_types/issue-38371.stderr
@@ -12,11 +12,13 @@ error[E0308]: mismatched types
   --> $DIR/issue-38371.rs:18:9
    |
 LL | fn agh(&&bar: &u32) {
-   |         ^^^^ expected u32, found reference
+   |         ^^^^
+   |         |
+   |         expected u32, found reference
+   |         help: you can probably remove the explicit borrow: `bar`
    |
    = note: expected type `u32`
               found type `&_`
-   = help: did you mean `bar: &u32`?
 
 error[E0308]: mismatched types
   --> $DIR/issue-38371.rs:21:8
diff --git a/src/test/ui/suggestions/match-ergonomics.rs b/src/test/ui/suggestions/match-ergonomics.rs
new file mode 100644
index 00000000000..c4fc01469bf
--- /dev/null
+++ b/src/test/ui/suggestions/match-ergonomics.rs
@@ -0,0 +1,41 @@
+fn main() {
+    let x = vec![1i32];
+    match &x[..] {
+        [&v] => {}, //~ ERROR mismatched types
+        _ => {},
+    }
+    match x {
+        [&v] => {}, //~ ERROR expected an array or slice
+        _ => {},
+    }
+    match &x[..] {
+        [v] => {},
+        _ => {},
+    }
+    match &x[..] {
+        &[v] => {},
+        _ => {},
+    }
+    match x {
+        [v] => {}, //~ ERROR expected an array or slice
+        _ => {},
+    }
+    let y = 1i32;
+    match &y {
+        &v => {},
+        _ => {},
+    }
+    match y {
+        &v => {}, //~ ERROR mismatched types
+        _ => {},
+    }
+    match &y {
+        v => {},
+        _ => {},
+    }
+    match y {
+        v => {},
+        _ => {},
+    }
+    if let [&v] = &x[..] {} //~ ERROR mismatched types
+}
diff --git a/src/test/ui/suggestions/match-ergonomics.stderr b/src/test/ui/suggestions/match-ergonomics.stderr
new file mode 100644
index 00000000000..b7497be6ceb
--- /dev/null
+++ b/src/test/ui/suggestions/match-ergonomics.stderr
@@ -0,0 +1,52 @@
+error[E0308]: mismatched types
+  --> $DIR/match-ergonomics.rs:4:10
+   |
+LL |         [&v] => {},
+   |          ^^
+   |          |
+   |          expected i32, found reference
+   |          help: you can probably remove the explicit borrow: `v`
+   |
+   = note: expected type `i32`
+              found type `&_`
+
+error[E0529]: expected an array or slice, found `std::vec::Vec<i32>`
+  --> $DIR/match-ergonomics.rs:8:9
+   |
+LL |         [&v] => {},
+   |         ^^^^ pattern cannot match with input type `std::vec::Vec<i32>`
+
+error[E0529]: expected an array or slice, found `std::vec::Vec<i32>`
+  --> $DIR/match-ergonomics.rs:20:9
+   |
+LL |         [v] => {},
+   |         ^^^ pattern cannot match with input type `std::vec::Vec<i32>`
+
+error[E0308]: mismatched types
+  --> $DIR/match-ergonomics.rs:29:9
+   |
+LL |         &v => {},
+   |         ^^
+   |         |
+   |         expected i32, found reference
+   |         help: you can probably remove the explicit borrow: `v`
+   |
+   = note: expected type `i32`
+              found type `&_`
+
+error[E0308]: mismatched types
+  --> $DIR/match-ergonomics.rs:40:13
+   |
+LL |     if let [&v] = &x[..] {}
+   |             ^^
+   |             |
+   |             expected i32, found reference
+   |             help: you can probably remove the explicit borrow: `v`
+   |
+   = note: expected type `i32`
+              found type `&_`
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0308, E0529.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/type-alias-enum-variants-priority.rs b/src/test/ui/type-alias-enum-variants-priority.rs
index db1da2b12e2..82cd21b09d3 100644
--- a/src/test/ui/type-alias-enum-variants-priority.rs
+++ b/src/test/ui/type-alias-enum-variants-priority.rs
@@ -1,5 +1,4 @@
 #![feature(type_alias_enum_variants)]
-#![deny(ambiguous_associated_items)]
 
 enum E {
     V
diff --git a/src/test/ui/type-alias-enum-variants-priority.stderr b/src/test/ui/type-alias-enum-variants-priority.stderr
index dcf7dc77ed5..b8271807b83 100644
--- a/src/test/ui/type-alias-enum-variants-priority.stderr
+++ b/src/test/ui/type-alias-enum-variants-priority.stderr
@@ -1,23 +1,19 @@
 error: ambiguous associated item
-  --> $DIR/type-alias-enum-variants-priority.rs:15:15
+  --> $DIR/type-alias-enum-variants-priority.rs:14:15
    |
 LL |     fn f() -> Self::V { 0 }
    |               ^^^^^^^ help: use fully-qualified syntax: `<E as Trait>::V`
    |
-note: lint level defined here
-  --> $DIR/type-alias-enum-variants-priority.rs:2:9
-   |
-LL | #![deny(ambiguous_associated_items)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: #[deny(ambiguous_associated_items)] on by default
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #57644 <https://github.com/rust-lang/rust/issues/57644>
 note: `V` could refer to variant defined here
-  --> $DIR/type-alias-enum-variants-priority.rs:5:5
+  --> $DIR/type-alias-enum-variants-priority.rs:4:5
    |
 LL |     V
    |     ^
 note: `V` could also refer to associated type defined here
-  --> $DIR/type-alias-enum-variants-priority.rs:9:5
+  --> $DIR/type-alias-enum-variants-priority.rs:8:5
    |
 LL |     type V;
    |     ^^^^^^^