Auto merge of #91555 - matthiaskrgr:rollup-pq0iaq7, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - #90529 (Skip reborrows in AbstractConstBuilder)
 - #91437 (Pretty print empty blocks as {})
 - #91450 (Don't suggest types whose inner type is erroneous)
 - #91535 (Stabilize `-Z emit-future-incompat` as `--json future-incompat`)

Failed merges:

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

src/test/pretty/ast-stmt-expr-attr.rs

@@ -1,6 +1,6 @@
 // pp-exact
 
-fn main() { }
+fn main() {}
 
 #[cfg(FALSE)]
 fn syntax() {
@@ -117,7 +117,7 @@ fn syntax() {
     let _ = #[attr] foo!(#! [attr]);
     let _ = #[attr] foo![];
     let _ = #[attr] foo![#! [attr]];
-    let _ = #[attr] foo! { };
+    let _ = #[attr] foo! {};
     let _ = #[attr] foo! { #! [attr] };
     let _ = #[attr] Foo{bar: baz,};
     let _ = #[attr] Foo{..foo};
@@ -135,7 +135,7 @@ fn syntax() {
         foo!();
 
         #[attr]
-        foo! { }
+        foo! {}
 
         #[attr]
         foo![];
@@ -170,6 +170,6 @@ fn syntax() {
     {
 
         #[attr]
-        foo! { }
+        foo! {}
     }
 }

src/test/pretty/attr-derive.rs

@@ -29,4 +29,4 @@ enum Enum {
     Qwerty,
 }
 
-fn main() { }
+fn main() {}

src/test/pretty/auto-trait.rs

@@ -2,8 +2,8 @@
 
 // pp-exact
 
-auto trait MyTrait { }
+auto trait MyTrait {}
 
-unsafe auto trait UnsafeMyTrait { }
+unsafe auto trait UnsafeMyTrait {}
 
-pub fn main() { }
+pub fn main() {}

src/test/pretty/block-comment-trailing-whitespace2.rs

@@ -1,9 +1,8 @@
 // compile-flags: --crate-type=lib
 
 // pp-exact
-fn f() {
-} /*
-  The next line should not be indented.
+fn f() {} /*
+          The next line should not be indented.
 
-  That one. It shouldn't have been indented.
-  */
+          That one. It shouldn't have been indented.
+          */

src/test/pretty/closure-reform-pretty.rs

@@ -3,14 +3,14 @@
 
 // pp-exact
 
-fn call_it(f: Box<FnMut(String) -> String>) { }
+fn call_it(f: Box<FnMut(String) -> String>) {}
 
-fn call_this<F>(f: F) where F: Fn(&str) + Send { }
+fn call_this<F>(f: F) where F: Fn(&str) + Send {}
 
-fn call_that<F>(f: F) where F: for<'a> Fn(&'a isize, &'a isize) -> isize { }
+fn call_that<F>(f: F) where F: for<'a> Fn(&'a isize, &'a isize) -> isize {}
 
-fn call_extern(f: fn() -> isize) { }
+fn call_extern(f: fn() -> isize) {}
 
-fn call_abid_extern(f: extern "C" fn() -> isize) { }
+fn call_abid_extern(f: extern "C" fn() -> isize) {}
 
-pub fn main() { }
+pub fn main() {}

src/test/pretty/disamb-stmt-expr.rs

@@ -7,4 +7,4 @@
 fn id<F>(f: F) -> isize where F: Fn() -> isize { f() }
 
 fn wsucc(_n: isize) -> isize { id(|| { 1 }) - 0 }
-fn main() { }
+fn main() {}

src/test/pretty/enum-variant-vis.rs

@@ -2,7 +2,7 @@
 
 // Check that the visibility is printed on an enum variant.
 
-fn main() { }
+fn main() {}
 
 #[cfg(FALSE)]
 enum Foo { pub V, }

src/test/pretty/example1.rs

@@ -1,3 +1,3 @@
 // pp-exact
 
-fn main() { }
+fn main() {}

src/test/pretty/example2.pp

@@ -1,3 +1,3 @@
 // pp-exact:example2.pp
 
-fn main() { }
+fn main() {}

src/test/pretty/example2.rs

@@ -1,3 +1,3 @@
 // pp-exact:example2.pp
 
-fn main() { }
+fn main() {}

src/test/pretty/expanded-and-path-remap-80832.pp

@@ -10,4 +10,4 @@ extern crate std;
 // pp-exact:expanded-and-path-remap-80832.pp
 // compile-flags: --remap-path-prefix {{src-base}}=the/src
 
-fn main() { }
+fn main() {}

src/test/pretty/fn-return.rs

@@ -1,7 +1,7 @@
 // pp-exact
 
-// Check that `fn f() -> () { }` does not print as `fn f() { }`.
+// Check that `fn f() -> () {}` does not print as `fn f() {}`.
 
-fn f() -> () { }
+fn f() -> () {}
 
-fn main() { }
+fn main() {}

src/test/pretty/fn-types.rs

@@ -1,5 +1,5 @@
 // pp-exact
 
-fn from_foreign_fn(_x: fn()) { }
-fn from_stack_closure<F>(_x: F) where F: Fn() { }
-fn main() { }
+fn from_foreign_fn(_x: fn()) {}
+fn from_stack_closure<F>(_x: F) where F: Fn() {}
+fn main() {}

src/test/pretty/fn-variadic.rs

@@ -12,4 +12,4 @@ pub unsafe extern "C" fn bar(_: i32, mut ap: ...) -> usize {
     ap.arg::<usize>()
 }
 
-fn main() { }
+fn main() {}

src/test/pretty/if-attr.rs

@@ -4,34 +4,34 @@
 fn simple_attr() {
 
     #[attr]
-    if true { }
+    if true {}
 
     #[allow_warnings]
-    if true { }
+    if true {}
 }
 
 #[cfg(FALSE)]
 fn if_else_chain() {
 
     #[first_attr]
-    if true { } else if false { } else { }
+    if true {} else if false {} else {}
 }
 
 #[cfg(FALSE)]
 fn if_let() {
 
     #[attr]
-    if let Some(_) = Some(true) { }
+    if let Some(_) = Some(true) {}
 }
 
 #[cfg(FALSE)]
 fn let_attr_if() {
-    let _ = #[attr] if let _ = 0 { };
-    let _ = #[attr] if true { };
+    let _ = #[attr] if let _ = 0 {};
+    let _ = #[attr] if true {};
 
-    let _ = #[attr] if let _ = 0 { } else { };
-    let _ = #[attr] if true { } else { };
+    let _ = #[attr] if let _ = 0 {} else {};
+    let _ = #[attr] if true {} else {};
 }
 
 
-fn main() { }
+fn main() {}

src/test/pretty/issue-12590-a.rs

@@ -6,4 +6,4 @@
 #[path = "issue-12590-b.rs"]
 mod issue_12590_b;
 
-fn main() { }
+fn main() {}

src/test/pretty/issue-12590-c.pp

@@ -13,7 +13,7 @@ extern crate std;
 #[path = "issue-12590-b.rs"]
 mod issue_12590_b {
 
-    fn b() { }
-    fn main() { }
+    fn b() {}
+    fn main() {}
 }
-fn main() { }
+fn main() {}

src/test/pretty/issue-12590-c.rs

@@ -7,4 +7,4 @@
 #[path = "issue-12590-b.rs"]
 mod issue_12590_b;
 
-fn main() { }
+fn main() {}

src/test/pretty/issue-19077.rs

@@ -4,8 +4,8 @@
 fn main() {
     match true {
         true if true => (),
-        false if false => unsafe { },
-        true => { }
+        false if false => unsafe {},
+        true => {}
         false => (),
     }
 }

src/test/pretty/issue-30731.rs

@@ -5,4 +5,4 @@
 // pretty-compare-only
 // pp-exact
 
-fn main() { b! { } c }
+fn main() { b! {} c }

src/test/pretty/issue-68710-field-attr-proc-mac-lost.rs

@@ -1,6 +1,6 @@
 // pp-exact
 
-fn main() { }
+fn main() {}
 
 struct C {
     field: u8,

src/test/pretty/lifetime.rs

@@ -1,5 +1,5 @@
 // pp-exact
 
-fn f1<'a, 'b, 'c>(_x: &'a u32, _y: &'b u32, _z: &'c u32) where 'c: 'a + 'b { }
+fn f1<'a, 'b, 'c>(_x: &'a u32, _y: &'b u32, _z: &'c u32) where 'c: 'a + 'b {}
 
-fn main() { }
+fn main() {}

src/test/pretty/macro.rs

@@ -4,4 +4,4 @@
 
 pub(crate) macro mac { ($arg : expr) => { $arg + $arg } }
 
-fn main() { }
+fn main() {}

src/test/pretty/macro_rules.rs

@@ -1,19 +1,19 @@
 // pp-exact
 
-macro_rules! brace { () => { } ; }
+macro_rules! brace { () => {} ; }
 
-macro_rules! bracket[() => { } ;];
+macro_rules! bracket[() => {} ;];
 
-macro_rules! paren(() => { } ;);
+macro_rules! paren(() => {} ;);
 
 macro_rules! matcher_brackets {
-    (paren) => { } ; (bracket) => { } ; (brace) => { } ;
+    (paren) => {} ; (bracket) => {} ; (brace) => {} ;
 }
 
 macro_rules! all_fragments {
     ($b : block, $e : expr, $i : ident, $it : item, $l : lifetime, $lit :
      literal, $m : meta, $p : pat, $pth : path, $s : stmt, $tt : tt, $ty : ty,
-     $vis : vis) => { } ;
+     $vis : vis) => {} ;
 }
 
-fn main() { }
+fn main() {}

src/test/pretty/nested-item-vis-defaultness.rs

@@ -2,7 +2,7 @@
 
 // pp-exact
 
-fn main() { }
+fn main() {}
 
 #[cfg(FALSE)]
 extern "C" {

src/test/pretty/path-type-bounds.rs

@@ -2,9 +2,9 @@
 
 
 trait Tr {
-    fn dummy(&self) { }
+    fn dummy(&self) {}
 }
-impl Tr for isize { }
+impl Tr for isize {}
 
 fn foo<'a>(x: Box<Tr + Sync + 'a>) -> Box<Tr + Sync + 'a> { x }
 

src/test/pretty/qpath-associated-type-bound.rs

@@ -8,9 +8,9 @@ mod m {
 }
 
 trait Tu {
-    fn dummy() { }
+    fn dummy() {}
 }
 
 fn foo<T: m::Tr>() { <T as m::Tr>::Ts::dummy(); }
 
-fn main() { }
+fn main() {}

src/test/pretty/stmt_expr_attributes.rs

@@ -4,7 +4,7 @@
 #![feature(rustc_attrs)]
 #![feature(stmt_expr_attributes)]
 
-fn main() { }
+fn main() {}
 
 fn _0() {
 
@@ -35,7 +35,7 @@ fn _2() {
 fn _3() {
 
     #[rustc_dummy]
-    match () { _ => { } }
+    match () { _ => {} }
 }
 
 fn _4() {
@@ -117,13 +117,13 @@ fn _9() {
     stmt_mac!();
 
     #[rustc_dummy]
-    stmt_mac! { };
+    stmt_mac! {};
 
     #[rustc_dummy]
     stmt_mac![];
 
     #[rustc_dummy]
-    stmt_mac! { }
+    stmt_mac! {}
 
     let _ = ();
 }
@@ -133,7 +133,7 @@ macro_rules! expr_mac { () => { () } }
 fn _10() {
     let _ = #[rustc_dummy] expr_mac!();
     let _ = #[rustc_dummy] expr_mac![];
-    let _ = #[rustc_dummy] expr_mac! { };
+    let _ = #[rustc_dummy] expr_mac! {};
 }
 
 fn _11() {
@@ -235,7 +235,7 @@ fn _11() {
     || #[rustc_dummy] return;
     let _ = #[rustc_dummy] expr_mac!();
     let _ = #[rustc_dummy] expr_mac![];
-    let _ = #[rustc_dummy] expr_mac! { };
+    let _ = #[rustc_dummy] expr_mac! {};
     let _ = #[rustc_dummy] Foo{data: (),};
     let _ = #[rustc_dummy] Foo{..s};
     let _ = #[rustc_dummy] Foo{data: (), ..s};
@@ -258,6 +258,6 @@ fn _12() {
     }
 }
 
-fn foo() { }
-fn foo3(_: i32, _: (), _: ()) { }
-fn qux(_: i32) { }
+fn foo() {}
+fn foo3(_: i32, _: (), _: ()) {}
+fn qux(_: i32) {}

src/test/pretty/tag-blank-lines.rs

@@ -5,4 +5,4 @@ enum foo {
     baz,
 }
 
-fn main() { }
+fn main() {}

src/test/pretty/trait-inner-attr.rs

@@ -4,4 +4,4 @@ trait Foo {
     #![allow(bar)]
 }
 
-fn main() { }
+fn main() {}

src/test/pretty/trait-polarity.rs

@@ -4,6 +4,6 @@
 
 struct Test;
 
-impl !Send for Test { }
+impl !Send for Test {}
 
-pub fn main() { }
+pub fn main() {}

src/test/pretty/trait-safety.rs

@@ -5,11 +5,11 @@ unsafe trait UnsafeTrait {
 }
 
 unsafe impl UnsafeTrait for isize {
-    fn foo(&self) { }
+    fn foo(&self) {}
 }
 
 pub unsafe trait PubUnsafeTrait {
     fn foo(&self);
 }
 
-fn main() { }
+fn main() {}

src/test/pretty/where-clauses.rs

@@ -2,4 +2,4 @@
 
 fn f<'a, 'b, T>(t: T) -> isize where T: 'a, 'a: 'b, T: Eq { 0 }
 
-fn main() { }
+fn main() {}

src/test/ui/async-await/issues/issue-60674.stdout

@@ -1,3 +1,3 @@
-async fn f(mut x : u8) { }
-async fn g((mut x, y, mut z) : (u8, u8, u8)) { }
-async fn g(mut x : u8, (a, mut b, c) : (u8, u8, u8), y : u8) { }
+async fn f(mut x : u8) {}
+async fn g((mut x, y, mut z) : (u8, u8, u8)) {}
+async fn g(mut x : u8, (a, mut b, c) : (u8, u8, u8), y : u8) {}

src/test/ui/attributes/issue-90873.stderr

@@ -8,7 +8,7 @@ LL | #![u=||{static d=||1;}]
    |      ^^^^^^^^^^^^^^^^^
 
 error: unexpected token: `{
-           impl std::ops::Neg for i8 { }
+           impl std::ops::Neg for i8 {}
        }`
   --> $DIR/issue-90873.rs:7:6
    |

src/test/ui/const-generics/defaults/pretty-printing-ast.stdout

@@ -11,9 +11,9 @@ use ::std::prelude::rust_2015::*;
 #[macro_use]
 extern crate std;
 
-trait Foo<const KIND : bool = true> { }
+trait Foo<const KIND : bool = true> {}
 
-fn foo<const SIZE : usize = 5>() { }
+fn foo<const SIZE : usize = 5>() {}
 
 struct Range<const FROM : usize = 0, const LEN : usize = 0, const TO : usize =
              FROM>;

src/test/ui/const-generics/generic_const_exprs/closures.stderr

@@ -4,7 +4,7 @@ error: overly complex generic constant
 LL | fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
    |                                   ^^^^-------^^
    |                                       |
-   |                                       dereferencing is not supported in generic constants
+   |                                       borrowing is not supported in generic constants
    |
    = help: consider moving this anonymous constant into a `const` function
    = note: this operation may be supported in the future

src/test/ui/const-generics/issues/issue-90455.rs

@@ -0,0 +1,12 @@
+#![feature(generic_const_exprs, adt_const_params)]
+#![allow(incomplete_features)]
+
+struct FieldElement<const N: &'static str> {
+    n: [u64; num_limbs(N)],
+    //~^ ERROR unconstrained generic constant
+}
+const fn num_limbs(_: &str) -> usize {
+    0
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-90455.stderr

@@ -0,0 +1,10 @@
+error: unconstrained generic constant
+  --> $DIR/issue-90455.rs:5:8
+   |
+LL |     n: [u64; num_limbs(N)],
+   |        ^^^^^^^^^^^^^^^^^^^
+   |
+   = help: try adding a `where` bound using this expression: `where [(); num_limbs(N)]:`
+
+error: aborting due to previous error
+

src/test/ui/hygiene/unpretty-debug.stdout

@@ -15,7 +15,7 @@ fn bar /* 0#0 */() {
     y /* 0#1 */ + x /* 0#0 */
 }
 
-fn y /* 0#0 */() { }
+fn y /* 0#0 */() {}
 
 /*
 Expansions:

src/test/ui/lint/future-incompat-test.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Zfuture-incompat-test -Zemit-future-incompat-report
+// compile-flags: -Zfuture-incompat-test
 // check-pass
 
 // The `-Zfuture-incompat-test flag causes any normal warning to be included

src/test/ui/lint/issue-87308.stdout

@@ -11,4 +11,4 @@ extern crate std;
 
 macro_rules! foo { () => { break 'x ; } }
 
-pub fn main() { loop { } }
+pub fn main() { loop {} }

src/test/ui/macros/nonterminal-matching.rs

@@ -16,7 +16,7 @@ macro complex_nonterminal($nt_item: item) {
         struct S;
     }
 
-    n!(a $nt_item b); //~ ERROR no rules expected the token `enum E { }`
+    n!(a $nt_item b); //~ ERROR no rules expected the token `enum E {}`
 }
 
 simple_nonterminal!(a, 'a, (x, y, z)); // OK

src/test/ui/macros/nonterminal-matching.stderr

@@ -1,4 +1,4 @@
-error: no rules expected the token `enum E { }`
+error: no rules expected the token `enum E {}`
   --> $DIR/nonterminal-matching.rs:19:10
    |
 LL |     macro n(a $nt_item b) {

src/test/ui/proc-macro/allowed-attr-stmt-expr.stdout

@@ -14,7 +14,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/allowed-attr-stmt-expr.rs:49:20: 49:21 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Foo { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Foo {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',
@@ -140,7 +140,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/allowed-attr-stmt-expr.rs:61:28: 61:29 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): second_make_stmt! (#[allow(dead_code)] struct Bar { }) ;
+PRINT-ATTR INPUT (DISPLAY): second_make_stmt! (#[allow(dead_code)] struct Bar {}) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "second_make_stmt",
@@ -201,7 +201,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/allowed-attr-stmt-expr.rs:64:57: 64:58 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] #[allow(dead_code)] struct Bar { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] #[allow(dead_code)] struct Bar {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',
@@ -257,7 +257,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/allowed-attr-stmt-expr.rs:64:54: 64:56 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Other { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Other {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',

src/test/ui/proc-macro/attr-complex-fn.stdout

@@ -1,4 +1,4 @@
-PRINT-ATTR INPUT (DISPLAY): fn foo < T : MyTrait < MyStruct < { true } >> > () { }
+PRINT-ATTR INPUT (DISPLAY): fn foo < T : MyTrait < MyStruct < { true } >> > () {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "fn",

src/test/ui/proc-macro/attr-stmt-expr.stdout

@@ -1,4 +1,4 @@
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Foo { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Foo {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',
@@ -124,7 +124,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/attr-stmt-expr.rs:53:28: 53:29 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): second_make_stmt! (#[allow(dead_code)] struct Bar { }) ;
+PRINT-ATTR INPUT (DISPLAY): second_make_stmt! (#[allow(dead_code)] struct Bar {}) ;
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "second_make_stmt",
@@ -185,7 +185,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/attr-stmt-expr.rs:56:57: 56:58 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] #[allow(dead_code)] struct Bar { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] #[allow(dead_code)] struct Bar {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',
@@ -241,7 +241,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/attr-stmt-expr.rs:56:54: 56:56 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Other { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Other {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',

src/test/ui/proc-macro/attribute-after-derive.stdout

@@ -83,7 +83,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/attribute-after-derive.rs:16:24: 19:2 (#0),
     },
 ]
-PRINT-DERIVE INPUT (DISPLAY): struct AttributeDerive { }
+PRINT-DERIVE INPUT (DISPLAY): struct AttributeDerive {}
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
@@ -99,7 +99,7 @@ PRINT-DERIVE INPUT (DEBUG): TokenStream [
         span: $DIR/attribute-after-derive.rs:16:24: 19:2 (#0),
     },
 ]
-PRINT-DERIVE INPUT (DISPLAY): #[print_attr] struct DeriveAttribute { }
+PRINT-DERIVE INPUT (DISPLAY): #[print_attr] struct DeriveAttribute {}
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',

src/test/ui/proc-macro/auxiliary/attr-args.rs

@@ -15,7 +15,7 @@ pub fn attr_with_args(args: TokenStream, input: TokenStream) -> TokenStream {
 
     let input = input.to_string();
 
-    assert_eq!(input, "fn foo() { }");
+    assert_eq!(input, "fn foo() {}");
 
     r#"
         fn foo() -> &'static str { "Hello, world!" }

src/test/ui/proc-macro/auxiliary/attr-on-trait.rs

@@ -10,6 +10,6 @@ use proc_macro::TokenStream;
 #[proc_macro_attribute]
 pub fn foo(attr: TokenStream, item: TokenStream) -> TokenStream {
     drop(attr);
-    assert_eq!(item.to_string(), "fn foo() { }");
+    assert_eq!(item.to_string(), "fn foo() {}");
     "fn foo(&self);".parse().unwrap()
 }

src/test/ui/proc-macro/cfg-eval-inner.stdout

@@ -3,7 +3,7 @@ PRINT-ATTR INPUT (DISPLAY): impl Foo <
  {
      #! [rustc_dummy(cursed_inner)] #! [allow(unused)] struct Inner
      { field : [u8 ; { #! [rustc_dummy(another_cursed_inner)] 1 }] } 0
- }] > { #! [rustc_dummy(evaluated_attr)] fn bar() { } }
+ }] > { #! [rustc_dummy(evaluated_attr)] fn bar() {} }
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "impl",

src/test/ui/proc-macro/derive-expand-order.stdout

@@ -1,5 +1,5 @@
-Derive First: #[derive(Second)] #[derive(Third, Fourth)] #[derive(Fifth)] pub struct Foo { }
-Derive Second: #[derive(Third, Fourth)] #[derive(Fifth)] pub struct Foo { }
-Derive Third: #[derive(Fifth)] pub struct Foo { }
-Derive Fourth: #[derive(Fifth)] pub struct Foo { }
-Derive Fifth: pub struct Foo { }
+Derive First: #[derive(Second)] #[derive(Third, Fourth)] #[derive(Fifth)] pub struct Foo {}
+Derive Second: #[derive(Third, Fourth)] #[derive(Fifth)] pub struct Foo {}
+Derive Third: #[derive(Fifth)] pub struct Foo {}
+Derive Fourth: #[derive(Fifth)] pub struct Foo {}
+Derive Fifth: pub struct Foo {}

src/test/ui/proc-macro/expr-stmt-nonterminal-tokens.stdout

@@ -202,7 +202,7 @@ PRINT-DERIVE INPUT (DEBUG): TokenStream [
         span: #8 bytes(430..483),
     },
 ]
-PRINT-DERIVE INPUT (DISPLAY): enum E { V = { let _ = { { } } ; 0 }, }
+PRINT-DERIVE INPUT (DISPLAY): enum E { V = { let _ = { {} } ; 0 }, }
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Ident {
         ident: "enum",

src/test/ui/proc-macro/inner-attrs.stdout

@@ -269,7 +269,7 @@ PRINT-ATTR_ARGS INPUT (DEBUG): TokenStream [
         span: $DIR/inner-attrs.rs:20:30: 20:36 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): fn foo() { }
+PRINT-ATTR INPUT (DISPLAY): fn foo() {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "fn",
@@ -552,7 +552,7 @@ PRINT-ATTR_ARGS INPUT (DEBUG): TokenStream [
         span: $DIR/inner-attrs.rs:27:30: 27:40 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): mod inline_mod { }
+PRINT-ATTR INPUT (DISPLAY): mod inline_mod {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "mod",
@@ -933,7 +933,7 @@ PRINT-ATTR_ARGS INPUT (DEBUG): TokenStream [
         span: $DIR/inner-attrs.rs:82:42: 82:47 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): fn weird_extern() { }
+PRINT-ATTR INPUT (DISPLAY): fn weird_extern() {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "fn",

src/test/ui/proc-macro/input-interpolated.stdout

@@ -53,7 +53,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: #4 bytes(432..433),
     },
 ]
-PRINT-DERIVE INPUT (DISPLAY): struct A { }
+PRINT-DERIVE INPUT (DISPLAY): struct A {}
 PRINT-DERIVE INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",

src/test/ui/proc-macro/issue-75734-pp-paren.stdout

@@ -1,4 +1,4 @@
-PRINT-ATTR INPUT (DISPLAY): fn main() { & | _ : u8 | { } ; mul_2! (1 + 1) ; }
+PRINT-ATTR INPUT (DISPLAY): fn main() { & | _ : u8 | {} ; mul_2! (1 + 1) ; }
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "fn",

src/test/ui/proc-macro/issue-75930-derive-cfg.stdout

@@ -8,8 +8,8 @@ struct Foo < #[cfg(FALSE)] A, B >
          #[cfg(FALSE)] struct Bar ; #[cfg(not(FALSE))] struct Inner ;
          #[cfg(FALSE)] let a = 25 ; match true
          {
-             #[cfg(FALSE)] true => { },
-             #[cfg_attr(not(FALSE), allow(warnings))] false => { }, _ => { }
+             #[cfg(FALSE)] true => {},
+             #[cfg_attr(not(FALSE), allow(warnings))] false => {}, _ => {}
          } ; #[print_helper(should_be_removed)] fn removed_fn()
          { #! [cfg(FALSE)] } #[print_helper(c)] #[cfg(not(FALSE))] fn
          kept_fn() { #! [cfg(not(FALSE))] let my_val = true ; } enum TupleEnum
@@ -1278,7 +1278,7 @@ PRINT-DERIVE INPUT (DISPLAY): #[print_helper(a)] #[allow(dead_code)] #[print_hel
     [u8 ;
      {
          #[cfg(not(FALSE))] struct Inner ; match true
-         { #[allow(warnings)] false => { }, _ => { } } ; #[print_helper(c)]
+         { #[allow(warnings)] false => {}, _ => {} } ; #[print_helper(c)]
          #[cfg(not(FALSE))] fn kept_fn()
          { #! [cfg(not(FALSE))] let my_val = true ; } enum TupleEnum
          { Foo(#[cfg(not(FALSE))] i32, u8) } struct

src/test/ui/proc-macro/issue-81007-item-attrs.stdout

@@ -1,4 +1,4 @@
-PRINT-ATTR INPUT (DISPLAY): #[doc = r" A doc comment"] struct Foo { }
+PRINT-ATTR INPUT (DISPLAY): #[doc = r" A doc comment"] struct Foo {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',
@@ -40,7 +40,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/issue-81007-item-attrs.rs:22:16: 22:18 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] #[doc = r" Another comment comment"] struct Bar { }
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] #[doc = r" Another comment comment"] struct Bar {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',

src/test/ui/proc-macro/nested-macro-rules.stdout

@@ -11,7 +11,7 @@ PRINT-BANG INPUT (DEBUG): TokenStream [
         span: $DIR/auxiliary/nested-macro-rules.rs:9:30: 9:35 (#6),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): struct FirstAttrStruct { }
+PRINT-ATTR INPUT (DISPLAY): struct FirstAttrStruct {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",
@@ -46,7 +46,7 @@ PRINT-BANG INPUT (DEBUG): TokenStream [
         span: $DIR/auxiliary/nested-macro-rules.rs:9:30: 9:35 (#15),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): struct SecondAttrStruct { }
+PRINT-ATTR INPUT (DISPLAY): struct SecondAttrStruct {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "struct",

src/test/ui/proc-macro/nonterminal-token-hygiene.stdout

@@ -64,7 +64,7 @@ macro inner /* 0#4 */ { () => { print_bang! { struct S; } } }
 struct S /* 0#5 */;
 // OK, not a duplicate definition of `S`
 
-fn main /* 0#0 */() { }
+fn main /* 0#0 */() {}
 
 /*
 Expansions:

src/test/ui/proc-macro/trailing-plus.stdout

@@ -1,4 +1,4 @@
-PRINT-ATTR INPUT (DISPLAY): fn foo < T > () where T : Copy + { }
+PRINT-ATTR INPUT (DISPLAY): fn foo < T > () where T : Copy + {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "fn",

src/test/ui/proc-macro/weird-braces.stdout

@@ -445,7 +445,7 @@ PRINT-ATTR_ARGS INPUT (DEBUG): TokenStream [
         span: $DIR/weird-braces.rs:20:30: 20:42 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): impl Bar < { 1 > 0 } > for Foo < { true } > { }
+PRINT-ATTR INPUT (DISPLAY): impl Bar < { 1 > 0 } > for Foo < { true } > {}
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Ident {
         ident: "impl",

src/test/ui/repr/issue-83921-pretty.pretty.stdout

@@ -13,7 +13,6 @@ extern crate std;
 // [pretty]compile-flags: -Zunpretty=everybody_loops
 // [pretty]check-pass
 #[repr("C")]
-struct A {
-}
+struct A {}
 
-fn main() { loop { } }
+fn main() { loop {} }

src/test/ui/rfc-2497-if-let-chains/ast-pretty-check.stdout

@@ -7,4 +7,4 @@ extern crate std;
 // build-pass (FIXME(62277): could be check-pass?)
 // compile-flags: -Z unpretty=expanded
 
-fn main() { if let 0 = 1 { } }
+fn main() { if let 0 = 1 {} }

src/test/ui/rfc-2565-param-attrs/auxiliary/param-attrs.rs

@@ -18,14 +18,14 @@ macro_rules! checker {
 }
 
 checker!(attr_extern, r#"extern "C" { fn ffi(#[a1] arg1 : i32, #[a2] ...) ; }"#);
-checker!(attr_extern_cvar, r#"unsafe extern "C" fn cvar(arg1 : i32, #[a1] mut args : ...) { }"#);
+checker!(attr_extern_cvar, r#"unsafe extern "C" fn cvar(arg1 : i32, #[a1] mut args : ...) {}"#);
 checker!(attr_alias, "type Alias = fn(#[a1] u8, #[a2] ...) ;");
 checker!(attr_free, "fn free(#[a1] arg1 : u8) { let lam = | #[a2] W(x), #[a3] y | () ; }");
-checker!(attr_inherent_1, "fn inherent1(#[a1] self, #[a2] arg1 : u8) { }");
-checker!(attr_inherent_2, "fn inherent2(#[a1] & self, #[a2] arg1 : u8) { }");
-checker!(attr_inherent_3, "fn inherent3 < 'a > (#[a1] & 'a mut self, #[a2] arg1 : u8) { }");
-checker!(attr_inherent_4, "fn inherent4 < 'a > (#[a1] self : Box < Self >, #[a2] arg1 : u8) { }");
-checker!(attr_inherent_issue_64682, "fn inherent5(#[a1] #[a2] arg1 : u8, #[a3] arg2 : u8) { }");
+checker!(attr_inherent_1, "fn inherent1(#[a1] self, #[a2] arg1 : u8) {}");
+checker!(attr_inherent_2, "fn inherent2(#[a1] & self, #[a2] arg1 : u8) {}");
+checker!(attr_inherent_3, "fn inherent3 < 'a > (#[a1] & 'a mut self, #[a2] arg1 : u8) {}");
+checker!(attr_inherent_4, "fn inherent4 < 'a > (#[a1] self : Box < Self >, #[a2] arg1 : u8) {}");
+checker!(attr_inherent_issue_64682, "fn inherent5(#[a1] #[a2] arg1 : u8, #[a3] arg2 : u8) {}");
 checker!(attr_trait_1, "fn trait1(#[a1] self, #[a2] arg1 : u8) ;");
 checker!(attr_trait_2, "fn trait2(#[a1] & self, #[a2] arg1 : u8) ;");
 checker!(attr_trait_3, "fn trait3 < 'a > (#[a1] & 'a mut self, #[a2] arg1 : u8) ;");
@@ -35,9 +35,9 @@ checker!(attr_trait_issue_64682, "fn trait5(#[a1] #[a2] arg1 : u8, #[a3] arg2 :
 checker!(rename_params, r#"impl Foo
 {
     fn hello(#[angery(true)] a : i32, #[a2] b : i32, #[what = "how"] c : u32)
-    { } fn
+    {} fn
     hello2(#[a1] #[a2] a : i32, #[what = "how"] b : i32, #[angery(true)] c :
-           u32) { } fn
+           u32) {} fn
     hello_self(#[a1] #[a2] & self, #[a1] #[a2] a : i32, #[what = "how"] b :
-               i32, #[angery(true)] c : u32) { }
+               i32, #[angery(true)] c : u32) {}
 }"#);

src/test/ui/typeck/issue-91450-inner-ty-error.rs

@@ -0,0 +1,7 @@
+// Regression test for #91450.
+// This test ensures that the compiler does not suggest `Foo<[type error]>` in diagnostic messages.
+
+fn foo() -> Option<_> {} //~ ERROR: [E0308]
+//~^ ERROR: the type placeholder `_` is not allowed
+
+fn main() {}

src/test/ui/typeck/issue-91450-inner-ty-error.stderr

@@ -0,0 +1,21 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-91450-inner-ty-error.rs:4:13
+   |
+LL | fn foo() -> Option<_> {}
+   |    ---      ^^^^^^^^^ expected enum `Option`, found `()`
+   |    |
+   |    implicitly returns `()` as its body has no tail or `return` expression
+   |
+   = note:   expected enum `Option<_>`
+           found unit type `()`
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures for return types
+  --> $DIR/issue-91450-inner-ty-error.rs:4:20
+   |
+LL | fn foo() -> Option<_> {}
+   |                    ^ not allowed in type signatures
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0121, E0308.
+For more information about an error, try `rustc --explain E0121`.