Remove braces from Rust 2015 panic macro

Author: nbdd0121

library/std/src/panic.rs

@@ -14,19 +14,19 @@ use crate::thread::Result;
 #[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
 #[rustc_macro_transparency = "semitransparent"]
 pub macro panic_2015 {
-    () => ({
+    () => (
         $crate::rt::begin_panic("explicit panic")
-    }),
-    ($msg:expr $(,)?) => ({
+    ),
+    ($msg:expr $(,)?) => (
         $crate::rt::begin_panic($msg)
-    }),
+    ),
     // Special-case the single-argument case for const_panic.
-    ("{}", $arg:expr $(,)?) => ({
+    ("{}", $arg:expr $(,)?) => (
         $crate::rt::panic_display(&$arg)
-    }),
-    ($fmt:expr, $($arg:tt)+) => ({
+    ),
+    ($fmt:expr, $($arg:tt)+) => (
         $crate::rt::panic_fmt($crate::const_format_args!($fmt, $($arg)+))
-    }),
+    ),
 }
 
 #[doc(hidden)]

src/test/ui/block-result/issue-5500.rs

@@ -2,6 +2,6 @@ fn main() {
     &panic!()
     //~^ ERROR mismatched types
     //~| expected unit type `()`
-    //~| found reference `&_`
-    //~| expected `()`, found reference
+    //~| found reference `&!`
+    //~| expected `()`, found `&!`
 }

src/test/ui/block-result/issue-5500.stderr

@@ -4,15 +4,10 @@ error[E0308]: mismatched types
 LL | fn main() {
    |           - expected `()` because of default return type
 LL |     &panic!()
-   |     ^^^^^^^^^ expected `()`, found reference
+   |     ^^^^^^^^^ expected `()`, found `&!`
    |
    = note: expected unit type `()`
-              found reference `&_`
-help: consider removing the borrow
-   |
-LL -     &panic!()
-LL +     panic!()
-   | 
+              found reference `&!`
 
 error: aborting due to previous error
 

src/test/ui/diverging-tuple-parts-39485.stderr

@@ -1,20 +1,13 @@
 error[E0308]: mismatched types
   --> $DIR/diverging-tuple-parts-39485.rs:8:5
    |
+LL | fn g() {
+   |        - help: try adding a return type: `-> &!`
 LL |     &panic!()
-   |     ^^^^^^^^^ expected `()`, found reference
+   |     ^^^^^^^^^ expected `()`, found `&!`
    |
    = note: expected unit type `()`
-              found reference `&_`
-help: try adding a return type
-   |
-LL | fn g() -> &_ {
-   |        +++++
-help: consider removing the borrow
-   |
-LL -     &panic!()
-LL +     panic!()
-   | 
+              found reference `&!`
 
 error[E0308]: mismatched types
   --> $DIR/diverging-tuple-parts-39485.rs:12:5

src/test/ui/issues/issue-5500-1.rs

@@ -11,5 +11,5 @@ struct TrieMapIterator<'a> {
 fn main() {
     let a = 5;
     let _iter = TrieMapIterator{node: &a};
-    _iter.node = &panic!()
+    _iter.node = &{panic!()}
 }