Auto merge of #2356 - rust-lang:slash_slash_at, r=RalfJung

require level and colon in `//~` style comments

implements #2348 (comment)

Author: bors

tests/fail/alloc/reallocate-change-alloc.rs

@@ -4,6 +4,6 @@ fn main() {
     unsafe {
         let x = alloc(Layout::from_size_align_unchecked(1, 1));
         let _y = realloc(x, Layout::from_size_align_unchecked(1, 1), 1);
-        let _z = *x; //~ ERROR dereferenced after this allocation got freed
+        let _z = *x; //~ ERROR: dereferenced after this allocation got freed
     }
 }

tests/fail/backtrace/bad-backtrace-decl.rs

@@ -7,7 +7,7 @@ fn main() {
     let frames = unsafe { miri_get_backtrace(0) };
     for frame in frames.into_iter() {
         unsafe {
-            miri_resolve_frame(*frame, 0); //~ ERROR Undefined Behavior: bad declaration of miri_resolve_frame - should return a struct with 5 fields
+            miri_resolve_frame(*frame, 0); //~ ERROR: Undefined Behavior: bad declaration of miri_resolve_frame - should return a struct with 5 fields
         }
     }
 }

tests/fail/backtrace/bad-backtrace-flags.rs

@@ -4,6 +4,6 @@ extern "Rust" {
 
 fn main() {
     unsafe {
-        miri_get_backtrace(2, std::ptr::null_mut()); //~ ERROR  unsupported operation: unknown `miri_get_backtrace` flags 2
+        miri_get_backtrace(2, std::ptr::null_mut()); //~ ERROR:  unsupported operation: unknown `miri_get_backtrace` flags 2
     }
 }

tests/fail/backtrace/bad-backtrace-ptr.rs

@@ -4,6 +4,6 @@ extern "Rust" {
 
 fn main() {
     unsafe {
-        miri_resolve_frame(std::ptr::null_mut(), 0); //~ ERROR null pointer is a dangling pointer
+        miri_resolve_frame(std::ptr::null_mut(), 0); //~ ERROR: null pointer is a dangling pointer
     }
 }

tests/fail/backtrace/bad-backtrace-resolve-flags.rs

@@ -20,6 +20,6 @@ fn main() {
         miri_get_backtrace(1, buf.as_mut_ptr());
 
         // miri_resolve_frame will error from an invalid backtrace before it will from invalid flags
-        miri_resolve_frame(buf[0], 2); //~ ERROR  unsupported operation: unknown `miri_resolve_frame` flags 2
+        miri_resolve_frame(buf[0], 2); //~ ERROR:  unsupported operation: unknown `miri_resolve_frame` flags 2
     }
 }

tests/fail/backtrace/bad-backtrace-resolve-names-flags.rs

@@ -11,6 +11,6 @@ fn main() {
         miri_get_backtrace(1, buf.as_mut_ptr());
 
         // miri_resolve_frame_names will error from an invalid backtrace before it will from invalid flags
-        miri_resolve_frame_names(buf[0], 2, std::ptr::null_mut(), std::ptr::null_mut()); //~ ERROR  unsupported operation: unknown `miri_resolve_frame_names` flags 2
+        miri_resolve_frame_names(buf[0], 2, std::ptr::null_mut(), std::ptr::null_mut()); //~ ERROR:  unsupported operation: unknown `miri_resolve_frame_names` flags 2
     }
 }

tests/fail/backtrace/bad-backtrace-size-flags.rs

@@ -4,6 +4,6 @@ extern "Rust" {
 
 fn main() {
     unsafe {
-        miri_backtrace_size(2); //~ ERROR  unsupported operation: unknown `miri_backtrace_size` flags 2
+        miri_backtrace_size(2); //~ ERROR:  unsupported operation: unknown `miri_backtrace_size` flags 2
     }
 }

tests/fail/box-cell-alias.rs

@@ -6,7 +6,7 @@ use std::cell::Cell;
 
 fn helper(val: Box<Cell<u8>>, ptr: *const Cell<u8>) -> u8 {
     val.set(10);
-    unsafe { (*ptr).set(20) }; //~ ERROR does not exist in the borrow stack
+    unsafe { (*ptr).set(20) }; //~ ERROR: does not exist in the borrow stack
     val.get()
 }
 

tests/fail/branchless-select-i128-pointer.rs

@@ -12,7 +12,7 @@ fn main() {
         // However, it drops provenance when transmuting to TwoPtrs, so this is UB.
         let val = unsafe {
             transmute::<_, &str>(
-                //~^ ERROR constructing invalid value: encountered a dangling reference
+                //~^ ERROR: constructing invalid value: encountered a dangling reference
                 !mask & transmute::<_, TwoPtrs>("false !")
                     | mask & transmute::<_, TwoPtrs>("true !"),
             )

tests/fail/breakpoint.rs

@@ -2,6 +2,6 @@
 
 fn main() {
     unsafe {
-        core::intrinsics::breakpoint() //~ ERROR Trace/breakpoint trap
+        core::intrinsics::breakpoint() //~ ERROR: Trace/breakpoint trap
     };
 }