Auto merge of #67964 - JohnTitor:rollup-pu5kosl, r=JohnTitor

Rollup of 13 pull requests

Successful merges:

 - #67566 (Add an unstable conversion from thread ID to u64)
 - #67671 (Account for `type X = impl Trait;` in lifetime suggestion)
 - #67727 (Stabilise vec::remove_item)
 - #67877 (Omit underscore constants from rustdoc)
 - #67880 (Handle multiple error fix suggestions carefuly)
 - #67898 (Improve hygiene of `newtype_index`)
 - #67908 (rustdoc: HTML escape const values)
 - #67909 (Fix ICE in const pretty printing and resolve FIXME)
 - #67929 (Formatting an example for method Vec.retain)
 - #67934 (Clean up E0178 explanation)
 - #67936 (fire "non_camel_case_types" for associated types)
 - #67943 (Missing module std in example.)
 - #67962 (Update books)

Failed merges:

r? @ghost

1 files changed, 18 insertions, 7 deletions

diff --git a/src/librustc_error_codes/error_codes/E0178.md b/src/librustc_error_codes/error_codes/E0178.md
index 07980ad83f1..0c6f918632f 100644
--- a/src/librustc_error_codes/error_codes/E0178.md
+++ b/src/librustc_error_codes/error_codes/E0178.md
@@ -1,16 +1,27 @@
-In types, the `+` type operator has low precedence, so it is often necessary
-to use parentheses.
+The `+` type operator was used in an ambiguous context.
 
-For example:
+Erroneous code example:
 
 ```compile_fail,E0178
 trait Foo {}
 
 struct Bar<'a> {
-    w: &'a Foo + Copy,   // error, use &'a (Foo + Copy)
-    x: &'a Foo + 'a,     // error, use &'a (Foo + 'a)
-    y: &'a mut Foo + 'a, // error, use &'a mut (Foo + 'a)
-    z: fn() -> Foo + 'a, // error, use fn() -> (Foo + 'a)
+    x: &'a Foo + 'a,     // error!
+    y: &'a mut Foo + 'a, // error!
+    z: fn() -> Foo + 'a, // error!
+}
+```
+
+In types, the `+` type operator has low precedence, so it is often necessary
+to use parentheses:
+
+```
+trait Foo {}
+
+struct Bar<'a> {
+    x: &'a (Foo + 'a),     // ok!
+    y: &'a mut (Foo + 'a), // ok!
+    z: fn() -> (Foo + 'a), // ok!
 }
 ```