Auto merge of #103426 - matthiaskrgr:rollup-n6dqdy8, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #103123 (Introduce `subst_iter` and `subst_iter_copied` on `EarlyBinder` )
 - #103328 (Do not suggest trivially false const predicates)
 - #103354 (Escape string literals when fixing overlong char literal)
 - #103355 (Handle return-position `impl Trait` in traits properly in `register_hidden_type`)
 - #103368 (Delay ambiguity span bug in normalize query iff not rustdoc)
 - #103388 (rustdoc: remove unused CSS class `.result-description`)
 - #103399 (Change `unknown_lint` applicability to `MaybeIncorrect`)
 - #103401 (Use functions for headings rustdoc GUI test)
 - #103412 (Fix typo in docs of `String::leak`.)

Failed merges:

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

1 files changed, 17 insertions, 2 deletions

diff --git a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
index 77c4fadab45..f075de71426 100644
--- a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
+++ b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
@@ -113,11 +113,26 @@ pub(crate) fn emit_unescape_error(
                 } else {
                     ("", "if you meant to write a `str` literal, use double quotes")
                 };
-
+                let mut escaped = String::with_capacity(lit.len());
+                let mut chrs = lit.chars().peekable();
+                while let Some(first) = chrs.next() {
+                    match (first, chrs.peek()) {
+                        ('\\', Some('"')) => {
+                            escaped.push('\\');
+                            escaped.push('"');
+                            chrs.next();
+                        }
+                        ('"', _) => {
+                            escaped.push('\\');
+                            escaped.push('"')
+                        }
+                        (c, _) => escaped.push(c),
+                    };
+                }
                 handler.span_suggestion(
                     span_with_quotes,
                     msg,
-                    format!("{}\"{}\"", prefix, lit),
+                    format!("{prefix}\"{escaped}\""),
                     Applicability::MachineApplicable,
                 );
             }