Rollup merge of #107633 - clubby789:option-string-coerce-fix, r=Nilstrieb

Fix suggestion for coercing Option<&String> to Option<&str>

Fixes #107604

This also makes the diagnostic `MachineApplicable`, and runs `rustfix` to check we're not producing incorrect code.

``@rustbot`` label +A-diagnostics

2 files changed, 11 insertions, 4 deletions

diff --git a/compiler/rustc_error_messages/locales/en-US/hir_typeck.ftl b/compiler/rustc_error_messages/locales/en-US/hir_typeck.ftl
index 0f13d29d0fc..05ac8db0db8 100644
--- a/compiler/rustc_error_messages/locales/en-US/hir_typeck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/hir_typeck.ftl
@@ -61,3 +61,5 @@ hir_typeck_lang_start_incorrect_ret_ty = the return type of the `start` lang ite
 hir_typeck_help_set_edition_cargo = set `edition = "{$edition}"` in `Cargo.toml`
 hir_typeck_help_set_edition_standalone = pass `--edition {$edition}` to `rustc`
 hir_typeck_note_edition_guide = for more on editions, read https://doc.rust-lang.org/edition-guide
+
+hir_typeck_convert_to_str = try converting the passed type into a `&str`
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index 6046e55c65c..3f433a0928c 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -3,7 +3,7 @@ use super::FnCtxt;
 use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel};
 use crate::method::probe::{IsSuggestion, Mode, ProbeScope};
 use rustc_ast::util::parser::{ExprPrecedence, PREC_POSTFIX};
-use rustc_errors::{Applicability, Diagnostic, MultiSpan};
+use rustc_errors::{fluent, Applicability, Diagnostic, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
 use rustc_hir::lang_items::LangItem;
@@ -414,11 +414,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if let ty::Adt(adt, _) = peeled.kind()
                     && Some(adt.did()) == self.tcx.lang_items().string()
                 {
+                    let sugg = if ref_cnt == 0 {
+                        ".as_deref()"
+                    } else {
+                        ".map(|x| x.as_str())"
+                    };
                     err.span_suggestion_verbose(
                         expr.span.shrink_to_hi(),
-                        "try converting the passed type into a `&str`",
-                        format!(".map(|x| &*{}x)", "*".repeat(ref_cnt)),
-                        Applicability::MaybeIncorrect,
+                        fluent::hir_typeck_convert_to_str,
+                        sugg,
+                        Applicability::MachineApplicable,
                     );
                     return true;
                 }