From 5a8c28541b74247f8ee68984cfc0994b5fd2c3f2 Mon Sep 17 00:00:00 2001
From: AndyJado <101876416+AndyJado@users.noreply.github.com>
Date: Thu, 1 Sep 2022 20:50:15 +0800
Subject: [PATCH 1/4] init

---
 .../src/diagnostics/mutability_errors.rs          | 15 +++++++--------
 .../rustc_borrowck/src/session_diagnostics.rs     | 11 +++++++++++
 .../locales/en-US/borrowck.ftl                    |  3 +++
 3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index dd9590016b990..a9f6a4df9209f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -1,3 +1,6 @@
+// #![deny(rustc::untranslatable_diagnostic)]
+// #![deny(rustc::diagnostic_outside_of_impl)]
+
 use rustc_errors::{
     Applicability, Diagnostic, DiagnosticBuilder, EmissionGuarantee, ErrorGuaranteed,
 };
@@ -19,6 +22,7 @@ use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{sym, BytePos, Span};
 
 use crate::diagnostics::BorrowedContentSource;
+use crate::session_diagnostics::ShowMutatingUpvar;
 use crate::MirBorrowckCtxt;
 use rustc_const_eval::util::collect_writes::FindAssignments;
 
@@ -864,14 +868,9 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             } else {
                 bug!("not an upvar")
             };
-            err.span_label(
-                *span,
-                format!(
-                    "calling `{}` requires mutable binding due to {}",
-                    self.describe_place(the_place_err).unwrap(),
-                    reason
-                ),
-            );
+            let place = self.describe_place(the_place_err).unwrap();
+            let sub_label = ShowMutatingUpvar::RequireMutableBinding { place, reason, span: *span };
+            err.subdiagnostic(sub_label);
         }
     }
 
diff --git a/compiler/rustc_borrowck/src/session_diagnostics.rs b/compiler/rustc_borrowck/src/session_diagnostics.rs
index 5d750c6ca8c7b..6aea649466906 100644
--- a/compiler/rustc_borrowck/src/session_diagnostics.rs
+++ b/compiler/rustc_borrowck/src/session_diagnostics.rs
@@ -157,3 +157,14 @@ pub(crate) enum RequireStaticErr {
         multi_span: MultiSpan,
     },
 }
+//mutability_errors.rs
+#[derive(SessionSubdiagnostic)]
+pub(crate) enum ShowMutatingUpvar {
+    #[label(borrowck::require_mutable_binding)]
+    RequireMutableBinding {
+        place: String,
+        reason: String,
+        #[primary_span]
+        span: Span,
+    },
+}
diff --git a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
index 67f2156f32e50..3b5e00cd516f9 100644
--- a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
@@ -58,3 +58,6 @@ borrowck_returned_lifetime_short =
 
 borrowck_used_impl_require_static =
     the used `impl` has a `'static` requirement
+
+borrowck_require_mutable_binding =
+    calling `{$place}` requires mutable binding due to {$reason}

From b7444c51bf17520d5b76118f415ec9a6187470e2 Mon Sep 17 00:00:00 2001
From: AndyJado <101876416+AndyJado@users.noreply.github.com>
Date: Thu, 1 Sep 2022 21:21:09 +0800
Subject: [PATCH 2/4] fnmutBumpfn

---
 .../src/diagnostics/mutability_errors.rs      | 10 ++++----
 .../rustc_borrowck/src/session_diagnostics.rs | 25 +++++++++++++++++++
 .../locales/en-US/borrowck.ftl                | 13 ++++++++++
 3 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index a9f6a4df9209f..1cf04ce496bdc 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -22,7 +22,7 @@ use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{sym, BytePos, Span};
 
 use crate::diagnostics::BorrowedContentSource;
-use crate::session_diagnostics::ShowMutatingUpvar;
+use crate::session_diagnostics::{FnMutBumpFn, ShowMutatingUpvar};
 use crate::MirBorrowckCtxt;
 use rustc_const_eval::util::collect_writes::FindAssignments;
 
@@ -971,7 +971,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
     /// Targeted error when encountering an `FnMut` closure where an `Fn` closure was expected.
     fn expected_fn_found_fn_mut_call(&self, err: &mut Diagnostic, sp: Span, act: &str) {
-        err.span_label(sp, format!("cannot {act}"));
+        err.subdiagnostic(FnMutBumpFn::Cannot { act, sp });
 
         let hir = self.infcx.tcx.hir();
         let closure_id = self.mir_hir_id();
@@ -1024,9 +1024,9 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     _ => None,
                 };
                 if let Some(span) = arg {
-                    err.span_label(span, "change this to accept `FnMut` instead of `Fn`");
-                    err.span_label(func.span, "expects `Fn` instead of `FnMut`");
-                    err.span_label(self.body.span, "in this closure");
+                    err.subdiagnostic(FnMutBumpFn::NotFnHere { span });
+                    err.subdiagnostic(FnMutBumpFn::NotFnMutHere { span: func.span });
+                    err.subdiagnostic(FnMutBumpFn::Here { span: self.body.span });
                     look_at_return = false;
                 }
             }
diff --git a/compiler/rustc_borrowck/src/session_diagnostics.rs b/compiler/rustc_borrowck/src/session_diagnostics.rs
index 6aea649466906..176851e39570d 100644
--- a/compiler/rustc_borrowck/src/session_diagnostics.rs
+++ b/compiler/rustc_borrowck/src/session_diagnostics.rs
@@ -168,3 +168,28 @@ pub(crate) enum ShowMutatingUpvar {
         span: Span,
     },
 }
+
+#[derive(SessionSubdiagnostic)]
+pub(crate) enum FnMutBumpFn<'a> {
+    #[label(borrowck::cannot_act)]
+    Cannot {
+        act: &'a str,
+        #[primary_span]
+        sp: Span,
+    },
+    #[label(borrowck::expects_fnmut_not_fn)]
+    NotFnHere {
+        #[primary_span]
+        span: Span,
+    },
+    #[label(borrowck::expects_fn_not_fnmut)]
+    NotFnMutHere {
+        #[primary_span]
+        span: Span,
+    },
+    #[label(borrowck::in_this_closure)]
+    Here {
+        #[primary_span]
+        span: Span,
+    },
+}
diff --git a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
index 3b5e00cd516f9..16d4239b897e6 100644
--- a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
@@ -61,3 +61,16 @@ borrowck_used_impl_require_static =
 
 borrowck_require_mutable_binding =
     calling `{$place}` requires mutable binding due to {$reason}
+
+borrowck_cannot_act =
+    cannot {$act}
+
+borrowck_expects_fnmut_not_fn =
+    change this to accept `FnMut` instead of `Fn`
+
+borrowck_expects_fn_not_fnmut =
+    expects `Fn` instead of `FnMut`
+
+borrowck_in_this_closure =
+    in this closure
+

From ceca8c33584ed08f080ac3370a4e788c5db018d8 Mon Sep 17 00:00:00 2001
From: AndyJado <101876416+AndyJado@users.noreply.github.com>
Date: Thu, 1 Sep 2022 21:29:50 +0800
Subject: [PATCH 3/4] remain case: empty fluent string

---
 .../src/diagnostics/mutability_errors.rs             | 12 +++++-------
 compiler/rustc_borrowck/src/session_diagnostics.rs   |  9 +++++++--
 .../rustc_error_messages/locales/en-US/borrowck.ftl  |  2 ++
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 1cf04ce496bdc..858f6579347bb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -1024,8 +1024,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     _ => None,
                 };
                 if let Some(span) = arg {
-                    err.subdiagnostic(FnMutBumpFn::NotFnHere { span });
-                    err.subdiagnostic(FnMutBumpFn::NotFnMutHere { span: func.span });
+                    err.subdiagnostic(FnMutBumpFn::AcceptFnMut { span });
+                    err.subdiagnostic(FnMutBumpFn::AcceptFn { span: func.span });
                     err.subdiagnostic(FnMutBumpFn::Here { span: self.body.span });
                     look_at_return = false;
                 }
@@ -1047,12 +1047,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     kind: hir::ImplItemKind::Fn(sig, _),
                     ..
                 }) => {
+                    //FIXME: empty string here don't pass lint
                     err.span_label(ident.span, "");
-                    err.span_label(
-                        sig.decl.output.span(),
-                        "change this to return `FnMut` instead of `Fn`",
-                    );
-                    err.span_label(self.body.span, "in this closure");
+                    err.subdiagnostic(FnMutBumpFn::ReturnFnMut { span: sig.decl.output.span() });
+                    err.subdiagnostic(FnMutBumpFn::Here { span: self.body.span });
                 }
                 _ => {}
             }
diff --git a/compiler/rustc_borrowck/src/session_diagnostics.rs b/compiler/rustc_borrowck/src/session_diagnostics.rs
index 176851e39570d..10d34f9a93d53 100644
--- a/compiler/rustc_borrowck/src/session_diagnostics.rs
+++ b/compiler/rustc_borrowck/src/session_diagnostics.rs
@@ -178,12 +178,12 @@ pub(crate) enum FnMutBumpFn<'a> {
         sp: Span,
     },
     #[label(borrowck::expects_fnmut_not_fn)]
-    NotFnHere {
+    AcceptFnMut {
         #[primary_span]
         span: Span,
     },
     #[label(borrowck::expects_fn_not_fnmut)]
-    NotFnMutHere {
+    AcceptFn {
         #[primary_span]
         span: Span,
     },
@@ -192,4 +192,9 @@ pub(crate) enum FnMutBumpFn<'a> {
         #[primary_span]
         span: Span,
     },
+    #[label(borrowck::return_fnmut)]
+    ReturnFnMut {
+        #[primary_span]
+        span: Span,
+    },
 }
diff --git a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
index 16d4239b897e6..70d84703cb558 100644
--- a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
@@ -74,3 +74,5 @@ borrowck_expects_fn_not_fnmut =
 borrowck_in_this_closure =
     in this closure
 
+borrowck_return_fnmut =
+    change this to return `FnMut` instead of `Fn`

From 8e04a1c1fc7ac593dd6cd19357a6cd0e417f0b17 Mon Sep 17 00:00:00 2001
From: AndyJado <101876416+AndyJado@users.noreply.github.com>
Date: Sat, 3 Sep 2022 11:53:17 +0800
Subject: [PATCH 4/4] empty_label

---
 .../rustc_borrowck/src/diagnostics/mutability_errors.rs    | 7 +++----
 compiler/rustc_borrowck/src/session_diagnostics.rs         | 7 ++++++-
 compiler/rustc_error_messages/locales/en-US/borrowck.ftl   | 2 ++
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 858f6579347bb..61c5676b4053a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -1,5 +1,5 @@
-// #![deny(rustc::untranslatable_diagnostic)]
-// #![deny(rustc::diagnostic_outside_of_impl)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 use rustc_errors::{
     Applicability, Diagnostic, DiagnosticBuilder, EmissionGuarantee, ErrorGuaranteed,
@@ -1047,8 +1047,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     kind: hir::ImplItemKind::Fn(sig, _),
                     ..
                 }) => {
-                    //FIXME: empty string here don't pass lint
-                    err.span_label(ident.span, "");
+                    err.subdiagnostic(FnMutBumpFn::EmptyLabel { span: ident.span });
                     err.subdiagnostic(FnMutBumpFn::ReturnFnMut { span: sig.decl.output.span() });
                     err.subdiagnostic(FnMutBumpFn::Here { span: self.body.span });
                 }
diff --git a/compiler/rustc_borrowck/src/session_diagnostics.rs b/compiler/rustc_borrowck/src/session_diagnostics.rs
index 10d34f9a93d53..a63bbfa32a1f8 100644
--- a/compiler/rustc_borrowck/src/session_diagnostics.rs
+++ b/compiler/rustc_borrowck/src/session_diagnostics.rs
@@ -157,7 +157,7 @@ pub(crate) enum RequireStaticErr {
         multi_span: MultiSpan,
     },
 }
-//mutability_errors.rs
+
 #[derive(SessionSubdiagnostic)]
 pub(crate) enum ShowMutatingUpvar {
     #[label(borrowck::require_mutable_binding)]
@@ -187,6 +187,11 @@ pub(crate) enum FnMutBumpFn<'a> {
         #[primary_span]
         span: Span,
     },
+    #[label(borrowck::empty_label)]
+    EmptyLabel {
+        #[primary_span]
+        span: Span,
+    },
     #[label(borrowck::in_this_closure)]
     Here {
         #[primary_span]
diff --git a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
index 70d84703cb558..3ef282daffb13 100644
--- a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
@@ -71,6 +71,8 @@ borrowck_expects_fnmut_not_fn =
 borrowck_expects_fn_not_fnmut =
     expects `Fn` instead of `FnMut`
 
+borrowck_empty_label = {""}
+
 borrowck_in_this_closure =
     in this closure