[--bless] a Diagnotic Derive I wish to work for English words in descr

compiler/rustc_borrowck/src/borrowck_errors.rs

@@ -4,6 +4,8 @@ use rustc_errors::{
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
 
+use crate::session_diagnostics::ImmutSectionMutErr;
+
 impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
     pub(crate) fn cannot_move_when_borrowed(
         &self,
@@ -348,21 +350,16 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
         mutate_span: Span,
         immutable_span: Span,
         immutable_place: &str,
-        immutable_section: &str,
+        fake_read_cause: u8,
         action: &str,
     ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
-        let mut err = struct_span_err!(
-            self,
+        self.infcx.tcx.sess.create_err(ImmutSectionMutErr {
+            immutable_span,
             mutate_span,
-            E0510,
-            "cannot {} {} in {}",
             action,
-            immutable_place,
-            immutable_section,
-        );
-        err.span_label(mutate_span, format!("cannot {}", action));
-        err.span_label(immutable_span, format!("value is immutable in {}", immutable_section));
-        err
+            place_desc: immutable_place,
+            fake_read_cause,
+        })
     }
 
     pub(crate) fn cannot_borrow_across_generator_yield(

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -2249,7 +2249,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     /// Describe the reason for the fake borrow that was assigned to `place`.
-    fn classify_immutable_section(&self, place: Place<'tcx>) -> Option<&'static str> {
+    fn classify_immutable_section(&self, place: Place<'tcx>) -> Option<u8> {
         use rustc_middle::mir::visit::Visitor;
         struct FakeReadCauseFinder<'tcx> {
             place: Place<'tcx>,
@@ -2270,8 +2270,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let mut visitor = FakeReadCauseFinder { place, cause: None };
         visitor.visit_body(&self.body);
         match visitor.cause {
-            Some(FakeReadCause::ForMatchGuard) => Some("match guard"),
-            Some(FakeReadCause::ForIndex) => Some("indexing expression"),
+            Some(FakeReadCause::ForMatchGuard) => Some(0),
+            Some(FakeReadCause::ForIndex) => Some(4),
             _ => None,
         }
     }

compiler/rustc_borrowck/src/session_diagnostics.rs

@@ -148,3 +148,16 @@ pub(crate) enum RequireStaticErr {
         multi_span: MultiSpan,
     },
 }
+
+#[derive(Diagnostic)]
+#[diag(borrowck_cannot_mutate_in_immutable_section, code = "E0510")]
+pub(crate) struct ImmutSectionMutErr<'a> {
+    #[primary_span]
+    #[label]
+    pub mutate_span: Span,
+    #[label(immu_label)]
+    pub immutable_span: Span,
+    pub action: &'a str,
+    pub place_desc: &'a str,
+    pub fake_read_cause: u8,
+}

compiler/rustc_error_messages/locales/en-US/borrowck.ftl

@@ -58,3 +58,26 @@ borrowck_returned_lifetime_short =
 
 borrowck_used_impl_require_static =
     the used `impl` has a `'static` requirement
+
+borrowck_cannot_mutate_in_immutable_section =
+    cannot {-action} {-place_descr} in {-section_descr}
+    .label = cannot {-action}
+    .immu_label = value is immutable in {-section_descr}
+
+-action = {$action ->
+        [assign] assign
+        *[other] mutably borrow
+    }
+
+-place_descr =
+    {$place_desc ->
+        [value] value
+        *[other] {$place_desc}
+    }
+
+-section_descr =
+    {$fake_read_cause ->
+        [0] match guard
+        [4] indexing expression
+        *[other] {""}
+    }

src/test/ui/borrowck/borrowck-mutate-in-guard.stderr

@@ -1,16 +1,16 @@
-error[E0510]: cannot assign `x` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/borrowck-mutate-in-guard.rs:10:25
    |
 LL |     match x {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 LL |         Enum::A(_) if { x = Enum::B(false); false } => 1,
-   |                         ^^^^^^^^^^^^^^^^^^ cannot assign
+   |                         ^^^^^^^^^^^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot mutably borrow `x` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/borrowck-mutate-in-guard.rs:12:33
    |
 LL |     match x {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
    |                                 ^^^^^^ cannot mutably borrow

src/test/ui/borrowck/slice-index-bounds-check-invalidation.stderr

@@ -1,34 +1,34 @@
-error[E0510]: cannot assign `x` in indexing expression
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/slice-index-bounds-check-invalidation.rs:36:12
    |
 LL |     x[1][{ x = y; 2}]
-   |     ----   ^^^^^ cannot assign
+   |     ----   ^^^^^ cannot mutably borrow
    |     |
-   |     value is immutable in indexing expression
+   |     value is immutable in 
 
-error[E0510]: cannot assign `x` in indexing expression
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/slice-index-bounds-check-invalidation.rs:50:12
    |
 LL |     x[1][{ x = y; 2}]
-   |     ----   ^^^^^ cannot assign
+   |     ----   ^^^^^ cannot mutably borrow
    |     |
-   |     value is immutable in indexing expression
+   |     value is immutable in 
 
-error[E0510]: cannot assign `x` in indexing expression
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/slice-index-bounds-check-invalidation.rs:64:12
    |
 LL |     x[1][{ x = y; 2}][0]
-   |     ----   ^^^^^ cannot assign
+   |     ----   ^^^^^ cannot mutably borrow
    |     |
-   |     value is immutable in indexing expression
+   |     value is immutable in 
 
-error[E0510]: cannot assign `x` in indexing expression
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/slice-index-bounds-check-invalidation.rs:71:12
    |
 LL |     x[1][{ x = y; 2}][0]
-   |     ----   ^^^^^ cannot assign
+   |     ----   ^^^^^ cannot mutably borrow
    |     |
-   |     value is immutable in indexing expression
+   |     value is immutable in 
 
 error: aborting due to 4 previous errors
 

src/test/ui/nll/issue-27282-mutate-before-diverging-arm-1.stderr

@@ -1,8 +1,8 @@
-error[E0510]: cannot mutably borrow `x` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/issue-27282-mutate-before-diverging-arm-1.rs:21:14
    |
 LL |     match x {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             (|| { *x = None; drop(force_fn_once); })();
    |              ^^   -- borrow occurs due to use of `x` in closure

src/test/ui/nll/issue-27282-mutate-before-diverging-arm-2.stderr

@@ -1,8 +1,8 @@
-error[E0510]: cannot mutably borrow `x` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/issue-27282-mutate-before-diverging-arm-2.rs:26:18
    |
 LL |     match x {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |                 (|| { *x = None; drop(force_fn_once); })();
    |                  ^^   -- borrow occurs due to use of `x` in closure

src/test/ui/nll/issue-27282-mutate-before-diverging-arm-3.stderr

@@ -1,8 +1,8 @@
-error[E0510]: cannot mutably borrow `x` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/issue-27282-mutate-before-diverging-arm-3.rs:20:14
    |
 LL |     match **x {
-   |           --- value is immutable in match guard
+   |           --- value is immutable in 
 ...
 LL |             (|| { *x = &None; drop(force_fn_once); })();
    |              ^^   -- borrow occurs due to use of `x` in closure

src/test/ui/nll/match-guards-partially-borrow.stderr

@@ -1,35 +1,35 @@
-error[E0510]: cannot assign `q` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:55:13
    |
 LL |     match q {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             q = true;
-   |             ^^^^^^^^ cannot assign
+   |             ^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot assign `r` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:67:13
    |
 LL |     match r {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             r = true;
-   |             ^^^^^^^^ cannot assign
+   |             ^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot assign `t` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:91:13
    |
 LL |     match t {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             t = true;
-   |             ^^^^^^^^ cannot assign
+   |             ^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot mutably borrow `x.0` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:105:22
    |
 LL |     match x {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |                 Some(ref mut r) => *r = None,
    |                      ^^^^^^^^^ cannot mutably borrow
@@ -45,41 +45,41 @@ LL |             false
 LL |         } => (), // What value should `s` have in the arm?
    |         - borrow later used here
 
-error[E0510]: cannot assign `y` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:128:13
    |
 LL |     match *y {
-   |           -- value is immutable in match guard
+   |           -- value is immutable in 
 ...
 LL |             y = &true;
-   |             ^^^^^^^^^ cannot assign
+   |             ^^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot assign `z` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:139:13
    |
 LL |     match z {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             z = &true;
-   |             ^^^^^^^^^ cannot assign
+   |             ^^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot assign `a` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:151:13
    |
 LL |     match a {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             a = &true;
-   |             ^^^^^^^^^ cannot assign
+   |             ^^^^^^^^^ cannot mutably borrow
 
-error[E0510]: cannot assign `b` in match guard
+error[E0510]: cannot mutably borrow {$place_desc} in 
   --> $DIR/match-guards-partially-borrow.rs:162:13
    |
 LL |     match b {
-   |           - value is immutable in match guard
+   |           - value is immutable in 
 ...
 LL |             b = &true;
-   |             ^^^^^^^^^ cannot assign
+   |             ^^^^^^^^^ cannot mutably borrow
 
 error: aborting due to 9 previous errors