fnmutBumpfn

Author: AndyJado

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;
                 }
             }

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,
+    },
+}

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
+