Rollup merge of #121085 - davidtwco:always-eager-diagnostics, r=nnethercote

errors: only eagerly translate subdiagnostics

Subdiagnostics don't need to be lazily translated, they can always be eagerly translated. Eager translation is slightly more complex as we need to have a `DiagCtxt` available to perform the translation, which involves slightly more threading of that context.

This slight increase in complexity should enable later simplifications - like passing `DiagCtxt` into `AddToDiagnostic` and moving Fluent messages into the diagnostic structs rather than having them in separate files (working on that was what led to this change).

r? ```@nnethercote```

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/rustc_mir_transform/src/errors.rs b/compiler/rustc_mir_transform/src/errors.rs
index 30de40e226c..ff4918df9a2 100644
--- a/compiler/rustc_mir_transform/src/errors.rs
+++ b/compiler/rustc_mir_transform/src/errors.rs
@@ -270,7 +270,7 @@ impl<'a> DecorateLint<'a, ()> for MustNotSupend<'_, '_> {
     fn decorate_lint<'b>(self, diag: &'b mut rustc_errors::DiagnosticBuilder<'a, ()>) {
         diag.span_label(self.yield_sp, fluent::_subdiag::label);
         if let Some(reason) = self.reason {
-            diag.subdiagnostic(reason);
+            diag.subdiagnostic(diag.dcx, reason);
         }
         diag.span_help(self.src_sp, fluent::_subdiag::help);
         diag.arg("pre", self.pre);