migrate dead.rs to translateable diagnostics

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

@@ -558,3 +558,9 @@ passes_incorrect_target =
         [one] argument
         *[other] arguments
     }
+
+passes_useless_assignment =
+    useless assignment of {$is_field_assign ->
+        [true] field
+        *[false] variable
+    } of type `{$ty}` to itself

compiler/rustc_errors/src/lib.rs

@@ -988,11 +988,7 @@ impl Handler {
     }
 
     pub fn has_errors(&self) -> Option<ErrorGuaranteed> {
-        if self.inner.borrow().has_errors() {
+        if self.inner.borrow().has_errors() { Some(ErrorGuaranteed(())) } else { None }
-            Some(ErrorGuaranteed(()))
-        } else {
-            None
-        }
     }
     pub fn has_errors_or_lint_errors(&self) -> Option<ErrorGuaranteed> {
         if self.inner.borrow().has_errors_or_lint_errors() {

compiler/rustc_passes/src/dead.rs

@@ -4,7 +4,7 @@
 
 use itertools::Itertools;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_errors::{pluralize, Applicability, DelayDm, MultiSpan};
+use rustc_errors::{pluralize, Applicability, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -18,6 +18,8 @@ use rustc_session::lint;
 use rustc_span::symbol::{sym, Symbol};
 use std::mem;
 
+use crate::errors::UselessAssignment;
+
 // Any local node that may call something in its body block should be
 // explored. For example, if it's a live Node::Item that is a
 // function, then we should explore its block to check for codes that
@@ -180,19 +182,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                 && !assign.span.from_expansion()
         {
                 let is_field_assign = matches!(lhs.kind, hir::ExprKind::Field(..));
-                self.tcx.struct_span_lint_hir(
+                self.tcx.emit_spanned_lint(
                     lint::builtin::DEAD_CODE,
                     assign.hir_id,
                     assign.span,
-                    DelayDm(|| format!(
+                    UselessAssignment { is_field_assign, ty: self.typeck_results().expr_ty(lhs) }
-                            "useless assignment of {} of type `{}` to itself",
-                            if is_field_assign { "field" } else { "variable" },
-                            self.typeck_results().expr_ty(lhs),
-                        )),
-                    |lint| {
-                        lint
-
-                    },
                 )
         }
     }

compiler/rustc_passes/src/errors.rs

@@ -7,7 +7,7 @@ use rustc_ast::Label;
 use rustc_errors::{error_code, Applicability, ErrorGuaranteed, IntoDiagnostic, MultiSpan};
 use rustc_hir::{self as hir, ExprKind, Target};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
-use rustc_middle::ty::MainDefinition;
+use rustc_middle::ty::{MainDefinition, Ty};
 use rustc_span::{Span, Symbol, DUMMY_SP};
 
 #[derive(LintDiagnostic)]
@@ -1265,3 +1265,10 @@ pub struct IncorrectTarget<'a> {
     pub actual_num: usize,
     pub at_least: bool,
 }
+
+#[derive(LintDiagnostic)]
+#[diag(passes::useless_assignment)]
+pub struct UselessAssignment<'a> {
+    pub is_field_assign: bool,
+    pub ty: Ty<'a>,
+}