lint: port missing debug impl diagnostics

Signed-off-by: David Wood <[email protected]>

Author: davidtwco

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

@@ -328,3 +328,6 @@ lint-builtin-impl-unsafe-method = implementation of an `unsafe` method
 lint-builtin-missing-doc = missing documentation for {$article} {$desc}
 
 lint-builtin-missing-copy-impl = type could implement `Copy`; consider adding `impl Copy`
+
+lint-builtin-missing-debug-impl =
+    type does not implement `{$debug}`; consider adding `#[derive(Debug)]` or a manual implementation

compiler/rustc_lint/src/builtin.rs

@@ -857,12 +857,9 @@ impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
 
         if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
             cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
-                lint.build(&format!(
-                    "type does not implement `{}`; consider adding `#[derive(Debug)]` \
-                     or a manual implementation",
-                    cx.tcx.def_path_str(debug)
-                ))
-                .emit();
+                lint.build(fluent::lint::builtin_missing_debug_impl)
+                    .set_arg("debug", cx.tcx.def_path_str(debug))
+                    .emit();
             });
         }
     }