Remove `LintDiagnostic::msg`

* instead simply set the primary message inside the lint decorator functions
* it used to be this way before [#]101986 which introduced `msg` to prevent
  good path delayed bugs (which no longer exist) from firing under certain
  circumstances when lints were suppressed / silenced
* this is no longer necessary for various reasons I presume
* it shaves off complexity and makes further changes easier to implement

1 files changed, 7 insertions, 6 deletions

diff --git a/compiler/rustc_hir_analysis/src/check_unused.rs b/compiler/rustc_hir_analysis/src/check_unused.rs
index aa5db4f6aa7..ed23dc2a827 100644
--- a/compiler/rustc_hir_analysis/src/check_unused.rs
+++ b/compiler/rustc_hir_analysis/src/check_unused.rs
@@ -35,11 +35,12 @@ fn check_unused_traits(tcx: TyCtxt<'_>, (): ()) {
             continue;
         }
         let (path, _) = item.expect_use();
-        let msg = if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(path.span) {
-            format!("unused import: `{snippet}`")
-        } else {
-            "unused import".to_owned()
-        };
-        tcx.node_span_lint(lint::builtin::UNUSED_IMPORTS, item.hir_id(), path.span, msg, |_| {});
+        tcx.node_span_lint(lint::builtin::UNUSED_IMPORTS, item.hir_id(), path.span, |lint| {
+            if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(path.span) {
+                lint.primary_message(format!("unused import: `{snippet}`"));
+            } else {
+                lint.primary_message("unused import");
+            }
+        });
     }
 }