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

2 files changed, 37 insertions, 47 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 8ce1271fc17..f4051561dae 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -13,7 +13,7 @@ use super::elaborate;
 use crate::infer::TyCtxtInferExt;
 use crate::traits::query::evaluate_obligation::InferCtxtExt;
 use crate::traits::{self, Obligation, ObligationCause};
-use rustc_errors::{DelayDm, FatalError, MultiSpan};
+use rustc_errors::{FatalError, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_middle::query::Providers;
@@ -162,41 +162,36 @@ fn lint_object_unsafe_trait(
 ) {
     // Using `CRATE_NODE_ID` is wrong, but it's hard to get a more precise id.
     // It's also hard to get a use site span, so we use the method definition span.
-    tcx.node_span_lint(
-        WHERE_CLAUSES_OBJECT_SAFETY,
-        hir::CRATE_HIR_ID,
-        span,
-        DelayDm(|| format!("the trait `{}` cannot be made into an object", tcx.def_path_str(trait_def_id))),
-        |err| {
-            let node = tcx.hir().get_if_local(trait_def_id);
-            let mut spans = MultiSpan::from_span(span);
-            if let Some(hir::Node::Item(item)) = node {
-                spans.push_span_label(
-                    item.ident.span,
-                    "this trait cannot be made into an object...",
-                );
-                spans.push_span_label(span, format!("...because {}", violation.error_msg()));
-            } else {
-                spans.push_span_label(
-                    span,
-                    format!(
-                        "the trait cannot be made into an object because {}",
-                        violation.error_msg()
-                    ),
-                );
-            };
-            err.span_note(
-                spans,
-                "for a trait to be \"object safe\" it needs to allow building a vtable to allow the \
+    tcx.node_span_lint(WHERE_CLAUSES_OBJECT_SAFETY, hir::CRATE_HIR_ID, span, |err| {
+        err.primary_message(format!(
+            "the trait `{}` cannot be made into an object",
+            tcx.def_path_str(trait_def_id)
+        ));
+        let node = tcx.hir().get_if_local(trait_def_id);
+        let mut spans = MultiSpan::from_span(span);
+        if let Some(hir::Node::Item(item)) = node {
+            spans.push_span_label(item.ident.span, "this trait cannot be made into an object...");
+            spans.push_span_label(span, format!("...because {}", violation.error_msg()));
+        } else {
+            spans.push_span_label(
+                span,
+                format!(
+                    "the trait cannot be made into an object because {}",
+                    violation.error_msg()
+                ),
+            );
+        };
+        err.span_note(
+            spans,
+            "for a trait to be \"object safe\" it needs to allow building a vtable to allow the \
                 call to be resolvable dynamically; for more information visit \
                 <https://doc.rust-lang.org/reference/items/traits.html#object-safety>",
-            );
-            if node.is_some() {
-                // Only provide the help if its a local trait, otherwise it's not
-                violation.solution().add_to(err);
-            }
-        },
-    );
+        );
+        if node.is_some() {
+            // Only provide the help if its a local trait, otherwise it's not
+            violation.solution().add_to(err);
+        }
+    });
 }
 
 fn sized_trait_bound_spans<'tcx>(
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 826bb706f48..c2727ae6bfd 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -21,7 +21,7 @@ use crate::traits::{
     self, coherence, FutureCompatOverlapErrorKind, ObligationCause, ObligationCtxt,
 };
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{codes::*, DelayDm, Diag, EmissionGuarantee};
+use rustc_errors::{codes::*, Diag, EmissionGuarantee};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::bug;
 use rustc_middle::ty::{self, ImplSubject, Ty, TyCtxt, TypeVisitableExt};
@@ -449,7 +449,7 @@ fn report_conflicting_impls<'tcx>(
         }
     }
 
-    let msg = DelayDm(|| {
+    let msg = || {
         format!(
             "conflicting implementations of trait `{}`{}{}",
             overlap.trait_ref.print_trait_sugared(),
@@ -459,7 +459,7 @@ fn report_conflicting_impls<'tcx>(
                 _ => "",
             }
         )
-    });
+    };
 
     // Don't report overlap errors if the header references error
     if let Err(err) = (overlap.trait_ref, overlap.self_ty).error_reported() {
@@ -471,7 +471,7 @@ fn report_conflicting_impls<'tcx>(
             let reported = if overlap.with_impl.is_local()
                 || tcx.ensure().orphan_check_impl(impl_def_id).is_ok()
             {
-                let mut err = tcx.dcx().struct_span_err(impl_span, msg);
+                let mut err = tcx.dcx().struct_span_err(impl_span, msg());
                 err.code(E0119);
                 decorate(tcx, &overlap, impl_span, &mut err);
                 err.emit()
@@ -485,15 +485,10 @@ fn report_conflicting_impls<'tcx>(
                 FutureCompatOverlapErrorKind::OrderDepTraitObjects => ORDER_DEPENDENT_TRAIT_OBJECTS,
                 FutureCompatOverlapErrorKind::LeakCheck => COHERENCE_LEAK_CHECK,
             };
-            tcx.node_span_lint(
-                lint,
-                tcx.local_def_id_to_hir_id(impl_def_id),
-                impl_span,
-                msg,
-                |err| {
-                    decorate(tcx, &overlap, impl_span, err);
-                },
-            );
+            tcx.node_span_lint(lint, tcx.local_def_id_to_hir_id(impl_def_id), impl_span, |err| {
+                err.primary_message(msg());
+                decorate(tcx, &overlap, impl_span, err);
+            });
             Ok(())
         }
     }