Auto merge of #125208 - fmease:lint-diags-store-their-span, r=<try>

Make lint diagnostics responsible for providing their primary span

### Summary and Rustc-Dev-Facing Changes

Instead of passing the primary span of lint diagnostics separately — namely to the functions `tcx.emit_span_lint` and `tcx.emit_node_span_lint` —, make lint diagnostics responsible for “storing” (providing) their span. I've removed the two aforementioned methods. You are now expected to use `tcx.emit_lint` and `tcx.emit_node_lint` respectively and to provide the primary span when deriving `LintDiagnostic` (via `#[primary_span]`) / implementing `LintDiagnostic` manually (via `LintDiagnostic::span`).

> [!NOTE]
> FIXME(fmease): Mention how early lints are handled.

### Motivation

Making the general format of `#[derive(LintDiagnostic)]` identical to `#[derive(Diagnostic)]`. I bet this has lead to slight confusion or annoyances before. Moreover, it enables deriving both traits at once (see #125169 for the motivation).

### Approach

As outlined in #125169 (comment), the naïve approach of doing the same as `Diagnostic` doesn't work for `LintDiagnostic`, i.e., setting the primary span with `Diag::span` inside `decorate_lint` (that's `into_diag` for `Diagnostic`) because `lint_level` (`lint_level_impl`) needs access to the primary spans before decorating the `Diag` to be able to filter out some lints (namely if they come from an external macro) etc.

Therefore, I had to introduce a new method to `LintDiagnostic`: `fn span(&self) -> Option<MultiSpan>` (similar to the existing method `LintDiagnostic::msg`).

### Commits

1. The 1st commit addresses [#125169 (comment)](#125169 (comment)). It contains the necessary changes to the linting APIs. It doesn't build on its own due to the removed APIs. Split out for easier reviewing.
2. The 2nd commit updates all existing lint diagnostics to use the new APIs. Most of them are mindless, monotonous, obvious changes. Some changes are *slightly* more involved out of necessity. I've verified (partly programmatically, partly manually) that all lint diags that used to have a primary span still have a primary span.
3. The 3rd commit updates the fulldeps UI tests that exercise the (lint) diagnostic API
4. The 4th commit fixes [#125169](#125169). I've only deduplicated the lint diagnostic structs mentioned in the issue and haven't gone looking for other structs that may benefit from deriving both `Diagnostic` and `LintDiagnostic` because I didn't have the time to do so yet.

### Meta

Fixes #125169.

I'll submit a rustc-dev-guide PR later.
I hope this doesn't need an MCP, it's pretty straight forward.

cc `@davidtwco`
r? `@nnethercote` or anyone on compiler who has the energy to review 82 files

Author: bors

compiler/rustc_borrowck/src/lib.rs

@@ -401,7 +401,7 @@ fn do_mir_borrowck<'tcx>(
 
         let mut_span = tcx.sess.source_map().span_until_non_whitespace(span);
 
-        tcx.emit_node_span_lint(UNUSED_MUT, lint_root, span, VarNeedNotMut { span: mut_span })
+        tcx.emit_node_lint(UNUSED_MUT, lint_root, VarNeedNotMut { span, mut_span })
     }
 
     let tainted_by_errors = mbcx.emit_errors();

compiler/rustc_borrowck/src/session_diagnostics.rs

@@ -50,8 +50,10 @@ pub(crate) struct GenericDoesNotLiveLongEnough {
 #[derive(LintDiagnostic)]
 #[diag(borrowck_var_does_not_need_mut)]
 pub(crate) struct VarNeedNotMut {
-    #[suggestion(style = "short", applicability = "machine-applicable", code = "")]
+    #[primary_span]
     pub span: Span,
+    #[suggestion(style = "short", applicability = "machine-applicable", code = "")]
+    pub mut_span: Span,
 }
 #[derive(Diagnostic)]
 #[diag(borrowck_var_cannot_escape_closure)]

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -170,11 +170,11 @@ pub(super) fn lint<'tcx, L>(
     tcx: TyCtxtAt<'tcx>,
     machine: &CompileTimeMachine<'tcx>,
     lint: &'static rustc_session::lint::Lint,
-    decorator: impl FnOnce(Vec<errors::FrameNote>) -> L,
+    decorator: impl FnOnce(Span, Vec<errors::FrameNote>) -> L,
 ) where
     L: for<'a> rustc_errors::LintDiagnostic<'a, ()>,
 {
     let (span, frames) = get_span_and_frames(tcx, &machine.stack);
 
-    tcx.emit_node_span_lint(lint, machine.best_lint_scope(*tcx), span, decorator(frames));
+    tcx.emit_node_lint(lint, machine.best_lint_scope(*tcx), decorator(span, frames));
 }

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -622,11 +622,10 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
                     .0
                     .is_error();
                 let span = ecx.cur_span();
-                ecx.tcx.emit_node_span_lint(
+                ecx.tcx.emit_node_lint(
                     rustc_session::lint::builtin::LONG_RUNNING_CONST_EVAL,
                     hir_id,
-                    span,
-                    LongRunning { item_span: ecx.tcx.span },
+                    LongRunning { span, item_span: ecx.tcx.span },
                 );
                 // If this was a hard error, don't bother continuing evaluation.
                 if is_error {

compiler/rustc_const_eval/src/errors.rs

@@ -197,6 +197,8 @@ pub(crate) struct InteriorMutableRefEscaping {
 #[diag(const_eval_long_running)]
 #[note]
 pub struct LongRunning {
+    #[primary_span]
+    pub span: Span,
     #[help]
     pub item_span: Span,
 }

compiler/rustc_errors/src/diagnostic.rs

@@ -195,8 +195,10 @@ pub trait SubdiagMessageOp<G: EmissionGuarantee> =
 /// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
 #[rustc_diagnostic_item = "LintDiagnostic"]
 pub trait LintDiagnostic<'a, G: EmissionGuarantee> {
-    /// Decorate and emit a lint.
+    /// Decorate a lint.
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, G>);
+
+    fn span(&self) -> Option<MultiSpan>;
 }
 
 #[derive(Clone, Debug, Encodable, Decodable)]

compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs

@@ -297,11 +297,11 @@ fn report_mismatched_rpitit_signature<'tcx>(
         });
 
     let span = unmatched_bound.unwrap_or(span);
-    tcx.emit_node_span_lint(
+    tcx.emit_node_lint(
         if is_internal { REFINING_IMPL_TRAIT_INTERNAL } else { REFINING_IMPL_TRAIT_REACHABLE },
         tcx.local_def_id_to_hir_id(impl_m_def_id.expect_local()),
-        span,
         crate::errors::ReturnPositionImplTraitInTraitRefined {
+            span,
             impl_return_span,
             trait_return_span,
             pre,

compiler/rustc_hir_analysis/src/check/errs.rs

@@ -79,10 +79,6 @@ fn handle_static_mut_ref(
         } else {
             (errors::MutRefSugg::Shared { lo, hi }, "shared")
         };
-        tcx.emit_node_span_lint(STATIC_MUT_REFS, hir_id, span, errors::RefOfMutStatic {
-            span,
-            sugg,
-            shared,
-        });
+        tcx.emit_node_lint(STATIC_MUT_REFS, hir_id, errors::RefOfMutStatic { span, sugg, shared });
     }
 }

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -2354,11 +2354,10 @@ fn lint_redundant_lifetimes<'tcx>(
                 && outlives_env.free_region_map().sub_free_regions(tcx, victim, candidate)
             {
                 shadowed.insert(victim);
-                tcx.emit_node_span_lint(
+                tcx.emit_node_lint(
                     rustc_lint_defs::builtin::REDUNDANT_LIFETIMES,
                     tcx.local_def_id_to_hir_id(def_id.expect_local()),
-                    tcx.def_span(def_id),
-                    RedundantLifetimeArgsLint { candidate, victim },
+                    RedundantLifetimeArgsLint { span: tcx.def_span(def_id), candidate, victim },
                 );
             }
         }
@@ -2369,6 +2368,8 @@ fn lint_redundant_lifetimes<'tcx>(
 #[diag(hir_analysis_redundant_lifetime_args)]
 #[note]
 struct RedundantLifetimeArgsLint<'tcx> {
+    #[primary_span]
+    pub span: Span,
     /// The lifetime we have found to be redundant.
     victim: ty::Region<'tcx>,
     // The lifetime we can replace the victim with.

compiler/rustc_hir_analysis/src/coherence/orphan.rs

@@ -494,18 +494,18 @@ fn lint_uncovered_ty_params<'tcx>(
         let name = tcx.item_name(param_def_id);
 
         match local_ty {
-            Some(local_type) => tcx.emit_node_span_lint(
+            Some(local_type) => tcx.emit_node_lint(
                 UNCOVERED_PARAM_IN_PROJECTION,
                 hir_id,
-                span,
-                errors::TyParamFirstLocalLint { span, note: (), param: name, local_type },
-            ),
-            None => tcx.emit_node_span_lint(
-                UNCOVERED_PARAM_IN_PROJECTION,
-                hir_id,
-                span,
-                errors::TyParamSomeLint { span, note: (), param: name },
+                errors::TyParamFirstLocal { span, note: (), param: name, local_type },
             ),
+            None => {
+                tcx.emit_node_lint(UNCOVERED_PARAM_IN_PROJECTION, hir_id, errors::TyParamSome {
+                    span,
+                    note: (),
+                    param: name,
+                })
+            }
         };
     }
 }

compiler/rustc_hir_analysis/src/errors.rs

@@ -1132,6 +1132,7 @@ pub(crate) enum LateBoundInApit {
 #[diag(hir_analysis_unused_associated_type_bounds)]
 #[note]
 pub(crate) struct UnusedAssociatedTypeBounds {
+    #[primary_span]
     #[suggestion(code = "")]
     pub span: Span,
 }
@@ -1141,6 +1142,8 @@ pub(crate) struct UnusedAssociatedTypeBounds {
 #[note]
 #[note(hir_analysis_feedback_note)]
 pub(crate) struct ReturnPositionImplTraitInTraitRefined<'tcx> {
+    #[primary_span]
+    pub span: Span,
     #[suggestion(applicability = "maybe-incorrect", code = "{pre}{return_ty}{post}")]
     pub impl_return_span: Span,
     #[label]
@@ -1379,9 +1382,7 @@ pub(crate) struct CrossCrateTraitsDefined {
     pub traits: String,
 }
 
-// FIXME(fmease): Deduplicate:
-
-#[derive(Diagnostic)]
+#[derive(Diagnostic, LintDiagnostic)]
 #[diag(hir_analysis_ty_param_first_local, code = E0210)]
 #[note]
 pub(crate) struct TyParamFirstLocal<'tcx> {
@@ -1394,19 +1395,7 @@ pub(crate) struct TyParamFirstLocal<'tcx> {
     pub local_type: Ty<'tcx>,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(hir_analysis_ty_param_first_local, code = E0210)]
-#[note]
-pub(crate) struct TyParamFirstLocalLint<'tcx> {
-    #[label]
-    pub span: Span,
-    #[note(hir_analysis_case_note)]
-    pub note: (),
-    pub param: Symbol,
-    pub local_type: Ty<'tcx>,
-}
-
-#[derive(Diagnostic)]
+#[derive(Diagnostic, LintDiagnostic)]
 #[diag(hir_analysis_ty_param_some, code = E0210)]
 #[note]
 pub(crate) struct TyParamSome {
@@ -1418,17 +1407,6 @@ pub(crate) struct TyParamSome {
     pub param: Symbol,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(hir_analysis_ty_param_some, code = E0210)]
-#[note]
-pub(crate) struct TyParamSomeLint {
-    #[label]
-    pub span: Span,
-    #[note(hir_analysis_only_note)]
-    pub note: (),
-    pub param: Symbol,
-}
-
 #[derive(Diagnostic)]
 pub(crate) enum OnlyCurrentTraits {
     #[diag(hir_analysis_only_current_traits_outside, code = E0117)]

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -194,16 +194,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // types's `DefId`, so the following loop removes all the `DefIds` of the associated types that have a
         // corresponding `Projection` clause
         for def_ids in associated_types.values_mut() {
-            for (projection_bound, span) in &projection_bounds {
+            for &(projection_bound, span) in &projection_bounds {
                 let def_id = projection_bound.projection_def_id();
                 // FIXME(#120456) - is `swap_remove` correct?
                 def_ids.swap_remove(&def_id);
                 if tcx.generics_require_sized_self(def_id) {
-                    tcx.emit_node_span_lint(
+                    tcx.emit_node_lint(
                         UNUSED_ASSOCIATED_TYPE_BOUNDS,
                         hir_id,
-                        *span,
-                        crate::errors::UnusedAssociatedTypeBounds { span: *span },
+                        crate::errors::UnusedAssociatedTypeBounds { span },
                     );
                 }
             }

compiler/rustc_hir_typeck/src/cast.rs

@@ -663,7 +663,8 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         };
         let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
         let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
-        fcx.tcx.emit_node_span_lint(lint, self.expr.hir_id, self.span, errors::TrivialCast {
+        fcx.tcx.emit_node_lint(lint, self.expr.hir_id, errors::TrivialCast {
+            span: self.span,
             numeric,
             expr_ty,
             cast_ty,
@@ -934,11 +935,11 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                             .collect::<Vec<_>>();
 
                         if !added.is_empty() {
-                            tcx.emit_node_span_lint(
+                            tcx.emit_node_lint(
                                 lint::builtin::PTR_CAST_ADD_AUTO_TO_OBJECT,
                                 self.expr.hir_id,
-                                self.span,
                                 errors::PtrCastAddAutoToObject {
+                                    span: self.span,
                                     traits_len: added.len(),
                                     traits: {
                                         let mut traits: Vec<_> = added
@@ -1097,11 +1098,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
             let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
 
-            fcx.tcx.emit_node_span_lint(
+            fcx.tcx.emit_node_lint(
                 lint::builtin::CENUM_IMPL_DROP_CAST,
                 self.expr.hir_id,
-                self.span,
-                errors::CastEnumDrop { expr_ty, cast_ty },
+                errors::CastEnumDrop { span: self.span, expr_ty, cast_ty },
             );
         }
     }
@@ -1130,12 +1130,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             (false, false) => errors::LossyProvenancePtr2IntSuggestion::Other { cast_span },
         };
 
-        let lint = errors::LossyProvenancePtr2Int { expr_ty, cast_ty, sugg };
-        fcx.tcx.emit_node_span_lint(
+        fcx.tcx.emit_node_lint(
             lint::builtin::LOSSY_PROVENANCE_CASTS,
             self.expr.hir_id,
-            self.span,
-            lint,
+            errors::LossyProvenancePtr2Int { span: self.span, expr_ty, cast_ty, sugg },
         );
     }
 
@@ -1146,12 +1144,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         };
         let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
         let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
-        let lint = errors::LossyProvenanceInt2Ptr { expr_ty, cast_ty, sugg };
-        fcx.tcx.emit_node_span_lint(
+        fcx.tcx.emit_node_lint(
             lint::builtin::FUZZY_PROVENANCE_CASTS,
             self.expr.hir_id,
-            self.span,
-            lint,
+            errors::LossyProvenanceInt2Ptr { span: self.span, expr_ty, cast_ty, sugg },
         );
     }