Remove ObligationCause::span() method

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -611,7 +611,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
         Err(terr) => {
             let mut diag = struct_span_code_err!(
                 tcx.dcx(),
-                cause.span(),
+                cause.span,
                 E0053,
                 "method `{}` has an incompatible return type for trait",
                 trait_m.name
@@ -1169,7 +1169,7 @@ fn extract_spans_for_error_reporting<'tcx>(
         TypeError::ArgumentMutability(i) | TypeError::ArgumentSorts(ExpectedFound { .. }, i) => {
             (impl_args.nth(i).unwrap(), trait_args.and_then(|mut args| args.nth(i)))
         }
-        _ => (cause.span(), tcx.hir().span_if_local(trait_m.def_id)),
+        _ => (cause.span, tcx.hir().span_if_local(trait_m.def_id)),
     }
 }
 

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -612,7 +612,7 @@ pub fn check_function_signature<'tcx>(
         match err {
             TypeError::ArgumentMutability(i)
             | TypeError::ArgumentSorts(ExpectedFound { .. }, i) => args.nth(i).unwrap(),
-            _ => cause.span(),
+            _ => cause.span,
         }
     }
 

compiler/rustc_hir_typeck/src/_match.rs

@@ -94,14 +94,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 (None, arm.body.span)
             };
 
-            let (span, code) = match prior_arm {
+            let code = match prior_arm {
                 // The reason for the first arm to fail is not that the match arms diverge,
                 // but rather that there's a prior obligation that doesn't hold.
-                None => {
-                    (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id, match_src))
-                }
-                Some((prior_arm_block_id, prior_arm_ty, prior_arm_span)) => (
-                    expr.span,
+                None => ObligationCauseCode::BlockTailExpression(arm.body.hir_id, match_src),
+                Some((prior_arm_block_id, prior_arm_ty, prior_arm_span)) => {
                     ObligationCauseCode::MatchExpressionArm(Box::new(MatchExpressionArmCause {
                         arm_block_id,
                         arm_span,
@@ -110,13 +107,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         prior_arm_ty,
                         prior_arm_span,
                         scrut_span: scrut.span,
+                        expr_span: expr.span,
                         source: match_src,
                         prior_non_diverging_arms: prior_non_diverging_arms.clone(),
                         tail_defines_return_position_impl_trait,
-                    })),
-                ),
+                    }))
+                }
             };
-            let cause = self.cause(span, code);
+            let cause = self.cause(arm_span, code);
 
             // This is the moral equivalent of `coercion.coerce(self, cause, arm.body, arm_ty)`.
             // We use it this way to be able to expand on the potential error and detect when a

compiler/rustc_hir_typeck/src/expr.rs

@@ -2027,7 +2027,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     }
                                     Err(_) => {
                                         span_bug!(
-                                            cause.span(),
+                                            cause.span,
                                             "subtyping remaining fields of type changing FRU failed: {target_ty} != {fru_ty}: {}::{}",
                                             variant.name,
                                             ident.name,

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -550,7 +550,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                     // This has/will have errored in wfcheck, which we cannot depend on from here, as typeck on functions
                     // may run before wfcheck if the function is used in const eval.
                     self.dcx().span_delayed_bug(
-                        cause.span(),
+                        cause.span,
                         format!("{self_ty} was a subtype of {method_self_ty} but now is not?"),
                     );
                 }

compiler/rustc_middle/src/traits/mod.rs

@@ -92,16 +92,6 @@ impl<'tcx> ObligationCause<'tcx> {
         ObligationCause { span, body_id: CRATE_DEF_ID, code: Default::default() }
     }
 
-    pub fn span(&self) -> Span {
-        match *self.code() {
-            ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
-                arm_span,
-                ..
-            }) => arm_span,
-            _ => self.span,
-        }
-    }
-
     #[inline]
     pub fn code(&self) -> &ObligationCauseCode<'tcx> {
         &self.code
@@ -517,10 +507,17 @@ pub struct MatchExpressionArmCause<'tcx> {
     pub prior_arm_block_id: Option<HirId>,
     pub prior_arm_ty: Ty<'tcx>,
     pub prior_arm_span: Span,
+    /// Span of the scrutinee of the match (the matched value).
     pub scrut_span: Span,
+    /// Source of the match, i.e. `match` or a desugaring.
     pub source: hir::MatchSource,
+    /// Span of the *whole* match expr.
+    pub expr_span: Span,
+    /// Spans of the previous arms except for those that diverge (i.e. evaluate to `!`).
+    ///
+    /// These are used for pointing out errors that may affect several arms.
     pub prior_non_diverging_arms: Vec<Span>,
-    // Is the expectation of this match expression an RPIT?
+    /// Is the expectation of this match expression an RPIT?
     pub tail_defines_return_position_impl_trait: Option<LocalDefId>,
 }
 

compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs

@@ -392,7 +392,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         Some(ty) if expected == ty => {
                             let source_map = self.tcx.sess.source_map();
                             err.span_suggestion(
-                                source_map.end_point(cause.span()),
+                                source_map.end_point(cause.span),
                                 "try removing this `?`",
                                 "",
                                 Applicability::MachineApplicable,
@@ -412,6 +412,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 source,
                 ref prior_non_diverging_arms,
                 scrut_span,
+                expr_span,
                 ..
             }) => match source {
                 hir::MatchSource::TryDesugar(scrut_hir_id) => {
@@ -430,7 +431,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             Some(ty) if expected == ty => {
                                 let source_map = self.tcx.sess.source_map();
                                 err.span_suggestion(
-                                    source_map.end_point(cause.span()),
+                                    source_map.end_point(cause.span),
                                     "try removing this `?`",
                                     "",
                                     Applicability::MachineApplicable,
@@ -460,12 +461,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             format!("this and all prior arms are found to be of type `{t}`"),
                         );
                     }
-                    let outer = if any_multiline_arm || !source_map.is_multiline(cause.span) {
+                    let outer = if any_multiline_arm || !source_map.is_multiline(expr_span) {
                         // Cover just `match` and the scrutinee expression, not
                         // the entire match body, to reduce diagram noise.
-                        cause.span.shrink_to_lo().to(scrut_span)
+                        expr_span.shrink_to_lo().to(scrut_span)
                     } else {
-                        cause.span
+                        expr_span
                     };
                     let msg = "`match` arms have incompatible types";
                     err.span_label(outer, msg);
@@ -1148,7 +1149,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         terr: TypeError<'tcx>,
         prefer_label: bool,
     ) {
-        let span = cause.span();
+        let span = cause.span;
 
         // For some types of errors, expected-found does not make
         // sense, so just ignore the values we were given.
@@ -1642,7 +1643,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         terr: TypeError<'tcx>,
     ) -> Vec<TypeErrorAdditionalDiags> {
         let mut suggestions = Vec::new();
-        let span = trace.cause.span();
+        let span = trace.cause.span;
         let values = self.resolve_vars_if_possible(trace.values);
         if let Some((expected, found)) = values.ty() {
             match (expected.kind(), found.kind()) {
@@ -1792,7 +1793,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     ) -> Diag<'a> {
         debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
 
-        let span = trace.cause.span();
+        let span = trace.cause.span;
         let failure_code = trace.cause.as_failure_code_diag(
             terr,
             span,

compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs

@@ -237,7 +237,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         expected_args: GenericArgsRef<'tcx>,
         actual_args: GenericArgsRef<'tcx>,
     ) -> Diag<'tcx> {
-        let span = cause.span();
+        let span = cause.span;
 
         let (leading_ellipsis, satisfy_span, where_span, dup_span, def_id) =
             if let ObligationCauseCode::WhereClause(def_id, span)

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1180,7 +1180,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                                             selcx.tcx(),
                                             selcx.tcx().require_lang_item(
                                                 LangItem::Sized,
-                                                Some(obligation.cause.span()),
+                                                Some(obligation.cause.span),
                                             ),
                                             [self_ty],
                                         ),
@@ -1600,7 +1600,7 @@ fn confirm_builtin_candidate<'cx, 'tcx>(
                 // exist. Instead, `Pointee<Metadata = ()>` should be a supertrait of `Sized`.
                 let sized_predicate = ty::TraitRef::new(
                     tcx,
-                    tcx.require_lang_item(LangItem::Sized, Some(obligation.cause.span())),
+                    tcx.require_lang_item(LangItem::Sized, Some(obligation.cause.span)),
                     [self_ty],
                 );
                 obligations.push(obligation.with(tcx, sized_predicate));

compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs

@@ -90,7 +90,7 @@ impl<'tcx> InferCtxt<'tcx> {
             assert!(!self.intercrate);
             let c_pred =
                 self.canonicalize_query(param_env.and(obligation.predicate), &mut _orig_values);
-            self.tcx.at(obligation.cause.span()).evaluate_obligation(c_pred)
+            self.tcx.at(obligation.cause.span).evaluate_obligation(c_pred)
         }
     }
 

tests/ui/wf/wf-dyn-incompat-trait-obj-match.rs

@@ -22,8 +22,8 @@ fn main() {
         Some(()) => &S,
         None => &R,  //~ ERROR E0308
     }
-    let t: &dyn Trait = match opt() { //~ ERROR E0038
+    let t: &dyn Trait = match opt() {
         Some(()) => &S, //~ ERROR E0038
-        None => &R,
+        None => &R, //~ ERROR E0038
     };
 }

tests/ui/wf/wf-dyn-incompat-trait-obj-match.stderr

@@ -31,14 +31,10 @@ LL | trait Trait: Sized {}
    = note: required for the cast from `&S` to `&dyn Trait`
 
 error[E0038]: the trait `Trait` cannot be made into an object
-  --> $DIR/wf-dyn-incompat-trait-obj-match.rs:25:25
+  --> $DIR/wf-dyn-incompat-trait-obj-match.rs:27:17
    |
-LL |       let t: &dyn Trait = match opt() {
-   |  _________________________^
-LL | |         Some(()) => &S,
-LL | |         None => &R,
-LL | |     };
-   | |_____^ `Trait` cannot be made into an object
+LL |         None => &R,
+   |                 ^^ `Trait` cannot be made into an object
    |
 note: for a trait to be "dyn-compatible" 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>
   --> $DIR/wf-dyn-incompat-trait-obj-match.rs:6:14