Rollup merge of #108010 - compiler-errors:can_eq-returns-bool, r=lcnr

Make `InferCtxt::can_eq` and `InferCtxt::can_sub` return booleans

Nobody matches on the result, nor does the result return anything useful...

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -1144,7 +1144,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 LateBoundRegionConversionTime::FnCall,
                                 tcx.fn_sig(method_did).subst(tcx, method_substs).input(0),
                             )
-                            && infcx.can_eq(self.param_env, ty, self_ty).is_ok()
+                            && infcx.can_eq(self.param_env, ty, self_ty)
                         {
                             err.span_suggestion_verbose(
                                 fn_call_span.shrink_to_lo(),

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2232,7 +2232,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                         tcx.erase_regions(impl_.self_ty()),
                                         tcx.erase_regions(qself_ty),
                                     )
-                                    .is_ok()
                             })
                             && tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
                         })

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1106,7 +1106,7 @@ fn compare_self_type<'tcx>(
 
         let infcx = tcx.infer_ctxt().build();
         let self_arg_ty = tcx.liberate_late_bound_regions(method.def_id, self_arg_ty);
-        let can_eq_self = |ty| infcx.can_eq(param_env, untransformed_self_ty, ty).is_ok();
+        let can_eq_self = |ty| infcx.can_eq(param_env, untransformed_self_ty, ty);
         match ExplicitSelf::determine(self_arg_ty, can_eq_self) {
             ExplicitSelf::ByValue => "self".to_owned(),
             ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(),

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1716,7 +1716,7 @@ fn receiver_is_valid<'tcx>(
     let cause =
         ObligationCause::new(span, wfcx.body_def_id, traits::ObligationCauseCode::MethodReceiver);
 
-    let can_eq_self = |ty| infcx.can_eq(wfcx.param_env, self_ty, ty).is_ok();
+    let can_eq_self = |ty| infcx.can_eq(wfcx.param_env, self_ty, ty);
 
     // `self: Self` is always valid.
     if can_eq_self(receiver_ty) {

compiler/rustc_hir_typeck/src/demand.rs

@@ -321,7 +321,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let mut param_args = FxHashMap::default();
                 let mut param_expected = FxHashMap::default();
                 let mut param_found = FxHashMap::default();
-                if self.can_eq(self.param_env, ty, found).is_ok() {
+                if self.can_eq(self.param_env, ty, found) {
                     // We only point at the first place where the found type was inferred.
                     for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
                         if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
@@ -369,7 +369,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 for (param, (arg, arg_ty)) in param_args.iter() {
                     let Some(expected) = param_expected.get(param) else { continue; };
                     let Some(found) = param_found.get(param) else { continue; };
-                    if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
+                    if !self.can_eq(self.param_env, *arg_ty, *found) { continue; }
                     self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
                 }
 
@@ -379,7 +379,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
                 if ty != prev
                     && param_args.is_empty()
-                    && self.can_eq(self.param_env, ty, found).is_ok()
+                    && self.can_eq(self.param_env, ty, found)
                 {
                     // We only point at the first place where the found type was inferred.
                     if !segment.ident.span.overlaps(mismatch_span) {
@@ -401,7 +401,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
                 if ty != prev
                     && let Some(span) = prev_span
-                    && self.can_eq(self.param_env, ty, found).is_ok()
+                    && self.can_eq(self.param_env, ty, found)
                 {
                     // We only point at the first place where the found type was inferred.
                     // We use the *previous* span because if the type is known *here* it means
@@ -764,7 +764,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let ty::Adt(expected_adt, substs) = expected.kind() {
             if let hir::ExprKind::Field(base, ident) = expr.kind {
                 let base_ty = self.typeck_results.borrow().expr_ty(base);
-                if self.can_eq(self.param_env, base_ty, expected).is_ok()
+                if self.can_eq(self.param_env, base_ty, expected)
                     && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
                 {
                     err.span_suggestion_verbose(
@@ -1357,7 +1357,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
                 _,
                 &ty::Ref(_, checked, _),
-            ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
+            ) if self.can_sub(self.param_env, checked, expected) => {
                 // We have `&T`, check if what was expected was `T`. If so,
                 // we may want to suggest removing a `&`.
                 if sm.is_imported(expr.span) {
@@ -2003,7 +2003,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
         let hir::StmtKind::Semi(tail_expr) = stmt.kind else { return; };
         let Some(ty) = self.node_ty_opt(tail_expr.hir_id) else { return; };
-        if self.can_eq(self.param_env, expected_ty, ty).is_ok() {
+        if self.can_eq(self.param_env, expected_ty, ty) {
             err.span_suggestion_short(
                 stmt.span.with_lo(tail_expr.span.hi()),
                 "remove this semicolon",

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1015,7 +1015,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let expr_inner_ty = substs.type_at(0);
             let expected_inner_ty = expected_substs.type_at(0);
             if let ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind()
-                && self.can_eq(self.param_env, *ty, expected_inner_ty).is_ok()
+                && self.can_eq(self.param_env, *ty, expected_inner_ty)
             {
                 let def_path = self.tcx.def_path_str(adt_def.did());
                 if self.type_is_copy_modulo_regions(self.param_env, *ty, expr.span) {
@@ -1054,7 +1054,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let Some(result_did) = self.tcx.get_diagnostic_item(sym::Result)
             && adt_def.did() == result_did
             // Check that the error types are equal
-            && self.can_eq(self.param_env, substs.type_at(1), expected_substs.type_at(1)).is_ok()
+            && self.can_eq(self.param_env, substs.type_at(1), expected_substs.type_at(1))
         {
             return suggest_copied_or_cloned();
         } else if let Some(option_did) = self.tcx.get_diagnostic_item(sym::Option)

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -936,7 +936,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         return false;
                     }
                 }
-                self.can_sub(self.param_env, fty.output(), expected).is_ok()
+                self.can_sub(self.param_env, fty.output(), expected)
             }),
             _ => false,
         }

compiler/rustc_hir_typeck/src/pat.rs

@@ -90,7 +90,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
             self.demand_eqtype_with_origin(&self.pattern_cause(ti, cause_span), expected, actual)?;
         if let Some(expr) = ti.origin_expr {
             self.suggest_fn_call(&mut diag, expr, expected, |output| {
-                self.can_eq(self.param_env, output, actual).is_ok()
+                self.can_eq(self.param_env, output, actual)
             });
         }
         Some(diag)
@@ -675,7 +675,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         match (expected.kind(), actual.kind(), ba) {
             (ty::Ref(_, inner_ty, _), _, hir::BindingAnnotation::NONE)
-                if self.can_eq(self.param_env, *inner_ty, actual).is_ok() =>
+                if self.can_eq(self.param_env, *inner_ty, actual) =>
             {
                 err.span_suggestion_verbose(
                     span.shrink_to_lo(),
@@ -685,7 +685,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 );
             }
             (_, ty::Ref(_, inner_ty, _), hir::BindingAnnotation::REF)
-                if self.can_eq(self.param_env, expected, *inner_ty).is_ok() =>
+                if self.can_eq(self.param_env, expected, *inner_ty) =>
             {
                 err.span_suggestion_verbose(
                     span.with_hi(span.lo() + BytePos(4)),

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -576,7 +576,7 @@ fn foo(&self) -> Self::T { String::new() }
                                 tcx.impl_defaultness(item.id.owner_id)
                             {
                                 let assoc_ty = tcx.bound_type_of(item.id.owner_id).subst_identity();
-                                if self.infcx.can_eq(param_env, assoc_ty, found).is_ok() {
+                                if self.infcx.can_eq(param_env, assoc_ty, found) {
                                     diag.span_label(
                                         item.span,
                                         "associated type defaults can't be assumed inside the \
@@ -598,7 +598,7 @@ fn foo(&self) -> Self::T { String::new() }
                     if let hir::AssocItemKind::Type = item.kind {
                         let assoc_ty = tcx.bound_type_of(item.id.owner_id).subst_identity();
 
-                        if self.infcx.can_eq(param_env, assoc_ty, found).is_ok() {
+                        if self.infcx.can_eq(param_env, assoc_ty, found) {
                             diag.span_label(item.span, "expected this associated type");
                             return true;
                         }

compiler/rustc_infer/src/infer/mod.rs

@@ -880,30 +880,20 @@ impl<'tcx> InferCtxt<'tcx> {
         self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup);
     }
 
-    pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
+    pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> bool
     where
         T: at::ToTrace<'tcx>,
     {
         let origin = &ObligationCause::dummy();
-        self.probe(|_| {
-            self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
-                // Ignore obligations, since we are unrolling
-                // everything anyway.
-            })
-        })
+        self.probe(|_| self.at(origin, param_env).sub(a, b).is_ok())
     }
 
-    pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
+    pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> bool
     where
         T: at::ToTrace<'tcx>,
     {
         let origin = &ObligationCause::dummy();
-        self.probe(|_| {
-            self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
-                // Ignore obligations, since we are unrolling
-                // everything anyway.
-            })
-        })
+        self.probe(|_| self.at(origin, param_env).eq(a, b).is_ok())
     }
 
     #[instrument(skip(self), level = "debug")]

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

@@ -1628,7 +1628,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 // Eventually I'll need to implement param-env-aware
                 // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
                 let param_env = ty::ParamEnv::empty();
-                if self.can_sub(param_env, error, implication).is_ok() {
+                if self.can_sub(param_env, error, implication) {
                     debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication);
                     return true;
                 }

compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs

@@ -72,7 +72,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
 
             let impl_self_ty = impl_trait_ref.self_ty();
 
-            if let Ok(..) = self.can_eq(param_env, trait_self_ty, impl_self_ty) {
+            if self.can_eq(param_env, trait_self_ty, impl_self_ty) {
                 self_match_impls.push((def_id, impl_substs));
 
                 if iter::zip(

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -748,10 +748,11 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             let real_ty = real_trait_pred.self_ty();
             // We `erase_late_bound_regions` here because `make_subregion` does not handle
             // `ReLateBound`, and we don't particularly care about the regions.
-            if self
-                .can_eq(obligation.param_env, self.tcx.erase_late_bound_regions(real_ty), arg_ty)
-                .is_err()
-            {
+            if !self.can_eq(
+                obligation.param_env,
+                self.tcx.erase_late_bound_regions(real_ty),
+                arg_ty,
+            ) {
                 continue;
             }
 
@@ -3690,7 +3691,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     let Some((span, (assoc, ty))) = entry else { continue; };
                     if primary_spans.is_empty() || type_diffs.iter().any(|diff| {
                         let Sorts(expected_found) = diff else { return false; };
-                        self.can_eq(param_env, expected_found.found, ty).is_ok()
+                        self.can_eq(param_env, expected_found.found, ty)
                     }) {
                         // FIXME: this doesn't quite work for `Iterator::collect`
                         // because we have `Vec<i32>` and `()`, but we'd want `i32`
@@ -3717,10 +3718,10 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         let ty_str = with_forced_trimmed_paths!(self.ty_to_string(ty));
 
                         let assoc = with_forced_trimmed_paths!(self.tcx.def_path_str(assoc));
-                        if self.can_eq(param_env, ty, *prev_ty).is_err() {
+                        if !self.can_eq(param_env, ty, *prev_ty) {
                             if type_diffs.iter().any(|diff| {
                                 let Sorts(expected_found) = diff else { return false; };
-                                self.can_eq(param_env, expected_found.found, ty).is_ok()
+                                self.can_eq(param_env, expected_found.found, ty)
                             }) {
                                 primary_spans.push(span);
                             }
@@ -3868,7 +3869,7 @@ fn hint_missing_borrow<'tcx>(
         let (found_ty, found_refs) = get_deref_type_and_refs(*found_arg);
         let (expected_ty, expected_refs) = get_deref_type_and_refs(*expected_arg);
 
-        if infcx.can_eq(param_env, found_ty, expected_ty).is_ok() {
+        if infcx.can_eq(param_env, found_ty, expected_ty) {
             // FIXME: This could handle more exotic cases like mutability mismatches too!
             if found_refs.len() < expected_refs.len()
                 && found_refs[..] == expected_refs[expected_refs.len() - found_refs.len()..]