Actually taint InferCtxt when a fulfillment error is emitted

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -119,16 +119,7 @@ where
 
     let errors = wfcx.select_all_or_error();
     if !errors.is_empty() {
-        let err = infcx.err_ctxt().report_fulfillment_errors(errors);
-        if tcx.dcx().has_errors().is_some() {
-            return Err(err);
-        } else {
-            // HACK(oli-obk): tests/ui/specialization/min_specialization/specialize_on_type_error.rs
-            // causes an delayed bug during normalization, without reporting an error, so we need
-            // to act as if no error happened, in order to let our callers continue and report an
-            // error later in check_impl_items_against_trait.
-            return Ok(());
-        }
+        return Err(infcx.err_ctxt().report_fulfillment_errors(errors));
     }
 
     debug!(?assumed_wf_types);

compiler/rustc_hir_typeck/src/writeback.rs

@@ -793,7 +793,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
     }
 
     fn report_error(&self, p: impl Into<ty::GenericArg<'tcx>>) -> ErrorGuaranteed {
-        if let Some(guar) = self.fcx.dcx().has_errors() {
+        if let Some(guar) = self.fcx.tainted_by_errors() {
             guar
         } else {
             self.fcx

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

@@ -2776,97 +2776,115 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 let mut this = "this bound";
                 let mut note = None;
                 let mut help = None;
-                if let ty::PredicateKind::Clause(clause) = predicate.kind().skip_binder()
-                    && let ty::ClauseKind::Trait(trait_pred) = clause
-                {
-                    let def_id = trait_pred.def_id();
-                    let visible_item = if let Some(local) = def_id.as_local() {
-                        // Check for local traits being reachable.
-                        let vis = &tcx.resolutions(()).effective_visibilities;
-                        // Account for non-`pub` traits in the root of the local crate.
-                        let is_locally_reachable = tcx.parent(def_id).is_crate_root();
-                        vis.is_reachable(local) || is_locally_reachable
-                    } else {
-                        // Check for foreign traits being reachable.
-                        tcx.visible_parent_map(()).get(&def_id).is_some()
-                    };
-                    if tcx.is_lang_item(def_id, LangItem::Sized) {
-                        // Check if this is an implicit bound, even in foreign crates.
-                        if tcx
-                            .generics_of(item_def_id)
-                            .own_params
-                            .iter()
-                            .any(|param| tcx.def_span(param.def_id) == span)
-                        {
-                            a = "an implicit `Sized`";
-                            this = "the implicit `Sized` requirement on this type parameter";
-                        }
-                        if let Some(hir::Node::TraitItem(hir::TraitItem {
-                            generics,
-                            kind: hir::TraitItemKind::Type(bounds, None),
-                            ..
-                        })) = tcx.hir().get_if_local(item_def_id)
-                        // Do not suggest relaxing if there is an explicit `Sized` obligation.
-                        && !bounds.iter()
-                            .filter_map(|bound| bound.trait_ref())
-                            .any(|tr| tr.trait_def_id() == tcx.lang_items().sized_trait())
-                        {
-                            let (span, separator) = if let [.., last] = bounds {
-                                (last.span().shrink_to_hi(), " +")
+                if let ty::PredicateKind::Clause(clause) = predicate.kind().skip_binder() {
+                    match clause {
+                        ty::ClauseKind::Trait(trait_pred) => {
+                            let def_id = trait_pred.def_id();
+                            let visible_item = if let Some(local) = def_id.as_local() {
+                                // Check for local traits being reachable.
+                                let vis = &tcx.resolutions(()).effective_visibilities;
+                                // Account for non-`pub` traits in the root of the local crate.
+                                let is_locally_reachable = tcx.parent(def_id).is_crate_root();
+                                vis.is_reachable(local) || is_locally_reachable
                             } else {
-                                (generics.span.shrink_to_hi(), ":")
+                                // Check for foreign traits being reachable.
+                                tcx.visible_parent_map(()).get(&def_id).is_some()
                             };
-                            err.span_suggestion_verbose(
-                                span,
-                                "consider relaxing the implicit `Sized` restriction",
-                                format!("{separator} ?Sized"),
-                                Applicability::MachineApplicable,
-                            );
+                            if tcx.is_lang_item(def_id, LangItem::Sized) {
+                                // Check if this is an implicit bound, even in foreign crates.
+                                if tcx
+                                    .generics_of(item_def_id)
+                                    .own_params
+                                    .iter()
+                                    .any(|param| tcx.def_span(param.def_id) == span)
+                                {
+                                    a = "an implicit `Sized`";
+                                    this =
+                                        "the implicit `Sized` requirement on this type parameter";
+                                }
+                                if let Some(hir::Node::TraitItem(hir::TraitItem {
+                                    generics,
+                                    kind: hir::TraitItemKind::Type(bounds, None),
+                                    ..
+                                })) = tcx.hir().get_if_local(item_def_id)
+                                    // Do not suggest relaxing if there is an explicit `Sized` obligation.
+                                    && !bounds.iter()
+                                        .filter_map(|bound| bound.trait_ref())
+                                        .any(|tr| tr.trait_def_id() == tcx.lang_items().sized_trait())
+                                {
+                                    let (span, separator) = if let [.., last] = bounds {
+                                        (last.span().shrink_to_hi(), " +")
+                                    } else {
+                                        (generics.span.shrink_to_hi(), ":")
+                                    };
+                                    err.span_suggestion_verbose(
+                                        span,
+                                        "consider relaxing the implicit `Sized` restriction",
+                                        format!("{separator} ?Sized"),
+                                        Applicability::MachineApplicable,
+                                    );
+                                }
+                            }
+                            if let DefKind::Trait = tcx.def_kind(item_def_id)
+                                && !visible_item
+                            {
+                                note = Some(format!(
+                                    "`{short_item_name}` is a \"sealed trait\", because to implement it \
+                                    you also need to implement `{}`, which is not accessible; this is \
+                                    usually done to force you to use one of the provided types that \
+                                    already implement it",
+                                    with_no_trimmed_paths!(tcx.def_path_str(def_id)),
+                                ));
+                                let impls_of = tcx.trait_impls_of(def_id);
+                                let impls = impls_of
+                                    .non_blanket_impls()
+                                    .values()
+                                    .flatten()
+                                    .chain(impls_of.blanket_impls().iter())
+                                    .collect::<Vec<_>>();
+                                if !impls.is_empty() {
+                                    let len = impls.len();
+                                    let mut types = impls
+                                        .iter()
+                                        .map(|t| {
+                                            with_no_trimmed_paths!(format!(
+                                                "  {}",
+                                                tcx.type_of(*t).instantiate_identity(),
+                                            ))
+                                        })
+                                        .collect::<Vec<_>>();
+                                    let post = if types.len() > 9 {
+                                        types.truncate(8);
+                                        format!("\nand {} others", len - 8)
+                                    } else {
+                                        String::new()
+                                    };
+                                    help = Some(format!(
+                                        "the following type{} implement{} the trait:\n{}{post}",
+                                        pluralize!(len),
+                                        if len == 1 { "s" } else { "" },
+                                        types.join("\n"),
+                                    ));
+                                }
+                            }
                         }
-                    }
-                    if let DefKind::Trait = tcx.def_kind(item_def_id)
-                        && !visible_item
-                    {
-                        note = Some(format!(
-                            "`{short_item_name}` is a \"sealed trait\", because to implement it \
-                             you also need to implement `{}`, which is not accessible; this is \
-                             usually done to force you to use one of the provided types that \
-                             already implement it",
-                            with_no_trimmed_paths!(tcx.def_path_str(def_id)),
-                        ));
-                        let impls_of = tcx.trait_impls_of(def_id);
-                        let impls = impls_of
-                            .non_blanket_impls()
-                            .values()
-                            .flatten()
-                            .chain(impls_of.blanket_impls().iter())
-                            .collect::<Vec<_>>();
-                        if !impls.is_empty() {
-                            let len = impls.len();
-                            let mut types = impls
-                                .iter()
-                                .map(|t| {
-                                    with_no_trimmed_paths!(format!(
-                                        "  {}",
-                                        tcx.type_of(*t).instantiate_identity(),
-                                    ))
-                                })
-                                .collect::<Vec<_>>();
-                            let post = if types.len() > 9 {
-                                types.truncate(8);
-                                format!("\nand {} others", len - 8)
+                        ty::ClauseKind::ConstArgHasType(..) => {
+                            let descr =
+                                format!("required by a const generic parameter in `{item_name}`");
+                            if span.is_visible(sm) {
+                                let msg = format!(
+                                    "required by this const generic parameter in `{short_item_name}`"
+                                );
+                                multispan.push_span_label(span, msg);
+                                err.span_note(multispan, descr);
                             } else {
-                                String::new()
-                            };
-                            help = Some(format!(
-                                "the following type{} implement{} the trait:\n{}{post}",
-                                pluralize!(len),
-                                if len == 1 { "s" } else { "" },
-                                types.join("\n"),
-                            ));
+                                err.span_note(tcx.def_span(item_def_id), descr);
+                            }
+                            return;
                         }
+                        _ => (),
                     }
-                };
+                }
                 let descr = format!("required by {a} bound in `{item_name}`");
                 if span.is_visible(sm) {
                     let msg = format!("required by {this} in `{short_item_name}`");

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

@@ -179,6 +179,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             for (error, suppressed) in iter::zip(&errors, &is_suppressed) {
                 if !suppressed && error.obligation.cause.span.from_expansion() == from_expansion {
                     let guar = self.report_fulfillment_error(error);
+                    self.infcx.set_tainted_by_errors(guar);
                     reported = Some(guar);
                     // We want to ignore desugarings here: spans are equivalent even
                     // if one is the result of a desugaring and the other is not.
@@ -2686,22 +2687,14 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 }
             }
 
-            // Given some `ConstArgHasType(?x, usize)`, we should not emit an error such as
-            // "type annotations needed: cannot satisfy the constant `_` has type `usize`"
-            // Instead we should emit a normal error suggesting the user to turbofish the
-            // const parameter that is currently being inferred. Unfortunately we cannot
-            // nicely emit such an error so we delay an ICE incase nobody else reports it
-            // for us.
-            ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
-                return self.tcx.sess.dcx().span_delayed_bug(
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ..)) => self
+                .emit_inference_failure_err(
+                    obligation.cause.body_id,
                     span,
-                    format!(
-                        "`ambiguous ConstArgHasType({:?}, {:?}) unaccompanied by inference error`",
-                        ct, ty
-                    ),
-                );
-            }
-
+                    ct.into(),
+                    ErrorCode::E0284,
+                    true,
+                ),
             ty::PredicateKind::NormalizesTo(ty::NormalizesTo { alias, term })
                 if term.is_infer() =>
             {

tests/incremental/const-generics/issue-64087.rs

@@ -6,4 +6,6 @@ fn combinator<T, const S: usize>() -> [T; S] {}
 fn main() {
     combinator().into_iter();
     //[cfail1]~^ ERROR type annotations needed
+    //[cfail1]~| ERROR type annotations needed
+    //[cfail1]~| ERROR type annotations needed
 }

tests/ui/const-generics/defaults/doesnt_infer.rs

@@ -12,4 +12,5 @@ fn main() {
     let foo = Foo::<1>::foo();
     let foo = Foo::foo();
     //~^ ERROR type annotations needed for `Foo<_>`
+    //~| ERROR type annotations needed
 }

tests/ui/const-generics/defaults/doesnt_infer.stderr

@@ -1,14 +1,37 @@
-error[E0282]: type annotations needed for `Foo<_>`
+error[E0284]: type annotations needed for `Foo<_>`
   --> $DIR/doesnt_infer.rs:13:9
    |
 LL |     let foo = Foo::foo();
-   |         ^^^
+   |         ^^^   ---------- type must be known at this point
    |
+note: required by a const generic parameter in `Foo::<N>::foo`
+  --> $DIR/doesnt_infer.rs:5:6
+   |
+LL | impl<const N: u32> Foo<N> {
+   |      ^^^^^^^^^^^^ required by this const generic parameter in `Foo::<N>::foo`
+LL |     fn foo() -> Self {
+   |        --- required by a bound in this associated function
+help: consider giving `foo` an explicit type, where the value of const parameter `N` is specified
+   |
+LL |     let foo: Foo<N> = Foo::foo();
+   |            ++++++++
+
+error[E0284]: type annotations needed for `Foo<_>`
+  --> $DIR/doesnt_infer.rs:13:9
+   |
+LL |     let foo = Foo::foo();
+   |         ^^^   --- type must be known at this point
+   |
+note: required by a const generic parameter in `Foo`
+  --> $DIR/doesnt_infer.rs:3:12
+   |
+LL | struct Foo<const N: u32 = 2>;
+   |            ^^^^^^^^^^^^^^^^ required by this const generic parameter in `Foo`
 help: consider giving `foo` an explicit type, where the value of const parameter `N` is specified
    |
 LL |     let foo: Foo<N> = Foo::foo();
    |            ++++++++
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0284`.

tests/ui/const-generics/defaults/rp_impl_trait_fail.stderr

@@ -31,18 +31,23 @@ LL |     1_u64
    |
    = help: the trait `Traitor<1, 2>` is implemented for `u64`
 
-error[E0282]: type annotations needed
+error[E0284]: type annotations needed
   --> $DIR/rp_impl_trait_fail.rs:28:5
    |
 LL |     uwu();
    |     ^^^ cannot infer the value of the const parameter `N` declared on the function `uwu`
    |
+note: required by a const generic parameter in `uwu`
+  --> $DIR/rp_impl_trait_fail.rs:16:8
+   |
+LL | fn uwu<const N: u8>() -> impl Traitor<N> {
+   |        ^^^^^^^^^^^ required by this const generic parameter in `uwu`
 help: consider specifying the generic argument
    |
 LL |     uwu::<N>();
    |        +++++
 
 error: aborting due to 4 previous errors
 
-Some errors have detailed explanations: E0277, E0282.
+Some errors have detailed explanations: E0277, E0284.
 For more information about an error, try `rustc --explain E0277`.