Rollup of 7 pull requests

compiler/rustc_hir_analysis/src/astconv/bounds.rs

@@ -8,6 +8,7 @@ use rustc_middle::ty::{self as ty, Ty, TypeVisitableExt};
 use rustc_span::symbol::Ident;
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::traits;
+use smallvec::SmallVec;
 
 use crate::astconv::{
     AstConv, ConvertedBinding, ConvertedBindingKind, OnlySelfBounds, PredicateFilter,
@@ -28,15 +29,11 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
         let tcx = self.tcx();
 
         // Try to find an unbound in bounds.
-        let mut unbound = None;
+        let mut unbounds: SmallVec<[_; 1]> = SmallVec::new();
         let mut search_bounds = |ast_bounds: &'tcx [hir::GenericBound<'tcx>]| {
             for ab in ast_bounds {
                 if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = ab {
-                    if unbound.is_none() {
-                        unbound = Some(&ptr.trait_ref);
-                    } else {
-                        tcx.sess.emit_err(errors::MultipleRelaxedDefaultBounds { span });
-                    }
+                    unbounds.push(ptr)
                 }
             }
         };
@@ -51,33 +48,41 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
             }
         }
 
+        if unbounds.len() > 1 {
+            tcx.sess.emit_err(errors::MultipleRelaxedDefaultBounds {
+                spans: unbounds.iter().map(|ptr| ptr.span).collect(),
+            });
+        }
+
         let sized_def_id = tcx.lang_items().sized_trait();
-        match (&sized_def_id, unbound) {
-            (Some(sized_def_id), Some(tpb))
-                if tpb.path.res == Res::Def(DefKind::Trait, *sized_def_id) =>
-            {
-                // There was in fact a `?Sized` bound, return without doing anything
-                return;
-            }
-            (_, Some(_)) => {
-                // There was a `?Trait` bound, but it was not `?Sized`; warn.
-                tcx.sess.span_warn(
-                    span,
-                    "default bound relaxed for a type parameter, but \
-                        this does nothing because the given bound is not \
-                        a default; only `?Sized` is supported",
-                );
-                // Otherwise, add implicitly sized if `Sized` is available.
-            }
-            _ => {
-                // There was no `?Sized` bound; add implicitly sized if `Sized` is available.
+
+        let mut seen_sized_unbound = false;
+        for unbound in unbounds {
+            if let Some(sized_def_id) = sized_def_id {
+                if unbound.trait_ref.path.res == Res::Def(DefKind::Trait, sized_def_id) {
+                    seen_sized_unbound = true;
+                    continue;
+                }
             }
+            // There was a `?Trait` bound, but it was not `?Sized`; warn.
+            tcx.sess.span_warn(
+                unbound.span,
+                "relaxing a default bound only does something for `?Sized`; \
+                all other traits are not bound by default",
+            );
         }
+
+        // If the above loop finished there was no `?Sized` bound; add implicitly sized if `Sized` is available.
         if sized_def_id.is_none() {
             // No lang item for `Sized`, so we can't add it as a bound.
             return;
         }
-        bounds.push_sized(tcx, self_ty, span);
+        if seen_sized_unbound {
+            // There was in fact a `?Sized` bound, return without doing anything
+        } else {
+            // There was no `?Sized` bound; add implicitly sized if `Sized` is available.
+            bounds.push_sized(tcx, self_ty, span);
+        }
     }
 
     /// This helper takes a *converted* parameter type (`param_ty`)

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -94,7 +94,7 @@ pub(super) fn enter_wf_checking_ctxt<'tcx, F>(
     f: F,
 ) -> Result<(), ErrorGuaranteed>
 where
-    F: for<'a> FnOnce(&WfCheckingCtxt<'a, 'tcx>),
+    F: for<'a> FnOnce(&WfCheckingCtxt<'a, 'tcx>) -> Result<(), ErrorGuaranteed>,
 {
     let param_env = tcx.param_env(body_def_id);
     let infcx = &tcx.infer_ctxt().build();
@@ -105,7 +105,7 @@ where
     if !tcx.features().trivial_bounds {
         wfcx.check_false_global_bounds()
     }
-    f(&mut wfcx);
+    f(&mut wfcx)?;
 
     let assumed_wf_types = wfcx.ocx.assumed_wf_types_and_report_errors(param_env, body_def_id)?;
 
@@ -875,6 +875,7 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) -> Result<(),
                         ty,
                         trait_def_id,
                     );
+                    Ok(())
                 })
             } else {
                 let mut diag = match ty.kind() {
@@ -961,6 +962,7 @@ fn check_associated_item(
                 let ty = tcx.type_of(item.def_id).instantiate_identity();
                 let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                 wfcx.register_wf_obligation(span, loc, ty.into());
+                Ok(())
             }
             ty::AssocKind::Fn => {
                 let sig = tcx.fn_sig(item.def_id).instantiate_identity();
@@ -972,7 +974,7 @@ fn check_associated_item(
                     hir_sig.decl,
                     item.def_id.expect_local(),
                 );
-                check_method_receiver(wfcx, hir_sig, item, self_ty);
+                check_method_receiver(wfcx, hir_sig, item, self_ty)
             }
             ty::AssocKind::Type => {
                 if let ty::AssocItemContainer::TraitContainer = item.container {
@@ -983,6 +985,7 @@ fn check_associated_item(
                     let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                     wfcx.register_wf_obligation(span, loc, ty.into());
                 }
+                Ok(())
             }
         }
     })
@@ -1097,6 +1100,7 @@ fn check_type_defn<'tcx>(
         }
 
         check_where_clauses(wfcx, item.span, item.owner_id.def_id);
+        Ok(())
     })
 }
 
@@ -1121,7 +1125,8 @@ fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) -> Result<(), ErrorGuarant
     }
 
     let res = enter_wf_checking_ctxt(tcx, item.span, def_id, |wfcx| {
-        check_where_clauses(wfcx, item.span, def_id)
+        check_where_clauses(wfcx, item.span, def_id);
+        Ok(())
     });
 
     // Only check traits, don't check trait aliases
@@ -1164,6 +1169,7 @@ fn check_item_fn(
     enter_wf_checking_ctxt(tcx, span, def_id, |wfcx| {
         let sig = tcx.fn_sig(def_id).instantiate_identity();
         check_fn_or_method(wfcx, ident.span, sig, decl, def_id);
+        Ok(())
     })
 }
 
@@ -1218,6 +1224,7 @@ fn check_item_type(
                 tcx.require_lang_item(LangItem::Sync, Some(ty_span)),
             );
         }
+        Ok(())
     })
 }
 
@@ -1276,6 +1283,7 @@ fn check_impl<'tcx>(
         }
 
         check_where_clauses(wfcx, item.span, item.owner_id.def_id);
+        Ok(())
     })
 }
 
@@ -1548,11 +1556,11 @@ fn check_method_receiver<'tcx>(
     fn_sig: &hir::FnSig<'_>,
     method: ty::AssocItem,
     self_ty: Ty<'tcx>,
-) {
+) -> Result<(), ErrorGuaranteed> {
     let tcx = wfcx.tcx();
 
     if !method.fn_has_self_parameter {
-        return;
+        return Ok(());
     }
 
     let span = fn_sig.decl.inputs[0].span;
@@ -1571,11 +1579,11 @@ fn check_method_receiver<'tcx>(
     if tcx.features().arbitrary_self_types {
         if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
             // Report error; `arbitrary_self_types` was enabled.
-            e0307(tcx, span, receiver_ty);
+            return Err(e0307(tcx, span, receiver_ty));
         }
     } else {
         if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, false) {
-            if receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
+            return Err(if receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
                 // Report error; would have worked with `arbitrary_self_types`.
                 feature_err(
                     &tcx.sess.parse_sess,
@@ -1587,16 +1595,17 @@ fn check_method_receiver<'tcx>(
                     ),
                 )
                 .help(HELP_FOR_SELF_TYPE)
-                .emit();
+                .emit()
             } else {
                 // Report error; would not have worked with `arbitrary_self_types`.
-                e0307(tcx, span, receiver_ty);
-            }
+                e0307(tcx, span, receiver_ty)
+            });
         }
     }
+    Ok(())
 }
 
-fn e0307(tcx: TyCtxt<'_>, span: Span, receiver_ty: Ty<'_>) {
+fn e0307(tcx: TyCtxt<'_>, span: Span, receiver_ty: Ty<'_>) -> ErrorGuaranteed {
     struct_span_err!(
         tcx.sess.diagnostic(),
         span,
@@ -1605,7 +1614,7 @@ fn e0307(tcx: TyCtxt<'_>, span: Span, receiver_ty: Ty<'_>) {
     )
     .note("type of `self` must be `Self` or a type that dereferences to it")
     .help(HELP_FOR_SELF_TYPE)
-    .emit();
+    .emit()
 }
 
 /// Returns whether `receiver_ty` would be considered a valid receiver type for `self_ty`. If

compiler/rustc_hir_analysis/src/errors.rs

@@ -96,7 +96,7 @@ pub struct CopyImplOnTypeWithDtor {
 #[diag(hir_analysis_multiple_relaxed_default_bounds, code = "E0203")]
 pub struct MultipleRelaxedDefaultBounds {
     #[primary_span]
-    pub span: Span,
+    pub spans: Vec<Span>,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -35,6 +35,7 @@ use rustc_span::def_id::DefIdSet;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Symbol;
 use rustc_span::{edit_distance, source_map, ExpnKind, FileName, MacroKind, Span};
+use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::error_reporting::on_unimplemented::OnUnimplementedNote;
 use rustc_trait_selection::traits::error_reporting::on_unimplemented::TypeErrCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
@@ -192,7 +193,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .span_if_local(def_id)
                     .unwrap_or_else(|| self.tcx.def_span(def_id));
                 err.span_label(sp, format!("private {kind} defined here"));
-                self.suggest_valid_traits(&mut err, out_of_scope_traits);
+                self.suggest_valid_traits(&mut err, out_of_scope_traits, true);
                 err.emit();
             }
 
@@ -2464,6 +2465,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         err: &mut Diagnostic,
         valid_out_of_scope_traits: Vec<DefId>,
+        explain: bool,
     ) -> bool {
         if !valid_out_of_scope_traits.is_empty() {
             let mut candidates = valid_out_of_scope_traits;
@@ -2476,7 +2478,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .find(|did| self.tcx.is_diagnostic_item(sym::TryInto, **did))
                 .copied();
 
-            err.help("items from traits can only be used if the trait is in scope");
+            if explain {
+                err.help("items from traits can only be used if the trait is in scope");
+            }
             let msg = format!(
                 "the following {traits_are} implemented but not in scope; \
                  perhaps add a `use` for {one_of_them}:",
@@ -2693,7 +2697,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
         }
-        if self.suggest_valid_traits(err, valid_out_of_scope_traits) {
+        if self.suggest_valid_traits(err, valid_out_of_scope_traits, true) {
             return;
         }
 
@@ -2970,29 +2974,49 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 (candidates, Vec::new())
             };
 
+            let impls_trait = |def_id: DefId| {
+                let args = ty::GenericArgs::for_item(self.tcx, def_id, |param, _| {
+                    if param.index == 0 {
+                        rcvr_ty.into()
+                    } else {
+                        self.infcx.var_for_def(span, param)
+                    }
+                });
+                self.infcx
+                    .type_implements_trait(def_id, args, self.param_env)
+                    .must_apply_modulo_regions()
+                    && param_type.is_none()
+            };
             match &potential_candidates[..] {
                 [] => {}
                 [trait_info] if trait_info.def_id.is_local() => {
-                    err.subdiagnostic(CandidateTraitNote {
-                        span: self.tcx.def_span(trait_info.def_id),
-                        trait_name: self.tcx.def_path_str(trait_info.def_id),
-                        item_name,
-                        action_or_ty: if trait_missing_method {
-                            "NONE".to_string()
-                        } else {
-                            param_type.map_or_else(
-                                || "implement".to_string(), // FIXME: it might only need to be imported into scope, not implemented.
-                                ToString::to_string,
-                            )
-                        },
-                    });
+                    if impls_trait(trait_info.def_id) {
+                        self.suggest_valid_traits(err, vec![trait_info.def_id], false);
+                    } else {
+                        err.subdiagnostic(CandidateTraitNote {
+                            span: self.tcx.def_span(trait_info.def_id),
+                            trait_name: self.tcx.def_path_str(trait_info.def_id),
+                            item_name,
+                            action_or_ty: if trait_missing_method {
+                                "NONE".to_string()
+                            } else {
+                                param_type.map_or_else(
+                                    || "implement".to_string(), // FIXME: it might only need to be imported into scope, not implemented.
+                                    ToString::to_string,
+                                )
+                            },
+                        });
+                    }
                 }
                 trait_infos => {
                     let mut msg = message(param_type.map_or_else(
                         || "implement".to_string(), // FIXME: it might only need to be imported into scope, not implemented.
                         |param| format!("restrict type parameter `{param}` with"),
                     ));
                     for (i, trait_info) in trait_infos.iter().enumerate() {
+                        if impls_trait(trait_info.def_id) {
+                            self.suggest_valid_traits(err, vec![trait_info.def_id], false);
+                        }
                         msg.push_str(&format!(
                             "\ncandidate #{}: `{}`",
                             i + 1,

compiler/rustc_middle/messages.ftl

@@ -12,6 +12,8 @@ middle_assert_coroutine_resume_after_return = coroutine resumed after completion
 middle_assert_divide_by_zero =
     attempt to divide `{$val}` by zero
 
+middle_assert_gen_resume_after_panic = `gen` fn or block cannot be further iterated on after it panicked
+
 middle_assert_misaligned_ptr_deref =
     misaligned pointer dereference: address must be a multiple of {$required} but is {$found}
 

compiler/rustc_middle/src/mir/terminator.rs

@@ -250,8 +250,7 @@ impl<O> AssertKind<O> {
                 middle_assert_coroutine_resume_after_return
             }
             ResumedAfterPanic(CoroutineKind::Async(_)) => middle_assert_async_resume_after_panic,
-            // FIXME(gen_blocks): custom error message for `gen` blocks
-            ResumedAfterPanic(CoroutineKind::Gen(_)) => middle_assert_async_resume_after_panic,
+            ResumedAfterPanic(CoroutineKind::Gen(_)) => middle_assert_gen_resume_after_panic,
             ResumedAfterPanic(CoroutineKind::Coroutine) => {
                 middle_assert_coroutine_resume_after_panic
             }

compiler/rustc_mir_build/src/thir/pattern/usefulness.rs

@@ -931,7 +931,7 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
             let specialized = pat.specialize(pcx, &ctor);
             for (subpat, column) in specialized.iter().zip(&mut specialized_columns) {
                 if subpat.is_or_pat() {
-                    column.patterns.extend(subpat.iter_fields())
+                    column.patterns.extend(subpat.flatten_or_pat())
                 } else {
                     column.patterns.push(subpat)
                 }

compiler/rustc_parse/messages.ftl

@@ -278,8 +278,8 @@ parse_found_expr_would_be_stmt = expected expression, found `{$token}`
 parse_function_body_equals_expr = function body cannot be `= expression;`
     .suggestion = surround the expression with `{"{"}` and `{"}"}` instead of `=` and `;`
 
-parse_gen_block = `gen` blocks are not yet implemented
-    .help = only the keyword is reserved for now
+parse_gen_fn = `gen` functions are not yet implemented
+    .help = for now you can use `gen {"{}"}` blocks and return `impl Iterator` instead
 
 parse_generic_args_in_pat_require_turbofish_syntax = generic args in patterns require the turbofish syntax