Auto merge of #68078 - Centril:rollup-qvq052k, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #66463 (Point at opaque and closure type definitions in type errors)
 - #67501 (Reduce special treatment for zsts)
 - #67820 (Parse the syntax described in RFC 2632)
 - #67922 (rustc_ast_lowering: misc cleanup & rustc dep reductions)
 - #68071 (Extend support of `_` in type parameters)
 - #68073 (expect `fn` after `const unsafe` / `const extern`)

Failed merges:

r? @ghost

src/librustc/infer/canonical/query_response.rs

@@ -22,7 +22,7 @@ use crate::traits::{Obligation, ObligationCause, PredicateObligation};
 use crate::ty::fold::TypeFoldable;
 use crate::ty::subst::{GenericArg, GenericArgKind};
 use crate::ty::{self, BoundVar, Ty, TyCtxt};
-use crate::util::captures::Captures;
+use rustc_data_structures::captures::Captures;
 use rustc_index::vec::Idx;
 use rustc_index::vec::IndexVec;
 use rustc_span::DUMMY_SP;

src/librustc/infer/error_reporting/mod.rs

@@ -68,9 +68,12 @@ use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::Node;
 
-use errors::{struct_span_err, Applicability, DiagnosticBuilder, DiagnosticStyledString};
+use errors::{
+    pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticStyledString,
+};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_error_codes::*;
-use rustc_span::{Pos, Span};
+use rustc_span::{DesugaringKind, Pos, Span};
 use rustc_target::spec::abi;
 use std::{cmp, fmt};
 
@@ -1289,6 +1292,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         mut values: Option<ValuePairs<'tcx>>,
         terr: &TypeError<'tcx>,
     ) {
+        let span = cause.span(self.tcx);
+
         // For some types of errors, expected-found does not make
         // sense, so just ignore the values we were given.
         match terr {
@@ -1298,6 +1303,100 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             _ => {}
         }
 
+        struct OpaqueTypesVisitor<'tcx> {
+            types: FxHashMap<TyCategory, FxHashSet<Span>>,
+            expected: FxHashMap<TyCategory, FxHashSet<Span>>,
+            found: FxHashMap<TyCategory, FxHashSet<Span>>,
+            ignore_span: Span,
+            tcx: TyCtxt<'tcx>,
+        }
+
+        impl<'tcx> OpaqueTypesVisitor<'tcx> {
+            fn visit_expected_found(
+                tcx: TyCtxt<'tcx>,
+                expected: Ty<'tcx>,
+                found: Ty<'tcx>,
+                ignore_span: Span,
+            ) -> Self {
+                let mut types_visitor = OpaqueTypesVisitor {
+                    types: Default::default(),
+                    expected: Default::default(),
+                    found: Default::default(),
+                    ignore_span,
+                    tcx,
+                };
+                // The visitor puts all the relevant encountered types in `self.types`, but in
+                // here we want to visit two separate types with no relation to each other, so we
+                // move the results from `types` to `expected` or `found` as appropriate.
+                expected.visit_with(&mut types_visitor);
+                std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
+                found.visit_with(&mut types_visitor);
+                std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
+                types_visitor
+            }
+
+            fn report(&self, err: &mut DiagnosticBuilder<'_>) {
+                self.add_labels_for_types(err, "expected", &self.expected);
+                self.add_labels_for_types(err, "found", &self.found);
+            }
+
+            fn add_labels_for_types(
+                &self,
+                err: &mut DiagnosticBuilder<'_>,
+                target: &str,
+                types: &FxHashMap<TyCategory, FxHashSet<Span>>,
+            ) {
+                for (key, values) in types.iter() {
+                    let count = values.len();
+                    let kind = key.descr();
+                    for sp in values {
+                        err.span_label(
+                            *sp,
+                            format!(
+                                "{}{}{} {}{}",
+                                if sp.is_desugaring(DesugaringKind::Async) {
+                                    "the `Output` of this `async fn`'s "
+                                } else if count == 1 {
+                                    "the "
+                                } else {
+                                    ""
+                                },
+                                if count > 1 { "one of the " } else { "" },
+                                target,
+                                kind,
+                                pluralize!(count),
+                            ),
+                        );
+                    }
+                }
+            }
+        }
+
+        impl<'tcx> ty::fold::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
+            fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+                if let Some((kind, def_id)) = TyCategory::from_ty(t) {
+                    let span = self.tcx.def_span(def_id);
+                    // Avoid cluttering the output when the "found" and error span overlap:
+                    //
+                    // error[E0308]: mismatched types
+                    //   --> $DIR/issue-20862.rs:2:5
+                    //    |
+                    // LL |     |y| x + y
+                    //    |     ^^^^^^^^^
+                    //    |     |
+                    //    |     the found closure
+                    //    |     expected `()`, found closure
+                    //    |
+                    //    = note: expected unit type `()`
+                    //                 found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
+                    if !self.ignore_span.overlaps(span) {
+                        self.types.entry(kind).or_default().insert(span);
+                    }
+                }
+                t.super_visit_with(self)
+            }
+        }
+
         debug!("note_type_err(diag={:?})", diag);
         let (expected_found, exp_found, is_simple_error) = match values {
             None => (None, None, false),
@@ -1306,6 +1405,13 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     ValuePairs::Types(exp_found) => {
                         let is_simple_err =
                             exp_found.expected.is_simple_text() && exp_found.found.is_simple_text();
+                        OpaqueTypesVisitor::visit_expected_found(
+                            self.tcx,
+                            exp_found.expected,
+                            exp_found.found,
+                            span,
+                        )
+                        .report(diag);
 
                         (is_simple_err, Some(exp_found))
                     }
@@ -1323,8 +1429,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             }
         };
 
-        let span = cause.span(self.tcx);
-
         // Ignore msg for object safe coercion
         // since E0038 message will be printed
         match terr {
@@ -1336,7 +1440,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 }
             }
         };
-
         if let Some((expected, found)) = expected_found {
             let expected_label = exp_found.map_or("type".into(), |ef| ef.expected.prefix_string());
             let found_label = exp_found.map_or("type".into(), |ef| ef.found.prefix_string());
@@ -1933,3 +2036,34 @@ impl<'tcx> ObligationCause<'tcx> {
         }
     }
 }
+
+/// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
+/// extra information about each type, but we only care about the category.
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+crate enum TyCategory {
+    Closure,
+    Opaque,
+    Generator,
+    Foreign,
+}
+
+impl TyCategory {
+    fn descr(&self) -> &'static str {
+        match self {
+            Self::Closure => "closure",
+            Self::Opaque => "opaque type",
+            Self::Generator => "generator",
+            Self::Foreign => "foreign type",
+        }
+    }
+
+    pub fn from_ty(ty: Ty<'_>) -> Option<(Self, DefId)> {
+        match ty.kind {
+            ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
+            ty::Opaque(def_id, _) => Some((Self::Opaque, def_id)),
+            ty::Generator(def_id, ..) => Some((Self::Generator, def_id)),
+            ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
+            _ => None,
+        }
+    }
+}

src/librustc/infer/outlives/verify.rs

@@ -3,7 +3,7 @@ use crate::infer::{GenericKind, VerifyBound};
 use crate::traits;
 use crate::ty::subst::{InternalSubsts, Subst};
 use crate::ty::{self, Ty, TyCtxt};
-use crate::util::captures::Captures;
+use rustc_data_structures::captures::Captures;
 use rustc_hir::def_id::DefId;
 
 /// The `TypeOutlives` struct has the job of "lowering" a `T: 'a`

src/librustc/lib.rs

@@ -100,7 +100,6 @@ pub mod ty;
 
 pub mod util {
     pub mod bug;
-    pub mod captures;
     pub mod common;
 }
 

src/librustc/middle/cstore.rs

@@ -5,8 +5,8 @@
 use crate::hir::map as hir_map;
 use crate::hir::map::definitions::{DefKey, DefPathTable};
 use crate::session::search_paths::PathKind;
-use crate::session::{CrateDisambiguator, Session};
-use crate::ty::{self, TyCtxt};
+use crate::session::CrateDisambiguator;
+use crate::ty::TyCtxt;
 
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{self, MetadataRef};
@@ -208,7 +208,6 @@ pub trait CrateStore {
     fn crate_is_private_dep_untracked(&self, cnum: CrateNum) -> bool;
     fn crate_disambiguator_untracked(&self, cnum: CrateNum) -> CrateDisambiguator;
     fn crate_hash_untracked(&self, cnum: CrateNum) -> Svh;
-    fn item_generics_cloned_untracked(&self, def: DefId, sess: &Session) -> ty::Generics;
 
     // This is basically a 1-based range of ints, which is a little
     // silly - I may fix that.

src/librustc/traits/error_reporting.rs

@@ -6,7 +6,7 @@ use super::{
     TraitNotObjectSafe,
 };
 
-use crate::infer::error_reporting::TypeAnnotationNeeded as ErrorCode;
+use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::{self, InferCtxt};
 use crate::mir::interpret::ErrorHandled;
@@ -446,7 +446,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 flags.push((sym::from_method, Some(method.to_string())));
             }
         }
-        if let Some(t) = self.get_parent_trait_ref(&obligation.cause.code) {
+        if let Some((t, _)) = self.get_parent_trait_ref(&obligation.cause.code) {
             flags.push((sym::parent_trait, Some(t)));
         }
 
@@ -665,13 +665,21 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     }
 
     /// Gets the parent trait chain start
-    fn get_parent_trait_ref(&self, code: &ObligationCauseCode<'tcx>) -> Option<String> {
+    fn get_parent_trait_ref(
+        &self,
+        code: &ObligationCauseCode<'tcx>,
+    ) -> Option<(String, Option<Span>)> {
         match code {
             &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
                 let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref);
                 match self.get_parent_trait_ref(&data.parent_code) {
                     Some(t) => Some(t),
-                    None => Some(parent_trait_ref.skip_binder().self_ty().to_string()),
+                    None => {
+                        let ty = parent_trait_ref.skip_binder().self_ty();
+                        let span =
+                            TyCategory::from_ty(ty).map(|(_, def_id)| self.tcx.def_span(def_id));
+                        Some((ty.to_string(), span))
+                    }
                 }
             }
             _ => None,
@@ -719,9 +727,15 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             return;
                         }
                         let trait_ref = trait_predicate.to_poly_trait_ref();
-                        let (post_message, pre_message) = self
+                        let (post_message, pre_message, type_def) = self
                             .get_parent_trait_ref(&obligation.cause.code)
-                            .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
+                            .map(|(t, s)| {
+                                (
+                                    format!(" in `{}`", t),
+                                    format!("within `{}`, ", t),
+                                    s.map(|s| (format!("within this `{}`", t), s)),
+                                )
+                            })
                             .unwrap_or_default();
 
                         let OnUnimplementedNote { message, label, note, enclosing_scope } =
@@ -795,6 +809,9 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                         } else {
                             err.span_label(span, explanation);
                         }
+                        if let Some((msg, span)) = type_def {
+                            err.span_label(span, &msg);
+                        }
                         if let Some(ref s) = note {
                             // If it has a custom `#[rustc_on_unimplemented]` note, let's display it
                             err.note(s.as_str());

src/librustc/traits/project.rs

@@ -17,7 +17,6 @@ use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
 use crate::ty::fold::{TypeFoldable, TypeFolder};
 use crate::ty::subst::{InternalSubsts, Subst};
 use crate::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt};
-use crate::util::common::FN_OUTPUT_NAME;
 use rustc_data_structures::snapshot_map::{Snapshot, SnapshotMap};
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
@@ -1364,7 +1363,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
         projection_ty: ty::ProjectionTy::from_ref_and_name(
             tcx,
             trait_ref,
-            Ident::with_dummy_span(FN_OUTPUT_NAME),
+            Ident::with_dummy_span(rustc_hir::FN_OUTPUT_NAME),
         ),
         ty: ret_type,
     });

src/librustc/ty/mod.rs

@@ -26,8 +26,8 @@ use crate::ty::layout::VariantIdx;
 use crate::ty::subst::{InternalSubsts, Subst, SubstsRef};
 use crate::ty::util::{Discr, IntTypeExt};
 use crate::ty::walk::TypeWalker;
-use crate::util::captures::Captures;
 use arena::SyncDroplessArena;
+use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};

src/librustc/ty/sty.rs

@@ -13,11 +13,10 @@ use crate::ty::layout::VariantIdx;
 use crate::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst, SubstsRef};
 use crate::ty::{self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable};
 use crate::ty::{List, ParamEnv, ParamEnvAnd, TyS};
-use crate::util::captures::Captures;
+use polonius_engine::Atom;
+use rustc_data_structures::captures::Captures;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-
-use polonius_engine::Atom;
 use rustc_index::vec::Idx;
 use rustc_macros::HashStable;
 use rustc_span::symbol::{kw, Symbol};

src/librustc/util/common.rs

@@ -5,14 +5,9 @@ use rustc_data_structures::sync::Lock;
 use std::fmt::Debug;
 use std::time::{Duration, Instant};
 
-use rustc_span::symbol::{sym, Symbol};
-
 #[cfg(test)]
 mod tests;
 
-// The name of the associated type for `Fn` return types.
-pub const FN_OUTPUT_NAME: Symbol = sym::Output;
-
 pub use errors::ErrorReported;
 
 pub fn to_readable_str(mut val: usize) -> String {

src/librustc_ast_lowering/item.rs

@@ -25,19 +25,16 @@ pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
     pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
 }
 
-impl<'a, 'lowering, 'hir> ItemLowerer<'a, 'lowering, 'hir> {
-    fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
-    where
-        F: FnOnce(&mut Self),
-    {
+impl ItemLowerer<'_, '_, '_> {
+    fn with_trait_impl_ref(&mut self, impl_ref: &Option<TraitRef>, f: impl FnOnce(&mut Self)) {
         let old = self.lctx.is_in_trait_impl;
-        self.lctx.is_in_trait_impl = if let &None = trait_impl_ref { false } else { true };
+        self.lctx.is_in_trait_impl = if let &None = impl_ref { false } else { true };
         f(self);
         self.lctx.is_in_trait_impl = old;
     }
 }
 
-impl<'a, 'lowering, 'hir> Visitor<'a> for ItemLowerer<'a, 'lowering, 'hir> {
+impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
     fn visit_mod(&mut self, m: &'a Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
         let hir_id = self.lctx.lower_node_id(n);
 
@@ -71,6 +68,12 @@ impl<'a, 'lowering, 'hir> Visitor<'a> for ItemLowerer<'a, 'lowering, 'hir> {
             self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
                 let this = &mut ItemLowerer { lctx: this };
                 if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.kind {
+                    if opt_trait_ref.as_ref().map(|tr| tr.constness.is_some()).unwrap_or(false) {
+                        this.lctx
+                            .diagnostic()
+                            .span_err(item.span, "const trait impls are not yet implemented");
+                    }
+
                     this.with_trait_impl_ref(opt_trait_ref, |this| visit::walk_item(this, item));
                 } else {
                     visit::walk_item(this, item);