Auto merge of rust-lang#102896 - matthiaskrgr:rollup-jg5xawz, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - rust-lang#101360 (Point out incompatible closure bounds)
 - rust-lang#101789 (`let`'s not needed in struct field definitions)
 - rust-lang#102846 (update to syn-1.0.102)
 - rust-lang#102871 (rustdoc: clean up overly complex `.trait-impl` CSS selectors)
 - rust-lang#102876 (suggest candidates for unresolved import)
 - rust-lang#102888 (Improve rustdoc-gui search-color test)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

Diff for: Cargo.lock

@@ -2721,11 +2721,11 @@ checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.37"
+version = "1.0.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec757218438d5fda206afc041538b2f6d889286160d649a86a24d37e1235afd1"
+checksum = "94e2ef8dbfc347b10c094890f778ee2e36ca9bb4262e86dc99cd217e35f3470b"
 dependencies = [
- "unicode-xid",
+ "unicode-ident",
 ]
 
 [[package]]
@@ -4719,13 +4719,13 @@ checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
 [[package]]
 name = "syn"
-version = "1.0.91"
+version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b683b2b825c8eef438b77c36a06dc262294da3d5a5813fac20da149241dcd44d"
+checksum = "3fcd952facd492f9be3ef0d0b7032a6e442ee9b361d4acc2b1d0c4aaa5f613a1"
 dependencies = [
  "proc-macro2",
  "quote",
- "unicode-xid",
+ "unicode-ident",
 ]
 
 [[package]]
@@ -5215,6 +5215,12 @@ dependencies = [
  "matches",
 ]
 
+[[package]]
+name = "unicode-ident"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ceab39d59e4c9499d4e5a8ee0e2735b891bb7308ac83dfb4e80cad195c9f6f3"
+
 [[package]]
 name = "unicode-normalization"
 version = "0.1.22"

Diff for: compiler/rustc_parse/src/parser/item.rs

@@ -1788,7 +1788,23 @@ impl<'a> Parser<'a> {
                     }
                 }
             } else {
-                self.expected_ident_found()
+                let mut err = self.expected_ident_found();
+                if let Some((ident, _)) = self.token.ident() && ident.as_str() == "let" {
+                    self.bump(); // `let`
+                    let span = self.prev_token.span.until(self.token.span);
+                    err.span_suggestion(
+                        span,
+                        "remove the let, the `let` keyword is not allowed in struct field definitions",
+                        String::new(),
+                        Applicability::MachineApplicable,
+                    );
+                    err.note("the `let` keyword is not allowed in `struct` fields");
+                    err.note("see <https://doc.rust-lang.org/book/ch05-01-defining-structs.html> for more information");
+                    err.emit();
+                    self.bump();
+                    return Ok(ident);
+                }
+                err
             };
             return Err(err);
         }

Diff for: compiler/rustc_resolve/src/diagnostics.rs

@@ -70,6 +70,7 @@ impl TypoSuggestion {
 }
 
 /// A free importable items suggested in case of resolution failure.
+#[derive(Debug, Clone)]
 pub(crate) struct ImportSuggestion {
     pub did: Option<DefId>,
     pub descr: &'static str,
@@ -139,6 +140,7 @@ impl<'a> Resolver<'a> {
                     if instead { Instead::Yes } else { Instead::No },
                     found_use,
                     IsPattern::No,
+                    IsImport::No,
                     path,
                 );
                 err.emit();
@@ -698,6 +700,7 @@ impl<'a> Resolver<'a> {
                         Instead::No,
                         FoundUse::Yes,
                         IsPattern::Yes,
+                        IsImport::No,
                         vec![],
                     );
                 }
@@ -1481,6 +1484,7 @@ impl<'a> Resolver<'a> {
             Instead::No,
             FoundUse::Yes,
             IsPattern::No,
+            IsImport::No,
             vec![],
         );
 
@@ -2449,6 +2453,34 @@ enum IsPattern {
     No,
 }
 
+/// Whether a binding is part of a use statement. Used for diagnostics.
+enum IsImport {
+    Yes,
+    No,
+}
+
+pub(crate) fn import_candidates(
+    session: &Session,
+    source_span: &IndexVec<LocalDefId, Span>,
+    err: &mut Diagnostic,
+    // This is `None` if all placement locations are inside expansions
+    use_placement_span: Option<Span>,
+    candidates: &[ImportSuggestion],
+) {
+    show_candidates(
+        session,
+        source_span,
+        err,
+        use_placement_span,
+        candidates,
+        Instead::Yes,
+        FoundUse::Yes,
+        IsPattern::No,
+        IsImport::Yes,
+        vec![],
+    );
+}
+
 /// When an entity with a given name is not available in scope, we search for
 /// entities with that name in all crates. This method allows outputting the
 /// results of this search in a programmer-friendly way
@@ -2462,6 +2494,7 @@ fn show_candidates(
     instead: Instead,
     found_use: FoundUse,
     is_pattern: IsPattern,
+    is_import: IsImport,
     path: Vec<Segment>,
 ) {
     if candidates.is_empty() {
@@ -2521,7 +2554,8 @@ fn show_candidates(
                 // produce an additional newline to separate the new use statement
                 // from the directly following item.
                 let additional_newline = if let FoundUse::Yes = found_use { "" } else { "\n" };
-                candidate.0 = format!("use {};\n{}", &candidate.0, additional_newline);
+                let add_use = if let IsImport::Yes = is_import { "" } else { "use " };
+                candidate.0 = format!("{}{};\n{}", add_use, &candidate.0, additional_newline);
             }
 
             err.span_suggestions(
@@ -2551,7 +2585,7 @@ fn show_candidates(
 
             err.note(&msg);
         }
-    } else {
+    } else if matches!(is_import, IsImport::No) {
         assert!(!inaccessible_path_strings.is_empty());
 
         let prefix =

Diff for: compiler/rustc_resolve/src/imports.rs

@@ -1,9 +1,9 @@
 //! A bunch of methods and structures more or less related to resolving imports.
 
-use crate::diagnostics::Suggestion;
+use crate::diagnostics::{import_candidates, Suggestion};
 use crate::Determinacy::{self, *};
 use crate::Namespace::{self, *};
-use crate::{module_to_string, names_to_string};
+use crate::{module_to_string, names_to_string, ImportSuggestion};
 use crate::{AmbiguityKind, BindingKey, ModuleKind, ResolutionError, Resolver, Segment};
 use crate::{Finalize, Module, ModuleOrUniformRoot, ParentScope, PerNS, ScopeSet};
 use crate::{NameBinding, NameBindingKind, PathResult};
@@ -406,6 +406,7 @@ struct UnresolvedImportError {
     label: Option<String>,
     note: Option<String>,
     suggestion: Option<Suggestion>,
+    candidate: Option<Vec<ImportSuggestion>>,
 }
 
 pub struct ImportResolver<'a, 'b> {
@@ -497,6 +498,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                     label: None,
                     note: None,
                     suggestion: None,
+                    candidate: None,
                 };
                 if path.contains("::") {
                     errors.push((path, err))
@@ -547,6 +549,16 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                 }
                 diag.multipart_suggestion(&msg, suggestions, applicability);
             }
+
+            if let Some(candidate) = &err.candidate {
+                import_candidates(
+                    self.r.session,
+                    &self.r.source_span,
+                    &mut diag,
+                    Some(err.span),
+                    &candidate,
+                )
+            }
         }
 
         diag.emit();
@@ -664,6 +676,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
             Some(finalize),
             ignore_binding,
         );
+
         let no_ambiguity = self.r.ambiguity_errors.len() == prev_ambiguity_errors_len;
         import.vis.set(orig_vis);
         let module = match path_res {
@@ -706,12 +719,14 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                                 String::from("a similar path exists"),
                                 Applicability::MaybeIncorrect,
                             )),
+                            candidate: None,
                         },
                         None => UnresolvedImportError {
                             span,
                             label: Some(label),
                             note: None,
                             suggestion,
+                            candidate: None,
                         },
                     };
                     return Some(err);
@@ -754,6 +769,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                             label: Some(String::from("cannot glob-import a module into itself")),
                             note: None,
                             suggestion: None,
+                            candidate: None,
                         });
                     }
                 }
@@ -919,11 +935,19 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                     }
                 };
 
+                let parent_suggestion =
+                    self.r.lookup_import_candidates(ident, TypeNS, &import.parent_scope, |_| true);
+
                 Some(UnresolvedImportError {
                     span: import.span,
                     label: Some(label),
                     note,
                     suggestion,
+                    candidate: if !parent_suggestion.is_empty() {
+                        Some(parent_suggestion)
+                    } else {
+                        None
+                    },
                 })
             } else {
                 // `resolve_ident_in_module` reported a privacy error.

Diff for: compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -1255,6 +1255,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         found_span,
                         found_trait_ref,
                         expected_trait_ref,
+                        obligation.cause.code(),
                     )
                 } else {
                     let (closure_span, found) = found_did

Diff for: compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -254,8 +254,15 @@ pub trait TypeErrCtxtExt<'tcx> {
         found_span: Option<Span>,
         found: ty::PolyTraitRef<'tcx>,
         expected: ty::PolyTraitRef<'tcx>,
+        cause: &ObligationCauseCode<'tcx>,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
 
+    fn note_conflicting_closure_bounds(
+        &self,
+        cause: &ObligationCauseCode<'tcx>,
+        err: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>,
+    );
+
     fn suggest_fully_qualified_path(
         &self,
         err: &mut Diagnostic,
@@ -1584,6 +1591,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         found_span: Option<Span>,
         found: ty::PolyTraitRef<'tcx>,
         expected: ty::PolyTraitRef<'tcx>,
+        cause: &ObligationCauseCode<'tcx>,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
         pub(crate) fn build_fn_sig_ty<'tcx>(
             infcx: &InferCtxt<'tcx>,
@@ -1645,9 +1653,68 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         let signature_kind = format!("{argument_kind} signature");
         err.note_expected_found(&signature_kind, expected_str, &signature_kind, found_str);
 
+        self.note_conflicting_closure_bounds(cause, &mut err);
+
         err
     }
 
+    // Add a note if there are two `Fn`-family bounds that have conflicting argument
+    // requirements, which will always cause a closure to have a type error.
+    fn note_conflicting_closure_bounds(
+        &self,
+        cause: &ObligationCauseCode<'tcx>,
+        err: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>,
+    ) {
+        // First, look for an `ExprBindingObligation`, which means we can get
+        // the unsubstituted predicate list of the called function. And check
+        // that the predicate that we failed to satisfy is a `Fn`-like trait.
+        if let ObligationCauseCode::ExprBindingObligation(def_id, _, _, idx) = cause
+            && let predicates = self.tcx.predicates_of(def_id).instantiate_identity(self.tcx)
+            && let Some(pred) = predicates.predicates.get(*idx)
+            && let ty::PredicateKind::Trait(trait_pred) = pred.kind().skip_binder()
+            && ty::ClosureKind::from_def_id(self.tcx, trait_pred.def_id()).is_some()
+        {
+            let expected_self =
+                self.tcx.anonymize_late_bound_regions(pred.kind().rebind(trait_pred.self_ty()));
+            let expected_substs = self
+                .tcx
+                .anonymize_late_bound_regions(pred.kind().rebind(trait_pred.trait_ref.substs));
+
+            // Find another predicate whose self-type is equal to the expected self type,
+            // but whose substs don't match.
+            let other_pred = std::iter::zip(&predicates.predicates, &predicates.spans)
+                .enumerate()
+                .find(|(other_idx, (pred, _))| match pred.kind().skip_binder() {
+                    ty::PredicateKind::Trait(trait_pred)
+                        if ty::ClosureKind::from_def_id(self.tcx, trait_pred.def_id())
+                            .is_some()
+                            && other_idx != idx
+                            // Make sure that the self type matches
+                            // (i.e. constraining this closure)
+                            && expected_self
+                                == self.tcx.anonymize_late_bound_regions(
+                                    pred.kind().rebind(trait_pred.self_ty()),
+                                )
+                            // But the substs don't match (i.e. incompatible args)
+                            && expected_substs
+                                != self.tcx.anonymize_late_bound_regions(
+                                    pred.kind().rebind(trait_pred.trait_ref.substs),
+                                ) =>
+                    {
+                        true
+                    }
+                    _ => false,
+                });
+            // If we found one, then it's very likely the cause of the error.
+            if let Some((_, (_, other_pred_span))) = other_pred {
+                err.span_note(
+                    *other_pred_span,
+                    "closure inferred to have a different signature due to this bound",
+                );
+            }
+        }
+    }
+
     fn suggest_fully_qualified_path(
         &self,
         err: &mut Diagnostic,

Diff for: src/bootstrap/Cargo.lock

@@ -445,9 +445,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.39"
+version = "1.0.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c54b25569025b7fc9651de43004ae593a75ad88543b17178aa5e1b9c4f15f56f"
+checksum = "94e2ef8dbfc347b10c094890f778ee2e36ca9bb4262e86dc99cd217e35f3470b"
 dependencies = [
  "unicode-ident",
 ]
@@ -596,9 +596,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.95"
+version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fbaf6116ab8924f39d52792136fb74fd60a80194cf1b1c6ffa6453eef1c3f942"
+checksum = "3fcd952facd492f9be3ef0d0b7032a6e442ee9b361d4acc2b1d0c4aaa5f613a1"
 dependencies = [
  "proc-macro2",
  "quote",

Diff for: src/ci/docker/host-x86_64/x86_64-gnu-tools/browser-ui-test.version

@@ -1 +1 @@
-0.12.0
+0.12.2