A couple datalog/borrowck cleanups

compiler/rustc_borrowck/src/consumers.rs

@@ -8,11 +8,12 @@ use rustc_middle::ty::TyCtxt;
 pub use super::borrow_set::{BorrowData, BorrowSet, TwoPhaseActivation};
 pub use super::constraints::OutlivesConstraint;
 pub use super::dataflow::{BorrowIndex, Borrows, calculate_borrows_out_of_scope_at_location};
-pub use super::facts::{AllFacts as PoloniusInput, PoloniusRegionVid, RustcFacts};
-pub use super::location::{LocationTable, RichLocation};
-pub use super::nll::PoloniusOutput;
 pub use super::place_ext::PlaceExt;
 pub use super::places_conflict::{PlaceConflictBias, places_conflict};
+pub use super::polonius::legacy::{
+    AllFacts as PoloniusInput, LocationTable, PoloniusOutput, PoloniusRegionVid, RichLocation,
+    RustcFacts,
+};
 pub use super::region_infer::RegionInferenceContext;
 
 /// Options determining the output behavior of [`get_body_with_borrowck_facts`].

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -1,6 +1,9 @@
 //! Borrow checker diagnostics.
 
+use std::collections::BTreeMap;
+
 use rustc_abi::{FieldIdx, VariantIdx};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::{Applicability, Diag, MultiSpan};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::{self as hir, CoroutineKind, LangItem};
@@ -17,10 +20,10 @@ use rustc_middle::mir::{
 use rustc_middle::ty::print::Print;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_middle::util::{CallDesugaringKind, call_kind};
-use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
+use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult, MoveOutIndex};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::source_map::Spanned;
-use rustc_span::{DUMMY_SP, Span, Symbol, sym};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{
@@ -68,6 +71,126 @@ pub(super) struct DescribePlaceOpt {
 
 pub(super) struct IncludingTupleField(pub(super) bool);
 
+enum BufferedDiag<'infcx> {
+    Error(Diag<'infcx>),
+    NonError(Diag<'infcx, ()>),
+}
+
+impl<'infcx> BufferedDiag<'infcx> {
+    fn sort_span(&self) -> Span {
+        match self {
+            BufferedDiag::Error(diag) => diag.sort_span,
+            BufferedDiag::NonError(diag) => diag.sort_span,
+        }
+    }
+}
+
+#[derive(Default)]
+pub(crate) struct BorrowckDiagnosticsBuffer<'infcx, 'tcx> {
+    /// This field keeps track of move errors that are to be reported for given move indices.
+    ///
+    /// There are situations where many errors can be reported for a single move out (see
+    /// #53807) and we want only the best of those errors.
+    ///
+    /// The `report_use_of_moved_or_uninitialized` function checks this map and replaces the
+    /// diagnostic (if there is one) if the `Place` of the error being reported is a prefix of
+    /// the `Place` of the previous most diagnostic. This happens instead of buffering the
+    /// error. Once all move errors have been reported, any diagnostics in this map are added
+    /// to the buffer to be emitted.
+    ///
+    /// `BTreeMap` is used to preserve the order of insertions when iterating. This is necessary
+    /// when errors in the map are being re-added to the error buffer so that errors with the
+    /// same primary span come out in a consistent order.
+    buffered_move_errors: BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, Diag<'infcx>)>,
+
+    buffered_mut_errors: FxIndexMap<Span, (Diag<'infcx>, usize)>,
+
+    /// Buffer of diagnostics to be reported. A mixture of error and non-error diagnostics.
+    buffered_diags: Vec<BufferedDiag<'infcx>>,
+}
+
+impl<'infcx, 'tcx> BorrowckDiagnosticsBuffer<'infcx, 'tcx> {
+    pub(crate) fn buffer_non_error(&mut self, diag: Diag<'infcx, ()>) {
+        self.buffered_diags.push(BufferedDiag::NonError(diag));
+    }
+}
+
+impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
+    pub(crate) fn buffer_error(&mut self, diag: Diag<'infcx>) {
+        self.diags_buffer.buffered_diags.push(BufferedDiag::Error(diag));
+    }
+
+    pub(crate) fn buffer_non_error(&mut self, diag: Diag<'infcx, ()>) {
+        self.diags_buffer.buffer_non_error(diag);
+    }
+
+    pub(crate) fn buffer_move_error(
+        &mut self,
+        move_out_indices: Vec<MoveOutIndex>,
+        place_and_err: (PlaceRef<'tcx>, Diag<'infcx>),
+    ) -> bool {
+        if let Some((_, diag)) =
+            self.diags_buffer.buffered_move_errors.insert(move_out_indices, place_and_err)
+        {
+            // Cancel the old diagnostic so we don't ICE
+            diag.cancel();
+            false
+        } else {
+            true
+        }
+    }
+
+    pub(crate) fn get_buffered_mut_error(&mut self, span: Span) -> Option<(Diag<'infcx>, usize)> {
+        // FIXME(#120456) - is `swap_remove` correct?
+        self.diags_buffer.buffered_mut_errors.swap_remove(&span)
+    }
+
+    pub(crate) fn buffer_mut_error(&mut self, span: Span, diag: Diag<'infcx>, count: usize) {
+        self.diags_buffer.buffered_mut_errors.insert(span, (diag, count));
+    }
+
+    pub(crate) fn emit_errors(&mut self) -> Option<ErrorGuaranteed> {
+        let mut res = self.infcx.tainted_by_errors();
+
+        // Buffer any move errors that we collected and de-duplicated.
+        for (_, (_, diag)) in std::mem::take(&mut self.diags_buffer.buffered_move_errors) {
+            // We have already set tainted for this error, so just buffer it.
+            self.buffer_error(diag);
+        }
+        for (_, (mut diag, count)) in std::mem::take(&mut self.diags_buffer.buffered_mut_errors) {
+            if count > 10 {
+                #[allow(rustc::diagnostic_outside_of_impl)]
+                #[allow(rustc::untranslatable_diagnostic)]
+                diag.note(format!("...and {} other attempted mutable borrows", count - 10));
+            }
+            self.buffer_error(diag);
+        }
+
+        if !self.diags_buffer.buffered_diags.is_empty() {
+            self.diags_buffer.buffered_diags.sort_by_key(|buffered_diag| buffered_diag.sort_span());
+            for buffered_diag in self.diags_buffer.buffered_diags.drain(..) {
+                match buffered_diag {
+                    BufferedDiag::Error(diag) => res = Some(diag.emit()),
+                    BufferedDiag::NonError(diag) => diag.emit(),
+                }
+            }
+        }
+
+        res
+    }
+
+    pub(crate) fn has_buffered_diags(&self) -> bool {
+        self.diags_buffer.buffered_diags.is_empty()
+    }
+
+    pub(crate) fn has_move_error(
+        &self,
+        move_out_indices: &[MoveOutIndex],
+    ) -> Option<&(PlaceRef<'tcx>, Diag<'infcx>)> {
+        self.diags_buffer.buffered_move_errors.get(move_out_indices)
+    }
+}
+
 impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     /// Adds a suggestion when a closure is invoked twice with a moved variable or when a closure
     /// is moved after being invoked.