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Provide help on closures capturing self causing borrow checker errors

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This commit is contained in:
yukang 2023-01-07 14:02:59 +08:00
parent 2b8590ef3b
commit c82545955e
5 changed files with 252 additions and 5 deletions
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150
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
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@ -1,4 +1,6 @@
use crate::diagnostics::mutability_errors::mut_borrow_of_mutable_ref;
use either::Either;
use hir::Closure;
use rustc_const_eval::util::CallKind;
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::FxHashSet;
@ -20,7 +22,7 @@ use rustc_middle::ty::{self, suggest_constraining_type_params, PredicateKind, Ty
use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
use rustc_span::def_id::LocalDefId;
use rustc_span::hygiene::DesugaringKind;
use rustc_span::symbol::sym;
use rustc_span::symbol::{kw, sym};
use rustc_span::{BytePos, Span, Symbol};
use rustc_trait_selection::infer::InferCtxtExt;
@ -39,6 +41,8 @@ use super::{
DescribePlaceOpt, RegionName, RegionNameSource, UseSpans,
};
use rustc_hir::def::Res;
#[derive(Debug)]
struct MoveSite {
/// Index of the "move out" that we found. The `MoveData` can
@ -356,7 +360,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
if let Some(hir::Node::Item(hir::Item {
kind: hir::ItemKind::Fn(_, _, body_id),
..
})) = hir.find(hir.local_def_id_to_hir_id(self.mir_def_id()))
})) = hir.find(self.mir_hir_id())
&& let Some(hir::Node::Expr(expr)) = hir.find(body_id.hir_id)
{
let place = &self.move_data.move_paths[mpi].place;
@ -948,7 +952,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
(BorrowKind::Mut { .. }, BorrowKind::Shared) => {
first_borrow_desc = "immutable ";
self.cannot_reborrow_already_borrowed(
let mut err = self.cannot_reborrow_already_borrowed(
span,
&desc_place,
&msg_place,
@ -958,7 +962,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
"immutable",
&msg_borrow,
None,
)
);
self.suggest_binding_for_closure_capture_self(
&mut err,
issued_borrow.borrowed_place,
&issued_spans,
);
err
}
(BorrowKind::Mut { .. }, BorrowKind::Mut { .. }) => {
@ -1240,6 +1250,138 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
}
fn suggest_binding_for_closure_capture_self(
&self,
err: &mut Diagnostic,
borrowed_place: Place<'tcx>,
issued_spans: &UseSpans<'tcx>,
) {
let UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return };
let hir = self.infcx.tcx.hir();
// check whether the borrowed place is capturing `self` by mut reference
let local = borrowed_place.local;
let Some(_) = self
.body
.local_decls
.get(local)
.map(|l| mut_borrow_of_mutable_ref(l, self.local_names[local])) else { return };
struct ExpressionFinder<'hir> {
capture_span: Span,
closure_change_spans: Vec<Span>,
closure_arg_span: Option<Span>,
in_closure: bool,
suggest_arg: String,
hir: rustc_middle::hir::map::Map<'hir>,
closure_local_id: Option<hir::HirId>,
closure_call_changes: Vec<(Span, String)>,
}
impl<'hir> Visitor<'hir> for ExpressionFinder<'hir> {
fn visit_expr(&mut self, e: &'hir hir::Expr<'hir>) {
if e.span.contains(self.capture_span) {
if let hir::ExprKind::Closure(&Closure {
movability: None,
body,
fn_arg_span,
fn_decl: hir::FnDecl{ inputs, .. },
..
}) = e.kind &&
let Some(hir::Node::Expr(body )) = self.hir.find(body.hir_id) {
self.suggest_arg = "this: &Self".to_string();
if inputs.len() > 0 {
self.suggest_arg.push_str(", ");
}
self.in_closure = true;
self.closure_arg_span = fn_arg_span;
self.visit_expr(body);
self.in_closure = false;
}
}
if let hir::Expr { kind: hir::ExprKind::Path(path), .. } = e {
if let hir::QPath::Resolved(_, hir::Path { segments: [seg], ..}) = path &&
seg.ident.name == kw::SelfLower && self.in_closure {
self.closure_change_spans.push(e.span);
}
}
hir::intravisit::walk_expr(self, e);
}
fn visit_local(&mut self, local: &'hir hir::Local<'hir>) {
if let hir::Pat { kind: hir::PatKind::Binding(_, hir_id, _ident, _), .. } = local.pat &&
let Some(init) = local.init
{
if let hir::Expr { kind: hir::ExprKind::Closure(&Closure {
movability: None,
..
}), .. } = init &&
init.span.contains(self.capture_span) {
self.closure_local_id = Some(*hir_id);
}
}
hir::intravisit::walk_local(self, local);
}
fn visit_stmt(&mut self, s: &'hir hir::Stmt<'hir>) {
if let hir::StmtKind::Semi(e) = s.kind &&
let hir::ExprKind::Call(hir::Expr { kind: hir::ExprKind::Path(path), ..}, args) = e.kind &&
let hir::QPath::Resolved(_, hir::Path { segments: [seg], ..}) = path &&
let Res::Local(hir_id) = seg.res &&
Some(hir_id) == self.closure_local_id {
let mut arg_str = "self".to_string();
if args.len() > 0 {
arg_str.push_str(", ");
}
self.closure_call_changes.push((seg.ident.span, arg_str));
}
hir::intravisit::walk_stmt(self, s);
}
}
if let Some(hir::Node::ImplItem(
hir::ImplItem { kind: hir::ImplItemKind::Fn(_fn_sig, body_id), .. }
)) = hir.find(self.mir_hir_id()) &&
let Some(hir::Node::Expr(expr)) = hir.find(body_id.hir_id) {
let mut finder = ExpressionFinder {
capture_span: *capture_kind_span,
closure_change_spans: vec![],
closure_arg_span: None,
in_closure: false,
suggest_arg: String::new(),
closure_local_id: None,
closure_call_changes: vec![],
hir,
};
finder.visit_expr(expr);
if finder.closure_change_spans.is_empty() || finder.closure_call_changes.is_empty() {
return;
}
let mut sugg = vec![];
let sm = self.infcx.tcx.sess.source_map();
if let Some(span) = finder.closure_arg_span {
sugg.push((sm.next_point(span.shrink_to_lo()).shrink_to_hi(), finder.suggest_arg));
}
for span in finder.closure_change_spans {
sugg.push((span, "this".to_string()));
}
for (span, suggest) in finder.closure_call_changes {
if let Ok(span) = sm.span_extend_while(span, |c| c != '(') {
sugg.push((sm.next_point(span).shrink_to_hi(), suggest));
}
}
err.multipart_suggestion_verbose(
"try explicitly pass `&Self` into the Closure as an argument",
sugg,
Applicability::MachineApplicable,
);
}
}
/// Returns the description of the root place for a conflicting borrow and the full
/// descriptions of the places that caused the conflict.
///