From 1c69947d1c40850c969c9deda73067d18ac6a2c9 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Mon, 6 Jan 2025 03:25:45 +0000
Subject: [PATCH] Try to explain borrow for tail expr temporary drop order
change in 2024
---
compiler/rustc_borrowck/messages.ftl | 5 ++-
.../src/diagnostics/explain_borrow.rs | 18 ++++-----
.../rustc_borrowck/src/diagnostics/mod.rs | 1 +
.../src/diagnostics/region_name.rs | 4 +-
compiler/rustc_borrowck/src/lib.rs | 23 +++++++++--
...hod_1.ElaborateDrops.after.panic-abort.mir | 1 +
...od_1.ElaborateDrops.after.panic-unwind.mir | 1 +
.../lint-tail-expr-drop-order-borrowck.rs | 26 ++++++++++---
.../lint-tail-expr-drop-order-borrowck.stderr | 38 ++++++++++++-------
9 files changed, 82 insertions(+), 35 deletions(-)
diff --git a/compiler/rustc_borrowck/messages.ftl b/compiler/rustc_borrowck/messages.ftl
index c1d5af59b1b5b..ada20e5c614f8 100644
--- a/compiler/rustc_borrowck/messages.ftl
+++ b/compiler/rustc_borrowck/messages.ftl
@@ -213,8 +213,9 @@ borrowck_suggest_create_fresh_reborrow =
borrowck_suggest_iterate_over_slice =
consider iterating over a slice of the `{$ty}`'s content to avoid moving into the `for` loop
-borrowck_tail_expr_drop_order = a temporary value will be dropped here before the execution exits the block in Edition 2024, which will raise borrow checking error
- .label = consider using a `let` binding to create a longer lived value; or replacing the `{"{"} .. {"}"}` block with curly brackets `( .. )`; or folding the rest of the expression into the surrounding `unsafe {"{"} .. {"}"}`
+borrowck_tail_expr_drop_order = relative drop order changing in Rust 2024
+ .label = this temporary value will be dropped at the end of the block
+ .note = consider using a `let` binding to ensure the value will live long enough
borrowck_ty_no_impl_copy =
{$is_partial_move ->
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 87017460e8ec3..1e0c1f3fed7a4 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -5,7 +5,7 @@
use std::assert_matches::assert_matches;
-use rustc_errors::{Applicability, Diag};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee};
use rustc_hir as hir;
use rustc_hir::intravisit::Visitor;
use rustc_index::IndexSlice;
@@ -61,12 +61,12 @@ impl<'tcx> BorrowExplanation<'tcx> {
pub(crate) fn is_explained(&self) -> bool {
!matches!(self, BorrowExplanation::Unexplained)
}
- pub(crate) fn add_explanation_to_diagnostic(
+ pub(crate) fn add_explanation_to_diagnostic<G: EmissionGuarantee>(
&self,
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
local_names: &IndexSlice<Local, Option<Symbol>>,
- err: &mut Diag<'_>,
+ err: &mut Diag<'_, G>,
borrow_desc: &str,
borrow_span: Option<Span>,
multiple_borrow_span: Option<(Span, Span)>,
@@ -349,10 +349,10 @@ impl<'tcx> BorrowExplanation<'tcx> {
}
}
- fn add_object_lifetime_default_note(
+ fn add_object_lifetime_default_note<G: EmissionGuarantee>(
&self,
tcx: TyCtxt<'tcx>,
- err: &mut Diag<'_>,
+ err: &mut Diag<'_, G>,
unsize_ty: Ty<'tcx>,
) {
if let ty::Adt(def, args) = unsize_ty.kind() {
@@ -406,9 +406,9 @@ impl<'tcx> BorrowExplanation<'tcx> {
}
}
- fn add_lifetime_bound_suggestion_to_diagnostic(
+ fn add_lifetime_bound_suggestion_to_diagnostic<G: EmissionGuarantee>(
&self,
- err: &mut Diag<'_>,
+ err: &mut Diag<'_, G>,
category: &ConstraintCategory<'tcx>,
span: Span,
region_name: &RegionName,
@@ -435,14 +435,14 @@ impl<'tcx> BorrowExplanation<'tcx> {
}
}
-fn suggest_rewrite_if_let(
+fn suggest_rewrite_if_let<G: EmissionGuarantee>(
tcx: TyCtxt<'_>,
expr: &hir::Expr<'_>,
pat: &str,
init: &hir::Expr<'_>,
conseq: &hir::Expr<'_>,
alt: Option<&hir::Expr<'_>>,
- err: &mut Diag<'_>,
+ err: &mut Diag<'_, G>,
) {
let source_map = tcx.sess.source_map();
err.span_note(
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index ebbdfea302cd3..b9b140a3f6b32 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -992,6 +992,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
kind,
};
}
+
normal_ret
}
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index bdb880b2bced3..9349b46ec5b0c 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -5,7 +5,7 @@ use std::fmt::{self, Display};
use std::iter;
use rustc_data_structures::fx::IndexEntry;
-use rustc_errors::Diag;
+use rustc_errors::{Diag, EmissionGuarantee};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_middle::ty::print::RegionHighlightMode;
@@ -108,7 +108,7 @@ impl RegionName {
}
}
- pub(crate) fn highlight_region_name(&self, diag: &mut Diag<'_>) {
+ pub(crate) fn highlight_region_name<G: EmissionGuarantee>(&self, diag: &mut Diag<'_, G>) {
match &self.source {
RegionNameSource::NamedLateParamRegion(span)
| RegionNameSource::NamedEarlyParamRegion(span) => {
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index a35dff99669a9..400bd51d87dfa 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -23,6 +23,7 @@ use std::ops::Deref;
use rustc_abi::FieldIdx;
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
use rustc_data_structures::graph::dominators::Dominators;
+use rustc_errors::LintDiagnostic;
use rustc_hir as hir;
use rustc_hir::CRATE_HIR_ID;
use rustc_hir::def_id::LocalDefId;
@@ -1195,11 +1196,27 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
return Control::Continue;
}
let borrowed = this.retrieve_borrow_spans(borrow).var_or_use_path_span();
- this.infcx.tcx.emit_node_span_lint(
+ let explain = this.explain_why_borrow_contains_point(
+ location,
+ borrow,
+ Some((WriteKind::StorageDeadOrDrop, place)),
+ );
+ this.infcx.tcx.node_span_lint(
TAIL_EXPR_DROP_ORDER,
CRATE_HIR_ID,
- place_span,
- session_diagnostics::TailExprDropOrder { borrowed },
+ borrowed,
+ |diag| {
+ session_diagnostics::TailExprDropOrder { borrowed }.decorate_lint(diag);
+ explain.add_explanation_to_diagnostic(
+ tcx,
+ this.body,
+ &this.local_names,
+ diag,
+ "",
+ None,
+ None,
+ );
+ },
);
// We may stop at the first case
Control::Break
diff --git a/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-abort.mir b/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-abort.mir
index e9bbe30bd774f..ee6e16d20fd8d 100644
--- a/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-abort.mir
+++ b/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-abort.mir
@@ -74,6 +74,7 @@ fn method_1(_1: Guard) -> () {
bb7: {
backward incompatible drop(_2);
+ backward incompatible drop(_4);
backward incompatible drop(_5);
goto -> bb21;
}
diff --git a/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-unwind.mir b/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-unwind.mir
index e9bbe30bd774f..ee6e16d20fd8d 100644
--- a/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-unwind.mir
+++ b/tests/mir-opt/tail_expr_drop_order_unwind.method_1.ElaborateDrops.after.panic-unwind.mir
@@ -74,6 +74,7 @@ fn method_1(_1: Guard) -> () {
bb7: {
backward incompatible drop(_2);
+ backward incompatible drop(_4);
backward incompatible drop(_5);
goto -> bb21;
}
diff --git a/tests/ui/drop/lint-tail-expr-drop-order-borrowck.rs b/tests/ui/drop/lint-tail-expr-drop-order-borrowck.rs
index 1bd5655d7fe1d..6f64d83f8a0c3 100644
--- a/tests/ui/drop/lint-tail-expr-drop-order-borrowck.rs
+++ b/tests/ui/drop/lint-tail-expr-drop-order-borrowck.rs
@@ -7,18 +7,20 @@
fn should_lint_with_potential_borrowck_err() {
let _ = { String::new().as_str() }.len();
- //~^ ERROR: a temporary value will be dropped here
+ //~^ ERROR: relative drop order changing
//~| WARN: this changes meaning in Rust 2024
- //~| NOTE: consider using a `let` binding
+ //~| NOTE: this temporary value will be dropped at the end of the block
+ //~| borrow later used by call
//~| NOTE: for more information, see
}
fn should_lint_with_unsafe_block() {
fn f(_: usize) {}
f(unsafe { String::new().as_str() }.len());
- //~^ ERROR: a temporary value will be dropped here
+ //~^ ERROR: relative drop order changing
//~| WARN: this changes meaning in Rust 2024
- //~| NOTE: consider using a `let` binding
+ //~| NOTE: this temporary value will be dropped at the end of the block
+ //~| borrow later used by call
//~| NOTE: for more information, see
}
@@ -27,11 +29,23 @@ fn should_lint_with_big_block() {
fn f<T>(_: T) {}
f({
&mut || 0
- //~^ ERROR: a temporary value will be dropped here
+ //~^ ERROR: relative drop order changing
//~| WARN: this changes meaning in Rust 2024
- //~| NOTE: consider using a `let` binding
+ //~| NOTE: this temporary value will be dropped at the end of the block
+ //~| borrow later used here
//~| NOTE: for more information, see
})
}
+fn another_temp_that_is_copy_in_arg() {
+ fn f() {}
+ fn g(_: &()) {}
+ g({ &f() });
+ //~^ ERROR: relative drop order changing
+ //~| WARN: this changes meaning in Rust 2024
+ //~| NOTE: this temporary value will be dropped at the end of the block
+ //~| borrow later used by call
+ //~| NOTE: for more information, see
+}
+
fn main() {}
diff --git a/tests/ui/drop/lint-tail-expr-drop-order-borrowck.stderr b/tests/ui/drop/lint-tail-expr-drop-order-borrowck.stderr
index 98ef0547c9075..a55e366dd0be1 100644
--- a/tests/ui/drop/lint-tail-expr-drop-order-borrowck.stderr
+++ b/tests/ui/drop/lint-tail-expr-drop-order-borrowck.stderr
@@ -1,10 +1,10 @@
-error: a temporary value will be dropped here before the execution exits the block in Edition 2024, which will raise borrow checking error
- --> $DIR/lint-tail-expr-drop-order-borrowck.rs:9:36
+error: relative drop order changing in Rust 2024
+ --> $DIR/lint-tail-expr-drop-order-borrowck.rs:9:15
|
LL | let _ = { String::new().as_str() }.len();
- | ------------- ^
+ | ^^^^^^^^^^^^^ --- borrow later used by call
| |
- | consider using a `let` binding to create a longer lived value; or replacing the `{ .. }` block with curly brackets `( .. )`; or folding the rest of the expression into the surrounding `unsafe { .. }`
+ | this temporary value will be dropped at the end of the block
|
= warning: this changes meaning in Rust 2024
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html>
@@ -14,27 +14,39 @@ note: the lint level is defined here
LL | #![deny(tail_expr_drop_order)]
| ^^^^^^^^^^^^^^^^^^^^
-error: a temporary value will be dropped here before the execution exits the block in Edition 2024, which will raise borrow checking error
- --> $DIR/lint-tail-expr-drop-order-borrowck.rs:18:37
+error: relative drop order changing in Rust 2024
+ --> $DIR/lint-tail-expr-drop-order-borrowck.rs:19:16
|
LL | f(unsafe { String::new().as_str() }.len());
- | ------------- ^
+ | ^^^^^^^^^^^^^ --- borrow later used by call
| |
- | consider using a `let` binding to create a longer lived value; or replacing the `{ .. }` block with curly brackets `( .. )`; or folding the rest of the expression into the surrounding `unsafe { .. }`
+ | this temporary value will be dropped at the end of the block
|
= warning: this changes meaning in Rust 2024
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html>
-error: a temporary value will be dropped here before the execution exits the block in Edition 2024, which will raise borrow checking error
- --> $DIR/lint-tail-expr-drop-order-borrowck.rs:29:17
+error: relative drop order changing in Rust 2024
+ --> $DIR/lint-tail-expr-drop-order-borrowck.rs:31:9
|
LL | &mut || 0
- | --------^
+ | ^^^^^^^^^
| |
- | consider using a `let` binding to create a longer lived value; or replacing the `{ .. }` block with curly brackets `( .. )`; or folding the rest of the expression into the surrounding `unsafe { .. }`
+ | this temporary value will be dropped at the end of the block
+ | borrow later used here
|
= warning: this changes meaning in Rust 2024
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html>
-error: aborting due to 3 previous errors
+error: relative drop order changing in Rust 2024
+ --> $DIR/lint-tail-expr-drop-order-borrowck.rs:43:9
+ |
+LL | g({ &f() });
+ | - ^^^^ this temporary value will be dropped at the end of the block
+ | |
+ | borrow later used by call
+ |
+ = warning: this changes meaning in Rust 2024
+ = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html>
+
+error: aborting due to 4 previous errors