From 317952677ad6a80b3751a075f42ffd2a8d142a84 Mon Sep 17 00:00:00 2001 From: yukang Date: Tue, 13 Feb 2024 05:24:32 +0800 Subject: [PATCH] Suggest a borrow when using dbg --- .../src/diagnostics/conflict_errors.rs | 65 +++++++++- tests/ui/borrowck/dbg-issue-120327.rs | 68 ++++++++++ tests/ui/borrowck/dbg-issue-120327.stderr | 117 ++++++++++++++++++ .../dbg-macro-move-semantics.stderr | 4 + 4 files changed, 252 insertions(+), 2 deletions(-) create mode 100644 tests/ui/borrowck/dbg-issue-120327.rs create mode 100644 tests/ui/borrowck/dbg-issue-120327.stderr diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs index 1cb74849017ab..c7f6840e401c6 100644 --- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs +++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs @@ -4,7 +4,7 @@ #![allow(rustc::untranslatable_diagnostic)] use either::Either; -use hir::ClosureKind; +use hir::{ClosureKind, Path}; use rustc_data_structures::captures::Captures; use rustc_data_structures::fx::FxIndexSet; use rustc_errors::{codes::*, struct_span_code_err, Applicability, Diag, MultiSpan}; @@ -16,6 +16,7 @@ use rustc_hir::{CoroutineKind, CoroutineSource, LangItem}; use rustc_middle::bug; use rustc_middle::hir::nested_filter::OnlyBodies; use rustc_middle::mir::tcx::PlaceTy; +use rustc_middle::mir::VarDebugInfoContents; use rustc_middle::mir::{ self, AggregateKind, BindingForm, BorrowKind, CallSource, ClearCrossCrate, ConstraintCategory, FakeBorrowKind, FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, MutBorrowKind, @@ -546,7 +547,14 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> { self.suggest_cloning(err, ty, expr, None, Some(move_spans)); } } - if let Some(pat) = finder.pat { + + self.suggest_ref_for_dbg_args(expr, place, move_span, err); + + // it's useless to suggest inserting `ref` when the span don't comes from local code + if let Some(pat) = finder.pat + && !move_span.is_dummy() + && !self.infcx.tcx.sess.source_map().is_imported(move_span) + { *in_pattern = true; let mut sugg = vec![(pat.span.shrink_to_lo(), "ref ".to_string())]; if let Some(pat) = finder.parent_pat { @@ -561,6 +569,59 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> { } } + // for dbg!(x) which may take ownership, suggest dbg!(&x) instead + // but here we actually do not check whether the macro name is `dbg!` + // so that we may extend the scope a bit larger to cover more cases + fn suggest_ref_for_dbg_args( + &self, + body: &hir::Expr<'_>, + place: &Place<'tcx>, + move_span: Span, + err: &mut Diag<'infcx>, + ) { + let var_info = self.body.var_debug_info.iter().find(|info| match info.value { + VarDebugInfoContents::Place(ref p) => p == place, + _ => false, + }); + let arg_name = if let Some(var_info) = var_info { + var_info.name + } else { + return; + }; + struct MatchArgFinder { + expr_span: Span, + match_arg_span: Option, + arg_name: Symbol, + } + impl Visitor<'_> for MatchArgFinder { + fn visit_expr(&mut self, e: &hir::Expr<'_>) { + // dbg! is expanded into a match pattern, we need to find the right argument span + if let hir::ExprKind::Match(expr, ..) = &e.kind + && let hir::ExprKind::Path(hir::QPath::Resolved( + _, + path @ Path { segments: [seg], .. }, + )) = &expr.kind + && seg.ident.name == self.arg_name + && self.expr_span.source_callsite().contains(expr.span) + { + self.match_arg_span = Some(path.span); + } + hir::intravisit::walk_expr(self, e); + } + } + + let mut finder = MatchArgFinder { expr_span: move_span, match_arg_span: None, arg_name }; + finder.visit_expr(body); + if let Some(macro_arg_span) = finder.match_arg_span { + err.span_suggestion_verbose( + macro_arg_span.shrink_to_lo(), + "consider borrowing instead of transferring ownership", + "&", + Applicability::MachineApplicable, + ); + } + } + fn report_use_of_uninitialized( &self, mpi: MovePathIndex, diff --git a/tests/ui/borrowck/dbg-issue-120327.rs b/tests/ui/borrowck/dbg-issue-120327.rs new file mode 100644 index 0000000000000..2de43f634877a --- /dev/null +++ b/tests/ui/borrowck/dbg-issue-120327.rs @@ -0,0 +1,68 @@ +fn s() -> String { + let a = String::new(); + dbg!(a); + return a; //~ ERROR use of moved value: +} + +fn m() -> String { + let a = String::new(); + dbg!(1, 2, a, 1, 2); + return a; //~ ERROR use of moved value: +} + +fn t(a: String) -> String { + let b: String = "".to_string(); + dbg!(a, b); + return b; //~ ERROR use of moved value: +} + +fn x(a: String) -> String { + let b: String = "".to_string(); + dbg!(a, b); + return a; //~ ERROR use of moved value: +} + +macro_rules! my_dbg { + () => { + eprintln!("[{}:{}:{}]", file!(), line!(), column!()) + }; + ($val:expr $(,)?) => { + match $val { + tmp => { + eprintln!("[{}:{}:{}] {} = {:#?}", + file!(), line!(), column!(), stringify!($val), &tmp); + tmp + } + } + }; + ($($val:expr),+ $(,)?) => { + ($(my_dbg!($val)),+,) + }; +} + +fn test_my_dbg() -> String { + let b: String = "".to_string(); + my_dbg!(b, 1); + return b; //~ ERROR use of moved value: +} + +fn test_not_macro() -> String { + let a = String::new(); + let _b = match a { + tmp => { + eprintln!("dbg: {}", tmp); + tmp + } + }; + return a; //~ ERROR use of moved value: +} + +fn get_expr(_s: String) {} + +fn test() { + let a: String = "".to_string(); + let _res = get_expr(dbg!(a)); + let _l = a.len(); //~ ERROR borrow of moved value +} + +fn main() {} diff --git a/tests/ui/borrowck/dbg-issue-120327.stderr b/tests/ui/borrowck/dbg-issue-120327.stderr new file mode 100644 index 0000000000000..efacc0c3f1341 --- /dev/null +++ b/tests/ui/borrowck/dbg-issue-120327.stderr @@ -0,0 +1,117 @@ +error[E0382]: use of moved value: `a` + --> $DIR/dbg-issue-120327.rs:4:12 + | +LL | let a = String::new(); + | - move occurs because `a` has type `String`, which does not implement the `Copy` trait +LL | dbg!(a); + | ------- value moved here +LL | return a; + | ^ value used here after move + | +help: consider borrowing instead of transferring ownership + | +LL | dbg!(&a); + | + + +error[E0382]: use of moved value: `a` + --> $DIR/dbg-issue-120327.rs:10:12 + | +LL | let a = String::new(); + | - move occurs because `a` has type `String`, which does not implement the `Copy` trait +LL | dbg!(1, 2, a, 1, 2); + | ------------------- value moved here +LL | return a; + | ^ value used here after move + | +help: consider borrowing instead of transferring ownership + | +LL | dbg!(1, 2, &a, 1, 2); + | + + +error[E0382]: use of moved value: `b` + --> $DIR/dbg-issue-120327.rs:16:12 + | +LL | let b: String = "".to_string(); + | - move occurs because `b` has type `String`, which does not implement the `Copy` trait +LL | dbg!(a, b); + | ---------- value moved here +LL | return b; + | ^ value used here after move + | +help: consider borrowing instead of transferring ownership + | +LL | dbg!(a, &b); + | + + +error[E0382]: use of moved value: `a` + --> $DIR/dbg-issue-120327.rs:22:12 + | +LL | fn x(a: String) -> String { + | - move occurs because `a` has type `String`, which does not implement the `Copy` trait +LL | let b: String = "".to_string(); +LL | dbg!(a, b); + | ---------- value moved here +LL | return a; + | ^ value used here after move + | +help: consider borrowing instead of transferring ownership + | +LL | dbg!(&a, b); + | + + +error[E0382]: use of moved value: `b` + --> $DIR/dbg-issue-120327.rs:46:12 + | +LL | tmp => { + | --- value moved here +... +LL | let b: String = "".to_string(); + | - move occurs because `b` has type `String`, which does not implement the `Copy` trait +LL | my_dbg!(b, 1); +LL | return b; + | ^ value used here after move + | +help: consider borrowing instead of transferring ownership + | +LL | my_dbg!(&b, 1); + | + +help: borrow this binding in the pattern to avoid moving the value + | +LL | ref tmp => { + | +++ + +error[E0382]: use of moved value: `a` + --> $DIR/dbg-issue-120327.rs:57:12 + | +LL | let a = String::new(); + | - move occurs because `a` has type `String`, which does not implement the `Copy` trait +LL | let _b = match a { +LL | tmp => { + | --- value moved here +... +LL | return a; + | ^ value used here after move + | +help: borrow this binding in the pattern to avoid moving the value + | +LL | ref tmp => { + | +++ + +error[E0382]: borrow of moved value: `a` + --> $DIR/dbg-issue-120327.rs:65:14 + | +LL | let a: String = "".to_string(); + | - move occurs because `a` has type `String`, which does not implement the `Copy` trait +LL | let _res = get_expr(dbg!(a)); + | ------- value moved here +LL | let _l = a.len(); + | ^ value borrowed here after move + | +help: consider borrowing instead of transferring ownership + | +LL | let _res = get_expr(dbg!(&a)); + | + + +error: aborting due to 7 previous errors + +For more information about this error, try `rustc --explain E0382`. diff --git a/tests/ui/rfcs/rfc-2361-dbg-macro/dbg-macro-move-semantics.stderr b/tests/ui/rfcs/rfc-2361-dbg-macro/dbg-macro-move-semantics.stderr index c2b9899e20db3..f515cb62c7cde 100644 --- a/tests/ui/rfcs/rfc-2361-dbg-macro/dbg-macro-move-semantics.stderr +++ b/tests/ui/rfcs/rfc-2361-dbg-macro/dbg-macro-move-semantics.stderr @@ -9,6 +9,10 @@ LL | let _ = dbg!(a); | ^^^^^^^ value used here after move | = note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info) +help: consider borrowing instead of transferring ownership + | +LL | let _ = dbg!(&a); + | + error: aborting due to 1 previous error