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chenyukangchenyukang
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Suggest a borrow when using dbg
1 parent c3d7fb3 commit 6ff8a84

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4 files changed

+250
-2
lines changed

4 files changed

+250
-2
lines changed

‎compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

+61-2
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
#![allow(rustc::untranslatable_diagnostic)]
55

66
use either::Either;
7-
use hir::ClosureKind;
7+
use hir::{ClosureKind, Path};
88
use rustc_data_structures::captures::Captures;
99
use rustc_data_structures::fx::FxIndexSet;
1010
use rustc_errors::{codes::*, struct_span_code_err, Applicability, Diag, MultiSpan};
@@ -494,7 +494,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
494494
self.suggest_cloning(err, ty, expr, None, Some(move_spans));
495495
}
496496
}
497-
if let Some(pat) = finder.pat {
497+
498+
self.suggest_ref_for_dbg_args(expr, span, move_span, err);
499+
500+
// it's useless to suggest inserting `ref` when the span don't comes from local code
501+
if let Some(pat) = finder.pat
502+
&& !move_span.is_dummy()
503+
&& !self.infcx.tcx.sess.source_map().is_imported(move_span)
504+
{
498505
*in_pattern = true;
499506
let mut sugg = vec![(pat.span.shrink_to_lo(), "ref ".to_string())];
500507
if let Some(pat) = finder.parent_pat {
@@ -509,6 +516,58 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
509516
}
510517
}
511518

519+
// for dbg!(x) which may take onwership, suggest dbg!(&x) instead
520+
// but here we actually do not check whether the macro name is `dbg!`
521+
// so that we may extend the scope a bit larger to cover more cases
522+
fn suggest_ref_for_dbg_args(
523+
&self,
524+
body: &hir::Expr<'_>,
525+
span: Option<Span>,
526+
move_span: Span,
527+
err: &mut Diag<'tcx>,
528+
) {
529+
let sm = self.infcx.tcx.sess.source_map();
530+
let arg_code = if let Some(span) = span
531+
&& let Ok(code) = sm.span_to_snippet(span)
532+
{
533+
code
534+
} else {
535+
return;
536+
};
537+
struct MatchArgFinder {
538+
expr_span: Span,
539+
match_arg_span: Option<Span>,
540+
arg_code: String,
541+
}
542+
impl Visitor<'_> for MatchArgFinder {
543+
fn visit_expr(&mut self, e: &hir::Expr<'_>) {
544+
// dbg! is expanded into a match pattern, we need to find the right argument span
545+
if let hir::ExprKind::Match(expr, ..) = &e.kind
546+
&& let hir::ExprKind::Path(hir::QPath::Resolved(
547+
_,
548+
path @ Path { segments: [seg], .. },
549+
)) = &expr.kind
550+
&& seg.ident.name.as_str() == &self.arg_code
551+
&& self.expr_span.source_callsite().contains(expr.span)
552+
{
553+
self.match_arg_span = Some(path.span);
554+
}
555+
hir::intravisit::walk_expr(self, e);
556+
}
557+
}
558+
559+
let mut finder = MatchArgFinder { expr_span: move_span, match_arg_span: None, arg_code };
560+
finder.visit_expr(body);
561+
if let Some(macro_arg_span) = finder.match_arg_span {
562+
err.span_suggestion_verbose(
563+
macro_arg_span.shrink_to_lo(),
564+
"consider borrowing instead of transferring ownership",
565+
"&",
566+
Applicability::MachineApplicable,
567+
);
568+
}
569+
}
570+
512571
fn report_use_of_uninitialized(
513572
&self,
514573
mpi: MovePathIndex,

‎tests/ui/borrowck/dbg-issue-120327.rs

+68
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,68 @@
1+
fn s() -> String {
2+
let a = String::new();
3+
dbg!(a);
4+
return a; //~ ERROR use of moved value:
5+
}
6+
7+
fn m() -> String {
8+
let a = String::new();
9+
dbg!(1, 2, a, 1, 2);
10+
return a; //~ ERROR use of moved value:
11+
}
12+
13+
fn t(a: String) -> String {
14+
let b: String = "".to_string();
15+
dbg!(a, b);
16+
return b; //~ ERROR use of moved value:
17+
}
18+
19+
fn x(a: String) -> String {
20+
let b: String = "".to_string();
21+
dbg!(a, b);
22+
return a; //~ ERROR use of moved value:
23+
}
24+
25+
macro_rules! my_dbg {
26+
() => {
27+
eprintln!("[{}:{}:{}]", file!(), line!(), column!())
28+
};
29+
($val:expr $(,)?) => {
30+
match $val {
31+
tmp => {
32+
eprintln!("[{}:{}:{}] {} = {:#?}",
33+
file!(), line!(), column!(), stringify!($val), &tmp);
34+
tmp
35+
}
36+
}
37+
};
38+
($($val:expr),+ $(,)?) => {
39+
($(my_dbg!($val)),+,)
40+
};
41+
}
42+
43+
fn test_my_dbg() -> String {
44+
let b: String = "".to_string();
45+
my_dbg!(b, 1);
46+
return b; //~ ERROR use of moved value:
47+
}
48+
49+
fn test_not_macro() -> String {
50+
let a = String::new();
51+
let _b = match a {
52+
tmp => {
53+
eprintln!("dbg: {}", tmp);
54+
tmp
55+
}
56+
};
57+
return a; //~ ERROR use of moved value:
58+
}
59+
60+
fn get_expr(_s: String) {}
61+
62+
fn test() {
63+
let a: String = "".to_string();
64+
let _res = get_expr(dbg!(a));
65+
let _l = a.len(); //~ ERROR borrow of moved value
66+
}
67+
68+
fn main() {}

‎tests/ui/borrowck/dbg-issue-120327.stderr

+117
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,117 @@
1+
error[E0382]: use of moved value: `a`
2+
--> $DIR/dbg-issue-120327.rs:4:12
3+
|
4+
LL | let a = String::new();
5+
| - move occurs because `a` has type `String`, which does not implement the `Copy` trait
6+
LL | dbg!(a);
7+
| ------- value moved here
8+
LL | return a;
9+
| ^ value used here after move
10+
|
11+
help: consider borrowing instead of transferring ownership
12+
|
13+
LL | dbg!(&a);
14+
| +
15+
16+
error[E0382]: use of moved value: `a`
17+
--> $DIR/dbg-issue-120327.rs:10:12
18+
|
19+
LL | let a = String::new();
20+
| - move occurs because `a` has type `String`, which does not implement the `Copy` trait
21+
LL | dbg!(1, 2, a, 1, 2);
22+
| ------------------- value moved here
23+
LL | return a;
24+
| ^ value used here after move
25+
|
26+
help: consider borrowing instead of transferring ownership
27+
|
28+
LL | dbg!(1, 2, &a, 1, 2);
29+
| +
30+
31+
error[E0382]: use of moved value: `b`
32+
--> $DIR/dbg-issue-120327.rs:16:12
33+
|
34+
LL | let b: String = "".to_string();
35+
| - move occurs because `b` has type `String`, which does not implement the `Copy` trait
36+
LL | dbg!(a, b);
37+
| ---------- value moved here
38+
LL | return b;
39+
| ^ value used here after move
40+
|
41+
help: consider borrowing instead of transferring ownership
42+
|
43+
LL | dbg!(a, &b);
44+
| +
45+
46+
error[E0382]: use of moved value: `a`
47+
--> $DIR/dbg-issue-120327.rs:22:12
48+
|
49+
LL | fn x(a: String) -> String {
50+
| - move occurs because `a` has type `String`, which does not implement the `Copy` trait
51+
LL | let b: String = "".to_string();
52+
LL | dbg!(a, b);
53+
| ---------- value moved here
54+
LL | return a;
55+
| ^ value used here after move
56+
|
57+
help: consider borrowing instead of transferring ownership
58+
|
59+
LL | dbg!(&a, b);
60+
| +
61+
62+
error[E0382]: use of moved value: `b`
63+
--> $DIR/dbg-issue-120327.rs:46:12
64+
|
65+
LL | tmp => {
66+
| --- value moved here
67+
...
68+
LL | let b: String = "".to_string();
69+
| - move occurs because `b` has type `String`, which does not implement the `Copy` trait
70+
LL | my_dbg!(b, 1);
71+
LL | return b;
72+
| ^ value used here after move
73+
|
74+
help: consider borrowing instead of transferring ownership
75+
|
76+
LL | my_dbg!(&b, 1);
77+
| +
78+
help: borrow this binding in the pattern to avoid moving the value
79+
|
80+
LL | ref tmp => {
81+
| +++
82+
83+
error[E0382]: use of moved value: `a`
84+
--> $DIR/dbg-issue-120327.rs:57:12
85+
|
86+
LL | let a = String::new();
87+
| - move occurs because `a` has type `String`, which does not implement the `Copy` trait
88+
LL | let _b = match a {
89+
LL | tmp => {
90+
| --- value moved here
91+
...
92+
LL | return a;
93+
| ^ value used here after move
94+
|
95+
help: borrow this binding in the pattern to avoid moving the value
96+
|
97+
LL | ref tmp => {
98+
| +++
99+
100+
error[E0382]: borrow of moved value: `a`
101+
--> $DIR/dbg-issue-120327.rs:65:14
102+
|
103+
LL | let a: String = "".to_string();
104+
| - move occurs because `a` has type `String`, which does not implement the `Copy` trait
105+
LL | let _res = get_expr(dbg!(a));
106+
| ------- value moved here
107+
LL | let _l = a.len();
108+
| ^ value borrowed here after move
109+
|
110+
help: consider borrowing instead of transferring ownership
111+
|
112+
LL | let _res = get_expr(dbg!(&a));
113+
| +
114+
115+
error: aborting due to 7 previous errors
116+
117+
For more information about this error, try `rustc --explain E0382`.

‎tests/ui/rfcs/rfc-2361-dbg-macro/dbg-macro-move-semantics.stderr

+4
Original file line numberDiff line numberDiff line change
@@ -9,6 +9,10 @@ LL | let _ = dbg!(a);
99
| ^^^^^^^ value used here after move
1010
|
1111
= note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
12+
help: consider borrowing instead of transferring ownership
13+
|
14+
LL | let _ = dbg!(&a);
15+
| +
1216

1317
error: aborting due to 1 previous error
1418

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