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Commit f926031

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When not finding assoc fn on type, look for builder fn
When we have a resolution error when looking at a fully qualified path on a type, look for all associated functions on inherent impls that return `Self` and mention them to the user. Fix #69512.
1 parent b049093 commit f926031

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8 files changed

+138
-0
lines changed

8 files changed

+138
-0
lines changed

‎compiler/rustc_hir_typeck/src/method/suggest.rs‎

Lines changed: 88 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -409,6 +409,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
409409
err.downgrade_to_delayed_bug();
410410
}
411411

412+
self.find_builder_fn(&mut err, rcvr_ty, source);
412413
if tcx.ty_is_opaque_future(rcvr_ty) && item_name.name == sym::poll {
413414
err.help(format!(
414415
"method `poll` found on `Pin<&mut {ty_str}>`, \
@@ -1407,6 +1408,93 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
14071408
}
14081409
}
14091410

1411+
/// Look at all the associated functions without receivers in the type's inherent impls
1412+
/// to look for builders that return `Self`, `Option<Self>` or `Result<Self, _>`.
1413+
fn find_builder_fn(&self, err: &mut Diagnostic, rcvr_ty: Ty<'tcx>, source: SelfSource<'tcx>) {
1414+
let ty::Adt(adt_def, _) = rcvr_ty.kind() else {
1415+
return;
1416+
};
1417+
let SelfSource::QPath(ty) = source else {
1418+
return;
1419+
};
1420+
let hir = self.tcx.hir();
1421+
if let Some(Node::Pat(_)) = hir.find(hir.parent_id(ty.hir_id)) {
1422+
// Do not suggest a fn call when a pattern is expected.
1423+
return;
1424+
}
1425+
let mut items = self
1426+
.tcx
1427+
.inherent_impls(adt_def.did())
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.iter()
1429+
.flat_map(|i| self.tcx.associated_items(i).in_definition_order())
1430+
// Only assoc fn with no receivers.
1431+
.filter(|item| matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter)
1432+
.filter_map(|item| {
1433+
// Only assoc fns that return `Self`, `Option<Self>` or `Result<Self, _>`.
1434+
let ret_ty = self.tcx.fn_sig(item.def_id).skip_binder().output();
1435+
let ret_ty = self.tcx.erase_late_bound_regions(ret_ty);
1436+
let ty::Adt(def, args) = ret_ty.kind() else {
1437+
return None;
1438+
};
1439+
// Check for `-> Self`
1440+
if self.can_eq(self.param_env, ret_ty, rcvr_ty) {
1441+
return Some((item.def_id, ret_ty));
1442+
}
1443+
// Check for `-> Option<Self>` or `-> Result<Self, _>`
1444+
if ![self.tcx.lang_items().option_type(), self.tcx.get_diagnostic_item(sym::Result)]
1445+
.contains(&Some(def.did()))
1446+
{
1447+
return None;
1448+
}
1449+
let arg = args.get(0)?.expect_ty();
1450+
if self.can_eq(self.param_env, rcvr_ty, arg) {
1451+
Some((item.def_id, ret_ty))
1452+
} else {
1453+
None
1454+
}
1455+
})
1456+
.collect::<Vec<_>>();
1457+
let post = if items.len() > 5 {
1458+
let items_len = items.len();
1459+
items.truncate(4);
1460+
format!("\nand {} others", items_len - 4)
1461+
} else {
1462+
String::new()
1463+
};
1464+
match &items[..] {
1465+
[] => {}
1466+
[(def_id, ret_ty)] => {
1467+
err.span_note(
1468+
self.tcx.def_span(def_id),
1469+
format!(
1470+
"if you're trying to build a new `{rcvr_ty}`, consider using `{}` which \
1471+
returns `{ret_ty}`",
1472+
self.tcx.def_path_str(def_id),
1473+
),
1474+
);
1475+
}
1476+
_ => {
1477+
let span: MultiSpan = items
1478+
.iter()
1479+
.map(|(def_id, _)| self.tcx.def_span(def_id))
1480+
.collect::<Vec<Span>>()
1481+
.into();
1482+
err.span_note(
1483+
span,
1484+
format!(
1485+
"if you're trying to build a new `{rcvr_ty}` consider using one of the \
1486+
following associated functions:\n{}{post}",
1487+
items
1488+
.iter()
1489+
.map(|(def_id, _ret_ty)| self.tcx.def_path_str(def_id))
1490+
.collect::<Vec<String>>()
1491+
.join("\n")
1492+
),
1493+
);
1494+
}
1495+
}
1496+
}
1497+
14101498
/// Suggest calling `Ty::method` if `.method()` isn't found because the method
14111499
/// doesn't take a `self` receiver.
14121500
fn suggest_associated_call_syntax(

‎tests/ui/atomic-from-mut-not-available.stderr‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,10 @@ error[E0599]: no function or associated item named `from_mut` found for struct `
33
|
44
LL | core::sync::atomic::AtomicU64::from_mut(&mut 0u64);
55
| ^^^^^^^^ function or associated item not found in `AtomicU64`
6+
|
7+
note: if you're trying to build a new `AtomicU64`, consider using `AtomicU64::new` which returns `AtomicU64`
8+
--> $SRC_DIR/core/src/sync/atomic.rs:LL:COL
9+
= note: this error originates in the macro `atomic_int` (in Nightly builds, run with -Z macro-backtrace for more info)
610

711
error: aborting due to previous error
812

‎tests/ui/parser/emoji-identifiers.stderr‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -75,6 +75,12 @@ LL | 👀::full_of✨()
7575
| |
7676
| function or associated item not found in `👀`
7777
| help: there is an associated function with a similar name: `full_of_✨`
78+
|
79+
note: if you're trying to build a new `👀`, consider using `👀::full_of_✨` which returns `👀`
80+
--> $DIR/emoji-identifiers.rs:4:5
81+
|
82+
LL | fn full_of_✨() -> 👀 {
83+
| ^^^^^^^^^^^^^^^^^^^^^
7884

7985
error[E0425]: cannot find function `i_like_to_😄_a_lot` in this scope
8086
--> $DIR/emoji-identifiers.rs:13:13
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
1+
use std::net::TcpStream;
2+
3+
fn main() {
4+
let stream = TcpStream::new(); //~ ERROR no function or associated item named `new` found
5+
}
Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,14 @@
1+
error[E0599]: no function or associated item named `new` found for struct `TcpStream` in the current scope
2+
--> $DIR/fn-new-doesnt-exist.rs:4:28
3+
|
4+
LL | let stream = TcpStream::new();
5+
| ^^^ function or associated item not found in `TcpStream`
6+
|
7+
note: if you're trying to build a new `TcpStream` consider using one of the following associated functions:
8+
TcpStream::connect
9+
TcpStream::connect_timeout
10+
--> $SRC_DIR/std/src/net/tcp.rs:LL:COL
11+
12+
error: aborting due to previous error
13+
14+
For more information about this error, try `rustc --explain E0599`.

‎tests/ui/resolve/issue-82865.stderr‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -15,6 +15,13 @@ LL | Box::z
1515
LL | mac!();
1616
| ------ in this macro invocation
1717
|
18+
note: if you're trying to build a new `Box<_, _>` consider using one of the following associated functions:
19+
Box::<T>::new
20+
Box::<T>::new_uninit
21+
Box::<T>::new_zeroed
22+
Box::<T>::try_new
23+
and 18 others
24+
--> $SRC_DIR/alloc/src/boxed.rs:LL:COL
1825
= note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
1926

2027
error: aborting due to 2 previous errors

‎tests/ui/suggestions/deref-path-method.stderr‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4,6 +4,13 @@ error[E0599]: no function or associated item named `contains` found for struct `
44
LL | Vec::contains(&vec, &0);
55
| ^^^^^^^^ function or associated item not found in `Vec<_, _>`
66
|
7+
note: if you're trying to build a new `Vec<_, _>` consider using one of the following associated functions:
8+
Vec::<T>::new
9+
Vec::<T>::with_capacity
10+
Vec::<T>::from_raw_parts
11+
Vec::<T, A>::new_in
12+
and 2 others
13+
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
714
help: the function `contains` is implemented on `[_]`
815
|
916
LL | <[_]>::contains(&vec, &0);

‎tests/ui/suggestions/issue-109291.stderr‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -6,6 +6,13 @@ LL | println!("Custom backtrace: {}", std::backtrace::Backtrace::forced_capt
66
| |
77
| function or associated item not found in `Backtrace`
88
| help: there is an associated function with a similar name: `force_capture`
9+
|
10+
note: if you're trying to build a new `Backtrace` consider using one of the following associated functions:
11+
Backtrace::capture
12+
Backtrace::force_capture
13+
Backtrace::disabled
14+
Backtrace::create
15+
--> $SRC_DIR/std/src/backtrace.rs:LL:COL
916

1017
error: aborting due to previous error
1118

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