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Commit 22633fe

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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.
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‎compiler/rustc_hir_typeck/src/method/suggest.rs‎

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Original file line numberDiff line numberDiff line change
@@ -409,6 +409,86 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
409409
err.downgrade_to_delayed_bug();
410410
}
411411

412+
if let (ty::Adt(adt_def, _), SelfSource::QPath(_)) = (rcvr_ty.kind(), source) {
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// Look at all the associated functions without receivers in the type's inherent impls
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// to look for builders that return `Self`, `Option<Self>` or `Result<Self, _>`.
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let mut items = self
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.tcx
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.inherent_impls(adt_def.did())
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.iter()
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.flat_map(|i| self.tcx.associated_items(i).in_definition_order())
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.filter(|item| {
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// Only assoc fn with no receivers.
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matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter
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})
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.filter_map(|item| {
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// Only assoc fns that return `Self`, `Option<Self>` or `Result<Self, _>`.
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let ret_ty = self.tcx.fn_sig(item.def_id).skip_binder().output();
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let ret_ty = self.tcx.erase_late_bound_regions(ret_ty);
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let ty::Adt(def, args) = ret_ty.kind() else {
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return None;
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};
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// Check for `-> Self`
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if self.can_eq(self.param_env, ret_ty, rcvr_ty) {
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return Some((item.def_id, ret_ty));
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}
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// Check for `-> Option<Self>` or `-> Result<Self, _>`
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if ![
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self.tcx.lang_items().option_type(),
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self.tcx.get_diagnostic_item(sym::Result),
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]
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.contains(&Some(def.did()))
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{
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return None;
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}
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let arg = args.get(0)?.expect_ty();
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if self.can_eq(self.param_env, rcvr_ty, arg) {
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Some((item.def_id, ret_ty))
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} else {
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None
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}
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})
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.collect::<Vec<_>>();
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let post = if items.len() > 5 {
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let items_len = items.len();
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items.truncate(4);
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format!("\nand {} others", items_len - 4)
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} else {
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String::new()
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};
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match &items[..] {
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[] => {}
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[(def_id, ret_ty)] => {
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err.span_note(
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self.tcx.def_span(def_id),
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format!(
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"if you're trying to build a new `{rcvr_ty}`, consider using `{}` \
466+
which returns `{ret_ty}`",
467+
self.tcx.def_path_str(def_id),
468+
),
469+
);
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}
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_ => {
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let span: MultiSpan = items
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.iter()
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.map(|(def_id, _)| self.tcx.def_span(def_id))
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.collect::<Vec<Span>>()
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.into();
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err.span_note(
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span,
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format!(
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"if you're trying to build a new `{rcvr_ty}` consider using one of the \
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following associated functions:\n{}{post}",
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items
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.iter()
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.map(|(def_id, _ret_ty)| self.tcx.def_path_str(def_id))
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.collect::<Vec<String>>()
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.join("\n")
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),
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);
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}
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}
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};
412492
if tcx.ty_is_opaque_future(rcvr_ty) && item_name.name == sym::poll {
413493
err.help(format!(
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"method `poll` found on `Pin<&mut {ty_str}>`, \

‎tests/ui/issues/issue-42880.stderr‎

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,14 @@ error[E0599]: no associated item named `String` found for struct `String` in the
33
|
44
LL | let f = |&Value::String(_)| ();
55
| ^^^^^^ associated item not found in `String`
6+
|
7+
note: if you're trying to build a new `String` consider using one of the following associated functions:
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String::new
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String::with_capacity
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String::from_utf8
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String::from_utf16
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and 7 others
13+
--> $SRC_DIR/alloc/src/string.rs:LL:COL
614

715
error: aborting due to previous error
816

‎tests/ui/parser/emoji-identifiers.stderr‎

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Original file line numberDiff line numberDiff line change
@@ -75,6 +75,12 @@ LL | 👀::full_of✨()
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| |
7676
| function or associated item not found in `👀`
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| 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
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}
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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
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--> $DIR/fn-new-doesnt-exist.rs:4:28
3+
|
4+
LL | let stream = TcpStream::new();
5+
| ^^^ function or associated item not found in `TcpStream`
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|
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
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| |
77
| function or associated item not found in `Backtrace`
88
| help: there is an associated function with a similar name: `force_capture`
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|
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
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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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