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Auto merge of #117006 - estebank:issue-69512, r=compiler-errors
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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.

```
error[E0599]: no function or associated item named `new` found for struct `TcpStream` in the current scope
   --> tests/ui/resolve/fn-new-doesnt-exist.rs:4:28
    |
4   |    let stream = TcpStream::new();
    |                            ^^^ function or associated item not found in `TcpStream`
    |
note: if you're trying to build a new `TcpStream` consider using one of the following associated functions:
      TcpStream::connect
      TcpStream::connect_timeout
   --> /home/gh-estebank/rust/library/std/src/net/tcp.rs:156:5
    |
156 |     pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
172 |     pub fn connect_timeout(addr: &SocketAddr, timeout: Duration) -> io::Result<TcpStream> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Fix #69512.
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bors committed Nov 7, 2023
2 parents 7b97a5c + f926031 commit 4e0fb98
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Showing 8 changed files with 138 additions and 0 deletions.
88 changes: 88 additions & 0 deletions compiler/rustc_hir_typeck/src/method/suggest.rs
Original file line number Diff line number Diff line change
Expand Up @@ -409,6 +409,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
err.downgrade_to_delayed_bug();
}

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

/// Look at all the associated functions without receivers in the type's inherent impls
/// to look for builders that return `Self`, `Option<Self>` or `Result<Self, _>`.
fn find_builder_fn(&self, err: &mut Diagnostic, rcvr_ty: Ty<'tcx>, source: SelfSource<'tcx>) {
let ty::Adt(adt_def, _) = rcvr_ty.kind() else {
return;
};
let SelfSource::QPath(ty) = source else {
return;
};
let hir = self.tcx.hir();
if let Some(Node::Pat(_)) = hir.find(hir.parent_id(ty.hir_id)) {
// Do not suggest a fn call when a pattern is expected.
return;
}
let mut items = self
.tcx
.inherent_impls(adt_def.did())
.iter()
.flat_map(|i| self.tcx.associated_items(i).in_definition_order())
// Only assoc fn with no receivers.
.filter(|item| matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter)
.filter_map(|item| {
// Only assoc fns that return `Self`, `Option<Self>` or `Result<Self, _>`.
let ret_ty = self.tcx.fn_sig(item.def_id).skip_binder().output();
let ret_ty = self.tcx.erase_late_bound_regions(ret_ty);
let ty::Adt(def, args) = ret_ty.kind() else {
return None;
};
// Check for `-> Self`
if self.can_eq(self.param_env, ret_ty, rcvr_ty) {
return Some((item.def_id, ret_ty));
}
// Check for `-> Option<Self>` or `-> Result<Self, _>`
if ![self.tcx.lang_items().option_type(), self.tcx.get_diagnostic_item(sym::Result)]
.contains(&Some(def.did()))
{
return None;
}
let arg = args.get(0)?.expect_ty();
if self.can_eq(self.param_env, rcvr_ty, arg) {
Some((item.def_id, ret_ty))
} else {
None
}
})
.collect::<Vec<_>>();
let post = if items.len() > 5 {
let items_len = items.len();
items.truncate(4);
format!("\nand {} others", items_len - 4)
} else {
String::new()
};
match &items[..] {
[] => {}
[(def_id, ret_ty)] => {
err.span_note(
self.tcx.def_span(def_id),
format!(
"if you're trying to build a new `{rcvr_ty}`, consider using `{}` which \
returns `{ret_ty}`",
self.tcx.def_path_str(def_id),
),
);
}
_ => {
let span: MultiSpan = items
.iter()
.map(|(def_id, _)| self.tcx.def_span(def_id))
.collect::<Vec<Span>>()
.into();
err.span_note(
span,
format!(
"if you're trying to build a new `{rcvr_ty}` consider using one of the \
following associated functions:\n{}{post}",
items
.iter()
.map(|(def_id, _ret_ty)| self.tcx.def_path_str(def_id))
.collect::<Vec<String>>()
.join("\n")
),
);
}
}
}

/// Suggest calling `Ty::method` if `.method()` isn't found because the method
/// doesn't take a `self` receiver.
fn suggest_associated_call_syntax(
Expand Down
4 changes: 4 additions & 0 deletions tests/ui/atomic-from-mut-not-available.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,10 @@ error[E0599]: no function or associated item named `from_mut` found for struct `
|
LL | core::sync::atomic::AtomicU64::from_mut(&mut 0u64);
| ^^^^^^^^ function or associated item not found in `AtomicU64`
|
note: if you're trying to build a new `AtomicU64`, consider using `AtomicU64::new` which returns `AtomicU64`
--> $SRC_DIR/core/src/sync/atomic.rs:LL:COL
= note: this error originates in the macro `atomic_int` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

Expand Down
6 changes: 6 additions & 0 deletions tests/ui/parser/emoji-identifiers.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,12 @@ LL | 👀::full_of✨()
| |
| function or associated item not found in `👀`
| help: there is an associated function with a similar name: `full_of_✨`
|
note: if you're trying to build a new `👀`, consider using `👀::full_of_✨` which returns `👀`
--> $DIR/emoji-identifiers.rs:4:5
|
LL | fn full_of_✨() -> 👀 {
| ^^^^^^^^^^^^^^^^^^^^^

error[E0425]: cannot find function `i_like_to_😄_a_lot` in this scope
--> $DIR/emoji-identifiers.rs:13:13
Expand Down
5 changes: 5 additions & 0 deletions tests/ui/resolve/fn-new-doesnt-exist.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
use std::net::TcpStream;

fn main() {
let stream = TcpStream::new(); //~ ERROR no function or associated item named `new` found
}
14 changes: 14 additions & 0 deletions tests/ui/resolve/fn-new-doesnt-exist.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
error[E0599]: no function or associated item named `new` found for struct `TcpStream` in the current scope
--> $DIR/fn-new-doesnt-exist.rs:4:28
|
LL | let stream = TcpStream::new();
| ^^^ function or associated item not found in `TcpStream`
|
note: if you're trying to build a new `TcpStream` consider using one of the following associated functions:
TcpStream::connect
TcpStream::connect_timeout
--> $SRC_DIR/std/src/net/tcp.rs:LL:COL

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.
7 changes: 7 additions & 0 deletions tests/ui/resolve/issue-82865.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,13 @@ LL | Box::z
LL | mac!();
| ------ in this macro invocation
|
note: if you're trying to build a new `Box<_, _>` consider using one of the following associated functions:
Box::<T>::new
Box::<T>::new_uninit
Box::<T>::new_zeroed
Box::<T>::try_new
and 18 others
--> $SRC_DIR/alloc/src/boxed.rs:LL:COL
= note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 2 previous errors
Expand Down
7 changes: 7 additions & 0 deletions tests/ui/suggestions/deref-path-method.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,13 @@ error[E0599]: no function or associated item named `contains` found for struct `
LL | Vec::contains(&vec, &0);
| ^^^^^^^^ function or associated item not found in `Vec<_, _>`
|
note: if you're trying to build a new `Vec<_, _>` consider using one of the following associated functions:
Vec::<T>::new
Vec::<T>::with_capacity
Vec::<T>::from_raw_parts
Vec::<T, A>::new_in
and 2 others
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
help: the function `contains` is implemented on `[_]`
|
LL | <[_]>::contains(&vec, &0);
Expand Down
7 changes: 7 additions & 0 deletions tests/ui/suggestions/issue-109291.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,13 @@ LL | println!("Custom backtrace: {}", std::backtrace::Backtrace::forced_capt
| |
| function or associated item not found in `Backtrace`
| help: there is an associated function with a similar name: `force_capture`
|
note: if you're trying to build a new `Backtrace` consider using one of the following associated functions:
Backtrace::capture
Backtrace::force_capture
Backtrace::disabled
Backtrace::create
--> $SRC_DIR/std/src/backtrace.rs:LL:COL

error: aborting due to previous error

Expand Down

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