Suggest field typo through derefs

Take into account implicit dereferences when suggesting fields.

```
error[E0609]: no field `longname` on type `Arc<S>`
  --> $DIR/suggest-field-through-deref.rs:10:15
   |
LL |     let _ = x.longname;
   |               ^^^^^^^^ help: a field with a similar name exists: `long_name`
```

CC rust-lang#78374 (comment)

Author: estebank

compiler/rustc_hir_typeck/src/expr.rs

@@ -2471,9 +2471,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ty::RawPtr(..) => {
                 self.suggest_first_deref_field(&mut err, expr, base, ident);
             }
-            ty::Adt(def, _) if !def.is_enum() => {
-                self.suggest_fields_on_recordish(&mut err, expr, def, ident);
-            }
             ty::Param(param_ty) => {
                 self.point_at_param_definition(&mut err, param_ty);
             }
@@ -2633,34 +2630,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.span_label(param_span, format!("type parameter '{param_name}' declared here"));
     }
 
-    fn suggest_fields_on_recordish(
-        &self,
-        err: &mut Diagnostic,
-        expr: &hir::Expr<'_>,
-        def: ty::AdtDef<'tcx>,
-        field: Ident,
-    ) {
-        let available_field_names = self.available_field_names(def.non_enum_variant(), expr, &[]);
-        if let Some(suggested_field_name) =
-            find_best_match_for_name(&available_field_names, field.name, None)
-        {
-            err.span_suggestion(
-                field.span,
-                "a field with a similar name exists",
-                suggested_field_name,
-                Applicability::MaybeIncorrect,
-            );
-        } else {
-            err.span_label(field.span, "unknown field");
-            if !available_field_names.is_empty() {
-                err.note(format!(
-                    "available fields are: {}",
-                    self.name_series_display(available_field_names),
-                ));
-            }
-        }
-    }
-
     fn maybe_suggest_array_indexing(
         &self,
         err: &mut Diagnostic,
@@ -2709,18 +2678,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let mut err = type_error_struct!(
             self.tcx().sess,
-            field.span,
+            span,
             expr_t,
             E0609,
             "no field `{field}` on type `{expr_t}`",
         );
 
         // try to add a suggestion in case the field is a nested field of a field of the Adt
         let mod_id = self.tcx.parent_module(id).to_def_id();
-        if let Some((fields, args)) =
-            self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
+        for (found_fields, args) in
+            self.get_field_candidates_considering_privacy(span, expr_t, mod_id, id)
         {
-            let candidate_fields: Vec<_> = fields
+            let field_names = found_fields.iter().map(|field| field.name).collect::<Vec<_>>();
+            let candidate_fields: Vec<_> = found_fields
+                .into_iter()
                 .filter_map(|candidate_field| {
                     self.check_for_nested_field_satisfying(
                         span,
@@ -2729,6 +2700,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         args,
                         vec![],
                         mod_id,
+                        id,
                     )
                 })
                 .map(|mut field_path| {
@@ -2753,6 +2725,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     candidate_fields.iter().map(|path| format!("{path}.")),
                     Applicability::MaybeIncorrect,
                 );
+            } else {
+                if let Some(field_name) = find_best_match_for_name(&field_names, field.name, None) {
+                    err.span_suggestion(
+                        field.span,
+                        "a field with a similar name exists",
+                        field_name,
+                        Applicability::MaybeIncorrect,
+                    );
+                } else if !field_names.is_empty() {
+                    let is = if field_names.len() == 1 { " is" } else { "s are" };
+                    err.note(format!(
+                        "available field{is}: {}",
+                        self.name_series_display(field_names),
+                    ));
+                }
             }
         }
         err
@@ -2781,33 +2768,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         base_ty: Ty<'tcx>,
         mod_id: DefId,
-    ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, GenericArgsRef<'tcx>)> {
+        hir_id: hir::HirId,
+    ) -> Vec<(Vec<&'tcx ty::FieldDef>, GenericArgsRef<'tcx>)> {
         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
 
-        for (base_t, _) in self.autoderef(span, base_ty) {
-            match base_t.kind() {
-                ty::Adt(base_def, args) if !base_def.is_enum() => {
-                    let tcx = self.tcx;
-                    let fields = &base_def.non_enum_variant().fields;
-                    // Some struct, e.g. some that impl `Deref`, have all private fields
-                    // because you're expected to deref them to access the _real_ fields.
-                    // This, for example, will help us suggest accessing a field through a `Box<T>`.
-                    if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
-                        continue;
+        self.autoderef(span, base_ty)
+            .filter_map(move |(base_t, _)| {
+                match base_t.kind() {
+                    ty::Adt(base_def, args) if !base_def.is_enum() => {
+                        let tcx = self.tcx;
+                        let fields = &base_def.non_enum_variant().fields;
+                        // Some struct, e.g. some that impl `Deref`, have all private fields
+                        // because you're expected to deref them to access the _real_ fields.
+                        // This, for example, will help us suggest accessing a field through a `Box<T>`.
+                        if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
+                            return None;
+                        }
+                        return Some((
+                            fields
+                                .iter()
+                                .filter(move |field| {
+                                    field.vis.is_accessible_from(mod_id, tcx)
+                                        && self.is_field_suggestable(field, hir_id, span)
+                                })
+                                // For compile-time reasons put a limit on number of fields we search
+                                .take(100)
+                                .collect::<Vec<_>>(),
+                            *args,
+                        ));
                     }
-                    return Some((
-                        fields
-                            .iter()
-                            .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
-                            // For compile-time reasons put a limit on number of fields we search
-                            .take(100),
-                        args,
-                    ));
+                    _ => None,
                 }
-                _ => {}
-            }
-        }
-        None
+            })
+            .collect()
     }
 
     /// This method is called after we have encountered a missing field error to recursively
@@ -2820,6 +2813,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         subst: GenericArgsRef<'tcx>,
         mut field_path: Vec<Ident>,
         mod_id: DefId,
+        hir_id: HirId,
     ) -> Option<Vec<Ident>> {
         debug!(
             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
@@ -2835,20 +2829,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let field_ty = candidate_field.ty(self.tcx, subst);
             if matches(candidate_field, field_ty) {
                 return Some(field_path);
-            } else if let Some((nested_fields, subst)) =
-                self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
-            {
-                // recursively search fields of `candidate_field` if it's a ty::Adt
-                for field in nested_fields {
-                    if let Some(field_path) = self.check_for_nested_field_satisfying(
-                        span,
-                        matches,
-                        field,
-                        subst,
-                        field_path.clone(),
-                        mod_id,
-                    ) {
-                        return Some(field_path);
+            } else {
+                for (nested_fields, subst) in
+                    self.get_field_candidates_considering_privacy(span, field_ty, mod_id, hir_id)
+                {
+                    // recursively search fields of `candidate_field` if it's a ty::Adt
+                    for field in nested_fields {
+                        if let Some(field_path) = self.check_for_nested_field_satisfying(
+                            span,
+                            matches,
+                            field,
+                            subst,
+                            field_path.clone(),
+                            mod_id,
+                            hir_id,
+                        ) {
+                            return Some(field_path);
+                        }
                     }
                 }
             }

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1983,69 +1983,72 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         item_name: Ident,
         return_type: Option<Ty<'tcx>>,
     ) {
-        if let SelfSource::MethodCall(expr) = source
-            && let mod_id = self.tcx.parent_module(expr.hir_id).to_def_id()
-            && let Some((fields, args)) =
-                self.get_field_candidates_considering_privacy(span, actual, mod_id)
-        {
-            let call_expr = self.tcx.hir().expect_expr(self.tcx.hir().parent_id(expr.hir_id));
+        if let SelfSource::MethodCall(expr) = source {
+            let mod_id = self.tcx.parent_module(expr.hir_id).to_def_id();
+            for (fields, args) in
+                self.get_field_candidates_considering_privacy(span, actual, mod_id, expr.hir_id)
+            {
+                let call_expr = self.tcx.hir().expect_expr(self.tcx.hir().parent_id(expr.hir_id));
 
-            let lang_items = self.tcx.lang_items();
-            let never_mention_traits = [
-                lang_items.clone_trait(),
-                lang_items.deref_trait(),
-                lang_items.deref_mut_trait(),
-                self.tcx.get_diagnostic_item(sym::AsRef),
-                self.tcx.get_diagnostic_item(sym::AsMut),
-                self.tcx.get_diagnostic_item(sym::Borrow),
-                self.tcx.get_diagnostic_item(sym::BorrowMut),
-            ];
-            let candidate_fields: Vec<_> = fields
-                .filter_map(|candidate_field| {
-                    self.check_for_nested_field_satisfying(
-                        span,
-                        &|_, field_ty| {
-                            self.lookup_probe_for_diagnostic(
-                                item_name,
-                                field_ty,
-                                call_expr,
-                                ProbeScope::TraitsInScope,
-                                return_type,
-                            )
-                            .is_ok_and(|pick| {
-                                !never_mention_traits
-                                    .iter()
-                                    .flatten()
-                                    .any(|def_id| self.tcx.parent(pick.item.def_id) == *def_id)
-                            })
-                        },
-                        candidate_field,
-                        args,
-                        vec![],
-                        mod_id,
-                    )
-                })
-                .map(|field_path| {
-                    field_path
-                        .iter()
-                        .map(|id| id.name.to_ident_string())
-                        .collect::<Vec<String>>()
-                        .join(".")
-                })
-                .collect();
+                let lang_items = self.tcx.lang_items();
+                let never_mention_traits = [
+                    lang_items.clone_trait(),
+                    lang_items.deref_trait(),
+                    lang_items.deref_mut_trait(),
+                    self.tcx.get_diagnostic_item(sym::AsRef),
+                    self.tcx.get_diagnostic_item(sym::AsMut),
+                    self.tcx.get_diagnostic_item(sym::Borrow),
+                    self.tcx.get_diagnostic_item(sym::BorrowMut),
+                ];
+                let candidate_fields: Vec<_> = fields
+                    .iter()
+                    .filter_map(|candidate_field| {
+                        self.check_for_nested_field_satisfying(
+                            span,
+                            &|_, field_ty| {
+                                self.lookup_probe_for_diagnostic(
+                                    item_name,
+                                    field_ty,
+                                    call_expr,
+                                    ProbeScope::TraitsInScope,
+                                    return_type,
+                                )
+                                .is_ok_and(|pick| {
+                                    !never_mention_traits
+                                        .iter()
+                                        .flatten()
+                                        .any(|def_id| self.tcx.parent(pick.item.def_id) == *def_id)
+                                })
+                            },
+                            candidate_field,
+                            args,
+                            vec![],
+                            mod_id,
+                            expr.hir_id,
+                        )
+                    })
+                    .map(|field_path| {
+                        field_path
+                            .iter()
+                            .map(|id| id.name.to_ident_string())
+                            .collect::<Vec<String>>()
+                            .join(".")
+                    })
+                    .collect();
 
-            let len = candidate_fields.len();
-            if len > 0 {
-                err.span_suggestions(
-                    item_name.span.shrink_to_lo(),
-                    format!(
-                        "{} of the expressions' fields {} a method of the same name",
-                        if len > 1 { "some" } else { "one" },
-                        if len > 1 { "have" } else { "has" },
-                    ),
-                    candidate_fields.iter().map(|path| format!("{path}.")),
-                    Applicability::MaybeIncorrect,
-                );
+                let len = candidate_fields.len();
+                if len > 0 {
+                    err.span_suggestions(
+                        item_name.span.shrink_to_lo(),
+                        format!(
+                            "{} of the expressions' fields {} a method of the same name",
+                            if len > 1 { "some" } else { "one" },
+                            if len > 1 { "have" } else { "has" },
+                        ),
+                        candidate_fields.iter().map(|path| format!("{path}.")),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
             }
         }
     }

tests/ui/async-await/suggest-switching-edition-on-await-cargo.rs

@@ -10,7 +10,6 @@ fn await_on_struct_missing() {
     let x = S;
     x.await;
     //~^ ERROR no field `await` on type
-    //~| NOTE unknown field
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
     //~| HELP set `edition = "2021"` in `Cargo.toml`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
@@ -32,7 +31,6 @@ fn await_on_struct_similar() {
 fn await_on_63533(x: Pin<&mut dyn Future<Output = ()>>) {
     x.await;
     //~^ ERROR no field `await` on type
-    //~| NOTE unknown field
     //~| NOTE to `.await` a `Future`, switch to Rust 2018
     //~| HELP set `edition = "2021"` in `Cargo.toml`
     //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide

tests/ui/async-await/suggest-switching-edition-on-await-cargo.stderr

@@ -2,14 +2,14 @@ error[E0609]: no field `await` on type `await_on_struct_missing::S`
   --> $DIR/suggest-switching-edition-on-await-cargo.rs:11:7
    |
 LL |     x.await;
-   |       ^^^^^ unknown field
+   |       ^^^^^
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
    = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `await_on_struct_similar::S`
-  --> $DIR/suggest-switching-edition-on-await-cargo.rs:24:7
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:23:7
    |
 LL |     x.await;
    |       ^^^^^ help: a field with a similar name exists: `awai`
@@ -19,17 +19,17 @@ LL |     x.await;
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `Pin<&mut dyn Future<Output = ()>>`
-  --> $DIR/suggest-switching-edition-on-await-cargo.rs:33:7
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:32:7
    |
 LL |     x.await;
-   |       ^^^^^ unknown field
+   |       ^^^^^
    |
    = note: to `.await` a `Future`, switch to Rust 2018 or later
    = help: set `edition = "2021"` in `Cargo.toml`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
 error[E0609]: no field `await` on type `impl Future<Output = ()>`
-  --> $DIR/suggest-switching-edition-on-await-cargo.rs:42:7
+  --> $DIR/suggest-switching-edition-on-await-cargo.rs:40:7
    |
 LL |     x.await;
    |       ^^^^^