Tweak output of import suggestions

When both `std::` and `core::` items are available, only suggest the `std::` ones. We ensure that in `no_std` crates we suggest `core::` items. Ensure that the list of items suggested to be imported are always in the order of local crate items, `std`/`core` items and finally foreign crate items. Tweak wording of import suggestion: if there are multiple items but they are all of the same kind, we use the kind name and not the generic "items". Fix #83564.
rust-lang · Jun 13, 2024 · c88548b · c88548b
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diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
@@ -2783,33 +2783,56 @@ fn show_candidates(
     // by iterating through a hash map, so make sure they are ordered:
     for path_strings in [&mut accessible_path_strings, &mut inaccessible_path_strings] {
         path_strings.sort_by(|a, b| a.0.cmp(&b.0));
+        path_strings.dedup_by(|a, b| a.0 == b.0);
         let core_path_strings =
             path_strings.extract_if(|p| p.0.starts_with("core::")).collect::<Vec<_>>();
-        path_strings.extend(core_path_strings);
-        path_strings.dedup_by(|a, b| a.0 == b.0);
+        let std_path_strings =
+            path_strings.extract_if(|p| p.0.starts_with("std::")).collect::<Vec<_>>();
+        let foreign_crate_path_strings =
+            path_strings.extract_if(|p| !p.0.starts_with("crate::")).collect::<Vec<_>>();
+
+        // We list the `crate` local paths first.
+        // Then we list the `std`/`core` paths.
+        if std_path_strings.len() == core_path_strings.len() {
+            // Do not list `core::` paths if we are already listing the `std::` ones.
+            path_strings.extend(std_path_strings);
+        } else {
+            path_strings.extend(std_path_strings);
+            path_strings.extend(core_path_strings);
+        }
+        // List all paths from foreign crates last.
+        path_strings.extend(foreign_crate_path_strings);
     }
-    accessible_path_strings.sort();
 
     if !accessible_path_strings.is_empty() {
-        let (determiner, kind, name, through) =
-            if let [(name, descr, _, _, via_import)] = &accessible_path_strings[..] {
-                (
-                    "this",
-                    *descr,
-                    format!(" `{name}`"),
-                    if *via_import { " through its public re-export" } else { "" },
-                )
-            } else {
-                ("one of these", "items", String::new(), "")
-            };
+        let (determiner, kind, s, name, through) = if let [(name, descr, _, _, via_import)] =
+            &accessible_path_strings[..]
+        {
+            (
+                "this",
+                *descr,
+                "",
+                format!(" `{name}`"),
+                if *via_import { " through its public re-export" } else { "" },
+            )
+        } else {
+            let descr_set: FxHashSet<&str> =
+                accessible_path_strings.iter().map(|(_, descr, _, _, _)| *descr).collect();
+            let items =
+                if descr_set.len() == 1 { descr_set.into_iter().next().unwrap() } else { "item" };
+            let s = if items.ends_with('s') { "es" } else { "s" };
+
+            ("one of these", items, s, String::new(), "")
+        };
 
         let instead = if let Instead::Yes = instead { " instead" } else { "" };
         let mut msg = if let DiagMode::Pattern = mode {
             format!(
-                "if you meant to match on {kind}{instead}{name}, use the full path in the pattern",
+                "if you meant to match on {kind}{s}{instead}{name}, use the full path in the \
+                 pattern",
             )
         } else {
-            format!("consider importing {determiner} {kind}{through}{instead}")
+            format!("consider importing {determiner} {kind}{s}{through}{instead}")
         };
 
         for note in accessible_path_strings.iter().flat_map(|cand| cand.3.as_ref()) {

diff --git a/src/tools/clippy/tests/ui/crashes/ice-6252.stderr b/src/tools/clippy/tests/ui/crashes/ice-6252.stderr
@@ -4,9 +4,7 @@ error[E0412]: cannot find type `PhantomData` in this scope
 LL |     _n: PhantomData,
    |         ^^^^^^^^^^^ not found in this scope
    |
-help: consider importing one of these items
-   |
-LL + use core::marker::PhantomData;
+help: consider importing this struct
    |
 LL + use std::marker::PhantomData;
    |

diff --git a/tests/ui/const-generics/issues/issue-82956.stderr b/tests/ui/const-generics/issues/issue-82956.stderr
@@ -4,7 +4,7 @@ error[E0433]: failed to resolve: use of undeclared type `IntoIter`
 LL |         let mut iter = IntoIter::new(self);
    |                        ^^^^^^^^ use of undeclared type `IntoIter`
    |
-help: consider importing one of these items
+help: consider importing one of these structs
    |
 LL + use std::array::IntoIter;
    |

diff --git a/tests/ui/consts/const_refs_to_static-ice-121413.rs b/tests/ui/consts/const_refs_to_static-ice-121413.rs
@@ -5,12 +5,16 @@
 // ignore-tidy-linelength
 #![feature(const_refs_to_static)]
 const REF_INTERIOR_MUT: &usize = {
+    //~^ HELP consider importing this struct
     static FOO: Sync = AtomicUsize::new(0);
     //~^ ERROR failed to resolve: use of undeclared type `AtomicUsize`
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| ERROR the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
     //~| ERROR the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
     //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+    //~| HELP if this is an object-safe trait, use `dyn`
+    //~| HELP the trait `Sized` is not implemented for `(dyn Sync + 'static)`
+    //~| HELP the trait `Sized` is not implemented for `(dyn Sync + 'static)`
     unsafe { &*(&FOO as *const _ as *const usize) }
 };
 pub fn main() {}
diff --git a/tests/ui/consts/const_refs_to_static-ice-121413.stderr b/tests/ui/consts/const_refs_to_static-ice-121413.stderr
@@ -1,5 +1,5 @@
 error[E0433]: failed to resolve: use of undeclared type `AtomicUsize`
-  --> $DIR/const_refs_to_static-ice-121413.rs:8:24
+  --> $DIR/const_refs_to_static-ice-121413.rs:9:24
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                        ^^^^^^^^^^^ use of undeclared type `AtomicUsize`
@@ -10,7 +10,7 @@ LL + use std::sync::atomic::AtomicUsize;
    |
 
 warning: trait objects without an explicit `dyn` are deprecated
-  --> $DIR/const_refs_to_static-ice-121413.rs:8:17
+  --> $DIR/const_refs_to_static-ice-121413.rs:9:17
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                 ^^^^
@@ -24,15 +24,15 @@ LL |     static FOO: dyn Sync = AtomicUsize::new(0);
    |                 +++
 
 error[E0277]: the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
-  --> $DIR/const_refs_to_static-ice-121413.rs:8:17
+  --> $DIR/const_refs_to_static-ice-121413.rs:9:17
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                 ^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `(dyn Sync + 'static)`
 
 error[E0277]: the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
-  --> $DIR/const_refs_to_static-ice-121413.rs:8:24
+  --> $DIR/const_refs_to_static-ice-121413.rs:9:24
    |
 LL |     static FOO: Sync = AtomicUsize::new(0);
    |                        ^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time

diff --git a/tests/ui/did_you_mean/issue-56028-there-is-an-enum-variant.stderr b/tests/ui/did_you_mean/issue-56028-there-is-an-enum-variant.stderr
@@ -22,7 +22,7 @@ error[E0425]: cannot find value `Set` in this scope
 LL | fn setup() -> Set { Set }
    |                     ^^^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these unit variants
    |
 LL + use AffixHeart::Set;
    |

diff --git a/tests/ui/hygiene/extern-prelude-from-opaque-fail-2018.stderr b/tests/ui/hygiene/extern-prelude-from-opaque-fail-2018.stderr
@@ -24,8 +24,7 @@ LL |         fn f() { my_core::mem::drop(0); }
 LL | a!();
    | ---- in this macro invocation
    |
-   = help: consider importing one of these items:
-           core::mem
+   = help: consider importing this module:
            std::mem
    = note: this error originates in the macro `a` (in Nightly builds, run with -Z macro-backtrace for more info)
 
@@ -35,9 +34,7 @@ error[E0433]: failed to resolve: use of undeclared crate or module `my_core`
 LL |     fn f() { my_core::mem::drop(0); }
    |              ^^^^^^^ use of undeclared crate or module `my_core`
    |
-help: consider importing one of these items
-   |
-LL +     use core::mem;
+help: consider importing this module
    |
 LL +     use std::mem;
    |

diff --git a/tests/ui/imports/cycle-import-in-std-1.stderr b/tests/ui/imports/cycle-import-in-std-1.stderr
@@ -4,8 +4,7 @@ error[E0432]: unresolved import `ops`
 LL | use ops::{self as std};
    |           ^^^^^^^^^^^ no external crate `ops`
    |
-   = help: consider importing one of these items instead:
-           core::ops
+   = help: consider importing this module instead:
            std::ops
 
 error: aborting due to 1 previous error

diff --git a/tests/ui/imports/cycle-import-in-std-2.stderr b/tests/ui/imports/cycle-import-in-std-2.stderr
@@ -4,8 +4,7 @@ error[E0432]: unresolved import `ops`
 LL | use ops::{self as std};
    |           ^^^^^^^^^^^ no external crate `ops`
    |
-   = help: consider importing one of these items instead:
-           core::ops
+   = help: consider importing this module instead:
            std::ops
 
 error: aborting due to 1 previous error

diff --git a/tests/ui/imports/import-alias-issue-121168.edition2018.stderr b/tests/ui/imports/import-alias-issue-121168.edition2018.stderr
@@ -4,7 +4,7 @@ error[E0412]: cannot find type `Foo` in this scope
 LL |     let _: Foo<i32> = todo!();
    |            ^^^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these structs
    |
 LL + use crate::nice_crate_name::Foo;
    |

diff --git a/tests/ui/imports/import-alias-issue-121168.edition2021.stderr b/tests/ui/imports/import-alias-issue-121168.edition2021.stderr
@@ -4,7 +4,7 @@ error[E0412]: cannot find type `Foo` in this scope
 LL |     let _: Foo<i32> = todo!();
    |            ^^^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these structs
    |
 LL + use crate::nice_crate_name::Foo;
    |

diff --git a/tests/ui/imports/issue-56125.stderr b/tests/ui/imports/issue-56125.stderr
@@ -4,16 +4,16 @@ error[E0432]: unresolved import `empty::issue_56125`
 LL |     use empty::issue_56125;
    |         ^^^^^^^^^^^^^^^^^^ no `issue_56125` in `m3::empty`
    |
-help: consider importing one of these items instead
+help: consider importing one of these modules instead
    |
+LL |     use crate::m3::last_segment::issue_56125;
+   |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     use crate::m3::non_last_segment::non_last_segment::issue_56125;
+   |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 LL |     use ::issue_56125::issue_56125;
    |         ~~~~~~~~~~~~~~~~~~~~~~~~~~
 LL |     use ::issue_56125::last_segment::issue_56125;
    |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     use ::issue_56125::non_last_segment::non_last_segment::issue_56125;
-   |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     use crate::m3::last_segment::issue_56125;
-   |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      and 1 other candidate
 
 error[E0659]: `issue_56125` is ambiguous

diff --git a/tests/ui/lint/use_suggestion_json.stderr b/tests/ui/lint/use_suggestion_json.stderr
@@ -95,7 +95,7 @@ mod foo {
   ],
   "children": [
     {
-      "message": "consider importing one of these items",
+      "message": "consider importing one of these structs",
       "code": null,
       "level": "help",
       "spans": [
@@ -386,7 +386,7 @@ mod foo {
 \u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\u001b[0m \u001b[0m\u001b[0m    let x: Iter;\u001b[0m
 \u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m\u001b[0m            \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;9m^^^^\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;9mnot found in this scope\u001b[0m
 \u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
-\u001b[0m\u001b[1m\u001b[38;5;14mhelp\u001b[0m\u001b[0m: consider importing one of these items\u001b[0m
+\u001b[0m\u001b[1m\u001b[38;5;14mhelp\u001b[0m\u001b[0m: consider importing one of these structs\u001b[0m
 \u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m
 \u001b[0m\u001b[1m\u001b[38;5;12mLL\u001b[0m\u001b[0m \u001b[0m\u001b[0m\u001b[38;5;10m+ use std::collections::binary_heap::Iter;\u001b[0m
 \u001b[0m   \u001b[0m\u001b[0m\u001b[1m\u001b[38;5;12m|\u001b[0m

diff --git a/tests/ui/namespace/namespace-mix.stderr b/tests/ui/namespace/namespace-mix.stderr
@@ -12,7 +12,7 @@ help: a tuple struct with a similar name exists
    |
 LL |     check(m1::TS);
    |               ~~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use m2::S;
    |
@@ -40,7 +40,7 @@ help: a tuple struct with a similar name exists
    |
 LL |     check(xm1::TS);
    |                ~~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use m2::S;
    |
@@ -66,7 +66,7 @@ help: a tuple variant with a similar name exists
    |
 LL |     check(m7::TV);
    |               ~~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use m8::V;
    |
@@ -94,7 +94,7 @@ help: a tuple variant with a similar name exists
    |
 LL |     check(xm7::TV);
    |                ~~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use m8::V;
    |

diff --git a/tests/ui/resolve/issue-16058.stderr b/tests/ui/resolve/issue-16058.stderr
@@ -4,7 +4,7 @@ error[E0574]: expected struct, variant or union type, found enum `Result`
 LL |         Result {
    |         ^^^^^^ not a struct, variant or union type
    |
-help: consider importing one of these items instead
+help: consider importing one of these type aliases instead
    |
 LL + use std::fmt::Result;
    |

diff --git a/tests/ui/resolve/issue-21221-1.stderr b/tests/ui/resolve/issue-21221-1.stderr
@@ -4,29 +4,29 @@ error[E0405]: cannot find trait `Mul` in this scope
 LL | impl Mul for Foo {
    |      ^^^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these traits
+   |
+LL + use std::ops::Mul;
    |
 LL + use mul1::Mul;
    |
 LL + use mul2::Mul;
    |
-LL + use std::ops::Mul;
-   |
 
 error[E0412]: cannot find type `Mul` in this scope
   --> $DIR/issue-21221-1.rs:58:16
    |
 LL | fn getMul() -> Mul {
    |                ^^^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these traits
+   |
+LL + use std::ops::Mul;
    |
 LL + use mul1::Mul;
    |
 LL + use mul2::Mul;
    |
-LL + use std::ops::Mul;
-   |
 
 error[E0405]: cannot find trait `ThisTraitReallyDoesntExistInAnyModuleReally` in this scope
   --> $DIR/issue-21221-1.rs:63:6

diff --git a/tests/ui/resolve/issue-21221-2.stderr b/tests/ui/resolve/issue-21221-2.stderr
@@ -4,7 +4,7 @@ error[E0405]: cannot find trait `T` in this scope
 LL | impl T for Foo { }
    |      ^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these traits
    |
 LL + use baz::T;
    |

diff --git a/tests/ui/resolve/issue-50599.stderr b/tests/ui/resolve/issue-50599.stderr
@@ -4,7 +4,7 @@ error[E0425]: cannot find value `LOG10_2` in module `std::f64`
 LL |     const M: usize = (f64::from(N) * std::f64::LOG10_2) as usize;
    |                                                ^^^^^^^ not found in `std::f64`
    |
-help: consider importing one of these items
+help: consider importing one of these constants
    |
 LL + use std::f128::consts::LOG10_2;
    |

diff --git a/tests/ui/resolve/issue-73427.stderr b/tests/ui/resolve/issue-73427.stderr
@@ -105,7 +105,7 @@ help: the following enum variant is available
    |
 LL |     (E::TupleWithFields(/* fields */)).foo();
    |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use std::f128::consts::E;
    |

diff --git a/tests/ui/resolve/privacy-enum-ctor.stderr b/tests/ui/resolve/privacy-enum-ctor.stderr
@@ -82,7 +82,7 @@ help: a function with a similar name exists
    |
 LL |     let _: E = m::f;
    |                   ~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use std::f128::consts::E;
    |
@@ -123,7 +123,7 @@ help: alternatively, the following enum variant is available
    |
 LL |     let _: E = (E::Fn(/* fields */));
    |                ~~~~~~~~~~~~~~~~~~~~~
-help: consider importing one of these items instead
+help: consider importing one of these constants instead
    |
 LL + use std::f128::consts::E;
    |

diff --git a/tests/ui/rfcs/rfc-2126-extern-absolute-paths/not-allowed.stderr b/tests/ui/rfcs/rfc-2126-extern-absolute-paths/not-allowed.stderr
@@ -4,10 +4,8 @@ error[E0432]: unresolved import `alloc`
 LL | use alloc;
    |     ^^^^^ no external crate `alloc`
    |
-help: consider importing one of these items instead
+help: consider importing this module instead
    |
-LL | use core::alloc;
-   |     ~~~~~~~~~~~
 LL | use std::alloc;
    |     ~~~~~~~~~~
 

diff --git a/tests/ui/rust-2018/issue-52202-use-suggestions.stderr b/tests/ui/rust-2018/issue-52202-use-suggestions.stderr
@@ -4,7 +4,7 @@ error[E0422]: cannot find struct, variant or union type `Drain` in this scope
 LL |     let _d = Drain {};
    |              ^^^^^ not found in this scope
    |
-help: consider importing one of these items
+help: consider importing one of these structs
    |
 LL + use crate::plumbing::Drain;
    |