fix incorrect suggestions in private import diagnostic

compiler/rustc_resolve/src/diagnostics.rs

@@ -2307,7 +2307,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         self.mention_default_field_values(source, ident, &mut err);
 
-        let mut not_publicly_reexported = false;
         if let Some((this_res, outer_ident)) = outermost_res {
             let mut import_suggestions = self.lookup_import_candidates(
                 outer_ident,
@@ -2332,7 +2331,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             );
             // If we suggest importing a public re-export, don't point at the definition.
             if point_to_def && ident.span != outer_ident.span {
-                not_publicly_reexported = true;
                 let label = errors::OuterIdentIsNotPubliclyReexported {
                     span: outer_ident.span,
                     outer_ident_descr: this_res.descr(),
@@ -2408,7 +2406,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let first_binding = decl;
         let mut next_binding = Some(decl);
         let mut next_ident = ident;
-        let mut path = vec![];
         while let Some(binding) = next_binding {
             let name = next_ident;
             next_binding = match binding.kind {
@@ -2428,18 +2425,18 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             };
 
             match binding.kind {
-                DeclKind::Import { import, .. } => {
-                    for segment in import.module_path.iter().skip(1) {
-                        // Don't include `{{root}}` in suggestions - it's an internal symbol
-                        // that should never be shown to users.
-                        if segment.ident.name != kw::PathRoot {
-                            path.push(segment.ident);
-                        }
-                    }
-                    sugg_paths.push((
-                        path.iter().cloned().chain(std::iter::once(ident)).collect::<Vec<_>>(),
-                        true, // re-export
-                    ));
+                DeclKind::Import { source_decl, import, .. } => {
+                    // Don't include `{{root}}` in suggestions - it's an internal symbol
+                    // that should never be shown to users.
+                    let path = import
+                        .module_path
+                        .iter()
+                        .filter(|seg| seg.ident.name != kw::PathRoot)
+                        .map(|seg| seg.ident.clone())
+                        .chain(std::iter::once(ident))
+                        .collect::<Vec<_>>();
+                    let through_reexport = !matches!(source_decl.kind, DeclKind::Def(_));
+                    sugg_paths.push((path, through_reexport));
                 }
                 DeclKind::Def(_) => {}
             }
@@ -2472,25 +2469,34 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             };
             err.subdiagnostic(note);
         }
-        // We prioritize shorter paths, non-core imports and direct imports over the alternatives.
-        sugg_paths.sort_by_key(|(p, reexport)| (p.len(), p[0].name == sym::core, *reexport));
-        for (sugg, reexport) in sugg_paths {
-            if not_publicly_reexported {
+        // The suggestion replaces `dedup_span` with a path reaching the failing ident.
+        // That's valid only when
+        // 1) the failing ident is the imported leaf, otherwise `as` renames and trailing segments
+        //    get dropped, and
+        // 2) the use isn't nested, otherwise `dedup_span` is one ident in `{...}`.
+        //
+        // See issue #156060.
+        let can_replace_use =
+            !single_nested && !outermost_res.is_some_and(|(_, outer)| outer.span != ident.span);
+        if can_replace_use {
+            // We prioritize shorter paths, non-core imports and direct imports over the
+            // alternatives.
+            sugg_paths.sort_by_key(|(p, reexport)| (p.len(), p[0].name == sym::core, *reexport));
+            for (sugg, reexport) in sugg_paths {
+                if sugg.len() <= 1 {
+                    // A single path segment suggestion is wrong. This happens on circular
+                    // imports. `tests/ui/imports/issue-55884-2.rs`
+                    continue;
+                }
+                let path = join_path_idents(sugg);
+                let sugg = if reexport {
+                    errors::ImportIdent::ThroughReExport { span: dedup_span, ident, path }
+                } else {
+                    errors::ImportIdent::Directly { span: dedup_span, ident, path }
+                };
+                err.subdiagnostic(sugg);
                 break;
             }
-            if sugg.len() <= 1 {
-                // A single path segment suggestion is wrong. This happens on circular imports.
-                // `tests/ui/imports/issue-55884-2.rs`
-                continue;
-            }
-            let path = join_path_idents(sugg);
-            let sugg = if reexport {
-                errors::ImportIdent::ThroughReExport { span: dedup_span, ident, path }
-            } else {
-                errors::ImportIdent::Directly { span: dedup_span, ident, path }
-            };
-            err.subdiagnostic(sugg);
-            break;
         }
 
         err.emit();

tests/ui/imports/ambiguous-import-visibility-globglob-priv.stderr

@@ -14,10 +14,10 @@ note: ...and refers to the struct `S` which is defined here
    |
 LL |     pub struct S {}
    |     ^^^^^^^^^^^^ you could import this directly
-help: import `S` through the re-export
+help: import `S` directly
    |
 LL - use crate::both::private::S;
-LL + use m::S;
+LL + use crate::m::S;
    |
 
 error[E0603]: struct import `S` is private
@@ -36,10 +36,10 @@ note: ...and refers to the struct `S` which is defined here
    |
 LL |     pub struct S {}
    |     ^^^^^^^^^^^^ you could import this directly
-help: import `S` through the re-export
+help: import `S` directly
    |
 LL -     use crate::both::private::S;
-LL +     use m::S;
+LL +     use crate::m::S;
    |
 
 error: aborting due to 2 previous errors

tests/ui/imports/issue-55884-2.stderr

@@ -24,6 +24,11 @@ note: ...and refers to the struct `ParseOptions` which is defined here
    |
 LL |     pub struct ParseOptions {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^ you could import this directly
+help: import `ParseOptions` directly
+   |
+LL - pub use parser::ParseOptions;
+LL + pub use options::ParseOptions;
+   |
 
 error: aborting due to 1 previous error
 

tests/ui/imports/private-import-nested-suggestion-156060.rs

@@ -0,0 +1,17 @@
+// Regression test for #156060.
+
+mod one {
+    pub struct One();
+}
+
+mod two {
+    use crate::one::One;
+    pub struct Two();
+}
+
+mod test {
+    use crate::two::{One, Two};
+    //~^ ERROR struct import `One` is private [E0603]
+}
+
+fn main() {}

tests/ui/imports/private-import-nested-suggestion-156060.stderr

@@ -0,0 +1,20 @@
+error[E0603]: struct import `One` is private
+  --> $DIR/private-import-nested-suggestion-156060.rs:13:22
+   |
+LL |     use crate::two::{One, Two};
+   |                      ^^^ private struct import
+   |
+note: the struct import `One` is defined here...
+  --> $DIR/private-import-nested-suggestion-156060.rs:8:9
+   |
+LL |     use crate::one::One;
+   |         ^^^^^^^^^^^^^^^
+note: ...and refers to the struct `One` which is defined here
+  --> $DIR/private-import-nested-suggestion-156060.rs:4:5
+   |
+LL |     pub struct One();
+   |     ^^^^^^^^^^^^^^^^^ you could import this directly
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0603`.

tests/ui/imports/private-import-suggestion-path-156244.edition_2015.stderr

@@ -0,0 +1,81 @@
+error[E0603]: struct import `One` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:17:12
+   |
+LL |     use b::One;
+   |            ^^^ private struct import
+   |
+note: the struct import `One` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:12:20
+   |
+LL |     use crate::a::{One, Two};
+   |                    ^^^
+note: ...and refers to the struct `One` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:7:5
+   |
+LL |     pub struct One;
+   |     ^^^^^^^^^^^^^^^ you could import this directly
+help: import `One` directly
+   |
+LL -     use b::One;
+LL +     use crate::a::One;
+   |
+
+error[E0603]: struct import `One` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:35:20
+   |
+LL |     use crate::b::{One, Two};
+   |                    ^^^ private struct import
+   |
+note: the struct import `One` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:12:20
+   |
+LL |     use crate::a::{One, Two};
+   |                    ^^^
+note: ...and refers to the struct `One` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:7:5
+   |
+LL |     pub struct One;
+   |     ^^^^^^^^^^^^^^^ you could import this directly
+
+error[E0603]: struct import `Two` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:35:25
+   |
+LL |     use crate::b::{One, Two};
+   |                         ^^^ private struct import
+   |
+note: the struct import `Two` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:12:25
+   |
+LL |     use crate::a::{One, Two};
+   |                         ^^^
+note: ...and refers to the struct `Two` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:8:5
+   |
+LL |     pub struct Two;
+   |     ^^^^^^^^^^^^^^^ you could import this directly
+
+error[E0603]: module import `inner` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:38:24
+   |
+LL |     use crate::rename::inner::Item as Item1;
+   |                        ^^^^^ private module import
+   |
+note: the module import `inner` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:31:9
+   |
+LL |     use crate::outer::actual as inner;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: ...and refers to the module `actual` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:25:5
+   |
+LL |     pub mod actual {
+   |     ^^^^^^^^^^^^^^ you could import this directly
+help: consider importing this struct instead
+   |
+LL -     use crate::rename::inner::Item as Item1;
+LL +     use outer::actual::Item as Item1;
+   |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0603`.

tests/ui/imports/private-import-suggestion-path-156244.edition_2018.stderr

@@ -0,0 +1,81 @@
+error[E0603]: struct import `One` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:20:19
+   |
+LL |     use crate::b::One;
+   |                   ^^^ private struct import
+   |
+note: the struct import `One` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:12:20
+   |
+LL |     use crate::a::{One, Two};
+   |                    ^^^
+note: ...and refers to the struct `One` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:7:5
+   |
+LL |     pub struct One;
+   |     ^^^^^^^^^^^^^^^ you could import this directly
+help: import `One` directly
+   |
+LL -     use crate::b::One;
+LL +     use crate::a::One;
+   |
+
+error[E0603]: struct import `One` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:35:20
+   |
+LL |     use crate::b::{One, Two};
+   |                    ^^^ private struct import
+   |
+note: the struct import `One` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:12:20
+   |
+LL |     use crate::a::{One, Two};
+   |                    ^^^
+note: ...and refers to the struct `One` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:7:5
+   |
+LL |     pub struct One;
+   |     ^^^^^^^^^^^^^^^ you could import this directly
+
+error[E0603]: struct import `Two` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:35:25
+   |
+LL |     use crate::b::{One, Two};
+   |                         ^^^ private struct import
+   |
+note: the struct import `Two` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:12:25
+   |
+LL |     use crate::a::{One, Two};
+   |                         ^^^
+note: ...and refers to the struct `Two` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:8:5
+   |
+LL |     pub struct Two;
+   |     ^^^^^^^^^^^^^^^ you could import this directly
+
+error[E0603]: module import `inner` is private
+  --> $DIR/private-import-suggestion-path-156244.rs:38:24
+   |
+LL |     use crate::rename::inner::Item as Item1;
+   |                        ^^^^^ private module import
+   |
+note: the module import `inner` is defined here...
+  --> $DIR/private-import-suggestion-path-156244.rs:31:9
+   |
+LL |     use crate::outer::actual as inner;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: ...and refers to the module `actual` which is defined here
+  --> $DIR/private-import-suggestion-path-156244.rs:25:5
+   |
+LL |     pub mod actual {
+   |     ^^^^^^^^^^^^^^ you could import this directly
+help: consider importing this struct instead
+   |
+LL -     use crate::rename::inner::Item as Item1;
+LL +     use crate::outer::actual::Item as Item1;
+   |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0603`.

tests/ui/imports/private-import-suggestion-path-156244.rs

@@ -0,0 +1,42 @@
+// PR #156244 comment
+//@ revisions: edition_2015 edition_2018
+//@[edition_2015] edition: 2015
+//@[edition_2018] edition: 2018
+
+mod a {
+    pub struct One;
+    pub struct Two;
+}
+
+mod b {
+    use crate::a::{One, Two};
+}
+
+mod test {
+    #[cfg(edition_2015)]
+    use b::One;
+    //[edition_2015]~^ ERROR struct import `One` is private [E0603]
+    #[cfg(edition_2018)]
+    use crate::b::One;
+    //[edition_2018]~^ ERROR struct import `One` is private [E0603]
+}
+
+mod outer {
+    pub mod actual {
+        pub struct Item;
+    }
+}
+
+mod rename {
+    use crate::outer::actual as inner;
+}
+
+mod bad {
+    use crate::b::{One, Two};
+    //~^ ERROR struct import `One` is private [E0603]
+    //~| ERROR struct import `Two` is private [E0603]
+    use crate::rename::inner::Item as Item1;
+    //~^ ERROR module import `inner` is private [E0603]
+}
+
+fn main() {}

tests/ui/imports/private-std-reexport-suggest-public.stderr

@@ -13,7 +13,7 @@ note: ...and refers to the module `mem` which is defined here
   --> $SRC_DIR/std/src/lib.rs:LL:COL
    |
    = note: you could import this directly
-help: import `mem` through the re-export
+help: import `mem` directly
    |
 LL -     use foo::mem;
 LL +     use std::mem;