Modify error message of importing inherent associated items when #[feature(import_trait_associated_functions)] is enabled

compiler/rustc_resolve/src/ident.rs

@@ -1943,11 +1943,23 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                             module_had_parse_errors,
                             module,
                             || {
-                                let label = format!(
-                                    "`{ident}` is {} {}, not a module",
-                                    res.article(),
-                                    res.descr()
-                                );
+                                // Excluding enums since their variants are valid import targets.
+                                let label = if matches!(
+                                    res,
+                                    Res::Def(DefKind::Struct | DefKind::Union, _,)
+                                ) && self
+                                    .tcx
+                                    .features()
+                                    .import_trait_associated_functions()
+                                {
+                                    "cannot import inherent associated items, only trait associated items".to_string()
+                                } else {
+                                    format!(
+                                        "`{ident}` is {} {}, not a module",
+                                        res.article(),
+                                        res.descr()
+                                    )
+                                };
                                 (label, None)
                             },
                         );

tests/ui/imports/import-inherent-148009.rs

@@ -0,0 +1,34 @@
+//! Check that when the feature `import_trait_associated_functions` is enabled,
+//! and one trys to import inherent associated items, the error message is
+//! updated to reflect that only trait associated items can be imported.
+//!
+//! Regression test for <https://github.com/rust-lang/rust/issues/148009>.
+
+//@ check-fail
+
+#![feature(import_trait_associated_functions)]
+
+pub struct TestStruct;
+
+impl TestStruct {
+    pub fn m1() {}
+    pub const C1: usize = 0;
+}
+
+pub use self::TestStruct::{C1, m1};
+//~^ ERROR unresolved import `self::TestStruct` [E0432]
+
+pub union TestUnion {
+    pub f: f32,
+    pub i: i32,
+}
+
+impl TestUnion {
+    pub fn m2() {}
+    pub const C2: usize = 0;
+}
+
+pub use self::TestUnion::{C2, m2};
+//~^ ERROR unresolved import `self::TestUnion` [E0432]
+
+fn main() {}

tests/ui/imports/import-inherent-148009.stderr

@@ -0,0 +1,15 @@
+error[E0432]: unresolved import `self::TestStruct`
+  --> $DIR/import-inherent-148009.rs:18:15
+   |
+LL | pub use self::TestStruct::{C1, m1};
+   |               ^^^^^^^^^^ cannot import inherent associated items, only trait associated items
+
+error[E0432]: unresolved import `self::TestUnion`
+  --> $DIR/import-inherent-148009.rs:31:15
+   |
+LL | pub use self::TestUnion::{C2, m2};
+   |               ^^^^^^^^^ cannot import inherent associated items, only trait associated items
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0432`.