3 files changed, 25 insertions, 6 deletions
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 9795299ed6d..dc26d4de57a 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1183,7 +1183,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             let in_module_is_extern = !in_module.def_id().is_local();
             in_module.for_each_child(self, |this, ident, ns, name_binding| {
                 // avoid non-importable candidates
-                if !name_binding.is_importable() {
+                if !name_binding.is_importable()
+                    // FIXME(import_trait_associated_functions): remove this when `import_trait_associated_functions` is stable
+                    || name_binding.is_assoc_const_or_fn()
+                        && !this.tcx.features().import_trait_associated_functions()
+                {
                     return;
                 }
 
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 5b1d8d622bd..cad45d3c293 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -17,9 +17,10 @@ use rustc_session::lint::builtin::{
     AMBIGUOUS_GLOB_REEXPORTS, HIDDEN_GLOB_REEXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE,
     REDUNDANT_IMPORTS, UNUSED_IMPORTS,
 };
+use rustc_session::parse::feature_err;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::hygiene::LocalExpnId;
-use rustc_span::{Ident, Span, Symbol, kw};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 use smallvec::SmallVec;
 use tracing::debug;
 
@@ -829,6 +830,17 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     // Don't update the resolution, because it was never added.
                     Err(Determined) if target.name == kw::Underscore => {}
                     Ok(binding) if binding.is_importable() => {
+                        if binding.is_assoc_const_or_fn()
+                            && !this.tcx.features().import_trait_associated_functions()
+                        {
+                            feature_err(
+                                this.tcx.sess,
+                                sym::import_trait_associated_functions,
+                                import.span,
+                                "`use` associated items of traits is unstable",
+                            )
+                            .emit();
+                        }
                         let imported_binding = this.import(binding, import);
                         target_bindings[ns].set(Some(imported_binding));
                         this.define(parent, target, ns, imported_binding);
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index cc9ed566eda..8e457e68eec 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -920,10 +920,13 @@ impl<'ra> NameBindingData<'ra> {
     }
 
     fn is_importable(&self) -> bool {
-        !matches!(
-            self.res(),
-            Res::Def(DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy, _)
-        )
+        !matches!(self.res(), Res::Def(DefKind::AssocTy, _))
+    }
+
+    // FIXME(import_trait_associated_functions): associate `const` or `fn` are not importable unless
+    // the feature `import_trait_associated_functions` is enable
+    fn is_assoc_const_or_fn(&self) -> bool {
+        matches!(self.res(), Res::Def(DefKind::AssocConst | DefKind::AssocFn, _))
     }
 
     fn macro_kind(&self) -> Option<MacroKind> {