From eaf47a30cb67bf1e802ee29bb8021b19a4df6095 Mon Sep 17 00:00:00 2001
From: clubby789 <jamie@hill-daniel.co.uk>
Date: Tue, 16 May 2023 19:08:57 +0000
Subject: [PATCH] Better diagnostic for `use Self::..`

---
 compiler/rustc_resolve/src/diagnostics.rs | 12 +++++++++++-
 tests/ui/use/use-self-type.stderr         |  2 +-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 6675b8ed59b26..5b7d9e40e866b 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1832,7 +1832,17 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             }
             (msg, None)
         } else if ident.name == kw::SelfUpper {
-            ("`Self` is only available in impls, traits, and type definitions".to_string(), None)
+            // As mentioned above, `opt_ns` being `None` indicates a module path in import.
+            // We can use this to improve a confusing error for, e.g. `use Self::Variant` in an
+            // impl
+            if opt_ns.is_none() {
+                ("`Self` cannot be used in imports".to_string(), None)
+            } else {
+                (
+                    "`Self` is only available in impls, traits, and type definitions".to_string(),
+                    None,
+                )
+            }
         } else if ident.name.as_str().chars().next().map_or(false, |c| c.is_ascii_uppercase()) {
             // Check whether the name refers to an item in the value namespace.
             let binding = if let Some(ribs) = ribs {
diff --git a/tests/ui/use/use-self-type.stderr b/tests/ui/use/use-self-type.stderr
index e615394115119..3da04a851f651 100644
--- a/tests/ui/use/use-self-type.stderr
+++ b/tests/ui/use/use-self-type.stderr
@@ -8,7 +8,7 @@ error[E0432]: unresolved import `Self`
   --> $DIR/use-self-type.rs:6:13
    |
 LL |         use Self::f;
-   |             ^^^^ `Self` is only available in impls, traits, and type definitions
+   |             ^^^^ `Self` cannot be used in imports
 
 error: aborting due to 2 previous errors