From c2622c922887368788674d1735a7705fc345a5b9 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Wed, 10 Mar 2021 16:33:18 +0100
Subject: Prefer names from outer DefMap over extern prelude

---
 crates/hir_def/src/nameres/path_resolution.rs | 16 ++++++++++-----
 crates/hir_ty/src/diagnostics.rs              | 29 +++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/crates/hir_def/src/nameres/path_resolution.rs b/crates/hir_def/src/nameres/path_resolution.rs
index 8258dcffb..db459b1ed 100644
--- a/crates/hir_def/src/nameres/path_resolution.rs
+++ b/crates/hir_def/src/nameres/path_resolution.rs
@@ -156,7 +156,7 @@ impl DefMap {
         }
     }
 
-    pub(super) fn resolve_path_fp_with_macro_single(
+    fn resolve_path_fp_with_macro_single(
         &self,
         db: &dyn DefDatabase,
         mode: ResolveMode,
@@ -384,10 +384,16 @@ impl DefMap {
                 }
             }
         };
-        let from_extern_prelude = self
-            .extern_prelude
-            .get(name)
-            .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public));
+        // Give precedence to names in outer `DefMap`s over the extern prelude; only check prelude
+        // from the crate DefMap.
+        let from_extern_prelude = match self.block {
+            Some(_) => PerNs::none(),
+            None => self
+                .extern_prelude
+                .get(name)
+                .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public)),
+        };
+
         let from_prelude = self.resolve_in_prelude(db, name);
 
         from_legacy_macro.or(from_scope_or_builtin).or(from_extern_prelude).or(from_prelude)
diff --git a/crates/hir_ty/src/diagnostics.rs b/crates/hir_ty/src/diagnostics.rs
index 6bca7aa0d..86f937e1d 100644
--- a/crates/hir_ty/src/diagnostics.rs
+++ b/crates/hir_ty/src/diagnostics.rs
@@ -705,6 +705,35 @@ fn x(a: S) {
         )
     }
 
+    #[test]
+    fn import_extern_crate_clash_with_inner_item() {
+        // This is more of a resolver test, but doesn't really work with the hir_def testsuite.
+
+        check_diagnostics(
+            r#"
+//- /lib.rs crate:lib deps:jwt
+mod permissions;
+
+use permissions::jwt;
+
+fn f() {
+    fn inner() {}
+    jwt::Claims {}; // should resolve to the local one with 0 fields, and not get a diagnostic
+}
+
+//- /permissions.rs
+pub mod jwt  {
+    pub struct Claims {}
+}
+
+//- /jwt/lib.rs crate:jwt
+pub struct Claims {
+    field: u8,
+}
+        "#,
+        );
+    }
+
     #[test]
     fn break_outside_of_loop() {
         check_diagnostics(
-- 
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