don't cycle when processing macros from prelude in prelude

crates/ra_hir/src/nameres/collector.rs

@@ -525,8 +525,10 @@ where
     fn collect(&mut self, items: &[raw::RawItem]) {
         // Prelude module is always considered to be `#[macro_use]`.
         if let Some(prelude_module) = self.def_collector.def_map.prelude {
-            tested_by!(prelude_is_macro_use);
-            self.def_collector.import_all_macros_exported(prelude_module);
+            if prelude_module.krate != self.def_collector.def_map.krate {
+                tested_by!(prelude_is_macro_use);
+                self.def_collector.import_all_macros_exported(prelude_module);
+            }
         }
 
         // This should be processed eagerly instead of deferred to resolving.

crates/ra_hir/src/nameres/tests/macros.rs

@@ -248,3 +248,32 @@ fn prelude_is_macro_use() {
    ⋮Baz: t v
     "###);
 }
+
+#[test]
+fn prelude_cycle() {
+    let map = def_map(
+        "
+        //- /lib.rs
+        #[prelude_import]
+        use self::prelude::*;
+
+        declare_mod!();
+
+        mod prelude {
+            macro_rules! declare_mod {
+                () => (mod foo {})
+            }
+        }
+        ",
+    );
+    assert_snapshot!(map, @r###"
+        ⋮crate
+        ⋮foo: t
+        ⋮prelude: t
+        ⋮
+        ⋮crate::prelude
+        ⋮declare_mod: m
+        ⋮
+        ⋮crate::foo
+    "###);
+}