fix: handle external mods imported via external->inline load hierarchy

src/modules.rs

@@ -321,7 +321,9 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
             (Some(Cow::Borrowed(ast::ModKind::Loaded(items, _, _))), _) => {
                 self.visit_mod_from_ast(items)
             }
-            (Some(Cow::Owned(..)), Cow::Owned(items)) => self.visit_mod_outside_ast(items),
+            (Some(Cow::Owned(ast::ModKind::Loaded(items, _, _))), _) | (_, Cow::Owned(items)) => {
+                self.visit_mod_outside_ast(items)
+            }
             (_, _) => Ok(()),
         }
     }

src/test/mod_resolver.rs

@@ -5,21 +5,39 @@ use super::read_config;
 
 use crate::{FileName, Input, Session};
 
-#[test]
-fn nested_out_of_line_mods_loaded() {
-    // See also https://github.com/rust-lang/rustfmt/issues/4874
-    let filename = "tests/mod-resolver/issue-4874/main.rs";
-    let input_file = PathBuf::from(filename);
+fn verify_mod_resolution(input_file_name: &str, exp_misformatted_files: &[&str]) {
+    let input_file = PathBuf::from(input_file_name);
     let config = read_config(&input_file);
     let mut session = Session::<io::Stdout>::new(config, None);
     let report = session
-        .format(Input::File(filename.into()))
+        .format(Input::File(input_file_name.into()))
         .expect("Should not have had any execution errors");
     let errors_by_file = &report.internal.borrow().0;
-    assert!(errors_by_file.contains_key(&FileName::Real(PathBuf::from(
-        "tests/mod-resolver/issue-4874/bar/baz.rs",
-    ))));
-    assert!(errors_by_file.contains_key(&FileName::Real(PathBuf::from(
-        "tests/mod-resolver/issue-4874/foo/qux.rs",
-    ))));
+    for exp_file in exp_misformatted_files {
+        assert!(errors_by_file.contains_key(&FileName::Real(PathBuf::from(exp_file))));
+    }
+}
+
+#[test]
+fn nested_out_of_line_mods_loaded() {
+    // See also https://github.com/rust-lang/rustfmt/issues/4874
+    verify_mod_resolution(
+        "tests/mod-resolver/issue-4874/main.rs",
+        &[
+            "tests/mod-resolver/issue-4874/bar/baz.rs",
+            "tests/mod-resolver/issue-4874/foo/qux.rs",
+        ],
+    );
+}
+
+#[test]
+fn out_of_line_nested_inline_within_out_of_line() {
+    // See also https://github.com/rust-lang/rustfmt/issues/5063
+    verify_mod_resolution(
+        "tests/mod-resolver/issue-5063/main.rs",
+        &[
+            "tests/mod-resolver/issue-5063/foo/bar/baz.rs",
+            "tests/mod-resolver/issue-5063/foo.rs",
+        ],
+    );
 }

tests/mod-resolver/issue-5063/foo.rs

@@ -0,0 +1,2 @@
+mod bar {
+        mod baz;}

tests/mod-resolver/issue-5063/foo/bar/baz.rs

@@ -0,0 +1 @@
+fn    baz()    {       }

tests/mod-resolver/issue-5063/main.rs

@@ -0,0 +1,5 @@
+fn main() {
+    println!("Hello, world!");
+}
+
+mod foo;