2 files changed, 80 insertions, 3 deletions

diff --git a/gcc/rust/ast/rust-ast-full-test.cc b/gcc/rust/ast/rust-ast-full-test.cc
index dfd9cdb..6033ce9 100644
--- a/gcc/rust/ast/rust-ast-full-test.cc
+++ b/gcc/rust/ast/rust-ast-full-test.cc
@@ -17,6 +17,9 @@ You should have received a copy of the GNU General Public License
 along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */
 
+// FIXME: This does not work on Windows
+#include <unistd.h>
+
 #include "rust-ast-full.h"
 #include "rust-diagnostics.h"
 #include "rust-ast-visitor.h"
@@ -4050,6 +4053,73 @@ Module::add_crate_name (std::vector<std::string> &names) const
     item->add_crate_name (names);
 }
 
+static bool
+file_exists (const std::string path)
+{
+  // Simply check if the file exists
+  // FIXME: This does not work on Windows
+  return access (path.c_str (), F_OK) != -1;
+}
+
+// FIXME: This function should also check if the module has a `path` outer
+// attribute and fetch the path from here in that case, i.e:
+// ```
+// #[path="<dir>/<subdir>/<file>.rs"]
+// mod <mod_name>;
+// ```
+std::string
+Module::get_filename ()
+{
+  rust_assert (kind == Module::ModuleKind::UNLOADED);
+
+  // This corresponds to the path of the file 'including' the module. So the
+  // file that contains the 'mod <file>;' directive
+  std::string including_fname (outer_filename);
+
+  std::string expected_file_path = module_name + ".rs";
+  std::string expected_dir_path = "mod.rs";
+
+  auto dir_slash_pos = including_fname.rfind (file_separator);
+  std::string current_directory_name;
+
+  // If we haven't found a file_separator, then we have to look for files in the
+  // current directory ('.')
+  if (dir_slash_pos == std::string::npos)
+    current_directory_name = std::string (".") + file_separator;
+  else
+    current_directory_name
+      = including_fname.substr (0, dir_slash_pos) + file_separator;
+
+  // FIXME: We also have to search for
+  // <directory>/<including_fname>/<module_name>.rs In rustc, this is done via
+  // the concept of `DirOwnernship`, which is based on whether or not the
+  // current file is titled `mod.rs`.
+
+  // First, we search for <directory>/<module_name>.rs
+  bool file_mod_found
+    = file_exists (current_directory_name + expected_file_path);
+
+  // Then, search for <directory>/<module_name>/mod.rs
+  current_directory_name += module_name + file_separator;
+  bool dir_mod_found = file_exists (current_directory_name + expected_dir_path);
+
+  bool multiple_candidates_found = file_mod_found && dir_mod_found;
+  bool no_candidates_found = !file_mod_found && !dir_mod_found;
+
+  if (multiple_candidates_found)
+    rust_error_at (locus,
+		   "two candidates found for module %s: %s.rs and %s%smod.rs",
+		   module_name.c_str (), module_name.c_str (),
+		   module_name.c_str (), file_separator);
+
+  if (no_candidates_found)
+    rust_error_at (locus, "no candidate found for module %s",
+		   module_name.c_str ());
+
+  return file_mod_found ? expected_file_path
+			: current_directory_name + expected_dir_path;
+}
+
 void
 Attribute::parse_attr_to_meta_item ()
 {
diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
index 32fb56f..dac76f5 100644
--- a/gcc/rust/ast/rust-item.h
+++ b/gcc/rust/ast/rust-item.h
@@ -977,6 +977,8 @@ private:
   Location locus;
   ModuleKind kind;
 
+  // Name of the file including the module
+  std::string outer_filename;
   // bool has_inner_attrs;
   std::vector<Attribute> inner_attrs;
   // bool has_items;
@@ -998,10 +1000,11 @@ public:
 
   // Unloaded module constructor
   Module (Identifier module_name, Visibility visibility,
-	  std::vector<Attribute> outer_attrs, Location locus)
+	  std::vector<Attribute> outer_attrs, Location locus,
+	  std::string outer_filename)
     : VisItem (std::move (visibility), std::move (outer_attrs)),
       module_name (module_name), locus (locus), kind (ModuleKind::UNLOADED),
-      inner_attrs (std::vector<Attribute> ()),
+      outer_filename (outer_filename), inner_attrs (std::vector<Attribute> ()),
       items (std::vector<std::unique_ptr<Item>> ())
   {}
 
@@ -1013,7 +1016,8 @@ public:
 	  std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
     : VisItem (std::move (visibility), std::move (outer_attrs)),
       module_name (name), locus (locus), kind (ModuleKind::LOADED),
-      inner_attrs (std::move (inner_attrs)), items (std::move (items))
+      outer_filename (std::string ()), inner_attrs (std::move (inner_attrs)),
+      items (std::move (items))
   {}
 
   // Copy constructor with vector clone
@@ -1049,6 +1053,9 @@ public:
     return *this;
   }
 
+  // Search for the filename associated with an external module
+  std::string get_filename ();
+
   void accept_vis (ASTVisitor &vis) override;
 
   /* Override that runs the function recursively on all items contained within