lexer: Add function to get original filename

When parsing an external module, it is important to be able to access
the original "including" file in order to resolve the path of the
desired module. Take the following example

```rust
// /project/src/foo.rs
mod bar; /* External module */
```

The file which contains the `bar` module could be located at
`/project/src/bar.rs`, or at `/project/src/foo/bar.rs` (careful, this isn't an exhaustive list
of all possible cases). We must therefore be able to access the
`/project/src` directory in order to find valid candidates for `mod
bar`

3 files changed, 13 insertions, 6 deletions

diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
index 32fb56f..9e57f5a 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
diff --git a/gcc/rust/lex/rust-lex.h b/gcc/rust/lex/rust-lex.h
index 902745f..1b37a9c 100644
--- a/gcc/rust/lex/rust-lex.h
+++ b/gcc/rust/lex/rust-lex.h
@@ -14,6 +14,7 @@ struct RAIIFile
 {
 private:
   FILE *file;
+  const char *filename;
 
   void close ()
   {
@@ -22,7 +23,7 @@ private:
   }
 
 public:
-  RAIIFile (const char *filename)
+  RAIIFile (const char *filename) : filename (filename)
   {
     if (strcmp (filename, "-") == 0)
       file = stdin;
@@ -47,6 +48,7 @@ public:
   ~RAIIFile () { close (); }
 
   FILE *get_raw () { return file; }
+  const char *get_filename () { return filename; }
 };
 
 class Lexer
@@ -136,6 +138,7 @@ public:
   void split_current_token (TokenId new_left, TokenId new_right);
 
   Linemap *get_line_map () { return line_map; }
+  std::string get_filename () { return std::string (input.get_filename ()); }
 
 private:
   // File for use as input.
diff --git a/gcc/rust/parse/rust-parse-impl.h b/gcc/rust/parse/rust-parse-impl.h
index c94c637..0e50168 100644
--- a/gcc/rust/parse/rust-parse-impl.h
+++ b/gcc/rust/parse/rust-parse-impl.h
@@ -2103,8 +2103,8 @@ Parser<ManagedTokenSource>::parse_module (AST::Visibility vis,
 
       return std::unique_ptr<AST::Module> (
 	new AST::Module (std::move (name), std::move (vis),
-			 std::move (outer_attrs),
-			 locus)); // module name?
+			 std::move (outer_attrs), locus,
+			 lexer.get_filename ()));
       case LEFT_CURLY: {
 	lexer.skip_token ();