import: Add cli extern crate resolution

This commit add the ability to specify the path to an extern crate
through the -frust-extern cli option. Path given as cli argument
shall resolve to the exact extern crate location.

gcc/rust/ChangeLog:

	* metadata/rust-imports.h: Make the function to load a given
	file public.
	* rust-session-manager.cc (Session::load_extern_crate): Change
	path resolution depending on extern crate declaration in cli
	arguments.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

2 files changed, 19 insertions, 5 deletions

diff --git a/gcc/rust/metadata/rust-imports.h b/gcc/rust/metadata/rust-imports.h
index 51cc4fc..c728adb 100644
--- a/gcc/rust/metadata/rust-imports.h
+++ b/gcc/rust/metadata/rust-imports.h
@@ -112,6 +112,8 @@ public:
   static Stream *open_package (const std::string &filename, Location location,
 			       const std::string &relative_import_path);
 
+  static Stream *try_package_in_directory (const std::string &, Location);
+
   // Constructor.
   Import (Stream *, Location);
 
@@ -153,8 +155,6 @@ public:
   void clear_stream () { this->stream_ = NULL; }
 
 private:
-  static Stream *try_package_in_directory (const std::string &, Location);
-
   static int try_suffixes (std::string *);
 
   static Stream *find_export_data (const std::string &filename, int fd,
diff --git a/gcc/rust/rust-session-manager.cc b/gcc/rust/rust-session-manager.cc
index 5888348..7a9e3bd 100644
--- a/gcc/rust/rust-session-manager.cc
+++ b/gcc/rust/rust-session-manager.cc
@@ -973,12 +973,26 @@ Session::load_extern_crate (const std::string &crate_name, location_t locus)
     }
 
   std::string relative_import_path = "";
-  Import::Stream *s
-    = Import::open_package (crate_name, locus, relative_import_path);
+  std::string import_name = crate_name;
+
+  // The path to the extern crate might have been specified by the user using
+  // -frust-extern
+  auto cli_extern_crate = extern_crates.find (crate_name);
+
+  Import::Stream *s;
+  if (cli_extern_crate != extern_crates.end ())
+    {
+      auto path = cli_extern_crate->second;
+      s = Import::try_package_in_directory (path, locus);
+    }
+  else
+    {
+      s = Import::open_package (import_name, locus, relative_import_path);
+    }
   if (s == NULL)
     {
       rust_error_at (locus, "failed to locate crate %<%s%>",
-		     crate_name.c_str ());
+		     import_name.c_str ());
       return UNKNOWN_NODEID;
     }