1 files changed, 46 insertions, 0 deletions

diff --git a/crates/ra_hir_expand/src/hygiene.rs b/crates/ra_hir_expand/src/hygiene.rs
new file mode 100644
index 000000000..77428ec99
--- /dev/null
+++ b/crates/ra_hir_expand/src/hygiene.rs
@@ -0,0 +1,46 @@
+//! This modules handles hygiene information.
+//!
+//! Specifically, `ast` + `Hygiene` allows you to create a `Name`. Note that, at
+//! this moment, this is horribly incomplete and handles only `$crate`.
+use ra_db::CrateId;
+use ra_syntax::ast;
+
+use crate::{
+    db::AstDatabase,
+    either::Either,
+    name::{AsName, Name},
+    HirFileId, HirFileIdRepr,
+};
+
+#[derive(Debug)]
+pub struct Hygiene {
+    // This is what `$crate` expands to
+    def_crate: Option<CrateId>,
+}
+
+impl Hygiene {
+    pub fn new(db: &impl AstDatabase, file_id: HirFileId) -> Hygiene {
+        let def_crate = match file_id.0 {
+            HirFileIdRepr::FileId(_) => None,
+            HirFileIdRepr::MacroFile(macro_file) => {
+                let loc = db.lookup_intern_macro(macro_file.macro_call_id);
+                Some(loc.def.krate)
+            }
+        };
+        Hygiene { def_crate }
+    }
+
+    pub fn new_unhygienic() -> Hygiene {
+        Hygiene { def_crate: None }
+    }
+
+    // FIXME: this should just return name
+    pub fn name_ref_to_name(&self, name_ref: ast::NameRef) -> Either<Name, CrateId> {
+        if let Some(def_crate) = self.def_crate {
+            if name_ref.text() == "$crate" {
+                return Either::B(def_crate);
+            }
+        }
+        Either::A(name_ref.as_name())
+    }
+}