3 files changed, 38 insertions, 8 deletions

diff --git a/crates/ra_hir/src/krate.rs b/crates/ra_hir/src/krate.rs
index 367ddbd21..61007cc29 100644
--- a/crates/ra_hir/src/krate.rs
+++ b/crates/ra_hir/src/krate.rs
@@ -1,15 +1,37 @@
-use crate::FileId;
+use crate::{HirDatabase, Module, Cancelable};
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
-pub struct CrateId(u32);
+pub use ra_db::CrateId;
 
+/// hir::Crate describes a single crate. It's the main inteface with which
+/// crate's dependencies interact. Mostly, it should be just a proxy for the
+/// root module.
 #[derive(Debug)]
 pub struct Crate {
-    root: FileId,
+    crate_id: CrateId,
 }
 
 impl Crate {
-    pub fn dependencies(&self) -> Vec<CrateId> {
-        Vec::new()
+    pub(crate) fn new(crate_id: CrateId) -> Crate {
+        Crate { crate_id }
+    }
+    pub fn dependencies(&self, db: &impl HirDatabase) -> Vec<Crate> {
+        let crate_graph = db.crate_graph();
+        crate_graph
+            .dependencies(self.crate_id)
+            .map(|dep| Crate::new(dep.crate_id()))
+            .collect()
+    }
+    pub fn root_module(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
+        let crate_graph = db.crate_graph();
+        let file_id = crate_graph.crate_root(self.crate_id);
+        let source_root_id = db.file_source_root(file_id);
+        let module_tree = db.module_tree(source_root_id)?;
+        // FIXME: teach module tree about crate roots instead of guessing
+        let (module_id, _) = ctry!(module_tree
+            .modules_with_sources()
+            .find(|(_, src)| src.file_id() == file_id));
+
+        let module = Module::new(db, source_root_id, module_id)?;
+        Ok(Some(module))
     }
 }
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 0fa2ec50f..578fde259 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -26,7 +26,6 @@ mod krate;
 mod module;
 mod function;
 
-
 use std::ops::Index;
 
 use ra_syntax::{SyntaxNodeRef, SyntaxNode};
diff --git a/crates/ra_hir/src/module.rs b/crates/ra_hir/src/module.rs
index e7a49f83a..c6bb76d56 100644
--- a/crates/ra_hir/src/module.rs
+++ b/crates/ra_hir/src/module.rs
@@ -12,7 +12,7 @@ use ra_db::{SourceRootId, FileId, Cancelable};
 use relative_path::RelativePathBuf;
 
 use crate::{
-    DefKind, DefLoc, DefId, Path, PathKind, HirDatabase, SourceItemId, SourceFileItemId,
+    DefKind, DefLoc, DefId, Path, PathKind, HirDatabase, SourceItemId, SourceFileItemId, Crate,
     arena::{Arena, Id},
 };
 
@@ -64,6 +64,15 @@ impl Module {
         })
     }
 
+    /// Returns the crate this module is part of.
+    pub fn krate(&self, db: &impl HirDatabase) -> Option<Crate> {
+        let root_id = self.module_id.crate_root(&self.tree);
+        let file_id = root_id.source(&self.tree).file_id();
+        let crate_graph = db.crate_graph();
+        let crate_id = crate_graph.crate_id_for_crate_root(file_id)?;
+        Some(Crate::new(crate_id))
+    }
+
     /// The root of the tree this module is part of
     pub fn crate_root(&self) -> Module {
         let root_id = self.module_id.crate_root(&self.tree);