Merge #816

816: Prelude & Edition 2015 import resolution r=matklad a=flodiebold

I implemented the prelude import, but it turned out to be useless without being able to resolve any of the imports in the prelude :sweat_smile: So I had to add some edition handling and handle 2015-style imports (at least the simplified scheme proposed in rust-lang/rust#57745). So now finally `Option` resolves :smile: 

One remaining problem is that we don't actually know the edition for sysroot crates. They're currently hardcoded to 2015, but there's already a bunch of PRs upgrading the editions of various rustc crates, so we'll have to detect the edition somehow, or just change the hardcoding to 2018 later, I guess...

~Also currently missing is completion for prelude names, though that shouldn't be hard to add. And `Vec` still doesn't resolve, so I need to look into that.~

Co-authored-by: Florian Diebold <[email protected]>

2 files changed, 33 insertions, 13 deletions

diff --git a/crates/ra_db/src/input.rs b/crates/ra_db/src/input.rs
index 8decc65c5..e45a510b3 100644
--- a/crates/ra_db/src/input.rs
+++ b/crates/ra_db/src/input.rs
@@ -56,15 +56,31 @@ pub struct CyclicDependencies;
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct CrateId(pub u32);
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Edition {
+    Edition2018,
+    Edition2015,
+}
+
+impl Edition {
+    pub fn from_string(s: &str) -> Edition {
+        match s {
+            "2015" => Edition::Edition2015,
+            "2018" | _ => Edition::Edition2018,
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 struct CrateData {
     file_id: FileId,
+    edition: Edition,
     dependencies: Vec<Dependency>,
 }
 
 impl CrateData {
-    fn new(file_id: FileId) -> CrateData {
-        CrateData { file_id, dependencies: Vec::new() }
+    fn new(file_id: FileId, edition: Edition) -> CrateData {
+        CrateData { file_id, edition, dependencies: Vec::new() }
     }
 
     fn add_dep(&mut self, name: SmolStr, crate_id: CrateId) {
@@ -85,9 +101,9 @@ impl Dependency {
 }
 
 impl CrateGraph {
-    pub fn add_crate_root(&mut self, file_id: FileId) -> CrateId {
+    pub fn add_crate_root(&mut self, file_id: FileId, edition: Edition) -> CrateId {
         let crate_id = CrateId(self.arena.len() as u32);
-        let prev = self.arena.insert(crate_id, CrateData::new(file_id));
+        let prev = self.arena.insert(crate_id, CrateData::new(file_id, edition));
         assert!(prev.is_none());
         crate_id
     }
@@ -112,6 +128,10 @@ impl CrateGraph {
         self.arena[&crate_id].file_id
     }
 
+    pub fn edition(&self, crate_id: CrateId) -> Edition {
+        self.arena[&crate_id].edition
+    }
+
     // TODO: this only finds one crate with the given root; we could have multiple
     pub fn crate_id_for_crate_root(&self, file_id: FileId) -> Option<CrateId> {
         let (&crate_id, _) = self.arena.iter().find(|(_crate_id, data)| data.file_id == file_id)?;
@@ -159,14 +179,14 @@ impl CrateGraph {
 
 #[cfg(test)]
 mod tests {
-    use super::{CrateGraph, FileId, SmolStr};
+    use super::{CrateGraph, FileId, SmolStr, Edition::Edition2018};
 
     #[test]
-    fn it_should_painc_because_of_cycle_dependencies() {
+    fn it_should_panic_because_of_cycle_dependencies() {
         let mut graph = CrateGraph::default();
-        let crate1 = graph.add_crate_root(FileId(1u32));
-        let crate2 = graph.add_crate_root(FileId(2u32));
-        let crate3 = graph.add_crate_root(FileId(3u32));
+        let crate1 = graph.add_crate_root(FileId(1u32), Edition2018);
+        let crate2 = graph.add_crate_root(FileId(2u32), Edition2018);
+        let crate3 = graph.add_crate_root(FileId(3u32), Edition2018);
         assert!(graph.add_dep(crate1, SmolStr::new("crate2"), crate2).is_ok());
         assert!(graph.add_dep(crate2, SmolStr::new("crate3"), crate3).is_ok());
         assert!(graph.add_dep(crate3, SmolStr::new("crate1"), crate1).is_err());
@@ -175,9 +195,9 @@ mod tests {
     #[test]
     fn it_works() {
         let mut graph = CrateGraph::default();
-        let crate1 = graph.add_crate_root(FileId(1u32));
-        let crate2 = graph.add_crate_root(FileId(2u32));
-        let crate3 = graph.add_crate_root(FileId(3u32));
+        let crate1 = graph.add_crate_root(FileId(1u32), Edition2018);
+        let crate2 = graph.add_crate_root(FileId(2u32), Edition2018);
+        let crate3 = graph.add_crate_root(FileId(3u32), Edition2018);
         assert!(graph.add_dep(crate1, SmolStr::new("crate2"), crate2).is_ok());
         assert!(graph.add_dep(crate2, SmolStr::new("crate3"), crate3).is_ok());
     }
diff --git a/crates/ra_db/src/lib.rs b/crates/ra_db/src/lib.rs
index 31442713d..e006c6d27 100644
--- a/crates/ra_db/src/lib.rs
+++ b/crates/ra_db/src/lib.rs
@@ -14,7 +14,7 @@ pub use ::salsa as salsa;
 pub use crate::{
     cancellation::Canceled,
     input::{
-        FileId, CrateId, SourceRoot, SourceRootId, CrateGraph, Dependency,
+        FileId, CrateId, SourceRoot, SourceRootId, CrateGraph, Dependency, Edition,
     },
     loc2id::LocationIntener,
 };