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 😅 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 😄 

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 <flodiebold@gmail.com>

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());
     }

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,
 };

crates/ra_hir/src/code_model_api.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use relative_path::RelativePathBuf;
-use ra_db::{CrateId, FileId, SourceRootId};
+use ra_db::{CrateId, FileId, SourceRootId, Edition};
 use ra_syntax::{ast::self, TreeArc, SyntaxNode};
 
 use crate::{
@@ -38,13 +38,20 @@ impl Crate {
     pub fn crate_id(&self) -> CrateId {
         self.crate_id
     }
+
     pub fn dependencies(&self, db: &impl PersistentHirDatabase) -> Vec<CrateDependency> {
         self.dependencies_impl(db)
     }
+
     pub fn root_module(&self, db: &impl PersistentHirDatabase) -> Option<Module> {
         self.root_module_impl(db)
     }
 
+    pub fn edition(&self, db: &impl PersistentHirDatabase) -> Edition {
+        let crate_graph = db.crate_graph();
+        crate_graph.edition(self.crate_id)
+    }
+
     // TODO: should this be in source_binder?
     pub fn source_root_crates(
         db: &impl PersistentHirDatabase,

crates/ra_hir/src/marks.rs

@@ -6,4 +6,5 @@ test_utils::marks!(
     type_var_resolves_to_int_var
     glob_enum
     glob_across_crates
+    std_prelude
 );

crates/ra_hir/src/mock.rs

@@ -3,6 +3,7 @@ use std::{sync::Arc, panic};
 use parking_lot::Mutex;
 use ra_db::{
     FilePosition, FileId, CrateGraph, SourceRoot, SourceRootId, SourceDatabase, salsa,
+    Edition,
 };
 use relative_path::RelativePathBuf;
 use test_utils::{parse_fixture, CURSOR_MARKER, extract_offset};
@@ -58,12 +59,12 @@ impl MockDatabase {
     pub fn set_crate_graph_from_fixture(&mut self, graph: CrateGraphFixture) {
         let mut ids = FxHashMap::default();
         let mut crate_graph = CrateGraph::default();
-        for (crate_name, (crate_root, _)) in graph.0.iter() {
+        for (crate_name, (crate_root, edition, _)) in graph.0.iter() {
             let crate_root = self.file_id_of(&crate_root);
-            let crate_id = crate_graph.add_crate_root(crate_root);
+            let crate_id = crate_graph.add_crate_root(crate_root, *edition);
             ids.insert(crate_name, crate_id);
         }
-        for (crate_name, (_, deps)) in graph.0.iter() {
+        for (crate_name, (_, _, deps)) in graph.0.iter() {
             let from = ids[crate_name];
             for dep in deps {
                 let to = ids[dep];
@@ -144,7 +145,7 @@ impl MockDatabase {
 
         if is_crate_root {
             let mut crate_graph = CrateGraph::default();
-            crate_graph.add_crate_root(file_id);
+            crate_graph.add_crate_root(file_id, Edition::Edition2018);
             self.set_crate_graph(Arc::new(crate_graph));
         }
         file_id
@@ -232,16 +233,19 @@ impl MockDatabase {
 }
 
 #[derive(Default)]
-pub struct CrateGraphFixture(pub FxHashMap<String, (String, Vec<String>)>);
+pub struct CrateGraphFixture(pub FxHashMap<String, (String, Edition, Vec<String>)>);
 
 #[macro_export]
 macro_rules! crate_graph {
-    ($($crate_name:literal: ($crate_path:literal, [$($dep:literal),*]),)*) => {{
+    ($($crate_name:literal: ($crate_path:literal, $($edition:literal,)? [$($dep:literal),*]),)*) => {{
         let mut res = $crate::mock::CrateGraphFixture::default();
         $(
+            #[allow(unused_mut, unused_assignments)]
+            let mut edition = ra_db::Edition::Edition2018;
+            $(edition = ra_db::Edition::from_string($edition);)?
             res.0.insert(
                 $crate_name.to_string(),
-                ($crate_path.to_string(), vec![$($dep.to_string()),*])
+                ($crate_path.to_string(), edition, vec![$($dep.to_string()),*])
             );
         )*
         res