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]>

4 files changed, 79 insertions, 5 deletions

diff --git a/crates/ra_ide_api/src/completion/complete_scope.rs b/crates/ra_ide_api/src/completion/complete_scope.rs
index 445788407..eeaf26d93 100644
--- a/crates/ra_ide_api/src/completion/complete_scope.rs
+++ b/crates/ra_ide_api/src/completion/complete_scope.rs
@@ -4,7 +4,7 @@ pub(super) fn complete_scope(acc: &mut Completions, ctx: &CompletionContext) {
     if !ctx.is_trivial_path {
         return;
     }
-    let names = ctx.resolver.all_names();
+    let names = ctx.resolver.all_names(ctx.db);
 
     names.into_iter().for_each(|(name, res)| {
         CompletionItem::new(CompletionKind::Reference, ctx.source_range(), name.to_string())
@@ -165,4 +165,23 @@ mod tests {
     fn completes_self_in_methods() {
         check_reference_completion("self_in_methods", r"impl S { fn foo(&self) { <|> } }")
     }
+
+    #[test]
+    fn completes_prelude() {
+        check_reference_completion(
+            "completes_prelude",
+            "
+            //- /main.rs
+            fn foo() { let x: <|> }
+
+            //- /std/lib.rs
+            #[prelude_import]
+            use prelude::*;
+
+            mod prelude {
+                struct Option;
+            }
+            ",
+        );
+    }
 }
diff --git a/crates/ra_ide_api/src/completion/snapshots/completion_item__completes_prelude.snap b/crates/ra_ide_api/src/completion/snapshots/completion_item__completes_prelude.snap
new file mode 100644
index 000000000..2b5a1a8ea
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/snapshots/completion_item__completes_prelude.snap
@@ -0,0 +1,54 @@
+---
+created: "2019-02-13T19:52:43.734834624Z"
+creator: [email protected]
+source: crates/ra_ide_api/src/completion/completion_item.rs
+expression: kind_completions
+---
+[
+    CompletionItem {
+        completion_kind: Reference,
+        label: "Option",
+        kind: Some(
+            Struct
+        ),
+        detail: None,
+        documentation: None,
+        lookup: None,
+        insert_text: None,
+        insert_text_format: PlainText,
+        source_range: [18; 18),
+        text_edit: None
+    },
+    CompletionItem {
+        completion_kind: Reference,
+        label: "foo",
+        kind: Some(
+            Function
+        ),
+        detail: Some(
+            "fn foo()"
+        ),
+        documentation: None,
+        lookup: None,
+        insert_text: Some(
+            "foo()$0"
+        ),
+        insert_text_format: Snippet,
+        source_range: [18; 18),
+        text_edit: None
+    },
+    CompletionItem {
+        completion_kind: Reference,
+        label: "std",
+        kind: Some(
+            Module
+        ),
+        detail: None,
+        documentation: None,
+        lookup: None,
+        insert_text: None,
+        insert_text_format: PlainText,
+        source_range: [18; 18),
+        text_edit: None
+    }
+]
diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
index de3ec4e0a..d77a56ce8 100644
--- a/crates/ra_ide_api/src/lib.rs
+++ b/crates/ra_ide_api/src/lib.rs
@@ -62,7 +62,8 @@ pub use ra_ide_api_light::{
     LineIndex, LineCol, translate_offset_with_edit,
 };
 pub use ra_db::{
-    Canceled, CrateGraph, CrateId, FileId, FilePosition, FileRange, SourceRootId
+    Canceled, CrateGraph, CrateId, FileId, FilePosition, FileRange, SourceRootId,
+    Edition
 };
 pub use hir::Documentation;
 
diff --git a/crates/ra_ide_api/src/mock_analysis.rs b/crates/ra_ide_api/src/mock_analysis.rs
index 017ac5de3..550d69641 100644
--- a/crates/ra_ide_api/src/mock_analysis.rs
+++ b/crates/ra_ide_api/src/mock_analysis.rs
@@ -3,7 +3,7 @@ use std::sync::Arc;
 use relative_path::RelativePathBuf;
 use test_utils::{extract_offset, extract_range, parse_fixture, CURSOR_MARKER};
 
-use crate::{Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, FilePosition, FileRange, SourceRootId};
+use crate::{Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, FilePosition, FileRange, SourceRootId, Edition::Edition2018};
 
 /// Mock analysis is used in test to bootstrap an AnalysisHost/Analysis
 /// from a set of in-memory files.
@@ -89,9 +89,9 @@ impl MockAnalysis {
             let path = RelativePathBuf::from_path(&path[1..]).unwrap();
             let file_id = FileId(i as u32 + 1);
             if path == "/lib.rs" || path == "/main.rs" {
-                root_crate = Some(crate_graph.add_crate_root(file_id));
+                root_crate = Some(crate_graph.add_crate_root(file_id, Edition2018));
             } else if path.ends_with("/lib.rs") {
-                let other_crate = crate_graph.add_crate_root(file_id);
+                let other_crate = crate_graph.add_crate_root(file_id, Edition2018);
                 let crate_name = path.parent().unwrap().file_name().unwrap();
                 if let Some(root_crate) = root_crate {
                     crate_graph.add_dep(root_crate, crate_name.into(), other_crate).unwrap();