10 files changed, 152 insertions, 21 deletions

diff --git a/crates/ra_analysis/src/completion.rs b/crates/ra_analysis/src/completion.rs
new file mode 100644
index 000000000..a0fd6828d
--- /dev/null
+++ b/crates/ra_analysis/src/completion.rs
@@ -0,0 +1,61 @@
+use ra_editor::{CompletionItem, find_node_at_offset, complete_module_items};
+use ra_syntax::{
+    AtomEdit, File, TextUnit, AstNode,
+    ast::{self, ModuleItemOwner},
+};
+
+use crate::{
+    FileId, Cancelable,
+    db::{self, SyntaxDatabase},
+    descriptors::module::{ModulesDatabase, ModuleTree, ModuleId},
+};
+
+pub(crate) fn resolve_based_completion(db: &db::RootDatabase, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
+    let file = db.file_syntax(file_id);
+    let module_tree = db.module_tree()?;
+    let file = {
+        let edit = AtomEdit::insert(offset, "intellijRulezz".to_string());
+        file.reparse(&edit)
+    };
+    let target_file = match find_target_module(&module_tree, file_id, &file, offset) {
+        None => return Ok(None),
+        Some(target_module) => {
+            let file_id = target_module.file_id(&module_tree);
+            db.file_syntax(file_id)
+        }
+    };
+    let mut res = Vec::new();
+    complete_module_items(target_file.ast().items(), None, &mut res);
+    Ok(Some(res))
+}
+
+pub(crate) fn find_target_module(module_tree: &ModuleTree, file_id: FileId, file: &File, offset: TextUnit) -> Option<ModuleId> {
+    let name_ref: ast::NameRef = find_node_at_offset(file.syntax(), offset)?;
+    let mut crate_path = crate_path(name_ref)?;
+    let module_id = module_tree.any_module_for_file(file_id)?;
+    crate_path.pop();
+    let mut target_module = module_id.root(&module_tree);
+    for name in crate_path {
+        target_module = target_module.child(module_tree, name.text().as_str())?;
+    }
+    Some(target_module)
+}
+
+fn crate_path(name_ref: ast::NameRef) -> Option<Vec<ast::NameRef>> {
+    let mut path = name_ref.syntax()
+        .parent().and_then(ast::PathSegment::cast)?
+        .parent_path();
+    let mut res = Vec::new();
+    loop {
+        let segment = path.segment()?;
+        match segment.kind()? {
+            ast::PathSegmentKind::Name(name) => res.push(name),
+            ast::PathSegmentKind::CrateKw => break,
+            ast::PathSegmentKind::SelfKw | ast::PathSegmentKind::SuperKw =>
+                return None,
+        }
+        path = path.qualifier()?;
+    }
+    res.reverse();
+    Some(res)
+}
diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index f142b6c43..f3e5b2887 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -5,7 +5,7 @@ use std::{
     sync::Arc,
 };
 
-use ra_editor::{self, find_node_at_offset, resolve_local_name, FileSymbol, LineIndex, LocalEdit};
+use ra_editor::{self, find_node_at_offset, resolve_local_name, FileSymbol, LineIndex, LocalEdit, CompletionItem};
 use ra_syntax::{
     ast::{self, ArgListOwner, Expr, NameOwner},
     AstNode, File, SmolStr,
@@ -197,6 +197,26 @@ impl AnalysisImpl {
     pub fn crate_root(&self, crate_id: CrateId) -> FileId {
         self.data.crate_graph.crate_roots[&crate_id]
     }
+    pub fn completions(&self, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
+        let mut res = Vec::new();
+        let mut has_completions = false;
+        let file = self.file_syntax(file_id);
+        if let Some(scope_based) = ra_editor::scope_completion(&file, offset) {
+            res.extend(scope_based);
+            has_completions = true;
+        }
+        let root = self.root(file_id);
+        if let Some(scope_based) = crate::completion::resolve_based_completion(root.db(), file_id, offset)? {
+            res.extend(scope_based);
+            has_completions = true;
+        }
+        let res = if has_completions {
+            Some(res)
+        } else {
+            None
+        };
+        Ok(res)
+    }
     pub fn approximately_resolve_symbol(
         &self,
         file_id: FileId,
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index 67a239a5c..7078e2d31 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -11,6 +11,7 @@ mod descriptors;
 mod imp;
 mod roots;
 mod symbol_index;
+mod completion;
 
 use std::{fmt::Debug, sync::Arc};
 
@@ -246,8 +247,7 @@ impl Analysis {
         Ok(ra_editor::highlight(&file))
     }
     pub fn completions(&self, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
-        let file = self.imp.file_syntax(file_id);
-        Ok(ra_editor::scope_completion(&file, offset))
+        self.imp.completions(file_id, offset)
     }
     pub fn assists(&self, file_id: FileId, range: TextRange) -> Cancelable<Vec<SourceChange>> {
         Ok(self.imp.assists(file_id, range))
diff --git a/crates/ra_analysis/src/roots.rs b/crates/ra_analysis/src/roots.rs
index aa0243720..1e9e613ac 100644
--- a/crates/ra_analysis/src/roots.rs
+++ b/crates/ra_analysis/src/roots.rs
@@ -1,7 +1,5 @@
 use std::{sync::Arc};
 
-use ra_editor::LineIndex;
-use ra_syntax::File;
 use rustc_hash::FxHashSet;
 use rayon::prelude::*;
 use salsa::Database;
@@ -10,7 +8,6 @@ use crate::{
     Cancelable,
     db::{self, FilesDatabase, SyntaxDatabase},
     imp::FileResolverImp,
-    descriptors::module::{ModulesDatabase, ModuleTree},
     symbol_index::SymbolIndex,
     FileId,
 };
diff --git a/crates/ra_analysis/tests/tests.rs b/crates/ra_analysis/tests/tests.rs
index 7ae3d0eeb..52fae71ae 100644
--- a/crates/ra_analysis/tests/tests.rs
+++ b/crates/ra_analysis/tests/tests.rs
@@ -264,3 +264,17 @@ fn test_find_all_refs_for_param_inside() {
     let refs = get_all_refs(code);
     assert_eq!(refs.len(), 2);
 }
+
+#[test]
+fn test_complete_crate_path() {
+    let snap = analysis(&[
+        ("/lib.rs", "mod foo; struct Spam;"),
+        ("/foo.rs", "use crate::Sp"),
+    ]);
+    let completions = snap.completions(FileId(2), 13.into()).unwrap().unwrap();
+    assert_eq_dbg(
+        r#"[CompletionItem { label: "foo", lookup: None, snippet: None },
+            CompletionItem { label: "Spam", lookup: None, snippet: None }]"#,
+        &completions,
+    );
+}
diff --git a/crates/ra_editor/src/completion.rs b/crates/ra_editor/src/completion.rs
index 8502b337d..0a3675255 100644
--- a/crates/ra_editor/src/completion.rs
+++ b/crates/ra_editor/src/completion.rs
@@ -2,7 +2,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 
 use ra_syntax::{
     algo::visit::{visitor, visitor_ctx, Visitor, VisitorCtx},
-    ast::{self, LoopBodyOwner, ModuleItemOwner},
+    ast::{self, AstChildren, LoopBodyOwner, ModuleItemOwner},
     text_utils::is_subrange,
     AstNode, File,
     SyntaxKind::*,
@@ -65,6 +65,21 @@ pub fn scope_completion(file: &File, offset: TextUnit) -> Option<Vec<CompletionI
     }
 }
 
+pub fn complete_module_items(items: AstChildren<ast::ModuleItem>, this_item: Option<ast::NameRef>, acc: &mut Vec<CompletionItem>) {
+    let scope = ModuleScope::new(items);
+    acc.extend(
+        scope
+            .entries()
+            .iter()
+            .filter(|entry| Some(entry.syntax()) != this_item.map(|it| it.syntax()))
+            .map(|entry| CompletionItem {
+                label: entry.name().to_string(),
+                lookup: None,
+                snippet: None,
+            }),
+    );
+}
+
 fn complete_name_ref(file: &File, name_ref: ast::NameRef, acc: &mut Vec<CompletionItem>) {
     if !is_node::<ast::Path>(name_ref.syntax()) {
         return;
@@ -77,18 +92,7 @@ fn complete_name_ref(file: &File, name_ref: ast::NameRef, acc: &mut Vec<Completi
             .accept(node)
         {
             if let Some(items) = items {
-                let scope = ModuleScope::new(items);
-                acc.extend(
-                    scope
-                        .entries()
-                        .iter()
-                        .filter(|entry| entry.syntax() != name_ref.syntax())
-                        .map(|entry| CompletionItem {
-                            label: entry.name().to_string(),
-                            lookup: None,
-                            snippet: None,
-                        }),
-                );
+                complete_module_items(items, Some(name_ref), acc);
             }
             break;
         } else if !visited_fn {
diff --git a/crates/ra_editor/src/lib.rs b/crates/ra_editor/src/lib.rs
index 94e9a18e4..b73eb4ac7 100644
--- a/crates/ra_editor/src/lib.rs
+++ b/crates/ra_editor/src/lib.rs
@@ -21,7 +21,7 @@ mod typing;
 
 pub use self::{
     code_actions::{add_derive, add_impl, flip_comma, introduce_variable, LocalEdit},
-    completion::{scope_completion, CompletionItem},
+    completion::{scope_completion, complete_module_items, CompletionItem},
     edit::{Edit, EditBuilder},
     extend_selection::extend_selection,
     folding_ranges::{folding_ranges, Fold, FoldKind},
diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index 98c7de361..096405a38 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -1371,6 +1371,10 @@ impl<'a> Path<'a> {
     pub fn segment(self) -> Option<PathSegment<'a>> {
         super::child_opt(self)
     }
+
+    pub fn qualifier(self) -> Option<Path<'a>> {
+        super::child_opt(self)
+    }
 }
 
 // PathExpr
diff --git a/crates/ra_syntax/src/ast/mod.rs b/crates/ra_syntax/src/ast/mod.rs
index 900426a8a..c033263a1 100644
--- a/crates/ra_syntax/src/ast/mod.rs
+++ b/crates/ra_syntax/src/ast/mod.rs
@@ -232,6 +232,36 @@ impl<'a> IfExpr<'a> {
     }
 }
 
+
+#[derive(Debug, Clone, Copy)]
+pub enum PathSegmentKind<'a> {
+    Name(NameRef<'a>),
+    SelfKw,
+    SuperKw,
+    CrateKw,
+}
+
+impl<'a> PathSegment<'a> {
+    pub fn parent_path(self) -> Path<'a> {
+        self.syntax().parent().and_then(Path::cast)
+            .expect("segments are always nested in paths")
+    }
+
+    pub fn kind(self) -> Option<PathSegmentKind<'a>> {
+        let res = if let Some(name_ref) = self.name_ref() {
+            PathSegmentKind::Name(name_ref)
+        } else {
+            match self.syntax().first_child()?.kind() {
+                SELF_KW => PathSegmentKind::SelfKw,
+                SUPER_KW => PathSegmentKind::SuperKw,
+                CRATE_KW => PathSegmentKind::CrateKw,
+                _ => return None,
+            }
+        };
+        Some(res)
+    }
+}
+
 fn child_opt<'a, P: AstNode<'a>, C: AstNode<'a>>(parent: P) -> Option<C> {
     children(parent).next()
 }
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 0830e02f2..c1c215e0d 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -531,7 +531,8 @@ Grammar(
         ),
         "Path": (
             options: [
-                ["segment", "PathSegment"]
+                ["segment", "PathSegment"],
+                ["qualifier", "Path"],
             ]
         ),
         "PathSegment": (