13 files changed, 1334 insertions, 111 deletions

diff --git a/crates/ra_analysis/src/completion.rs b/crates/ra_analysis/src/completion.rs
index 0141d132e..340ae3f66 100644
--- a/crates/ra_analysis/src/completion.rs
+++ b/crates/ra_analysis/src/completion.rs
@@ -1,16 +1,32 @@
-use ra_editor::{CompletionItem, find_node_at_offset};
+use rustc_hash::{FxHashMap, FxHashSet};
+use ra_editor::{find_node_at_offset};
 use ra_syntax::{
-    AtomEdit, File, TextUnit, AstNode,
-    ast::{self, ModuleItemOwner, AstChildren},
+    AtomEdit, File, TextUnit, AstNode, SyntaxNodeRef,
+    algo::visit::{visitor, visitor_ctx, Visitor, VisitorCtx},
+    ast::{self, AstChildren, LoopBodyOwner, ModuleItemOwner},
+    SyntaxKind::*,
 };
 
 use crate::{
     FileId, Cancelable,
     input::FilesDatabase,
     db::{self, SyntaxDatabase},
-    descriptors::module::{ModulesDatabase, ModuleTree, ModuleId, scope::ModuleScope},
+    descriptors::DescriptorDatabase,
+    descriptors::function::FnScopes,
+    descriptors::module::{ModuleTree, ModuleId, ModuleScope},
 };
 
+
+#[derive(Debug)]
+pub struct CompletionItem {
+    /// What user sees in pop-up
+    pub label: String,
+    /// What string is used for filtering, defaults to label
+    pub lookup: Option<String>,
+    /// What is inserted, defaults to label
+    pub snippet: Option<String>,
+}
+
 pub(crate) fn resolve_based_completion(db: &db::RootDatabase, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
     let source_root_id = db.file_source_root(file_id);
     let file = db.file_syntax(file_id);
@@ -72,3 +88,602 @@ fn crate_path(name_ref: ast::NameRef) -> Option<Vec<ast::NameRef>> {
     res.reverse();
     Some(res)
 }
+
+
+pub(crate) fn scope_completion(
+    db: &db::RootDatabase,
+    file_id: FileId,
+    offset: TextUnit,
+) -> Option<Vec<CompletionItem>> {
+    let original_file = db.file_syntax(file_id);
+    // Insert a fake ident to get a valid parse tree
+    let file = {
+        let edit = AtomEdit::insert(offset, "intellijRulezz".to_string());
+        original_file.reparse(&edit)
+    };
+    let mut has_completions = false;
+    let mut res = Vec::new();
+    if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(file.syntax(), offset) {
+        has_completions = true;
+        complete_name_ref(&file, name_ref, &mut res);
+        // special case, `trait T { fn foo(i_am_a_name_ref) {} }`
+        if is_node::<ast::Param>(name_ref.syntax()) {
+            param_completions(name_ref.syntax(), &mut res);
+        }
+        let name_range = name_ref.syntax().range();
+        let top_node = name_ref
+            .syntax()
+            .ancestors()
+            .take_while(|it| it.range() == name_range)
+            .last()
+            .unwrap();
+        match top_node.parent().map(|it| it.kind()) {
+            Some(ROOT) | Some(ITEM_LIST) => complete_mod_item_snippets(&mut res),
+            _ => (),
+        }
+    }
+    if let Some(name) = find_node_at_offset::<ast::Name>(file.syntax(), offset) {
+        if is_node::<ast::Param>(name.syntax()) {
+            has_completions = true;
+            param_completions(name.syntax(), &mut res);
+        }
+    }
+    if has_completions {
+        Some(res)
+    } else {
+        None
+    }
+}
+
+fn complete_module_items(
+    file: &File,
+    items: AstChildren<ast::ModuleItem>,
+    this_item: Option<ast::NameRef>,
+    acc: &mut Vec<CompletionItem>,
+) {
+    let scope = ModuleScope::from_items(items);
+    acc.extend(
+        scope
+            .entries()
+            .iter()
+            .filter(|entry| {
+                let syntax = entry.ptr().resolve(file);
+                Some(syntax.borrowed()) != 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;
+    }
+    let mut visited_fn = false;
+    for node in name_ref.syntax().ancestors() {
+        if let Some(items) = visitor()
+            .visit::<ast::Root, _>(|it| Some(it.items()))
+            .visit::<ast::Module, _>(|it| Some(it.item_list()?.items()))
+            .accept(node)
+        {
+            if let Some(items) = items {
+                complete_module_items(file, items, Some(name_ref), acc);
+            }
+            break;
+        } else if !visited_fn {
+            if let Some(fn_def) = ast::FnDef::cast(node) {
+                visited_fn = true;
+                complete_expr_keywords(&file, fn_def, name_ref, acc);
+                complete_expr_snippets(acc);
+                let scopes = FnScopes::new(fn_def);
+                complete_fn(name_ref, &scopes, acc);
+            }
+        }
+    }
+}
+
+fn param_completions(ctx: SyntaxNodeRef, acc: &mut Vec<CompletionItem>) {
+    let mut params = FxHashMap::default();
+    for node in ctx.ancestors() {
+        let _ = visitor_ctx(&mut params)
+            .visit::<ast::Root, _>(process)
+            .visit::<ast::ItemList, _>(process)
+            .accept(node);
+    }
+    params
+        .into_iter()
+        .filter_map(|(label, (count, param))| {
+            let lookup = param.pat()?.syntax().text().to_string();
+            if count < 2 {
+                None
+            } else {
+                Some((label, lookup))
+            }
+        })
+        .for_each(|(label, lookup)| {
+            acc.push(CompletionItem {
+                label,
+                lookup: Some(lookup),
+                snippet: None,
+            })
+        });
+
+    fn process<'a, N: ast::FnDefOwner<'a>>(
+        node: N,
+        params: &mut FxHashMap<String, (u32, ast::Param<'a>)>,
+    ) {
+        node.functions()
+            .filter_map(|it| it.param_list())
+            .flat_map(|it| it.params())
+            .for_each(|param| {
+                let text = param.syntax().text().to_string();
+                params.entry(text).or_insert((0, param)).0 += 1;
+            })
+    }
+}
+
+fn is_node<'a, N: AstNode<'a>>(node: SyntaxNodeRef<'a>) -> bool {
+    match node.ancestors().filter_map(N::cast).next() {
+        None => false,
+        Some(n) => n.syntax().range() == node.range(),
+    }
+}
+
+fn complete_expr_keywords(
+    file: &File,
+    fn_def: ast::FnDef,
+    name_ref: ast::NameRef,
+    acc: &mut Vec<CompletionItem>,
+) {
+    acc.push(keyword("if", "if $0 {}"));
+    acc.push(keyword("match", "match $0 {}"));
+    acc.push(keyword("while", "while $0 {}"));
+    acc.push(keyword("loop", "loop {$0}"));
+
+    if let Some(off) = name_ref.syntax().range().start().checked_sub(2.into()) {
+        if let Some(if_expr) = find_node_at_offset::<ast::IfExpr>(file.syntax(), off) {
+            if if_expr.syntax().range().end() < name_ref.syntax().range().start() {
+                acc.push(keyword("else", "else {$0}"));
+                acc.push(keyword("else if", "else if $0 {}"));
+            }
+        }
+    }
+    if is_in_loop_body(name_ref) {
+        acc.push(keyword("continue", "continue"));
+        acc.push(keyword("break", "break"));
+    }
+    acc.extend(complete_return(fn_def, name_ref));
+}
+
+fn is_in_loop_body(name_ref: ast::NameRef) -> bool {
+    for node in name_ref.syntax().ancestors() {
+        if node.kind() == FN_DEF || node.kind() == LAMBDA_EXPR {
+            break;
+        }
+        let loop_body = visitor()
+            .visit::<ast::ForExpr, _>(LoopBodyOwner::loop_body)
+            .visit::<ast::WhileExpr, _>(LoopBodyOwner::loop_body)
+            .visit::<ast::LoopExpr, _>(LoopBodyOwner::loop_body)
+            .accept(node);
+        if let Some(Some(body)) = loop_body {
+            if name_ref.syntax().range().is_subrange(&body.syntax().range()) {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+fn complete_return(fn_def: ast::FnDef, name_ref: ast::NameRef) -> Option<CompletionItem> {
+    // let is_last_in_block = name_ref.syntax().ancestors().filter_map(ast::Expr::cast)
+    //     .next()
+    //     .and_then(|it| it.syntax().parent())
+    //     .and_then(ast::Block::cast)
+    //     .is_some();
+
+    // if is_last_in_block {
+    //     return None;
+    // }
+
+    let is_stmt = match name_ref
+        .syntax()
+        .ancestors()
+        .filter_map(ast::ExprStmt::cast)
+        .next()
+    {
+        None => false,
+        Some(expr_stmt) => expr_stmt.syntax().range() == name_ref.syntax().range(),
+    };
+    let snip = match (is_stmt, fn_def.ret_type().is_some()) {
+        (true, true) => "return $0;",
+        (true, false) => "return;",
+        (false, true) => "return $0",
+        (false, false) => "return",
+    };
+    Some(keyword("return", snip))
+}
+
+fn keyword(kw: &str, snip: &str) -> CompletionItem {
+    CompletionItem {
+        label: kw.to_string(),
+        lookup: None,
+        snippet: Some(snip.to_string()),
+    }
+}
+
+fn complete_expr_snippets(acc: &mut Vec<CompletionItem>) {
+    acc.push(CompletionItem {
+        label: "pd".to_string(),
+        lookup: None,
+        snippet: Some("eprintln!(\"$0 = {:?}\", $0);".to_string()),
+    });
+    acc.push(CompletionItem {
+        label: "ppd".to_string(),
+        lookup: None,
+        snippet: Some("eprintln!(\"$0 = {:#?}\", $0);".to_string()),
+    });
+}
+
+fn complete_mod_item_snippets(acc: &mut Vec<CompletionItem>) {
+    acc.push(CompletionItem {
+        label: "tfn".to_string(),
+        lookup: None,
+        snippet: Some("#[test]\nfn $1() {\n    $0\n}".to_string()),
+    });
+    acc.push(CompletionItem {
+        label: "pub(crate)".to_string(),
+        lookup: None,
+        snippet: Some("pub(crate) $0".to_string()),
+    })
+}
+
+fn complete_fn(name_ref: ast::NameRef, scopes: &FnScopes, acc: &mut Vec<CompletionItem>) {
+    let mut shadowed = FxHashSet::default();
+    acc.extend(
+        scopes
+            .scope_chain(name_ref.syntax())
+            .flat_map(|scope| scopes.entries(scope).iter())
+            .filter(|entry| shadowed.insert(entry.name()))
+            .map(|entry| CompletionItem {
+                label: entry.name().to_string(),
+                lookup: None,
+                snippet: None,
+            }),
+    );
+    if scopes.self_param.is_some() {
+        acc.push(CompletionItem {
+            label: "self".to_string(),
+            lookup: None,
+            snippet: None,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::{assert_eq_dbg, extract_offset};
+
+    use crate::FileId;
+    use crate::mock_analysis::MockAnalysis;
+
+    use super::*;
+
+    fn check_scope_completion(code: &str, expected_completions: &str) {
+        let (off, code) = extract_offset(&code);
+        let analysis = MockAnalysis::with_files(&[("/main.rs", &code)]).analysis();
+        let file_id = FileId(1);
+        let completions = scope_completion(&analysis.imp.db, file_id, off)
+            .unwrap()
+            .into_iter()
+            .filter(|c| c.snippet.is_none())
+            .collect::<Vec<_>>();
+        assert_eq_dbg(expected_completions, &completions);
+    }
+
+    fn check_snippet_completion(code: &str, expected_completions: &str) {
+        let (off, code) = extract_offset(&code);
+        let analysis = MockAnalysis::with_files(&[("/main.rs", &code)]).analysis();
+        let file_id = FileId(1);
+        let completions = scope_completion(&analysis.imp.db, file_id, off)
+            .unwrap()
+            .into_iter()
+            .filter(|c| c.snippet.is_some())
+            .collect::<Vec<_>>();
+        assert_eq_dbg(expected_completions, &completions);
+    }
+
+    #[test]
+    fn test_completion_let_scope() {
+        check_scope_completion(
+            r"
+            fn quux(x: i32) {
+                let y = 92;
+                1 + <|>;
+                let z = ();
+            }
+            ",
+            r#"[CompletionItem { label: "y", lookup: None, snippet: None },
+                   CompletionItem { label: "x", lookup: None, snippet: None },
+                   CompletionItem { label: "quux", lookup: None, snippet: None }]"#,
+        );
+    }
+
+    #[test]
+    fn test_completion_if_let_scope() {
+        check_scope_completion(
+            r"
+            fn quux() {
+                if let Some(x) = foo() {
+                    let y = 92;
+                };
+                if let Some(a) = bar() {
+                    let b = 62;
+                    1 + <|>
+                }
+            }
+            ",
+            r#"[CompletionItem { label: "b", lookup: None, snippet: None },
+                   CompletionItem { label: "a", lookup: None, snippet: None },
+                   CompletionItem { label: "quux", lookup: None, snippet: None }]"#,
+        );
+    }
+
+    #[test]
+    fn test_completion_for_scope() {
+        check_scope_completion(
+            r"
+            fn quux() {
+                for x in &[1, 2, 3] {
+                    <|>
+                }
+            }
+            ",
+            r#"[CompletionItem { label: "x", lookup: None, snippet: None },
+                   CompletionItem { label: "quux", lookup: None, snippet: None }]"#,
+        );
+    }
+
+    #[test]
+    fn test_completion_mod_scope() {
+        check_scope_completion(
+            r"
+            struct Foo;
+            enum Baz {}
+            fn quux() {
+                <|>
+            }
+            ",
+            r#"[CompletionItem { label: "Foo", lookup: None, snippet: None },
+                   CompletionItem { label: "Baz", lookup: None, snippet: None },
+                   CompletionItem { label: "quux", lookup: None, snippet: None }]"#,
+        );
+    }
+
+    #[test]
+    fn test_completion_mod_scope_no_self_use() {
+        check_scope_completion(
+            r"
+            use foo<|>;
+            ",
+            r#"[]"#,
+        );
+    }
+
+    #[test]
+    fn test_completion_mod_scope_nested() {
+        check_scope_completion(
+            r"
+            struct Foo;
+            mod m {
+                struct Bar;
+                fn quux() { <|> }
+            }
+            ",
+            r#"[CompletionItem { label: "Bar", lookup: None, snippet: None },
+                   CompletionItem { label: "quux", lookup: None, snippet: None }]"#,
+        );
+    }
+
+    #[test]
+    fn test_complete_type() {
+        check_scope_completion(
+            r"
+            struct Foo;
+            fn x() -> <|>
+        ",
+            r#"[CompletionItem { label: "Foo", lookup: None, snippet: None },
+               CompletionItem { label: "x", lookup: None, snippet: None }]"#,
+        )
+    }
+
+    #[test]
+    fn test_complete_shadowing() {
+        check_scope_completion(
+            r"
+            fn foo() -> {
+                let bar = 92;
+                {
+                    let bar = 62;
+                    <|>
+                }
+            }
+        ",
+            r#"[CompletionItem { label: "bar", lookup: None, snippet: None },
+               CompletionItem { label: "foo", lookup: None, snippet: None }]"#,
+        )
+    }
+
+    #[test]
+    fn test_complete_self() {
+        check_scope_completion(
+            r"
+            impl S { fn foo(&self) { <|> } }
+        ",
+            r#"[CompletionItem { label: "self", lookup: None, snippet: None }]"#,
+        )
+    }
+
+    #[test]
+    fn test_completion_kewords() {
+        check_snippet_completion(r"
+            fn quux() {
+                <|>
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+    }
+
+    #[test]
+    fn test_completion_else() {
+        check_snippet_completion(r"
+            fn quux() {
+                if true {
+                    ()
+                } <|>
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "else", lookup: None, snippet: Some("else {$0}") },
+                   CompletionItem { label: "else if", lookup: None, snippet: Some("else if $0 {}") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+    }
+
+    #[test]
+    fn test_completion_return_value() {
+        check_snippet_completion(r"
+            fn quux() -> i32 {
+                <|>
+                92
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return $0;") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+        check_snippet_completion(r"
+            fn quux() {
+                <|>
+                92
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return;") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+    }
+
+    #[test]
+    fn test_completion_return_no_stmt() {
+        check_snippet_completion(r"
+            fn quux() -> i32 {
+                match () {
+                    () => <|>
+                }
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return $0") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+    }
+
+    #[test]
+    fn test_continue_break_completion() {
+        check_snippet_completion(r"
+            fn quux() -> i32 {
+                loop { <|> }
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "continue", lookup: None, snippet: Some("continue") },
+                   CompletionItem { label: "break", lookup: None, snippet: Some("break") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return $0") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+        check_snippet_completion(r"
+            fn quux() -> i32 {
+                loop { || { <|> } }
+            }
+            ", r#"[CompletionItem { label: "if", lookup: None, snippet: Some("if $0 {}") },
+                   CompletionItem { label: "match", lookup: None, snippet: Some("match $0 {}") },
+                   CompletionItem { label: "while", lookup: None, snippet: Some("while $0 {}") },
+                   CompletionItem { label: "loop", lookup: None, snippet: Some("loop {$0}") },
+                   CompletionItem { label: "return", lookup: None, snippet: Some("return $0") },
+                   CompletionItem { label: "pd", lookup: None, snippet: Some("eprintln!(\"$0 = {:?}\", $0);") },
+                   CompletionItem { label: "ppd", lookup: None, snippet: Some("eprintln!(\"$0 = {:#?}\", $0);") }]"#);
+    }
+
+    #[test]
+    fn test_param_completion_last_param() {
+        check_scope_completion(r"
+            fn foo(file_id: FileId) {}
+            fn bar(file_id: FileId) {}
+            fn baz(file<|>) {}
+        ", r#"[CompletionItem { label: "file_id: FileId", lookup: Some("file_id"), snippet: None }]"#);
+    }
+
+    #[test]
+    fn test_param_completion_nth_param() {
+        check_scope_completion(r"
+            fn foo(file_id: FileId) {}
+            fn bar(file_id: FileId) {}
+            fn baz(file<|>, x: i32) {}
+        ", r#"[CompletionItem { label: "file_id: FileId", lookup: Some("file_id"), snippet: None }]"#);
+    }
+
+    #[test]
+    fn test_param_completion_trait_param() {
+        check_scope_completion(r"
+            pub(crate) trait SourceRoot {
+                pub fn contains(&self, file_id: FileId) -> bool;
+                pub fn module_map(&self) -> &ModuleMap;
+                pub fn lines(&self, file_id: FileId) -> &LineIndex;
+                pub fn syntax(&self, file<|>)
+            }
+        ", r#"[CompletionItem { label: "self", lookup: None, snippet: None },
+               CompletionItem { label: "SourceRoot", lookup: None, snippet: None },
+               CompletionItem { label: "file_id: FileId", lookup: Some("file_id"), snippet: None }]"#);
+    }
+
+    #[test]
+    fn test_item_snippets() {
+        // check_snippet_completion(r"
+        //     <|>
+        //     ",
+        //     r##"[CompletionItem { label: "tfn", lookup: None, snippet: Some("#[test]\nfn $1() {\n    $0\n}") }]"##,
+        // );
+        check_snippet_completion(r"
+            #[cfg(test)]
+            mod tests {
+                <|>
+            }
+            ",
+            r##"[CompletionItem { label: "tfn", lookup: None, snippet: Some("#[test]\nfn $1() {\n    $0\n}") },
+                 CompletionItem { label: "pub(crate)", lookup: None, snippet: Some("pub(crate) $0") }]"##,
+        );
+    }
+}
diff --git a/crates/ra_analysis/src/db.rs b/crates/ra_analysis/src/db.rs
index e7a5d5e2f..fe6587f20 100644
--- a/crates/ra_analysis/src/db.rs
+++ b/crates/ra_analysis/src/db.rs
@@ -9,7 +9,10 @@ use salsa;
 use crate::{
     db,
     Cancelable, Canceled,
-    descriptors::module::{SubmodulesQuery, ModuleTreeQuery, ModulesDatabase, ModuleScopeQuery},
+    descriptors::{
+        DescriptorDatabase, SubmodulesQuery, ModuleTreeQuery, ModuleScopeQuery,
+        FnSyntaxQuery, FnScopesQuery
+    },
     symbol_index::SymbolIndex,
     syntax_ptr::{SyntaxPtrDatabase, ResolveSyntaxPtrQuery},
     FileId,
@@ -63,10 +66,12 @@ salsa::database_storage! {
             fn file_lines() for FileLinesQuery;
             fn file_symbols() for FileSymbolsQuery;
         }
-        impl ModulesDatabase {
+        impl DescriptorDatabase {
             fn module_tree() for ModuleTreeQuery;
             fn module_descriptor() for SubmodulesQuery;
             fn module_scope() for ModuleScopeQuery;
+            fn fn_syntax() for FnSyntaxQuery;
+            fn fn_scopes() for FnScopesQuery;
         }
         impl SyntaxPtrDatabase {
             fn resolve_syntax_ptr() for ResolveSyntaxPtrQuery;
diff --git a/crates/ra_analysis/src/descriptors/function/imp.rs b/crates/ra_analysis/src/descriptors/function/imp.rs
new file mode 100644
index 000000000..0a006f733
--- /dev/null
+++ b/crates/ra_analysis/src/descriptors/function/imp.rs
@@ -0,0 +1,26 @@
+use std::sync::Arc;
+
+use ra_syntax::{
+    ast::{AstNode, FnDef, FnDefNode},
+};
+
+use crate::{
+    descriptors::{
+        DescriptorDatabase,
+        function::{FnId, FnScopes},
+    },
+};
+
+/// Resolve `FnId` to the corresponding `SyntaxNode`
+/// TODO: this should return something more type-safe then `SyntaxNode`
+pub(crate) fn fn_syntax(db: &impl DescriptorDatabase, fn_id: FnId) -> FnDefNode {
+    let syntax = db.resolve_syntax_ptr(fn_id.0);
+    let fn_def = FnDef::cast(syntax.borrowed()).unwrap();
+    FnDefNode::new(fn_def)
+}
+
+pub(crate) fn fn_scopes(db: &impl DescriptorDatabase, fn_id: FnId) -> Arc<FnScopes> {
+    let syntax = db.fn_syntax(fn_id);
+    let res = FnScopes::new(syntax.ast());
+    Arc::new(res)
+}
diff --git a/crates/ra_analysis/src/descriptors/function/mod.rs b/crates/ra_analysis/src/descriptors/function/mod.rs
new file mode 100644
index 000000000..bb68b0ce7
--- /dev/null
+++ b/crates/ra_analysis/src/descriptors/function/mod.rs
@@ -0,0 +1,83 @@
+pub(super) mod imp;
+mod scope;
+
+use ra_syntax::{
+    ast::{self, AstNode, NameOwner}
+};
+
+use crate::{
+    FileId,
+    syntax_ptr::SyntaxPtr
+};
+
+pub(crate) use self::scope::{FnScopes, resolve_local_name};
+
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub(crate) struct FnId(SyntaxPtr);
+
+impl FnId {
+    pub(crate) fn new(file_id: FileId, fn_def: ast::FnDef) -> FnId {
+        let ptr = SyntaxPtr::new(file_id, fn_def.syntax());
+        FnId(ptr)
+    }
+}
+
+
+#[derive(Debug, Clone)]
+pub struct FnDescriptor {
+    pub name: String,
+    pub label: String,
+    pub ret_type: Option<String>,
+    pub params: Vec<String>,
+}
+
+impl FnDescriptor {
+    pub fn new(node: ast::FnDef) -> Option<Self> {
+        let name = node.name()?.text().to_string();
+
+        // Strip the body out for the label.
+        let label: String = if let Some(body) = node.body() {
+            let body_range = body.syntax().range();
+            let label: String = node
+                .syntax()
+                .children()
+                .filter(|child| !child.range().is_subrange(&body_range))
+                .map(|node| node.text().to_string())
+                .collect();
+            label
+        } else {
+            node.syntax().text().to_string()
+        };
+
+        let params = FnDescriptor::param_list(node);
+        let ret_type = node.ret_type().map(|r| r.syntax().text().to_string());
+
+        Some(FnDescriptor {
+            name,
+            ret_type,
+            params,
+            label,
+        })
+    }
+
+    fn param_list(node: ast::FnDef) -> Vec<String> {
+        let mut res = vec![];
+        if let Some(param_list) = node.param_list() {
+            if let Some(self_param) = param_list.self_param() {
+                res.push(self_param.syntax().text().to_string())
+            }
+
+            // Maybe use param.pat here? See if we can just extract the name?
+            //res.extend(param_list.params().map(|p| p.syntax().text().to_string()));
+            res.extend(
+                param_list
+                    .params()
+                    .filter_map(|p| p.pat())
+                    .map(|pat| pat.syntax().text().to_string()),
+            );
+        }
+        res
+    }
+}
+
diff --git a/crates/ra_analysis/src/descriptors/function/scope.rs b/crates/ra_analysis/src/descriptors/function/scope.rs
new file mode 100644
index 000000000..d9929414c
--- /dev/null
+++ b/crates/ra_analysis/src/descriptors/function/scope.rs
@@ -0,0 +1,433 @@
+use rustc_hash::{FxHashMap, FxHashSet};
+
+use ra_syntax::{
+    algo::generate,
+    ast::{self, ArgListOwner, LoopBodyOwner, NameOwner},
+    AstNode, SmolStr, SyntaxNodeRef,
+};
+
+use crate::syntax_ptr::LocalSyntaxPtr;
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub(crate) struct ScopeId(u32);
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct FnScopes {
+    pub(crate) self_param: Option<LocalSyntaxPtr>,
+    scopes: Vec<ScopeData>,
+    scope_for: FxHashMap<LocalSyntaxPtr, ScopeId>,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct ScopeEntry {
+    name: SmolStr,
+    ptr: LocalSyntaxPtr,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+struct ScopeData {
+    parent: Option<ScopeId>,
+    entries: Vec<ScopeEntry>,
+}
+
+impl FnScopes {
+    pub(crate) fn new(fn_def: ast::FnDef) -> FnScopes {
+        let mut scopes = FnScopes {
+            self_param: fn_def
+                .param_list()
+                .and_then(|it| it.self_param())
+                .map(|it| LocalSyntaxPtr::new(it.syntax())),
+            scopes: Vec::new(),
+            scope_for: FxHashMap::default(),
+        };
+        let root = scopes.root_scope();
+        scopes.add_params_bindings(root, fn_def.param_list());
+        if let Some(body) = fn_def.body() {
+            compute_block_scopes(body, &mut scopes, root)
+        }
+        scopes
+    }
+    pub(crate) fn entries(&self, scope: ScopeId) -> &[ScopeEntry] {
+        &self.get(scope).entries
+    }
+    pub fn scope_chain<'a>(&'a self, node: SyntaxNodeRef) -> impl Iterator<Item = ScopeId> + 'a {
+        generate(self.scope_for(node), move |&scope| {
+            self.get(scope).parent
+        })
+    }
+    fn root_scope(&mut self) -> ScopeId {
+        let res = ScopeId(self.scopes.len() as u32);
+        self.scopes.push(ScopeData {
+            parent: None,
+            entries: vec![],
+        });
+        res
+    }
+    fn new_scope(&mut self, parent: ScopeId) -> ScopeId {
+        let res = ScopeId(self.scopes.len() as u32);
+        self.scopes.push(ScopeData {
+            parent: Some(parent),
+            entries: vec![],
+        });
+        res
+    }
+    fn add_bindings(&mut self, scope: ScopeId, pat: ast::Pat) {
+        let entries = pat
+            .syntax()
+            .descendants()
+            .filter_map(ast::BindPat::cast)
+            .filter_map(ScopeEntry::new);
+        self.get_mut(scope).entries.extend(entries);
+    }
+    fn add_params_bindings(&mut self, scope: ScopeId, params: Option<ast::ParamList>) {
+        params
+            .into_iter()
+            .flat_map(|it| it.params())
+            .filter_map(|it| it.pat())
+            .for_each(|it| self.add_bindings(scope, it));
+    }
+    fn set_scope(&mut self, node: SyntaxNodeRef, scope: ScopeId) {
+        self.scope_for.insert(LocalSyntaxPtr::new(node), scope);
+    }
+    fn scope_for(&self, node: SyntaxNodeRef) -> Option<ScopeId> {
+        node.ancestors()
+            .map(LocalSyntaxPtr::new)
+            .filter_map(|it| self.scope_for.get(&it).map(|&scope| scope))
+            .next()
+    }
+    fn get(&self, scope: ScopeId) -> &ScopeData {
+        &self.scopes[scope.0 as usize]
+    }
+    fn get_mut(&mut self, scope: ScopeId) -> &mut ScopeData {
+        &mut self.scopes[scope.0 as usize]
+    }
+}
+
+impl ScopeEntry {
+    fn new(pat: ast::BindPat) -> Option<ScopeEntry> {
+        let name = pat.name()?;
+        let res = ScopeEntry {
+            name: name.text(),
+            ptr: LocalSyntaxPtr::new(pat.syntax()),
+        };
+        Some(res)
+    }
+    pub(crate) fn name(&self) -> &SmolStr {
+        &self.name
+    }
+    pub(crate) fn ptr(&self) -> LocalSyntaxPtr {
+        self.ptr
+    }
+}
+
+fn compute_block_scopes(block: ast::Block, scopes: &mut FnScopes, mut scope: ScopeId) {
+    for stmt in block.statements() {
+        match stmt {
+            ast::Stmt::LetStmt(stmt) => {
+                if let Some(expr) = stmt.initializer() {
+                    scopes.set_scope(expr.syntax(), scope);
+                    compute_expr_scopes(expr, scopes, scope);
+                }
+                scope = scopes.new_scope(scope);
+                if let Some(pat) = stmt.pat() {
+                    scopes.add_bindings(scope, pat);
+                }
+            }
+            ast::Stmt::ExprStmt(expr_stmt) => {
+                if let Some(expr) = expr_stmt.expr() {
+                    scopes.set_scope(expr.syntax(), scope);
+                    compute_expr_scopes(expr, scopes, scope);
+                }
+            }
+        }
+    }
+    if let Some(expr) = block.expr() {
+        scopes.set_scope(expr.syntax(), scope);
+        compute_expr_scopes(expr, scopes, scope);
+    }
+}
+
+fn compute_expr_scopes(expr: ast::Expr, scopes: &mut FnScopes, scope: ScopeId) {
+    match expr {
+        ast::Expr::IfExpr(e) => {
+            let cond_scope = e
+                .condition()
+                .and_then(|cond| compute_cond_scopes(cond, scopes, scope));
+            if let Some(block) = e.then_branch() {
+                compute_block_scopes(block, scopes, cond_scope.unwrap_or(scope));
+            }
+            if let Some(block) = e.else_branch() {
+                compute_block_scopes(block, scopes, scope);
+            }
+        }
+        ast::Expr::BlockExpr(e) => {
+            if let Some(block) = e.block() {
+                compute_block_scopes(block, scopes, scope);
+            }
+        }
+        ast::Expr::LoopExpr(e) => {
+            if let Some(block) = e.loop_body() {
+                compute_block_scopes(block, scopes, scope);
+            }
+        }
+        ast::Expr::WhileExpr(e) => {
+            let cond_scope = e
+                .condition()
+                .and_then(|cond| compute_cond_scopes(cond, scopes, scope));
+            if let Some(block) = e.loop_body() {
+                compute_block_scopes(block, scopes, cond_scope.unwrap_or(scope));
+            }
+        }
+        ast::Expr::ForExpr(e) => {
+            if let Some(expr) = e.iterable() {
+                compute_expr_scopes(expr, scopes, scope);
+            }
+            let mut scope = scope;
+            if let Some(pat) = e.pat() {
+                scope = scopes.new_scope(scope);
+                scopes.add_bindings(scope, pat);
+            }
+            if let Some(block) = e.loop_body() {
+                compute_block_scopes(block, scopes, scope);
+            }
+        }
+        ast::Expr::LambdaExpr(e) => {
+            let scope = scopes.new_scope(scope);
+            scopes.add_params_bindings(scope, e.param_list());
+            if let Some(body) = e.body() {
+                scopes.set_scope(body.syntax(), scope);
+                compute_expr_scopes(body, scopes, scope);
+            }
+        }
+        ast::Expr::CallExpr(e) => {
+            compute_call_scopes(e.expr(), e.arg_list(), scopes, scope);
+        }
+        ast::Expr::MethodCallExpr(e) => {
+            compute_call_scopes(e.expr(), e.arg_list(), scopes, scope);
+        }
+        ast::Expr::MatchExpr(e) => {
+            if let Some(expr) = e.expr() {
+                compute_expr_scopes(expr, scopes, scope);
+            }
+            for arm in e.match_arm_list().into_iter().flat_map(|it| it.arms()) {
+                let scope = scopes.new_scope(scope);
+                for pat in arm.pats() {
+                    scopes.add_bindings(scope, pat);
+                }
+                if let Some(expr) = arm.expr() {
+                    compute_expr_scopes(expr, scopes, scope);
+                }
+            }
+        }
+        _ => expr
+            .syntax()
+            .children()
+            .filter_map(ast::Expr::cast)
+            .for_each(|expr| compute_expr_scopes(expr, scopes, scope)),
+    };
+
+    fn compute_call_scopes(
+        receiver: Option<ast::Expr>,
+        arg_list: Option<ast::ArgList>,
+        scopes: &mut FnScopes,
+        scope: ScopeId,
+    ) {
+        arg_list
+            .into_iter()
+            .flat_map(|it| it.args())
+            .chain(receiver)
+            .for_each(|expr| compute_expr_scopes(expr, scopes, scope));
+    }
+
+    fn compute_cond_scopes(
+        cond: ast::Condition,
+        scopes: &mut FnScopes,
+        scope: ScopeId,
+    ) -> Option<ScopeId> {
+        if let Some(expr) = cond.expr() {
+            compute_expr_scopes(expr, scopes, scope);
+        }
+        if let Some(pat) = cond.pat() {
+            let s = scopes.new_scope(scope);
+            scopes.add_bindings(s, pat);
+            Some(s)
+        } else {
+            None
+        }
+    }
+}
+
+pub fn resolve_local_name<'a>(
+    name_ref: ast::NameRef,
+    scopes: &'a FnScopes,
+) -> Option<&'a ScopeEntry> {
+    let mut shadowed = FxHashSet::default();
+    let ret = scopes
+        .scope_chain(name_ref.syntax())
+        .flat_map(|scope| scopes.entries(scope).iter())
+        .filter(|entry| shadowed.insert(entry.name()))
+        .filter(|entry| entry.name() == &name_ref.text())
+        .nth(0);
+    ret
+}
+
+#[cfg(test)]
+mod tests {
+    use ra_syntax::File;
+    use test_utils::extract_offset;
+    use ra_editor::{find_node_at_offset};
+
+    use super::*;
+
+
+    fn do_check(code: &str, expected: &[&str]) {
+        let (off, code) = extract_offset(code);
+        let code = {
+            let mut buf = String::new();
+            let off = u32::from(off) as usize;
+            buf.push_str(&code[..off]);
+            buf.push_str("marker");
+            buf.push_str(&code[off..]);
+            buf
+        };
+        let file = File::parse(&code);
+        let marker: ast::PathExpr = find_node_at_offset(file.syntax(), off).unwrap();
+        let fn_def: ast::FnDef = find_node_at_offset(file.syntax(), off).unwrap();
+        let scopes = FnScopes::new(fn_def);
+        let actual = scopes
+            .scope_chain(marker.syntax())
+            .flat_map(|scope| scopes.entries(scope))
+            .map(|it| it.name())
+            .collect::<Vec<_>>();
+        assert_eq!(actual.as_slice(), expected);
+    }
+
+    #[test]
+    fn test_lambda_scope() {
+        do_check(
+            r"
+            fn quux(foo: i32) {
+                let f = |bar, baz: i32| {
+                    <|>
+                };
+            }",
+            &["bar", "baz", "foo"],
+        );
+    }
+
+    #[test]
+    fn test_call_scope() {
+        do_check(
+            r"
+            fn quux() {
+                f(|x| <|> );
+            }",
+            &["x"],
+        );
+    }
+
+    #[test]
+    fn test_metod_call_scope() {
+        do_check(
+            r"
+            fn quux() {
+                z.f(|x| <|> );
+            }",
+            &["x"],
+        );
+    }
+
+    #[test]
+    fn test_loop_scope() {
+        do_check(
+            r"
+            fn quux() {
+                loop {
+                    let x = ();
+                    <|>
+                };
+            }",
+            &["x"],
+        );
+    }
+
+    #[test]
+    fn test_match() {
+        do_check(
+            r"
+            fn quux() {
+                match () {
+                    Some(x) => {
+                        <|>
+                    }
+                };
+            }",
+            &["x"],
+        );
+    }
+
+    #[test]
+    fn test_shadow_variable() {
+        do_check(
+            r"
+            fn foo(x: String) {
+                let x : &str = &x<|>;
+            }",
+            &["x"],
+        );
+    }
+
+    fn do_check_local_name(code: &str, expected_offset: u32) {
+        let (off, code) = extract_offset(code);
+        let file = File::parse(&code);
+        let fn_def: ast::FnDef = find_node_at_offset(file.syntax(), off).unwrap();
+        let name_ref: ast::NameRef = find_node_at_offset(file.syntax(), off).unwrap();
+
+        let scopes = FnScopes::new(fn_def);
+
+        let local_name_entry = resolve_local_name(name_ref, &scopes).unwrap();
+        let local_name = local_name_entry.ptr().resolve(&file);
+        let expected_name =
+            find_node_at_offset::<ast::Name>(file.syntax(), expected_offset.into()).unwrap();
+        assert_eq!(local_name.range(), expected_name.syntax().range());
+    }
+
+    #[test]
+    fn test_resolve_local_name() {
+        do_check_local_name(
+            r#"
+            fn foo(x: i32, y: u32) {
+                {
+                    let z = x * 2;
+                }
+                {
+                    let t = x<|> * 3;
+                }
+            }"#,
+            21,
+        );
+    }
+
+    #[test]
+    fn test_resolve_local_name_declaration() {
+        do_check_local_name(
+            r#"
+            fn foo(x: String) {
+                let x : &str = &x<|>;
+            }"#,
+            21,
+        );
+    }
+
+    #[test]
+    fn test_resolve_local_name_shadow() {
+        do_check_local_name(
+            r"
+        fn foo(x: String) {
+            let x : &str = &x;
+            x<|>
+        }",
+            46,
+        );
+    }
+}
diff --git a/crates/ra_analysis/src/descriptors/mod.rs b/crates/ra_analysis/src/descriptors/mod.rs
index 0220f7d5d..0c4991757 100644
--- a/crates/ra_analysis/src/descriptors/mod.rs
+++ b/crates/ra_analysis/src/descriptors/mod.rs
@@ -1,62 +1,46 @@
 pub(crate) mod module;
+pub(crate) mod function;
+
+use std::sync::Arc;
 
 use ra_syntax::{
-    ast::{self, AstNode, NameOwner},
+    SmolStr,
+    ast::{FnDefNode},
 };
 
-#[derive(Debug, Clone)]
-pub struct FnDescriptor {
-    pub name: String,
-    pub label: String,
-    pub ret_type: Option<String>,
-    pub params: Vec<String>,
-}
-
-impl FnDescriptor {
-    pub fn new(node: ast::FnDef) -> Option<Self> {
-        let name = node.name()?.text().to_string();
-
-        // Strip the body out for the label.
-        let label: String = if let Some(body) = node.body() {
-            let body_range = body.syntax().range();
-            let label: String = node
-                .syntax()
-                .children()
-                .filter(|child| !child.range().is_subrange(&body_range))
-                .map(|node| node.text().to_string())
-                .collect();
-            label
-        } else {
-            node.syntax().text().to_string()
-        };
-
-        let params = FnDescriptor::param_list(node);
-        let ret_type = node.ret_type().map(|r| r.syntax().text().to_string());
-
-        Some(FnDescriptor {
-            name,
-            ret_type,
-            params,
-            label,
-        })
-    }
+use crate::{
+    FileId, Cancelable,
+    db::SyntaxDatabase,
+    descriptors::module::{ModuleTree, ModuleId, ModuleScope},
+    descriptors::function::{FnId, FnScopes},
+    input::SourceRootId,
+    syntax_ptr::SyntaxPtrDatabase,
+};
 
-    fn param_list(node: ast::FnDef) -> Vec<String> {
-        let mut res = vec![];
-        if let Some(param_list) = node.param_list() {
-            if let Some(self_param) = param_list.self_param() {
-                res.push(self_param.syntax().text().to_string())
-            }
 
-            // Maybe use param.pat here? See if we can just extract the name?
-            //res.extend(param_list.params().map(|p| p.syntax().text().to_string()));
-            res.extend(
-                param_list
-                    .params()
-                    .filter_map(|p| p.pat())
-                    .map(|pat| pat.syntax().text().to_string()),
-            );
+salsa::query_group! {
+    pub(crate) trait DescriptorDatabase: SyntaxDatabase + SyntaxPtrDatabase {
+        fn module_tree(source_root_id: SourceRootId) -> Cancelable<Arc<ModuleTree>> {
+            type ModuleTreeQuery;
+            use fn module::imp::module_tree;
+        }
+        fn submodules(file_id: FileId) -> Cancelable<Arc<Vec<SmolStr>>> {
+            type SubmodulesQuery;
+            use fn module::imp::submodules;
+        }
+        fn module_scope(source_root_id: SourceRootId, module_id: ModuleId) -> Cancelable<Arc<ModuleScope>> {
+            type ModuleScopeQuery;
+            use fn module::imp::module_scope;
+        }
+        fn fn_syntax(fn_id: FnId) -> FnDefNode {
+            type FnSyntaxQuery;
+            // Don't retain syntax trees in memory
+            storage volatile;
+            use fn function::imp::fn_syntax;
+        }
+        fn fn_scopes(fn_id: FnId) -> Arc<FnScopes> {
+            type FnScopesQuery;
+            use fn function::imp::fn_scopes;
         }
-        res
     }
 }
diff --git a/crates/ra_analysis/src/descriptors/module/imp.rs b/crates/ra_analysis/src/descriptors/module/imp.rs
index 5fdaad137..dae3a356d 100644
--- a/crates/ra_analysis/src/descriptors/module/imp.rs
+++ b/crates/ra_analysis/src/descriptors/module/imp.rs
@@ -10,14 +10,15 @@ use ra_syntax::{
 use crate::{
     FileId, Cancelable, FileResolverImp, db,
     input::{SourceRoot, SourceRootId},
+    descriptors::DescriptorDatabase,
 };
 
 use super::{
-    ModuleData, ModuleTree, ModuleId, LinkId, LinkData, Problem, ModulesDatabase, ModuleScope
+    ModuleData, ModuleTree, ModuleId, LinkId, LinkData, Problem, ModuleScope
 };
 
 
-pub(super) fn submodules(db: &impl ModulesDatabase, file_id: FileId) -> Cancelable<Arc<Vec<SmolStr>>> {
+pub(crate) fn submodules(db: &impl DescriptorDatabase, file_id: FileId) -> Cancelable<Arc<Vec<SmolStr>>> {
     db::check_canceled(db)?;
     let file = db.file_syntax(file_id);
     let root = file.ast();
@@ -25,7 +26,7 @@ pub(super) fn submodules(db: &impl ModulesDatabase, file_id: FileId) -> Cancelab
     Ok(Arc::new(submodules))
 }
 
-pub(super) fn modules(root: ast::Root<'_>) -> impl Iterator<Item = (SmolStr, ast::Module<'_>)> {
+pub(crate) fn modules(root: ast::Root<'_>) -> impl Iterator<Item = (SmolStr, ast::Module<'_>)> {
     root.modules().filter_map(|module| {
         let name = module.name()?.text();
         if !module.has_semi() {
@@ -35,8 +36,8 @@ pub(super) fn modules(root: ast::Root<'_>) -> impl Iterator<Item = (SmolStr, ast
     })
 }
 
-pub(super) fn module_scope(
-    db: &impl ModulesDatabase,
+pub(crate) fn module_scope(
+    db: &impl DescriptorDatabase,
     source_root_id: SourceRootId,
     module_id: ModuleId,
 ) -> Cancelable<Arc<ModuleScope>> {
@@ -47,8 +48,8 @@ pub(super) fn module_scope(
     Ok(Arc::new(res))
 }
 
-pub(super) fn module_tree(
-    db: &impl ModulesDatabase,
+pub(crate) fn module_tree(
+    db: &impl DescriptorDatabase,
     source_root: SourceRootId,
 ) -> Cancelable<Arc<ModuleTree>> {
     db::check_canceled(db)?;
@@ -64,7 +65,7 @@ pub struct Submodule {
 
 
 fn create_module_tree<'a>(
-    db: &impl ModulesDatabase,
+    db: &impl DescriptorDatabase,
     source_root: SourceRootId,
 ) -> Cancelable<ModuleTree> {
     let mut tree = ModuleTree {
@@ -88,7 +89,7 @@ fn create_module_tree<'a>(
 }
 
 fn build_subtree(
-    db: &impl ModulesDatabase,
+    db: &impl DescriptorDatabase,
     source_root: &SourceRoot,
     tree: &mut ModuleTree,
     visited: &mut FxHashSet<FileId>,
diff --git a/crates/ra_analysis/src/descriptors/module/mod.rs b/crates/ra_analysis/src/descriptors/module/mod.rs
index 9e5d73f94..667553f74 100644
--- a/crates/ra_analysis/src/descriptors/module/mod.rs
+++ b/crates/ra_analysis/src/descriptors/module/mod.rs
@@ -1,37 +1,13 @@
-mod imp;
+pub(super) mod imp;
 pub(crate) mod scope;
 
-use std::sync::Arc;
-
 use relative_path::RelativePathBuf;
 use ra_syntax::{ast::{self, NameOwner, AstNode}, SmolStr, SyntaxNode};
 
-use crate::{
-    FileId, Cancelable,
-    db::SyntaxDatabase,
-    input::SourceRootId,
-};
+use crate::FileId;
 
 pub(crate) use self::scope::ModuleScope;
 
-salsa::query_group! {
-    pub(crate) trait ModulesDatabase: SyntaxDatabase {
-        fn module_tree(source_root_id: SourceRootId) -> Cancelable<Arc<ModuleTree>> {
-            type ModuleTreeQuery;
-            use fn imp::module_tree;
-        }
-        fn submodules(file_id: FileId) -> Cancelable<Arc<Vec<SmolStr>>> {
-            type SubmodulesQuery;
-            use fn imp::submodules;
-        }
-        fn module_scope(source_root_id: SourceRootId, module_id: ModuleId) -> Cancelable<Arc<ModuleScope>> {
-            type ModuleScopeQuery;
-            use fn imp::module_scope;
-        }
-    }
-}
-
-
 #[derive(Debug, PartialEq, Eq, Hash)]
 pub(crate) struct ModuleTree {
     mods: Vec<ModuleData>,
diff --git a/crates/ra_analysis/src/descriptors/module/scope.rs b/crates/ra_analysis/src/descriptors/module/scope.rs
index da58ddce0..846b8b44f 100644
--- a/crates/ra_analysis/src/descriptors/module/scope.rs
+++ b/crates/ra_analysis/src/descriptors/module/scope.rs
@@ -2,8 +2,8 @@
 
 
 use ra_syntax::{
-    ast::{self, AstChildren, ModuleItemOwner},
-    File, AstNode, SmolStr, SyntaxNode, SyntaxNodeRef,
+    ast::{self, ModuleItemOwner},
+    File, AstNode, SmolStr,
 };
 
 use crate::syntax_ptr::LocalSyntaxPtr;
@@ -30,8 +30,12 @@ enum EntryKind {
 
 impl ModuleScope {
     pub fn new(file: &File) -> ModuleScope {
+        ModuleScope::from_items(file.ast().items())
+    }
+
+    pub fn from_items<'a>(items: impl Iterator<Item = ast::ModuleItem<'a>>) -> ModuleScope {
         let mut entries = Vec::new();
-        for item in file.ast().items() {
+        for item in items {
             let entry = match item {
                 ast::ModuleItem::StructDef(item) => Entry::new(item),
                 ast::ModuleItem::EnumDef(item) => Entry::new(item),
@@ -99,7 +103,7 @@ fn collect_imports(tree: ast::UseTree, acc: &mut Vec<Entry>) {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use ra_syntax::{ast::ModuleItemOwner, File};
+    use ra_syntax::{File};
 
     fn do_check(code: &str, expected: &[&str]) {
         let file = File::parse(&code);
diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index efb3182a6..38d4b6a23 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -3,7 +3,7 @@ use std::{
     sync::Arc,
 };
 
-use ra_editor::{self, find_node_at_offset, resolve_local_name, FileSymbol, LineIndex, LocalEdit, CompletionItem};
+use ra_editor::{self, find_node_at_offset, FileSymbol, LineIndex, LocalEdit};
 use ra_syntax::{
     ast::{self, ArgListOwner, Expr, NameOwner},
     AstNode, File, SmolStr,
@@ -21,9 +21,14 @@ use crate::{
         self, SyntaxDatabase, FileSyntaxQuery,
     },
     input::{SourceRootId, FilesDatabase, SourceRoot, WORKSPACE},
-    descriptors::module::{ModulesDatabase, ModuleTree, Problem},
-    descriptors::{FnDescriptor},
+    descriptors::{
+        DescriptorDatabase,
+        module::{ModuleTree, Problem},
+        function::{FnDescriptor, FnId},
+    },
+    completion::{scope_completion, resolve_based_completion, CompletionItem},
     symbol_index::SymbolIndex,
+    syntax_ptr::SyntaxPtrDatabase,
     CrateGraph, CrateId, Diagnostic, FileId, FileResolver, FileSystemEdit, Position,
     Query, SourceChange, SourceFileEdit, Cancelable,
 };
@@ -175,7 +180,7 @@ impl AnalysisHostImpl {
 
 #[derive(Debug)]
 pub(crate) struct AnalysisImpl {
-    db: db::RootDatabase,
+    pub(crate) db: db::RootDatabase,
 }
 
 impl AnalysisImpl {
@@ -245,12 +250,11 @@ impl AnalysisImpl {
     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) {
+        if let Some(scope_based) = scope_completion(&self.db, file_id, offset) {
             res.extend(scope_based);
             has_completions = true;
         }
-        if let Some(scope_based) = crate::completion::resolve_based_completion(&self.db, file_id, offset)? {
+        if let Some(scope_based) = resolve_based_completion(&self.db, file_id, offset)? {
             res.extend(scope_based);
             has_completions = true;
         }
@@ -271,7 +275,7 @@ impl AnalysisImpl {
         let syntax = file.syntax();
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(syntax, offset) {
             // First try to resolve the symbol locally
-            return if let Some((name, range)) = resolve_local_name(name_ref) {
+            return if let Some((name, range)) = resolve_local_name(&self.db, file_id, name_ref) {
                 let mut vec = vec![];
                 vec.push((
                     file_id,
@@ -325,7 +329,7 @@ impl AnalysisImpl {
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(syntax, offset) {
 
             // We are only handing local references for now
-            if let Some(resolved) = resolve_local_name(name_ref) {
+            if let Some(resolved) = resolve_local_name(&self.db, file_id, name_ref) {
 
                 ret.push((file_id, resolved.1));
 
@@ -333,7 +337,7 @@ impl AnalysisImpl {
 
                     let refs : Vec<_> = fn_def.syntax().descendants()
                         .filter_map(ast::NameRef::cast)
-                        .filter(|&n: &ast::NameRef| resolve_local_name(n) == Some(resolved.clone()))
+                        .filter(|&n: &ast::NameRef| resolve_local_name(&self.db, file_id, n) == Some(resolved.clone()))
                         .collect();
 
                     for r in refs {
@@ -597,3 +601,16 @@ impl<'a> FnCallNode<'a> {
         }
     }
 }
+
+fn resolve_local_name(
+    db: &db::RootDatabase,
+    file_id: FileId,
+    name_ref: ast::NameRef,
+) -> Option<(SmolStr, TextRange)> {
+    let fn_def = name_ref.syntax().ancestors().find_map(ast::FnDef::cast)?;
+    let fn_id = FnId::new(file_id, fn_def);
+    let scopes = db.fn_scopes(fn_id);
+    let scope_entry = crate::descriptors::function::resolve_local_name(name_ref, &scopes)?;
+    let syntax = db.resolve_syntax_ptr(scope_entry.ptr().into_global(file_id));
+    Some((scope_entry.name().clone(), syntax.range()))
+}
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index 363c72c0b..776010281 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -13,6 +13,7 @@ mod imp;
 mod symbol_index;
 mod completion;
 mod syntax_ptr;
+mod mock_analysis;
 
 use std::{
     fmt,
@@ -29,11 +30,13 @@ use crate::{
 };
 
 pub use crate::{
-    descriptors::FnDescriptor,
-    input::{FileId, FileResolver, CrateGraph, CrateId}
+    descriptors::function::FnDescriptor,
+    completion::CompletionItem,
+    input::{FileId, FileResolver, CrateGraph, CrateId},
+    mock_analysis::MockAnalysis,
 };
 pub use ra_editor::{
-    CompletionItem, FileSymbol, Fold, FoldKind, HighlightedRange, LineIndex, Runnable,
+    FileSymbol, Fold, FoldKind, HighlightedRange, LineIndex, Runnable,
     RunnableKind, StructureNode,
 };
 
@@ -197,7 +200,7 @@ impl Query {
 
 #[derive(Debug)]
 pub struct Analysis {
-    imp: AnalysisImpl,
+    pub(crate) imp: AnalysisImpl,
 }
 
 impl Analysis {
diff --git a/crates/ra_analysis/src/mock_analysis.rs b/crates/ra_analysis/src/mock_analysis.rs
new file mode 100644
index 000000000..1c1dbee7c
--- /dev/null
+++ b/crates/ra_analysis/src/mock_analysis.rs
@@ -0,0 +1,71 @@
+
+use std::sync::Arc;
+
+use relative_path::{RelativePath, RelativePathBuf};
+
+use crate::{
+    AnalysisChange, Analysis, AnalysisHost, FileId, FileResolver,
+};
+
+/// Mock analysis is used in test to bootstrap an AnalysisHost/Analysis
+/// from a set of in-memory files.
+#[derive(Debug, Default)]
+pub struct MockAnalysis {
+    files: Vec<(String, String)>,
+}
+
+impl MockAnalysis {
+    pub fn new() -> MockAnalysis {
+        MockAnalysis::default()
+    }
+    pub fn with_files(files: &[(&str, &str)]) -> MockAnalysis {
+        let files = files.iter()
+            .map(|it| (it.0.to_string(), it.1.to_string()))
+            .collect();
+        MockAnalysis { files }
+    }
+    pub fn analysis_host(self) -> AnalysisHost {
+        let mut host = AnalysisHost::new();
+        let mut file_map = Vec::new();
+        let mut change = AnalysisChange::new();
+        for (id, (path, contents)) in self.files.into_iter().enumerate() {
+            let file_id = FileId((id + 1) as u32);
+            assert!(path.starts_with('/'));
+            let path = RelativePathBuf::from_path(&path[1..]).unwrap();
+            change.add_file(file_id, contents);
+            file_map.push((file_id, path));
+        }
+        change.set_file_resolver(Arc::new(FileMap(file_map)));
+        host.apply_change(change);
+        host
+    }
+    pub fn analysis(self) -> Analysis {
+        self.analysis_host().analysis()
+    }
+}
+
+#[derive(Debug)]
+struct FileMap(Vec<(FileId, RelativePathBuf)>);
+
+impl FileMap {
+    fn iter<'a>(&'a self) -> impl Iterator<Item = (FileId, &'a RelativePath)> + 'a {
+        self.0
+            .iter()
+            .map(|(id, path)| (*id, path.as_relative_path()))
+    }
+
+    fn path(&self, id: FileId) -> &RelativePath {
+        self.iter().find(|&(it, _)| it == id).unwrap().1
+    }
+}
+
+impl FileResolver for FileMap {
+    fn file_stem(&self, id: FileId) -> String {
+        self.path(id).file_stem().unwrap().to_string()
+    }
+    fn resolve(&self, id: FileId, rel: &RelativePath) -> Option<FileId> {
+        let path = self.path(id).join(rel).normalize();
+        let id = self.iter().find(|&(_, p)| path == p)?.0;
+        Some(id)
+    }
+}
diff --git a/crates/ra_analysis/src/syntax_ptr.rs b/crates/ra_analysis/src/syntax_ptr.rs
index 6dc89cb43..c3c904633 100644
--- a/crates/ra_analysis/src/syntax_ptr.rs
+++ b/crates/ra_analysis/src/syntax_ptr.rs
@@ -12,6 +12,7 @@ salsa::query_group! {
     pub(crate) trait SyntaxPtrDatabase: SyntaxDatabase {
         fn resolve_syntax_ptr(ptr: SyntaxPtr) -> SyntaxNode {
             type ResolveSyntaxPtrQuery;
+            // Don't retain syntax trees in memory
             storage volatile;
         }
     }
@@ -83,6 +84,10 @@ impl LocalSyntaxPtr {
                 .unwrap_or_else(|| panic!("can't resolve local ptr to SyntaxNode: {:?}", self))
         }
     }
+
+    pub(crate) fn into_global(self, file_id: FileId) -> SyntaxPtr {
+        SyntaxPtr { file_id, local: self}
+    }
 }