23 files changed, 4255 insertions, 0 deletions

diff --git a/crates/ra_ide_api/Cargo.toml b/crates/ra_ide_api/Cargo.toml
new file mode 100644
index 000000000..d42a664b6
--- /dev/null
+++ b/crates/ra_ide_api/Cargo.toml
@@ -0,0 +1,23 @@
+[package]
+edition = "2018"
+name = "ra_ide_api"
+version = "0.1.0"
+authors = ["Aleksey Kladov <[email protected]>"]
+
+[dependencies]
+itertools = "0.8.0"
+log = "0.4.5"
+relative-path = "0.4.0"
+rayon = "1.0.2"
+fst = "0.3.1"
+salsa = "0.9.1"
+rustc-hash = "1.0"
+parking_lot = "0.7.0"
+unicase = "2.2.0"
+
+ra_syntax = { path = "../ra_syntax" }
+ra_ide_api_light = { path = "../ra_ide_api_light" }
+ra_text_edit = { path = "../ra_text_edit" }
+ra_db = { path = "../ra_db" }
+hir = { path = "../ra_hir", package = "ra_hir" }
+test_utils = { path = "../test_utils" }
diff --git a/crates/ra_ide_api/src/call_info.rs b/crates/ra_ide_api/src/call_info.rs
new file mode 100644
index 000000000..27b760780
--- /dev/null
+++ b/crates/ra_ide_api/src/call_info.rs
@@ -0,0 +1,451 @@
+use std::cmp::{max, min};
+
+use ra_db::{SyntaxDatabase, Cancelable};
+use ra_syntax::{
+    AstNode, SyntaxNode, TextUnit, TextRange,
+    SyntaxKind::FN_DEF,
+    ast::{self, ArgListOwner, DocCommentsOwner},
+    algo::find_node_at_offset,
+};
+
+use crate::{FilePosition, CallInfo, db::RootDatabase};
+
+/// Computes parameter information for the given call expression.
+pub(crate) fn call_info(db: &RootDatabase, position: FilePosition) -> Cancelable<Option<CallInfo>> {
+    let file = db.source_file(position.file_id);
+    let syntax = file.syntax();
+
+    // Find the calling expression and it's NameRef
+    let calling_node = ctry!(FnCallNode::with_node(syntax, position.offset));
+    let name_ref = ctry!(calling_node.name_ref());
+
+    // Resolve the function's NameRef (NOTE: this isn't entirely accurate).
+    let file_symbols = db.index_resolve(name_ref)?;
+    let symbol = ctry!(file_symbols.into_iter().find(|it| it.ptr.kind() == FN_DEF));
+    let fn_file = db.source_file(symbol.file_id);
+    let fn_def = symbol.ptr.resolve(&fn_file);
+    let fn_def = ast::FnDef::cast(&fn_def).unwrap();
+    let mut call_info = ctry!(CallInfo::new(fn_def));
+    // If we have a calling expression let's find which argument we are on
+    let num_params = call_info.parameters.len();
+    let has_self = fn_def.param_list().and_then(|l| l.self_param()).is_some();
+
+    if num_params == 1 {
+        if !has_self {
+            call_info.active_parameter = Some(0);
+        }
+    } else if num_params > 1 {
+        // Count how many parameters into the call we are.
+        // TODO: This is best effort for now and should be fixed at some point.
+        // It may be better to see where we are in the arg_list and then check
+        // where offset is in that list (or beyond).
+        // Revisit this after we get documentation comments in.
+        if let Some(ref arg_list) = calling_node.arg_list() {
+            let start = arg_list.syntax().range().start();
+
+            let range_search = TextRange::from_to(start, position.offset);
+            let mut commas: usize = arg_list
+                .syntax()
+                .text()
+                .slice(range_search)
+                .to_string()
+                .matches(',')
+                .count();
+
+            // If we have a method call eat the first param since it's just self.
+            if has_self {
+                commas += 1;
+            }
+
+            call_info.active_parameter = Some(commas);
+        }
+    }
+
+    Ok(Some(call_info))
+}
+
+enum FnCallNode<'a> {
+    CallExpr(&'a ast::CallExpr),
+    MethodCallExpr(&'a ast::MethodCallExpr),
+}
+
+impl<'a> FnCallNode<'a> {
+    pub fn with_node(syntax: &'a SyntaxNode, offset: TextUnit) -> Option<FnCallNode<'a>> {
+        if let Some(expr) = find_node_at_offset::<ast::CallExpr>(syntax, offset) {
+            return Some(FnCallNode::CallExpr(expr));
+        }
+        if let Some(expr) = find_node_at_offset::<ast::MethodCallExpr>(syntax, offset) {
+            return Some(FnCallNode::MethodCallExpr(expr));
+        }
+        None
+    }
+
+    pub fn name_ref(&self) -> Option<&'a ast::NameRef> {
+        match *self {
+            FnCallNode::CallExpr(call_expr) => Some(match call_expr.expr()?.kind() {
+                ast::ExprKind::PathExpr(path_expr) => path_expr.path()?.segment()?.name_ref()?,
+                _ => return None,
+            }),
+
+            FnCallNode::MethodCallExpr(call_expr) => call_expr
+                .syntax()
+                .children()
+                .filter_map(ast::NameRef::cast)
+                .nth(0),
+        }
+    }
+
+    pub fn arg_list(&self) -> Option<&'a ast::ArgList> {
+        match *self {
+            FnCallNode::CallExpr(expr) => expr.arg_list(),
+            FnCallNode::MethodCallExpr(expr) => expr.arg_list(),
+        }
+    }
+}
+
+impl CallInfo {
+    fn new(node: &ast::FnDef) -> Option<Self> {
+        let mut doc = None;
+
+        // Strip the body out for the label.
+        let mut 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()
+        };
+
+        if let Some((comment_range, docs)) = extract_doc_comments(node) {
+            let comment_range = comment_range
+                .checked_sub(node.syntax().range().start())
+                .unwrap();
+            let start = comment_range.start().to_usize();
+            let end = comment_range.end().to_usize();
+
+            // Remove the comment from the label
+            label.replace_range(start..end, "");
+
+            // Massage markdown
+            let mut processed_lines = Vec::new();
+            let mut in_code_block = false;
+            for line in docs.lines() {
+                if line.starts_with("```") {
+                    in_code_block = !in_code_block;
+                }
+
+                let line = if in_code_block && line.starts_with("```") && !line.contains("rust") {
+                    "```rust".into()
+                } else {
+                    line.to_string()
+                };
+
+                processed_lines.push(line);
+            }
+
+            if !processed_lines.is_empty() {
+                doc = Some(processed_lines.join("\n"));
+            }
+        }
+
+        Some(CallInfo {
+            parameters: param_list(node),
+            label: label.trim().to_owned(),
+            doc,
+            active_parameter: None,
+        })
+    }
+}
+
+fn extract_doc_comments(node: &ast::FnDef) -> Option<(TextRange, String)> {
+    if node.doc_comments().count() == 0 {
+        return None;
+    }
+
+    let comment_text = node.doc_comment_text();
+
+    let (begin, end) = node
+        .doc_comments()
+        .map(|comment| comment.syntax().range())
+        .map(|range| (range.start().to_usize(), range.end().to_usize()))
+        .fold((std::usize::MAX, std::usize::MIN), |acc, range| {
+            (min(acc.0, range.0), max(acc.1, range.1))
+        });
+
+    let range = TextRange::from_to(TextUnit::from_usize(begin), TextUnit::from_usize(end));
+
+    Some((range, comment_text))
+}
+
+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
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::mock_analysis::single_file_with_position;
+
+    fn call_info(text: &str) -> CallInfo {
+        let (analysis, position) = single_file_with_position(text);
+        analysis.call_info(position).unwrap().unwrap()
+    }
+
+    #[test]
+    fn test_fn_signature_two_args_first() {
+        let info = call_info(
+            r#"fn foo(x: u32, y: u32) -> u32 {x + y}
+fn bar() { foo(<|>3, ); }"#,
+        );
+
+        assert_eq!(info.parameters, vec!("x".to_string(), "y".to_string()));
+        assert_eq!(info.active_parameter, Some(0));
+    }
+
+    #[test]
+    fn test_fn_signature_two_args_second() {
+        let info = call_info(
+            r#"fn foo(x: u32, y: u32) -> u32 {x + y}
+fn bar() { foo(3, <|>); }"#,
+        );
+
+        assert_eq!(info.parameters, vec!("x".to_string(), "y".to_string()));
+        assert_eq!(info.active_parameter, Some(1));
+    }
+
+    #[test]
+    fn test_fn_signature_for_impl() {
+        let info = call_info(
+            r#"struct F; impl F { pub fn new() { F{}} }
+fn bar() {let _ : F = F::new(<|>);}"#,
+        );
+
+        assert_eq!(info.parameters, Vec::<String>::new());
+        assert_eq!(info.active_parameter, None);
+    }
+
+    #[test]
+    fn test_fn_signature_for_method_self() {
+        let info = call_info(
+            r#"struct F;
+impl F {
+    pub fn new() -> F{
+        F{}
+    }
+
+    pub fn do_it(&self) {}
+}
+
+fn bar() {
+    let f : F = F::new();
+    f.do_it(<|>);
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["&self".to_string()]);
+        assert_eq!(info.active_parameter, None);
+    }
+
+    #[test]
+    fn test_fn_signature_for_method_with_arg() {
+        let info = call_info(
+            r#"struct F;
+impl F {
+    pub fn new() -> F{
+        F{}
+    }
+
+    pub fn do_it(&self, x: i32) {}
+}
+
+fn bar() {
+    let f : F = F::new();
+    f.do_it(<|>);
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["&self".to_string(), "x".to_string()]);
+        assert_eq!(info.active_parameter, Some(1));
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs_simple() {
+        let info = call_info(
+            r#"
+/// test
+// non-doc-comment
+fn foo(j: u32) -> u32 {
+    j
+}
+
+fn bar() {
+    let _ = foo(<|>);
+}
+"#,
+        );
+
+        assert_eq!(info.parameters, vec!["j".to_string()]);
+        assert_eq!(info.active_parameter, Some(0));
+        assert_eq!(info.label, "fn foo(j: u32) -> u32".to_string());
+        assert_eq!(info.doc, Some("test".into()));
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs() {
+        let info = call_info(
+            r#"
+/// Adds one to the number given.
+///
+/// # Examples
+///
+/// ```
+/// let five = 5;
+///
+/// assert_eq!(6, my_crate::add_one(5));
+/// ```
+pub fn add_one(x: i32) -> i32 {
+    x + 1
+}
+
+pub fn do() {
+    add_one(<|>
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["x".to_string()]);
+        assert_eq!(info.active_parameter, Some(0));
+        assert_eq!(info.label, "pub fn add_one(x: i32) -> i32".to_string());
+        assert_eq!(
+            info.doc,
+            Some(
+                r#"Adds one to the number given.
+
+# Examples
+
+```rust
+let five = 5;
+
+assert_eq!(6, my_crate::add_one(5));
+```"#
+                    .into()
+            )
+        );
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs_impl() {
+        let info = call_info(
+            r#"
+struct addr;
+impl addr {
+    /// Adds one to the number given.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let five = 5;
+    ///
+    /// assert_eq!(6, my_crate::add_one(5));
+    /// ```
+    pub fn add_one(x: i32) -> i32 {
+        x + 1
+    }
+}
+
+pub fn do_it() {
+    addr {};
+    addr::add_one(<|>);
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["x".to_string()]);
+        assert_eq!(info.active_parameter, Some(0));
+        assert_eq!(info.label, "pub fn add_one(x: i32) -> i32".to_string());
+        assert_eq!(
+            info.doc,
+            Some(
+                r#"Adds one to the number given.
+
+# Examples
+
+```rust
+let five = 5;
+
+assert_eq!(6, my_crate::add_one(5));
+```"#
+                    .into()
+            )
+        );
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs_from_actix() {
+        let info = call_info(
+            r#"
+pub trait WriteHandler<E>
+where
+    Self: Actor,
+    Self::Context: ActorContext,
+{
+    /// Method is called when writer emits error.
+    ///
+    /// If this method returns `ErrorAction::Continue` writer processing
+    /// continues otherwise stream processing stops.
+    fn error(&mut self, err: E, ctx: &mut Self::Context) -> Running {
+        Running::Stop
+    }
+
+    /// Method is called when writer finishes.
+    ///
+    /// By default this method stops actor's `Context`.
+    fn finished(&mut self, ctx: &mut Self::Context) {
+        ctx.stop()
+    }
+}
+
+pub fn foo() {
+    WriteHandler r;
+    r.finished(<|>);
+}
+
+"#,
+        );
+
+        assert_eq!(
+            info.parameters,
+            vec!["&mut self".to_string(), "ctx".to_string()]
+        );
+        assert_eq!(info.active_parameter, Some(1));
+        assert_eq!(
+            info.doc,
+            Some(
+                r#"Method is called when writer finishes.
+
+By default this method stops actor's `Context`."#
+                    .into()
+            )
+        );
+    }
+
+}
diff --git a/crates/ra_ide_api/src/completion.rs b/crates/ra_ide_api/src/completion.rs
new file mode 100644
index 000000000..ce777a771
--- /dev/null
+++ b/crates/ra_ide_api/src/completion.rs
@@ -0,0 +1,77 @@
+mod completion_item;
+mod completion_context;
+
+mod complete_dot;
+mod complete_fn_param;
+mod complete_keyword;
+mod complete_snippet;
+mod complete_path;
+mod complete_scope;
+
+use ra_db::SyntaxDatabase;
+
+use crate::{
+    db,
+    Cancelable, FilePosition,
+    completion::{
+        completion_item::{Completions, CompletionKind},
+        completion_context::CompletionContext,
+    },
+};
+
+pub use crate::completion::completion_item::{CompletionItem, InsertText, CompletionItemKind};
+
+/// Main entry point for completion. We run completion as a two-phase process.
+///
+/// First, we look at the position and collect a so-called `CompletionContext.
+/// This is a somewhat messy process, because, during completion, syntax tree is
+/// incomplete and can look really weird.
+///
+/// Once the context is collected, we run a series of completion routines which
+/// look at the context and produce completion items. One subtelty about this
+/// phase is that completion engine should not filter by the substring which is
+/// already present, it should give all possible variants for the identifier at
+/// the caret. In other words, for
+///
+/// ```no-run
+/// fn f() {
+///     let foo = 92;
+///     let _ = bar<|>
+/// }
+/// ```
+///
+/// `foo` *should* be present among the completion variants. Filtering by
+/// identifier prefix/fuzzy match should be done higher in the stack, together
+/// with ordering of completions (currently this is done by the client).
+pub(crate) fn completions(
+    db: &db::RootDatabase,
+    position: FilePosition,
+) -> Cancelable<Option<Completions>> {
+    let original_file = db.source_file(position.file_id);
+    let ctx = ctry!(CompletionContext::new(db, &original_file, position)?);
+
+    let mut acc = Completions::default();
+
+    complete_fn_param::complete_fn_param(&mut acc, &ctx);
+    complete_keyword::complete_expr_keyword(&mut acc, &ctx);
+    complete_keyword::complete_use_tree_keyword(&mut acc, &ctx);
+    complete_snippet::complete_expr_snippet(&mut acc, &ctx);
+    complete_snippet::complete_item_snippet(&mut acc, &ctx);
+    complete_path::complete_path(&mut acc, &ctx)?;
+    complete_scope::complete_scope(&mut acc, &ctx)?;
+    complete_dot::complete_dot(&mut acc, &ctx)?;
+
+    Ok(Some(acc))
+}
+
+#[cfg(test)]
+fn check_completion(code: &str, expected_completions: &str, kind: CompletionKind) {
+    use crate::mock_analysis::{single_file_with_position, analysis_and_position};
+    let (analysis, position) = if code.contains("//-") {
+        analysis_and_position(code)
+    } else {
+        single_file_with_position(code)
+    };
+    let completions = completions(&analysis.db, position).unwrap().unwrap();
+    completions.assert_match(expected_completions, kind);
+}
diff --git a/crates/ra_ide_api/src/completion/complete_dot.rs b/crates/ra_ide_api/src/completion/complete_dot.rs
new file mode 100644
index 000000000..5d4e60dc5
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_dot.rs
@@ -0,0 +1,121 @@
+use hir::{Ty, Def};
+
+use crate::Cancelable;
+use crate::completion::{CompletionContext, Completions, CompletionKind, CompletionItem, CompletionItemKind};
+
+/// Complete dot accesses, i.e. fields or methods (currently only fields).
+pub(super) fn complete_dot(acc: &mut Completions, ctx: &CompletionContext) -> Cancelable<()> {
+    let (function, receiver) = match (&ctx.function, ctx.dot_receiver) {
+        (Some(function), Some(receiver)) => (function, receiver),
+        _ => return Ok(()),
+    };
+    let infer_result = function.infer(ctx.db)?;
+    let syntax_mapping = function.body_syntax_mapping(ctx.db)?;
+    let expr = match syntax_mapping.node_expr(receiver) {
+        Some(expr) => expr,
+        None => return Ok(()),
+    };
+    let receiver_ty = infer_result[expr].clone();
+    if !ctx.is_method_call {
+        complete_fields(acc, ctx, receiver_ty)?;
+    }
+    Ok(())
+}
+
+fn complete_fields(acc: &mut Completions, ctx: &CompletionContext, receiver: Ty) -> Cancelable<()> {
+    for receiver in receiver.autoderef(ctx.db) {
+        match receiver {
+            Ty::Adt { def_id, .. } => {
+                match def_id.resolve(ctx.db)? {
+                    Def::Struct(s) => {
+                        let variant_data = s.variant_data(ctx.db)?;
+                        for field in variant_data.fields() {
+                            CompletionItem::new(
+                                CompletionKind::Reference,
+                                field.name().to_string(),
+                            )
+                            .kind(CompletionItemKind::Field)
+                            .add_to(acc);
+                        }
+                    }
+                    // TODO unions
+                    _ => {}
+                }
+            }
+            Ty::Tuple(fields) => {
+                for (i, _ty) in fields.iter().enumerate() {
+                    CompletionItem::new(CompletionKind::Reference, i.to_string())
+                        .kind(CompletionItemKind::Field)
+                        .add_to(acc);
+                }
+            }
+            _ => {}
+        };
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::*;
+
+    fn check_ref_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Reference);
+    }
+
+    #[test]
+    fn test_struct_field_completion() {
+        check_ref_completion(
+            r"
+            struct A { the_field: u32 }
+            fn foo(a: A) {
+               a.<|>
+            }
+            ",
+            r#"the_field"#,
+        );
+    }
+
+    #[test]
+    fn test_struct_field_completion_self() {
+        check_ref_completion(
+            r"
+            struct A { the_field: u32 }
+            impl A {
+                fn foo(self) {
+                    self.<|>
+                }
+            }
+            ",
+            r#"the_field"#,
+        );
+    }
+
+    #[test]
+    fn test_struct_field_completion_autoderef() {
+        check_ref_completion(
+            r"
+            struct A { the_field: u32 }
+            impl A {
+                fn foo(&self) {
+                    self.<|>
+                }
+            }
+            ",
+            r#"the_field"#,
+        );
+    }
+
+    #[test]
+    fn test_no_struct_field_completion_for_method_call() {
+        check_ref_completion(
+            r"
+            struct A { the_field: u32 }
+            fn foo(a: A) {
+               a.<|>()
+            }
+            ",
+            r#""#,
+        );
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/complete_fn_param.rs b/crates/ra_ide_api/src/completion/complete_fn_param.rs
new file mode 100644
index 000000000..c1739e47e
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_fn_param.rs
@@ -0,0 +1,102 @@
+use ra_syntax::{
+    algo::visit::{visitor_ctx, VisitorCtx},
+    ast,
+    AstNode,
+};
+use rustc_hash::FxHashMap;
+
+use crate::completion::{CompletionContext, Completions, CompletionKind, CompletionItem};
+
+/// Complete repeated parametes, both name and type. For example, if all
+/// functions in a file have a `spam: &mut Spam` parameter, a completion with
+/// `spam: &mut Spam` insert text/label and `spam` lookup string will be
+/// suggested.
+pub(super) fn complete_fn_param(acc: &mut Completions, ctx: &CompletionContext) {
+    if !ctx.is_param {
+        return;
+    }
+
+    let mut params = FxHashMap::default();
+    for node in ctx.leaf.ancestors() {
+        let _ = visitor_ctx(&mut params)
+            .visit::<ast::SourceFile, _>(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)| {
+            CompletionItem::new(CompletionKind::Magic, label)
+                .lookup_by(lookup)
+                .add_to(acc)
+        });
+
+    fn process<'a, N: ast::FnDefOwner>(
+        node: &'a N,
+        params: &mut FxHashMap<String, (u32, &'a ast::Param)>,
+    ) {
+        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;
+            })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::*;
+
+    fn check_magic_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Magic);
+    }
+
+    #[test]
+    fn test_param_completion_last_param() {
+        check_magic_completion(
+            r"
+            fn foo(file_id: FileId) {}
+            fn bar(file_id: FileId) {}
+            fn baz(file<|>) {}
+            ",
+            r#"file_id "file_id: FileId""#,
+        );
+    }
+
+    #[test]
+    fn test_param_completion_nth_param() {
+        check_magic_completion(
+            r"
+            fn foo(file_id: FileId) {}
+            fn bar(file_id: FileId) {}
+            fn baz(file<|>, x: i32) {}
+            ",
+            r#"file_id "file_id: FileId""#,
+        );
+    }
+
+    #[test]
+    fn test_param_completion_trait_param() {
+        check_magic_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#"file_id "file_id: FileId""#,
+        );
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/complete_keyword.rs b/crates/ra_ide_api/src/completion/complete_keyword.rs
new file mode 100644
index 000000000..d350f06ce
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_keyword.rs
@@ -0,0 +1,339 @@
+use ra_syntax::{
+    algo::visit::{visitor, Visitor},
+    AstNode,
+    ast::{self, LoopBodyOwner},
+    SyntaxKind::*, SyntaxNode,
+};
+
+use crate::completion::{CompletionContext, CompletionItem, Completions, CompletionKind, CompletionItemKind};
+
+pub(super) fn complete_use_tree_keyword(acc: &mut Completions, ctx: &CompletionContext) {
+    // complete keyword "crate" in use stmt
+    match (ctx.use_item_syntax.as_ref(), ctx.path_prefix.as_ref()) {
+        (Some(_), None) => {
+            CompletionItem::new(CompletionKind::Keyword, "crate")
+                .kind(CompletionItemKind::Keyword)
+                .lookup_by("crate")
+                .snippet("crate::")
+                .add_to(acc);
+            CompletionItem::new(CompletionKind::Keyword, "self")
+                .kind(CompletionItemKind::Keyword)
+                .lookup_by("self")
+                .add_to(acc);
+            CompletionItem::new(CompletionKind::Keyword, "super")
+                .kind(CompletionItemKind::Keyword)
+                .lookup_by("super")
+                .add_to(acc);
+        }
+        (Some(_), Some(_)) => {
+            CompletionItem::new(CompletionKind::Keyword, "self")
+                .kind(CompletionItemKind::Keyword)
+                .lookup_by("self")
+                .add_to(acc);
+            CompletionItem::new(CompletionKind::Keyword, "super")
+                .kind(CompletionItemKind::Keyword)
+                .lookup_by("super")
+                .add_to(acc);
+        }
+        _ => {}
+    }
+}
+
+fn keyword(kw: &str, snippet: &str) -> CompletionItem {
+    CompletionItem::new(CompletionKind::Keyword, kw)
+        .kind(CompletionItemKind::Keyword)
+        .snippet(snippet)
+        .build()
+}
+
+pub(super) fn complete_expr_keyword(acc: &mut Completions, ctx: &CompletionContext) {
+    if !ctx.is_trivial_path {
+        return;
+    }
+
+    let fn_def = match ctx.function_syntax {
+        Some(it) => it,
+        None => return,
+    };
+    acc.add(keyword("if", "if $0 {}"));
+    acc.add(keyword("match", "match $0 {}"));
+    acc.add(keyword("while", "while $0 {}"));
+    acc.add(keyword("loop", "loop {$0}"));
+
+    if ctx.after_if {
+        acc.add(keyword("else", "else {$0}"));
+        acc.add(keyword("else if", "else if $0 {}"));
+    }
+    if is_in_loop_body(ctx.leaf) {
+        if ctx.can_be_stmt {
+            acc.add(keyword("continue", "continue;"));
+            acc.add(keyword("break", "break;"));
+        } else {
+            acc.add(keyword("continue", "continue"));
+            acc.add(keyword("break", "break"));
+        }
+    }
+    acc.add_all(complete_return(fn_def, ctx.can_be_stmt));
+}
+
+fn is_in_loop_body(leaf: &SyntaxNode) -> bool {
+    for node in leaf.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 leaf.range().is_subrange(&body.syntax().range()) {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+fn complete_return(fn_def: &ast::FnDef, can_be_stmt: bool) -> Option<CompletionItem> {
+    let snip = match (can_be_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))
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{CompletionKind, check_completion};
+    fn check_keyword_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Keyword);
+    }
+
+    #[test]
+    fn completes_keywords_in_use_stmt() {
+        check_keyword_completion(
+            r"
+            use <|>
+            ",
+            r#"
+            crate "crate" "crate::"
+            self "self"
+            super "super"
+            "#,
+        );
+
+        check_keyword_completion(
+            r"
+            use a::<|>
+            ",
+            r#"
+            self "self"
+            super "super"
+            "#,
+        );
+
+        check_keyword_completion(
+            r"
+            use a::{b, <|>}
+            ",
+            r#"
+            self "self"
+            super "super"
+            "#,
+        );
+    }
+
+    #[test]
+    fn completes_various_keywords_in_function() {
+        check_keyword_completion(
+            r"
+            fn quux() {
+                <|>
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return;"
+            "#,
+        );
+    }
+
+    #[test]
+    fn completes_else_after_if() {
+        check_keyword_completion(
+            r"
+            fn quux() {
+                if true {
+                    ()
+                } <|>
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            else "else {$0}"
+            else if "else if $0 {}"
+            return "return;"
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_completion_return_value() {
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                <|>
+                92
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return $0;"
+            "#,
+        );
+        check_keyword_completion(
+            r"
+            fn quux() {
+                <|>
+                92
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return;"
+            "#,
+        );
+    }
+
+    #[test]
+    fn dont_add_semi_after_return_if_not_a_statement() {
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                match () {
+                    () => <|>
+                }
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return $0"
+            "#,
+        );
+    }
+
+    #[test]
+    fn last_return_in_block_has_semi() {
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                if condition {
+                    <|>
+                }
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return $0;"
+            "#,
+        );
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                if condition {
+                    <|>
+                }
+                let x = 92;
+                x
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return $0;"
+            "#,
+        );
+    }
+
+    #[test]
+    fn completes_break_and_continue_in_loops() {
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                loop { <|> }
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            continue "continue;"
+            break "break;"
+            return "return $0;"
+            "#,
+        );
+        // No completion: lambda isolates control flow
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                loop { || { <|> } }
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return $0;"
+            "#,
+        );
+    }
+
+    #[test]
+    fn no_semi_after_break_continue_in_expr() {
+        check_keyword_completion(
+            r"
+            fn f() {
+                loop {
+                    match () {
+                        () => br<|>
+                    }
+                }
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            continue "continue"
+            break "break"
+            return "return"
+            "#,
+        )
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/complete_path.rs b/crates/ra_ide_api/src/completion/complete_path.rs
new file mode 100644
index 000000000..4723a65a6
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_path.rs
@@ -0,0 +1,128 @@
+use crate::{
+    Cancelable,
+    completion::{CompletionItem, CompletionItemKind, Completions, CompletionKind, CompletionContext},
+};
+
+pub(super) fn complete_path(acc: &mut Completions, ctx: &CompletionContext) -> Cancelable<()> {
+    let (path, module) = match (&ctx.path_prefix, &ctx.module) {
+        (Some(path), Some(module)) => (path.clone(), module),
+        _ => return Ok(()),
+    };
+    let def_id = match module.resolve_path(ctx.db, &path)?.take_types() {
+        Some(it) => it,
+        None => return Ok(()),
+    };
+    match def_id.resolve(ctx.db)? {
+        hir::Def::Module(module) => {
+            let module_scope = module.scope(ctx.db)?;
+            module_scope.entries().for_each(|(name, res)| {
+                CompletionItem::new(CompletionKind::Reference, name.to_string())
+                    .from_resolution(ctx, res)
+                    .add_to(acc)
+            });
+        }
+        hir::Def::Enum(e) => e
+            .variants(ctx.db)?
+            .into_iter()
+            .for_each(|(name, _variant)| {
+                CompletionItem::new(CompletionKind::Reference, name.to_string())
+                    .kind(CompletionItemKind::EnumVariant)
+                    .add_to(acc)
+            }),
+        _ => return Ok(()),
+    };
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{CompletionKind, check_completion};
+
+    fn check_reference_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Reference);
+    }
+
+    #[test]
+    fn completes_use_item_starting_with_self() {
+        check_reference_completion(
+            r"
+            use self::m::<|>;
+
+            mod m {
+                struct Bar;
+            }
+            ",
+            "Bar",
+        );
+    }
+
+    #[test]
+    fn completes_use_item_starting_with_crate() {
+        check_reference_completion(
+            "
+            //- /lib.rs
+            mod foo;
+            struct Spam;
+            //- /foo.rs
+            use crate::Sp<|>
+            ",
+            "Spam;foo",
+        );
+    }
+
+    #[test]
+    fn completes_nested_use_tree() {
+        check_reference_completion(
+            "
+            //- /lib.rs
+            mod foo;
+            struct Spam;
+            //- /foo.rs
+            use crate::{Sp<|>};
+            ",
+            "Spam;foo",
+        );
+    }
+
+    #[test]
+    fn completes_deeply_nested_use_tree() {
+        check_reference_completion(
+            "
+            //- /lib.rs
+            mod foo;
+            pub mod bar {
+                pub mod baz {
+                    pub struct Spam;
+                }
+            }
+            //- /foo.rs
+            use crate::{bar::{baz::Sp<|>}};
+            ",
+            "Spam",
+        );
+    }
+
+    #[test]
+    fn completes_enum_variant() {
+        check_reference_completion(
+            "
+            //- /lib.rs
+            enum E { Foo, Bar(i32) }
+            fn foo() { let _ = E::<|> }
+            ",
+            "Foo;Bar",
+        );
+    }
+
+    #[test]
+    fn dont_render_function_parens_in_use_item() {
+        check_reference_completion(
+            "
+            //- /lib.rs
+            mod m { pub fn foo() {} }
+            use crate::m::f<|>;
+            ",
+            "foo",
+        )
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/complete_scope.rs b/crates/ra_ide_api/src/completion/complete_scope.rs
new file mode 100644
index 000000000..ee9052d3d
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_scope.rs
@@ -0,0 +1,192 @@
+use rustc_hash::FxHashSet;
+use ra_syntax::TextUnit;
+
+use crate::{
+    Cancelable,
+    completion::{CompletionItem, CompletionItemKind, Completions, CompletionKind, CompletionContext},
+};
+
+pub(super) fn complete_scope(acc: &mut Completions, ctx: &CompletionContext) -> Cancelable<()> {
+    if !ctx.is_trivial_path {
+        return Ok(());
+    }
+    let module = match &ctx.module {
+        Some(it) => it,
+        None => return Ok(()),
+    };
+    if let Some(function) = &ctx.function {
+        let scopes = function.scopes(ctx.db)?;
+        complete_fn(acc, &scopes, ctx.offset);
+    }
+
+    let module_scope = module.scope(ctx.db)?;
+    let (file_id, _) = module.defenition_source(ctx.db)?;
+    module_scope
+        .entries()
+        .filter(|(_name, res)| {
+            // Don't expose this item
+            // FIXME: this penetrates through all kinds of abstractions,
+            // we need to figura out the way to do it less ugly.
+            match res.import {
+                None => true,
+                Some(import) => {
+                    let range = import.range(ctx.db, file_id);
+                    !range.is_subrange(&ctx.leaf.range())
+                }
+            }
+        })
+        .for_each(|(name, res)| {
+            CompletionItem::new(CompletionKind::Reference, name.to_string())
+                .from_resolution(ctx, res)
+                .add_to(acc)
+        });
+    Ok(())
+}
+
+fn complete_fn(acc: &mut Completions, scopes: &hir::ScopesWithSyntaxMapping, offset: TextUnit) {
+    let mut shadowed = FxHashSet::default();
+    scopes
+        .scope_chain_for_offset(offset)
+        .flat_map(|scope| scopes.scopes.entries(scope).iter())
+        .filter(|entry| shadowed.insert(entry.name()))
+        .for_each(|entry| {
+            CompletionItem::new(CompletionKind::Reference, entry.name().to_string())
+                .kind(CompletionItemKind::Binding)
+                .add_to(acc)
+        });
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{CompletionKind, check_completion};
+
+    fn check_reference_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Reference);
+    }
+
+    #[test]
+    fn completes_bindings_from_let() {
+        check_reference_completion(
+            r"
+            fn quux(x: i32) {
+                let y = 92;
+                1 + <|>;
+                let z = ();
+            }
+            ",
+            r#"y;x;quux "quux($0)""#,
+        );
+    }
+
+    #[test]
+    fn completes_bindings_from_if_let() {
+        check_reference_completion(
+            r"
+            fn quux() {
+                if let Some(x) = foo() {
+                    let y = 92;
+                };
+                if let Some(a) = bar() {
+                    let b = 62;
+                    1 + <|>
+                }
+            }
+            ",
+            r#"b;a;quux "quux()$0""#,
+        );
+    }
+
+    #[test]
+    fn completes_bindings_from_for() {
+        check_reference_completion(
+            r"
+            fn quux() {
+                for x in &[1, 2, 3] {
+                    <|>
+                }
+            }
+            ",
+            r#"x;quux "quux()$0""#,
+        );
+    }
+
+    #[test]
+    fn completes_module_items() {
+        check_reference_completion(
+            r"
+            struct Foo;
+            enum Baz {}
+            fn quux() {
+                <|>
+            }
+            ",
+            r#"quux "quux()$0";Foo;Baz"#,
+        );
+    }
+
+    #[test]
+    fn completes_module_items_in_nested_modules() {
+        check_reference_completion(
+            r"
+            struct Foo;
+            mod m {
+                struct Bar;
+                fn quux() { <|> }
+            }
+            ",
+            r#"quux "quux()$0";Bar"#,
+        );
+    }
+
+    #[test]
+    fn completes_return_type() {
+        check_reference_completion(
+            r"
+            struct Foo;
+            fn x() -> <|>
+            ",
+            r#"Foo;x "x()$0""#,
+        )
+    }
+
+    #[test]
+    fn dont_show_both_completions_for_shadowing() {
+        check_reference_completion(
+            r"
+            fn foo() -> {
+                let bar = 92;
+                {
+                    let bar = 62;
+                    <|>
+                }
+            }
+            ",
+            r#"bar;foo "foo()$0""#,
+        )
+    }
+
+    #[test]
+    fn completes_self_in_methods() {
+        check_reference_completion(r"impl S { fn foo(&self) { <|> } }", "self")
+    }
+
+    #[test]
+    fn inserts_parens_for_function_calls() {
+        check_reference_completion(
+            r"
+            fn no_args() {}
+            fn main() { no_<|> }
+            ",
+            r#"no_args "no_args()$0"
+               main "main()$0""#,
+        );
+        check_reference_completion(
+            r"
+            fn with_args(x: i32, y: String) {}
+            fn main() { with_<|> }
+            ",
+            r#"main "main()$0"
+               with_args "with_args($0)""#,
+        );
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/complete_snippet.rs b/crates/ra_ide_api/src/completion/complete_snippet.rs
new file mode 100644
index 000000000..a495751dd
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/complete_snippet.rs
@@ -0,0 +1,73 @@
+use crate::completion::{CompletionItem, Completions, CompletionKind, CompletionItemKind, CompletionContext, completion_item::Builder};
+
+fn snippet(label: &str, snippet: &str) -> Builder {
+    CompletionItem::new(CompletionKind::Snippet, label)
+        .snippet(snippet)
+        .kind(CompletionItemKind::Snippet)
+}
+
+pub(super) fn complete_expr_snippet(acc: &mut Completions, ctx: &CompletionContext) {
+    if !(ctx.is_trivial_path && ctx.function_syntax.is_some()) {
+        return;
+    }
+    snippet("pd", "eprintln!(\"$0 = {:?}\", $0);").add_to(acc);
+    snippet("ppd", "eprintln!(\"$0 = {:#?}\", $0);").add_to(acc);
+}
+
+pub(super) fn complete_item_snippet(acc: &mut Completions, ctx: &CompletionContext) {
+    if !ctx.is_new_item {
+        return;
+    }
+    snippet(
+        "Test function",
+        "\
+#[test]
+fn ${1:feature}() {
+    $0
+}",
+    )
+    .lookup_by("tfn")
+    .add_to(acc);
+
+    snippet("pub(crate)", "pub(crate) $0").add_to(acc);
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{CompletionKind, check_completion};
+    fn check_snippet_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Snippet);
+    }
+
+    #[test]
+    fn completes_snippets_in_expressions() {
+        check_snippet_completion(
+            r"fn foo(x: i32) { <|> }",
+            r##"
+            pd "eprintln!(\"$0 = {:?}\", $0);"
+            ppd "eprintln!(\"$0 = {:#?}\", $0);"
+            "##,
+        );
+    }
+
+    #[test]
+    fn completes_snippets_in_items() {
+        // check_snippet_completion(r"
+        //     <|>
+        //     ",
+        //     r##"[CompletionItem { label: "Test function", lookup: None, snippet: Some("#[test]\nfn test_${1:feature}() {\n$0\n}"##,
+        // );
+        check_snippet_completion(
+            r"
+            #[cfg(test)]
+            mod tests {
+                <|>
+            }
+            ",
+            r##"
+            tfn "Test function" "#[test]\nfn ${1:feature}() {\n    $0\n}"
+            pub(crate) "pub(crate) $0"
+            "##,
+        );
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/completion_context.rs b/crates/ra_ide_api/src/completion/completion_context.rs
new file mode 100644
index 000000000..01786bb69
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/completion_context.rs
@@ -0,0 +1,205 @@
+use ra_text_edit::AtomTextEdit;
+use ra_syntax::{
+    AstNode, SyntaxNode, SourceFile, TextUnit, TextRange,
+    ast,
+    algo::{find_leaf_at_offset, find_covering_node, find_node_at_offset},
+    SyntaxKind::*,
+};
+use hir::source_binder;
+
+use crate::{db, FilePosition, Cancelable};
+
+/// `CompletionContext` is created early during completion to figure out, where
+/// exactly is the cursor, syntax-wise.
+#[derive(Debug)]
+pub(super) struct CompletionContext<'a> {
+    pub(super) db: &'a db::RootDatabase,
+    pub(super) offset: TextUnit,
+    pub(super) leaf: &'a SyntaxNode,
+    pub(super) module: Option<hir::Module>,
+    pub(super) function: Option<hir::Function>,
+    pub(super) function_syntax: Option<&'a ast::FnDef>,
+    pub(super) use_item_syntax: Option<&'a ast::UseItem>,
+    pub(super) is_param: bool,
+    /// A single-indent path, like `foo`.
+    pub(super) is_trivial_path: bool,
+    /// If not a trivial, path, the prefix (qualifier).
+    pub(super) path_prefix: Option<hir::Path>,
+    pub(super) after_if: bool,
+    /// `true` if we are a statement or a last expr in the block.
+    pub(super) can_be_stmt: bool,
+    /// Something is typed at the "top" level, in module or impl/trait.
+    pub(super) is_new_item: bool,
+    /// The receiver if this is a field or method access, i.e. writing something.<|>
+    pub(super) dot_receiver: Option<&'a ast::Expr>,
+    /// If this is a method call in particular, i.e. the () are already there.
+    pub(super) is_method_call: bool,
+}
+
+impl<'a> CompletionContext<'a> {
+    pub(super) fn new(
+        db: &'a db::RootDatabase,
+        original_file: &'a SourceFile,
+        position: FilePosition,
+    ) -> Cancelable<Option<CompletionContext<'a>>> {
+        let module = source_binder::module_from_position(db, position)?;
+        let leaf =
+            ctry!(find_leaf_at_offset(original_file.syntax(), position.offset).left_biased());
+        let mut ctx = CompletionContext {
+            db,
+            leaf,
+            offset: position.offset,
+            module,
+            function: None,
+            function_syntax: None,
+            use_item_syntax: None,
+            is_param: false,
+            is_trivial_path: false,
+            path_prefix: None,
+            after_if: false,
+            can_be_stmt: false,
+            is_new_item: false,
+            dot_receiver: None,
+            is_method_call: false,
+        };
+        ctx.fill(original_file, position.offset);
+        Ok(Some(ctx))
+    }
+
+    fn fill(&mut self, original_file: &'a SourceFile, offset: TextUnit) {
+        // Insert a fake ident to get a valid parse tree. We will use this file
+        // to determine context, though the original_file will be used for
+        // actual completion.
+        let file = {
+            let edit = AtomTextEdit::insert(offset, "intellijRulezz".to_string());
+            original_file.reparse(&edit)
+        };
+
+        // First, let's try to complete a reference to some declaration.
+        if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(file.syntax(), offset) {
+            // Special case, `trait T { fn foo(i_am_a_name_ref) {} }`.
+            // See RFC#1685.
+            if is_node::<ast::Param>(name_ref.syntax()) {
+                self.is_param = true;
+                return;
+            }
+            self.classify_name_ref(original_file, name_ref);
+        }
+
+        // Otherwise, see if this is a declaration. We can use heuristics to
+        // suggest declaration names, see `CompletionKind::Magic`.
+        if let Some(name) = find_node_at_offset::<ast::Name>(file.syntax(), offset) {
+            if is_node::<ast::Param>(name.syntax()) {
+                self.is_param = true;
+                return;
+            }
+        }
+    }
+    fn classify_name_ref(&mut self, original_file: &'a SourceFile, name_ref: &ast::NameRef) {
+        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(SOURCE_FILE) | Some(ITEM_LIST) => {
+                self.is_new_item = true;
+                return;
+            }
+            _ => (),
+        }
+
+        self.use_item_syntax = self.leaf.ancestors().find_map(ast::UseItem::cast);
+
+        self.function_syntax = self
+            .leaf
+            .ancestors()
+            .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
+            .find_map(ast::FnDef::cast);
+        match (&self.module, self.function_syntax) {
+            (Some(module), Some(fn_def)) => {
+                let function = source_binder::function_from_module(self.db, module, fn_def);
+                self.function = Some(function);
+            }
+            _ => (),
+        }
+
+        let parent = match name_ref.syntax().parent() {
+            Some(it) => it,
+            None => return,
+        };
+        if let Some(segment) = ast::PathSegment::cast(parent) {
+            let path = segment.parent_path();
+            if let Some(mut path) = hir::Path::from_ast(path) {
+                if !path.is_ident() {
+                    path.segments.pop().unwrap();
+                    self.path_prefix = Some(path);
+                    return;
+                }
+            }
+            if path.qualifier().is_none() {
+                self.is_trivial_path = true;
+
+                // Find either enclosing expr statement (thing with `;`) or a
+                // block. If block, check that we are the last expr.
+                self.can_be_stmt = name_ref
+                    .syntax()
+                    .ancestors()
+                    .find_map(|node| {
+                        if let Some(stmt) = ast::ExprStmt::cast(node) {
+                            return Some(stmt.syntax().range() == name_ref.syntax().range());
+                        }
+                        if let Some(block) = ast::Block::cast(node) {
+                            return Some(
+                                block.expr().map(|e| e.syntax().range())
+                                    == Some(name_ref.syntax().range()),
+                            );
+                        }
+                        None
+                    })
+                    .unwrap_or(false);
+
+                if let Some(off) = name_ref.syntax().range().start().checked_sub(2.into()) {
+                    if let Some(if_expr) =
+                        find_node_at_offset::<ast::IfExpr>(original_file.syntax(), off)
+                    {
+                        if if_expr.syntax().range().end() < name_ref.syntax().range().start() {
+                            self.after_if = true;
+                        }
+                    }
+                }
+            }
+        }
+        if let Some(field_expr) = ast::FieldExpr::cast(parent) {
+            // The receiver comes before the point of insertion of the fake
+            // ident, so it should have the same range in the non-modified file
+            self.dot_receiver = field_expr
+                .expr()
+                .map(|e| e.syntax().range())
+                .and_then(|r| find_node_with_range(original_file.syntax(), r));
+        }
+        if let Some(method_call_expr) = ast::MethodCallExpr::cast(parent) {
+            // As above
+            self.dot_receiver = method_call_expr
+                .expr()
+                .map(|e| e.syntax().range())
+                .and_then(|r| find_node_with_range(original_file.syntax(), r));
+            self.is_method_call = true;
+        }
+    }
+}
+
+fn find_node_with_range<N: AstNode>(syntax: &SyntaxNode, range: TextRange) -> Option<&N> {
+    let node = find_covering_node(syntax, range);
+    node.ancestors().find_map(N::cast)
+}
+
+fn is_node<N: AstNode>(node: &SyntaxNode) -> bool {
+    match node.ancestors().filter_map(N::cast).next() {
+        None => false,
+        Some(n) => n.syntax().range() == node.range(),
+    }
+}
diff --git a/crates/ra_ide_api/src/completion/completion_item.rs b/crates/ra_ide_api/src/completion/completion_item.rs
new file mode 100644
index 000000000..a25b87bee
--- /dev/null
+++ b/crates/ra_ide_api/src/completion/completion_item.rs
@@ -0,0 +1,244 @@
+use hir::PerNs;
+
+use crate::completion::CompletionContext;
+
+/// `CompletionItem` describes a single completion variant in the editor pop-up.
+/// It is basically a POD with various properties. To construct a
+/// `CompletionItem`, use `new` method and the `Builder` struct.
+#[derive(Debug)]
+pub struct CompletionItem {
+    /// Used only internally in tests, to check only specific kind of
+    /// completion.
+    completion_kind: CompletionKind,
+    label: String,
+    lookup: Option<String>,
+    snippet: Option<String>,
+    kind: Option<CompletionItemKind>,
+}
+
+pub enum InsertText {
+    PlainText { text: String },
+    Snippet { text: String },
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CompletionItemKind {
+    Snippet,
+    Keyword,
+    Module,
+    Function,
+    Struct,
+    Enum,
+    EnumVariant,
+    Binding,
+    Field,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) enum CompletionKind {
+    /// Parser-based keyword completion.
+    Keyword,
+    /// Your usual "complete all valid identifiers".
+    Reference,
+    /// "Secret sauce" completions.
+    Magic,
+    Snippet,
+}
+
+impl CompletionItem {
+    pub(crate) fn new(completion_kind: CompletionKind, label: impl Into<String>) -> Builder {
+        let label = label.into();
+        Builder {
+            completion_kind,
+            label,
+            lookup: None,
+            snippet: None,
+            kind: None,
+        }
+    }
+    /// What user sees in pop-up in the UI.
+    pub fn label(&self) -> &str {
+        &self.label
+    }
+    /// What string is used for filtering.
+    pub fn lookup(&self) -> &str {
+        self.lookup
+            .as_ref()
+            .map(|it| it.as_str())
+            .unwrap_or(self.label())
+    }
+    /// What is inserted.
+    pub fn insert_text(&self) -> InsertText {
+        match &self.snippet {
+            None => InsertText::PlainText {
+                text: self.label.clone(),
+            },
+            Some(it) => InsertText::Snippet { text: it.clone() },
+        }
+    }
+
+    pub fn kind(&self) -> Option<CompletionItemKind> {
+        self.kind
+    }
+}
+
+/// A helper to make `CompletionItem`s.
+#[must_use]
+pub(crate) struct Builder {
+    completion_kind: CompletionKind,
+    label: String,
+    lookup: Option<String>,
+    snippet: Option<String>,
+    kind: Option<CompletionItemKind>,
+}
+
+impl Builder {
+    pub(crate) fn add_to(self, acc: &mut Completions) {
+        acc.add(self.build())
+    }
+
+    pub(crate) fn build(self) -> CompletionItem {
+        CompletionItem {
+            label: self.label,
+            lookup: self.lookup,
+            snippet: self.snippet,
+            kind: self.kind,
+            completion_kind: self.completion_kind,
+        }
+    }
+    pub(crate) fn lookup_by(mut self, lookup: impl Into<String>) -> Builder {
+        self.lookup = Some(lookup.into());
+        self
+    }
+    pub(crate) fn snippet(mut self, snippet: impl Into<String>) -> Builder {
+        self.snippet = Some(snippet.into());
+        self
+    }
+    pub(crate) fn kind(mut self, kind: CompletionItemKind) -> Builder {
+        self.kind = Some(kind);
+        self
+    }
+    pub(super) fn from_resolution(
+        mut self,
+        ctx: &CompletionContext,
+        resolution: &hir::Resolution,
+    ) -> Builder {
+        let resolved = resolution.def_id.and_then(|d| d.resolve(ctx.db).ok());
+        let kind = match resolved {
+            PerNs {
+                types: Some(hir::Def::Module(..)),
+                ..
+            } => CompletionItemKind::Module,
+            PerNs {
+                types: Some(hir::Def::Struct(..)),
+                ..
+            } => CompletionItemKind::Struct,
+            PerNs {
+                types: Some(hir::Def::Enum(..)),
+                ..
+            } => CompletionItemKind::Enum,
+            PerNs {
+                values: Some(hir::Def::Function(function)),
+                ..
+            } => return self.from_function(ctx, function),
+            _ => return self,
+        };
+        self.kind = Some(kind);
+        self
+    }
+
+    fn from_function(mut self, ctx: &CompletionContext, function: hir::Function) -> Builder {
+        // If not an import, add parenthesis automatically.
+        if ctx.use_item_syntax.is_none() {
+            if function.signature(ctx.db).args().is_empty() {
+                self.snippet = Some(format!("{}()$0", self.label));
+            } else {
+                self.snippet = Some(format!("{}($0)", self.label));
+            }
+        }
+        self.kind = Some(CompletionItemKind::Function);
+        self
+    }
+}
+
+impl Into<CompletionItem> for Builder {
+    fn into(self) -> CompletionItem {
+        self.build()
+    }
+}
+
+/// Represents an in-progress set of completions being built.
+#[derive(Debug, Default)]
+pub(crate) struct Completions {
+    buf: Vec<CompletionItem>,
+}
+
+impl Completions {
+    pub(crate) fn add(&mut self, item: impl Into<CompletionItem>) {
+        self.buf.push(item.into())
+    }
+    pub(crate) fn add_all<I>(&mut self, items: I)
+    where
+        I: IntoIterator,
+        I::Item: Into<CompletionItem>,
+    {
+        items.into_iter().for_each(|item| self.add(item.into()))
+    }
+
+    #[cfg(test)]
+    pub(crate) fn assert_match(&self, expected: &str, kind: CompletionKind) {
+        let expected = normalize(expected);
+        let actual = self.debug_render(kind);
+        test_utils::assert_eq_text!(expected.as_str(), actual.as_str(),);
+
+        /// Normalize the textual representation of `Completions`:
+        /// replace `;` with newlines, normalize whitespace
+        fn normalize(expected: &str) -> String {
+            use ra_syntax::{tokenize, TextUnit, TextRange, SyntaxKind::SEMI};
+            let mut res = String::new();
+            for line in expected.trim().lines() {
+                let line = line.trim();
+                let mut start_offset: TextUnit = 0.into();
+                // Yep, we use rust tokenize in completion tests :-)
+                for token in tokenize(line) {
+                    let range = TextRange::offset_len(start_offset, token.len);
+                    start_offset += token.len;
+                    if token.kind == SEMI {
+                        res.push('\n');
+                    } else {
+                        res.push_str(&line[range]);
+                    }
+                }
+
+                res.push('\n');
+            }
+            res
+        }
+    }
+
+    #[cfg(test)]
+    fn debug_render(&self, kind: CompletionKind) -> String {
+        let mut res = String::new();
+        for c in self.buf.iter() {
+            if c.completion_kind == kind {
+                if let Some(lookup) = &c.lookup {
+                    res.push_str(lookup);
+                    res.push_str(&format!(" {:?}", c.label));
+                } else {
+                    res.push_str(&c.label);
+                }
+                if let Some(snippet) = &c.snippet {
+                    res.push_str(&format!(" {:?}", snippet));
+                }
+                res.push('\n');
+            }
+        }
+        res
+    }
+}
+
+impl Into<Vec<CompletionItem>> for Completions {
+    fn into(self) -> Vec<CompletionItem> {
+        self.buf
+    }
+}
diff --git a/crates/ra_ide_api/src/db.rs b/crates/ra_ide_api/src/db.rs
new file mode 100644
index 000000000..9d46609ec
--- /dev/null
+++ b/crates/ra_ide_api/src/db.rs
@@ -0,0 +1,128 @@
+use std::{fmt, sync::Arc};
+
+use salsa::{self, Database};
+use ra_db::{LocationIntener, BaseDatabase, FileId};
+
+use crate::{symbol_index, LineIndex};
+
+#[derive(Debug)]
+pub(crate) struct RootDatabase {
+    runtime: salsa::Runtime<RootDatabase>,
+    id_maps: Arc<IdMaps>,
+}
+
+#[derive(Default)]
+struct IdMaps {
+    defs: LocationIntener<hir::DefLoc, hir::DefId>,
+    macros: LocationIntener<hir::MacroCallLoc, hir::MacroCallId>,
+}
+
+impl fmt::Debug for IdMaps {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("IdMaps")
+            .field("n_defs", &self.defs.len())
+            .finish()
+    }
+}
+
+impl salsa::Database for RootDatabase {
+    fn salsa_runtime(&self) -> &salsa::Runtime<RootDatabase> {
+        &self.runtime
+    }
+}
+
+impl Default for RootDatabase {
+    fn default() -> RootDatabase {
+        let mut db = RootDatabase {
+            runtime: salsa::Runtime::default(),
+            id_maps: Default::default(),
+        };
+        db.query_mut(ra_db::CrateGraphQuery)
+            .set((), Default::default());
+        db.query_mut(ra_db::LocalRootsQuery)
+            .set((), Default::default());
+        db.query_mut(ra_db::LibraryRootsQuery)
+            .set((), Default::default());
+        db
+    }
+}
+
+impl salsa::ParallelDatabase for RootDatabase {
+    fn snapshot(&self) -> salsa::Snapshot<RootDatabase> {
+        salsa::Snapshot::new(RootDatabase {
+            runtime: self.runtime.snapshot(self),
+            id_maps: self.id_maps.clone(),
+        })
+    }
+}
+
+impl BaseDatabase for RootDatabase {}
+
+impl AsRef<LocationIntener<hir::DefLoc, hir::DefId>> for RootDatabase {
+    fn as_ref(&self) -> &LocationIntener<hir::DefLoc, hir::DefId> {
+        &self.id_maps.defs
+    }
+}
+
+impl AsRef<LocationIntener<hir::MacroCallLoc, hir::MacroCallId>> for RootDatabase {
+    fn as_ref(&self) -> &LocationIntener<hir::MacroCallLoc, hir::MacroCallId> {
+        &self.id_maps.macros
+    }
+}
+
+salsa::query_group! {
+    pub(crate) trait LineIndexDatabase: ra_db::FilesDatabase + BaseDatabase {
+        fn line_index(file_id: FileId) -> Arc<LineIndex> {
+            type LineIndexQuery;
+        }
+    }
+}
+
+fn line_index(db: &impl ra_db::FilesDatabase, file_id: FileId) -> Arc<LineIndex> {
+    let text = db.file_text(file_id);
+    Arc::new(LineIndex::new(&*text))
+}
+
+salsa::database_storage! {
+    pub(crate) struct RootDatabaseStorage for RootDatabase {
+        impl ra_db::FilesDatabase {
+            fn file_text() for ra_db::FileTextQuery;
+            fn file_relative_path() for ra_db::FileRelativePathQuery;
+            fn file_source_root() for ra_db::FileSourceRootQuery;
+            fn source_root() for ra_db::SourceRootQuery;
+            fn local_roots() for ra_db::LocalRootsQuery;
+            fn library_roots() for ra_db::LibraryRootsQuery;
+            fn crate_graph() for ra_db::CrateGraphQuery;
+        }
+        impl ra_db::SyntaxDatabase {
+            fn source_file() for ra_db::SourceFileQuery;
+        }
+        impl LineIndexDatabase {
+            fn line_index() for LineIndexQuery;
+        }
+        impl symbol_index::SymbolsDatabase {
+            fn file_symbols() for symbol_index::FileSymbolsQuery;
+            fn library_symbols() for symbol_index::LibrarySymbolsQuery;
+        }
+        impl hir::db::HirDatabase {
+            fn hir_source_file() for hir::db::HirSourceFileQuery;
+            fn expand_macro_invocation() for hir::db::ExpandMacroCallQuery;
+            fn module_tree() for hir::db::ModuleTreeQuery;
+            fn fn_scopes() for hir::db::FnScopesQuery;
+            fn file_items() for hir::db::SourceFileItemsQuery;
+            fn file_item() for hir::db::FileItemQuery;
+            fn input_module_items() for hir::db::InputModuleItemsQuery;
+            fn item_map() for hir::db::ItemMapQuery;
+            fn submodules() for hir::db::SubmodulesQuery;
+            fn infer() for hir::db::InferQuery;
+            fn type_for_def() for hir::db::TypeForDefQuery;
+            fn type_for_field() for hir::db::TypeForFieldQuery;
+            fn struct_data() for hir::db::StructDataQuery;
+            fn enum_data() for hir::db::EnumDataQuery;
+            fn impls_in_module() for hir::db::ImplsInModuleQuery;
+            fn body_hir() for hir::db::BodyHirQuery;
+            fn body_syntax_mapping() for hir::db::BodySyntaxMappingQuery;
+            fn fn_signature() for hir::db::FnSignatureQuery;
+        }
+    }
+}
diff --git a/crates/ra_ide_api/src/extend_selection.rs b/crates/ra_ide_api/src/extend_selection.rs
new file mode 100644
index 000000000..c3c809c9f
--- /dev/null
+++ b/crates/ra_ide_api/src/extend_selection.rs
@@ -0,0 +1,56 @@
+use ra_db::SyntaxDatabase;
+use ra_syntax::{
+    SyntaxNode, AstNode, SourceFile,
+    ast, algo::find_covering_node,
+};
+
+use crate::{
+    TextRange, FileRange,
+    db::RootDatabase,
+};
+
+pub(crate) fn extend_selection(db: &RootDatabase, frange: FileRange) -> TextRange {
+    let source_file = db.source_file(frange.file_id);
+    if let Some(range) = extend_selection_in_macro(db, &source_file, frange) {
+        return range;
+    }
+    ra_ide_api_light::extend_selection(source_file.syntax(), frange.range).unwrap_or(frange.range)
+}
+
+fn extend_selection_in_macro(
+    _db: &RootDatabase,
+    source_file: &SourceFile,
+    frange: FileRange,
+) -> Option<TextRange> {
+    let macro_call = find_macro_call(source_file.syntax(), frange.range)?;
+    let (off, exp) = hir::MacroDef::ast_expand(macro_call)?;
+    let dst_range = exp.map_range_forward(frange.range - off)?;
+    let dst_range = ra_ide_api_light::extend_selection(&exp.syntax(), dst_range)?;
+    let src_range = exp.map_range_back(dst_range)? + off;
+    Some(src_range)
+}
+
+fn find_macro_call(node: &SyntaxNode, range: TextRange) -> Option<&ast::MacroCall> {
+    find_covering_node(node, range)
+        .ancestors()
+        .find_map(ast::MacroCall::cast)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::mock_analysis::single_file_with_range;
+    use test_utils::assert_eq_dbg;
+
+    #[test]
+    fn extend_selection_inside_macros() {
+        let (analysis, frange) = single_file_with_range(
+            "
+            fn main() {
+                ctry!(foo(|x| <|>x<|>));
+            }
+        ",
+        );
+        let r = analysis.extend_selection(frange);
+        assert_eq_dbg("[51; 56)", &r);
+    }
+}
diff --git a/crates/ra_ide_api/src/goto_defenition.rs b/crates/ra_ide_api/src/goto_defenition.rs
new file mode 100644
index 000000000..fcd8d315e
--- /dev/null
+++ b/crates/ra_ide_api/src/goto_defenition.rs
@@ -0,0 +1,139 @@
+use ra_db::{FileId, Cancelable, SyntaxDatabase};
+use ra_syntax::{
+    TextRange, AstNode, ast, SyntaxKind::{NAME, MODULE},
+    algo::find_node_at_offset,
+};
+
+use crate::{FilePosition, NavigationTarget, db::RootDatabase};
+
+pub(crate) fn goto_defenition(
+    db: &RootDatabase,
+    position: FilePosition,
+) -> Cancelable<Option<Vec<NavigationTarget>>> {
+    let file = db.source_file(position.file_id);
+    let syntax = file.syntax();
+    if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(syntax, position.offset) {
+        return Ok(Some(reference_defenition(db, position.file_id, name_ref)?));
+    }
+    if let Some(name) = find_node_at_offset::<ast::Name>(syntax, position.offset) {
+        return name_defenition(db, position.file_id, name);
+    }
+    Ok(None)
+}
+
+pub(crate) fn reference_defenition(
+    db: &RootDatabase,
+    file_id: FileId,
+    name_ref: &ast::NameRef,
+) -> Cancelable<Vec<NavigationTarget>> {
+    if let Some(fn_descr) =
+        hir::source_binder::function_from_child_node(db, file_id, name_ref.syntax())?
+    {
+        let scope = fn_descr.scopes(db)?;
+        // First try to resolve the symbol locally
+        if let Some(entry) = scope.resolve_local_name(name_ref) {
+            let nav = NavigationTarget {
+                file_id,
+                name: entry.name().to_string().into(),
+                range: entry.ptr().range(),
+                kind: NAME,
+                ptr: None,
+            };
+            return Ok(vec![nav]);
+        };
+    }
+    // If that fails try the index based approach.
+    let navs = db
+        .index_resolve(name_ref)?
+        .into_iter()
+        .map(NavigationTarget::from_symbol)
+        .collect();
+    Ok(navs)
+}
+
+fn name_defenition(
+    db: &RootDatabase,
+    file_id: FileId,
+    name: &ast::Name,
+) -> Cancelable<Option<Vec<NavigationTarget>>> {
+    if let Some(module) = name.syntax().parent().and_then(ast::Module::cast) {
+        if module.has_semi() {
+            if let Some(child_module) =
+                hir::source_binder::module_from_declaration(db, file_id, module)?
+            {
+                let (file_id, _) = child_module.defenition_source(db)?;
+                let name = match child_module.name(db)? {
+                    Some(name) => name.to_string().into(),
+                    None => "".into(),
+                };
+                let nav = NavigationTarget {
+                    file_id,
+                    name,
+                    range: TextRange::offset_len(0.into(), 0.into()),
+                    kind: MODULE,
+                    ptr: None,
+                };
+                return Ok(Some(vec![nav]));
+            }
+        }
+    }
+    Ok(None)
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::assert_eq_dbg;
+    use crate::mock_analysis::analysis_and_position;
+
+    #[test]
+    fn goto_defenition_works_in_items() {
+        let (analysis, pos) = analysis_and_position(
+            "
+            //- /lib.rs
+            struct Foo;
+            enum E { X(Foo<|>) }
+            ",
+        );
+
+        let symbols = analysis.goto_defenition(pos).unwrap().unwrap();
+        assert_eq_dbg(
+            r#"[NavigationTarget { file_id: FileId(1), name: "Foo",
+                                   kind: STRUCT_DEF, range: [0; 11),
+                                   ptr: Some(LocalSyntaxPtr { range: [0; 11), kind: STRUCT_DEF }) }]"#,
+            &symbols,
+        );
+    }
+
+    #[test]
+    fn goto_defenition_works_for_module_declaration() {
+        let (analysis, pos) = analysis_and_position(
+            "
+            //- /lib.rs
+            mod <|>foo;
+            //- /foo.rs
+            // empty
+        ",
+        );
+
+        let symbols = analysis.goto_defenition(pos).unwrap().unwrap();
+        assert_eq_dbg(
+            r#"[NavigationTarget { file_id: FileId(2), name: "foo", kind: MODULE, range: [0; 0), ptr: None }]"#,
+            &symbols,
+        );
+
+        let (analysis, pos) = analysis_and_position(
+            "
+            //- /lib.rs
+            mod <|>foo;
+            //- /foo/mod.rs
+            // empty
+        ",
+        );
+
+        let symbols = analysis.goto_defenition(pos).unwrap().unwrap();
+        assert_eq_dbg(
+            r#"[NavigationTarget { file_id: FileId(2), name: "foo", kind: MODULE, range: [0; 0), ptr: None }]"#,
+            &symbols,
+        );
+    }
+}
diff --git a/crates/ra_ide_api/src/hover.rs b/crates/ra_ide_api/src/hover.rs
new file mode 100644
index 000000000..475524ee1
--- /dev/null
+++ b/crates/ra_ide_api/src/hover.rs
@@ -0,0 +1,257 @@
+use ra_db::{Cancelable, SyntaxDatabase};
+use ra_syntax::{
+    AstNode, SyntaxNode, TreePtr,
+    ast::{self, NameOwner},
+    algo::{find_covering_node, find_node_at_offset, find_leaf_at_offset, visit::{visitor, Visitor}},
+};
+
+use crate::{db::RootDatabase, RangeInfo, FilePosition, FileRange, NavigationTarget};
+
+pub(crate) fn hover(
+    db: &RootDatabase,
+    position: FilePosition,
+) -> Cancelable<Option<RangeInfo<String>>> {
+    let file = db.source_file(position.file_id);
+    let mut res = Vec::new();
+
+    let mut range = None;
+    if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(file.syntax(), position.offset) {
+        let navs = crate::goto_defenition::reference_defenition(db, position.file_id, name_ref)?;
+        for nav in navs {
+            res.extend(doc_text_for(db, nav)?)
+        }
+        if !res.is_empty() {
+            range = Some(name_ref.syntax().range())
+        }
+    }
+    if range.is_none() {
+        let node = find_leaf_at_offset(file.syntax(), position.offset).find_map(|leaf| {
+            leaf.ancestors()
+                .find(|n| ast::Expr::cast(*n).is_some() || ast::Pat::cast(*n).is_some())
+        });
+        let node = ctry!(node);
+        let frange = FileRange {
+            file_id: position.file_id,
+            range: node.range(),
+        };
+        res.extend(type_of(db, frange)?);
+        range = Some(node.range());
+    };
+
+    let range = ctry!(range);
+    if res.is_empty() {
+        return Ok(None);
+    }
+    let res = RangeInfo::new(range, res.join("\n\n---\n"));
+    Ok(Some(res))
+}
+
+pub(crate) fn type_of(db: &RootDatabase, frange: FileRange) -> Cancelable<Option<String>> {
+    let file = db.source_file(frange.file_id);
+    let syntax = file.syntax();
+    let leaf_node = find_covering_node(syntax, frange.range);
+    // if we picked identifier, expand to pattern/expression
+    let node = leaf_node
+        .ancestors()
+        .take_while(|it| it.range() == leaf_node.range())
+        .find(|&it| ast::Expr::cast(it).is_some() || ast::Pat::cast(it).is_some())
+        .unwrap_or(leaf_node);
+    let parent_fn = ctry!(node.ancestors().find_map(ast::FnDef::cast));
+    let function = ctry!(hir::source_binder::function_from_source(
+        db,
+        frange.file_id,
+        parent_fn
+    )?);
+    let infer = function.infer(db)?;
+    let syntax_mapping = function.body_syntax_mapping(db)?;
+    if let Some(expr) = ast::Expr::cast(node).and_then(|e| syntax_mapping.node_expr(e)) {
+        Ok(Some(infer[expr].to_string()))
+    } else if let Some(pat) = ast::Pat::cast(node).and_then(|p| syntax_mapping.node_pat(p)) {
+        Ok(Some(infer[pat].to_string()))
+    } else {
+        Ok(None)
+    }
+}
+
+// FIXME: this should not really use navigation target. Rather, approximatelly
+// resovled symbol should return a `DefId`.
+fn doc_text_for(db: &RootDatabase, nav: NavigationTarget) -> Cancelable<Option<String>> {
+    let result = match (nav.description(db), nav.docs(db)) {
+        (Some(desc), Some(docs)) => Some("```rust\n".to_string() + &*desc + "\n```\n\n" + &*docs),
+        (Some(desc), None) => Some("```rust\n".to_string() + &*desc + "\n```"),
+        (None, Some(docs)) => Some(docs),
+        _ => None,
+    };
+
+    Ok(result)
+}
+
+impl NavigationTarget {
+    fn node(&self, db: &RootDatabase) -> Option<TreePtr<SyntaxNode>> {
+        let source_file = db.source_file(self.file_id);
+        let source_file = source_file.syntax();
+        let node = source_file
+            .descendants()
+            .find(|node| node.kind() == self.kind && node.range() == self.range)?
+            .to_owned();
+        Some(node)
+    }
+
+    fn docs(&self, db: &RootDatabase) -> Option<String> {
+        let node = self.node(db)?;
+        fn doc_comments<N: ast::DocCommentsOwner>(node: &N) -> Option<String> {
+            let comments = node.doc_comment_text();
+            if comments.is_empty() {
+                None
+            } else {
+                Some(comments)
+            }
+        }
+
+        visitor()
+            .visit(doc_comments::<ast::FnDef>)
+            .visit(doc_comments::<ast::StructDef>)
+            .visit(doc_comments::<ast::EnumDef>)
+            .visit(doc_comments::<ast::TraitDef>)
+            .visit(doc_comments::<ast::Module>)
+            .visit(doc_comments::<ast::TypeDef>)
+            .visit(doc_comments::<ast::ConstDef>)
+            .visit(doc_comments::<ast::StaticDef>)
+            .accept(&node)?
+    }
+
+    /// Get a description of this node.
+    ///
+    /// e.g. `struct Name`, `enum Name`, `fn Name`
+    fn description(&self, db: &RootDatabase) -> Option<String> {
+        // TODO: After type inference is done, add type information to improve the output
+        let node = self.node(db)?;
+        // TODO: Refactor to be have less repetition
+        visitor()
+            .visit(|node: &ast::FnDef| {
+                let mut string = "fn ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::StructDef| {
+                let mut string = "struct ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::EnumDef| {
+                let mut string = "enum ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::TraitDef| {
+                let mut string = "trait ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::Module| {
+                let mut string = "mod ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::TypeDef| {
+                let mut string = "type ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::ConstDef| {
+                let mut string = "const ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .visit(|node: &ast::StaticDef| {
+                let mut string = "static ".to_string();
+                node.name()?.syntax().text().push_to(&mut string);
+                Some(string)
+            })
+            .accept(&node)?
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use ra_syntax::TextRange;
+    use crate::mock_analysis::{single_file_with_position, single_file_with_range};
+
+    #[test]
+    fn hover_shows_type_of_an_expression() {
+        let (analysis, position) = single_file_with_position(
+            "
+            pub fn foo() -> u32 { 1 }
+
+            fn main() {
+                let foo_test = foo()<|>;
+            }
+            ",
+        );
+        let hover = analysis.hover(position).unwrap().unwrap();
+        assert_eq!(hover.range, TextRange::from_to(95.into(), 100.into()));
+        assert_eq!(hover.info, "u32");
+    }
+
+    #[test]
+    fn hover_for_local_variable() {
+        let (analysis, position) = single_file_with_position("fn func(foo: i32) { fo<|>o; }");
+        let hover = analysis.hover(position).unwrap().unwrap();
+        assert_eq!(hover.info, "i32");
+    }
+
+    #[test]
+    fn hover_for_local_variable_pat() {
+        let (analysis, position) = single_file_with_position("fn func(fo<|>o: i32) {}");
+        let hover = analysis.hover(position).unwrap().unwrap();
+        assert_eq!(hover.info, "i32");
+    }
+
+    #[test]
+    fn test_type_of_for_function() {
+        let (analysis, range) = single_file_with_range(
+            "
+            pub fn foo() -> u32 { 1 };
+
+            fn main() {
+                let foo_test = <|>foo()<|>;
+            }
+            ",
+        );
+
+        let type_name = analysis.type_of(range).unwrap().unwrap();
+        assert_eq!("u32", &type_name);
+    }
+
+    // FIXME: improve type_of to make this work
+    #[test]
+    fn test_type_of_for_expr_1() {
+        let (analysis, range) = single_file_with_range(
+            "
+            fn main() {
+                let foo = <|>1 + foo_test<|>;
+            }
+            ",
+        );
+
+        let type_name = analysis.type_of(range).unwrap().unwrap();
+        assert_eq!("[unknown]", &type_name);
+    }
+
+    // FIXME: improve type_of to make this work
+    #[test]
+    fn test_type_of_for_expr_2() {
+        let (analysis, range) = single_file_with_range(
+            "
+            fn main() {
+                let foo: usize = 1;
+                let bar = <|>1 + foo_test<|>;
+            }
+            ",
+        );
+
+        let type_name = analysis.type_of(range).unwrap().unwrap();
+        assert_eq!("[unknown]", &type_name);
+    }
+
+}
diff --git a/crates/ra_ide_api/src/imp.rs b/crates/ra_ide_api/src/imp.rs
new file mode 100644
index 000000000..7c60ab7d6
--- /dev/null
+++ b/crates/ra_ide_api/src/imp.rs
@@ -0,0 +1,309 @@
+use std::sync::Arc;
+
+use salsa::Database;
+
+use hir::{
+    self, Problem, source_binder,
+};
+use ra_db::{FilesDatabase, SourceRoot, SourceRootId, SyntaxDatabase};
+use ra_ide_api_light::{self, assists, LocalEdit, Severity};
+use ra_syntax::{
+    TextRange, AstNode, SourceFile,
+    ast::{self, NameOwner},
+    algo::find_node_at_offset,
+    SyntaxKind::*,
+};
+
+use crate::{
+    AnalysisChange,
+    Cancelable, NavigationTarget,
+    CrateId, db, Diagnostic, FileId, FilePosition, FileRange, FileSystemEdit,
+    Query, RootChange, SourceChange, SourceFileEdit,
+    symbol_index::{LibrarySymbolsQuery, FileSymbol},
+};
+
+impl db::RootDatabase {
+    pub(crate) fn apply_change(&mut self, change: AnalysisChange) {
+        log::info!("apply_change {:?}", change);
+        // self.gc_syntax_trees();
+        if !change.new_roots.is_empty() {
+            let mut local_roots = Vec::clone(&self.local_roots());
+            for (root_id, is_local) in change.new_roots {
+                self.query_mut(ra_db::SourceRootQuery)
+                    .set(root_id, Default::default());
+                if is_local {
+                    local_roots.push(root_id);
+                }
+            }
+            self.query_mut(ra_db::LocalRootsQuery)
+                .set((), Arc::new(local_roots));
+        }
+
+        for (root_id, root_change) in change.roots_changed {
+            self.apply_root_change(root_id, root_change);
+        }
+        for (file_id, text) in change.files_changed {
+            self.query_mut(ra_db::FileTextQuery).set(file_id, text)
+        }
+        if !change.libraries_added.is_empty() {
+            let mut libraries = Vec::clone(&self.library_roots());
+            for library in change.libraries_added {
+                libraries.push(library.root_id);
+                self.query_mut(ra_db::SourceRootQuery)
+                    .set(library.root_id, Default::default());
+                self.query_mut(LibrarySymbolsQuery)
+                    .set_constant(library.root_id, Arc::new(library.symbol_index));
+                self.apply_root_change(library.root_id, library.root_change);
+            }
+            self.query_mut(ra_db::LibraryRootsQuery)
+                .set((), Arc::new(libraries));
+        }
+        if let Some(crate_graph) = change.crate_graph {
+            self.query_mut(ra_db::CrateGraphQuery)
+                .set((), Arc::new(crate_graph))
+        }
+    }
+
+    fn apply_root_change(&mut self, root_id: SourceRootId, root_change: RootChange) {
+        let mut source_root = SourceRoot::clone(&self.source_root(root_id));
+        for add_file in root_change.added {
+            self.query_mut(ra_db::FileTextQuery)
+                .set(add_file.file_id, add_file.text);
+            self.query_mut(ra_db::FileRelativePathQuery)
+                .set(add_file.file_id, add_file.path.clone());
+            self.query_mut(ra_db::FileSourceRootQuery)
+                .set(add_file.file_id, root_id);
+            source_root.files.insert(add_file.path, add_file.file_id);
+        }
+        for remove_file in root_change.removed {
+            self.query_mut(ra_db::FileTextQuery)
+                .set(remove_file.file_id, Default::default());
+            source_root.files.remove(&remove_file.path);
+        }
+        self.query_mut(ra_db::SourceRootQuery)
+            .set(root_id, Arc::new(source_root));
+    }
+
+    #[allow(unused)]
+    /// Ideally, we should call this function from time to time to collect heavy
+    /// syntax trees. However, if we actually do that, everything is recomputed
+    /// for some reason. Needs investigation.
+    fn gc_syntax_trees(&mut self) {
+        self.query(ra_db::SourceFileQuery)
+            .sweep(salsa::SweepStrategy::default().discard_values());
+        self.query(hir::db::SourceFileItemsQuery)
+            .sweep(salsa::SweepStrategy::default().discard_values());
+        self.query(hir::db::FileItemQuery)
+            .sweep(salsa::SweepStrategy::default().discard_values());
+    }
+}
+
+impl db::RootDatabase {
+    /// This returns `Vec` because a module may be included from several places. We
+    /// don't handle this case yet though, so the Vec has length at most one.
+    pub(crate) fn parent_module(
+        &self,
+        position: FilePosition,
+    ) -> Cancelable<Vec<NavigationTarget>> {
+        let module = match source_binder::module_from_position(self, position)? {
+            None => return Ok(Vec::new()),
+            Some(it) => it,
+        };
+        let (file_id, ast_module) = match module.declaration_source(self)? {
+            None => return Ok(Vec::new()),
+            Some(it) => it,
+        };
+        let name = ast_module.name().unwrap();
+        Ok(vec![NavigationTarget {
+            file_id,
+            name: name.text().clone(),
+            range: name.syntax().range(),
+            kind: MODULE,
+            ptr: None,
+        }])
+    }
+    /// Returns `Vec` for the same reason as `parent_module`
+    pub(crate) fn crate_for(&self, file_id: FileId) -> Cancelable<Vec<CrateId>> {
+        let module = match source_binder::module_from_file_id(self, file_id)? {
+            Some(it) => it,
+            None => return Ok(Vec::new()),
+        };
+        let krate = match module.krate(self)? {
+            Some(it) => it,
+            None => return Ok(Vec::new()),
+        };
+        Ok(vec![krate.crate_id()])
+    }
+    pub(crate) fn find_all_refs(
+        &self,
+        position: FilePosition,
+    ) -> Cancelable<Vec<(FileId, TextRange)>> {
+        let file = self.source_file(position.file_id);
+        // Find the binding associated with the offset
+        let (binding, descr) = match find_binding(self, &file, position)? {
+            None => return Ok(Vec::new()),
+            Some(it) => it,
+        };
+
+        let mut ret = binding
+            .name()
+            .into_iter()
+            .map(|name| (position.file_id, name.syntax().range()))
+            .collect::<Vec<_>>();
+        ret.extend(
+            descr
+                .scopes(self)?
+                .find_all_refs(binding)
+                .into_iter()
+                .map(|ref_desc| (position.file_id, ref_desc.range)),
+        );
+
+        return Ok(ret);
+
+        fn find_binding<'a>(
+            db: &db::RootDatabase,
+            source_file: &'a SourceFile,
+            position: FilePosition,
+        ) -> Cancelable<Option<(&'a ast::BindPat, hir::Function)>> {
+            let syntax = source_file.syntax();
+            if let Some(binding) = find_node_at_offset::<ast::BindPat>(syntax, position.offset) {
+                let descr = ctry!(source_binder::function_from_child_node(
+                    db,
+                    position.file_id,
+                    binding.syntax(),
+                )?);
+                return Ok(Some((binding, descr)));
+            };
+            let name_ref = ctry!(find_node_at_offset::<ast::NameRef>(syntax, position.offset));
+            let descr = ctry!(source_binder::function_from_child_node(
+                db,
+                position.file_id,
+                name_ref.syntax(),
+            )?);
+            let scope = descr.scopes(db)?;
+            let resolved = ctry!(scope.resolve_local_name(name_ref));
+            let resolved = resolved.ptr().resolve(source_file);
+            let binding = ctry!(find_node_at_offset::<ast::BindPat>(
+                syntax,
+                resolved.range().end()
+            ));
+            Ok(Some((binding, descr)))
+        }
+    }
+
+    pub(crate) fn diagnostics(&self, file_id: FileId) -> Cancelable<Vec<Diagnostic>> {
+        let syntax = self.source_file(file_id);
+
+        let mut res = ra_ide_api_light::diagnostics(&syntax)
+            .into_iter()
+            .map(|d| Diagnostic {
+                range: d.range,
+                message: d.msg,
+                severity: d.severity,
+                fix: d.fix.map(|fix| SourceChange::from_local_edit(file_id, fix)),
+            })
+            .collect::<Vec<_>>();
+        if let Some(m) = source_binder::module_from_file_id(self, file_id)? {
+            for (name_node, problem) in m.problems(self)? {
+                let source_root = self.file_source_root(file_id);
+                let diag = match problem {
+                    Problem::UnresolvedModule { candidate } => {
+                        let create_file = FileSystemEdit::CreateFile {
+                            source_root,
+                            path: candidate.clone(),
+                        };
+                        let fix = SourceChange {
+                            label: "create module".to_string(),
+                            source_file_edits: Vec::new(),
+                            file_system_edits: vec![create_file],
+                            cursor_position: None,
+                        };
+                        Diagnostic {
+                            range: name_node.range(),
+                            message: "unresolved module".to_string(),
+                            severity: Severity::Error,
+                            fix: Some(fix),
+                        }
+                    }
+                    Problem::NotDirOwner { move_to, candidate } => {
+                        let move_file = FileSystemEdit::MoveFile {
+                            src: file_id,
+                            dst_source_root: source_root,
+                            dst_path: move_to.clone(),
+                        };
+                        let create_file = FileSystemEdit::CreateFile {
+                            source_root,
+                            path: move_to.join(candidate),
+                        };
+                        let fix = SourceChange {
+                            label: "move file and create module".to_string(),
+                            source_file_edits: Vec::new(),
+                            file_system_edits: vec![move_file, create_file],
+                            cursor_position: None,
+                        };
+                        Diagnostic {
+                            range: name_node.range(),
+                            message: "can't declare module at this location".to_string(),
+                            severity: Severity::Error,
+                            fix: Some(fix),
+                        }
+                    }
+                };
+                res.push(diag)
+            }
+        };
+        Ok(res)
+    }
+
+    pub(crate) fn assists(&self, frange: FileRange) -> Vec<SourceChange> {
+        let file = self.source_file(frange.file_id);
+        assists::assists(&file, frange.range)
+            .into_iter()
+            .map(|local_edit| SourceChange::from_local_edit(frange.file_id, local_edit))
+            .collect()
+    }
+
+    pub(crate) fn rename(
+        &self,
+        position: FilePosition,
+        new_name: &str,
+    ) -> Cancelable<Vec<SourceFileEdit>> {
+        let res = self
+            .find_all_refs(position)?
+            .iter()
+            .map(|(file_id, text_range)| SourceFileEdit {
+                file_id: *file_id,
+                edit: {
+                    let mut builder = ra_text_edit::TextEditBuilder::default();
+                    builder.replace(*text_range, new_name.into());
+                    builder.finish()
+                },
+            })
+            .collect::<Vec<_>>();
+        Ok(res)
+    }
+    pub(crate) fn index_resolve(&self, name_ref: &ast::NameRef) -> Cancelable<Vec<FileSymbol>> {
+        let name = name_ref.text();
+        let mut query = Query::new(name.to_string());
+        query.exact();
+        query.limit(4);
+        crate::symbol_index::world_symbols(self, query)
+    }
+}
+
+impl SourceChange {
+    pub(crate) fn from_local_edit(file_id: FileId, edit: LocalEdit) -> SourceChange {
+        let file_edit = SourceFileEdit {
+            file_id,
+            edit: edit.edit,
+        };
+        SourceChange {
+            label: edit.label,
+            source_file_edits: vec![file_edit],
+            file_system_edits: vec![],
+            cursor_position: edit
+                .cursor_position
+                .map(|offset| FilePosition { offset, file_id }),
+        }
+    }
+}
diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
new file mode 100644
index 000000000..7e9ca2034
--- /dev/null
+++ b/crates/ra_ide_api/src/lib.rs
@@ -0,0 +1,515 @@
+//! ra_ide_api crate provides "ide-centric" APIs for the rust-analyzer. That is,
+//! it generally operates with files and text ranges, and returns results as
+//! Strings, suitable for displaying to the human.
+//!
+//! What powers this API are the `RootDatabase` struct, which defines a `salsa`
+//! database, and the `ra_hir` crate, where majority of the analysis happens.
+//! However, IDE specific bits of the analysis (most notably completion) happen
+//! in this crate.
+//!
+//! The sibling `ra_ide_api_light` handles thouse bits of IDE functionality
+//! which are restricted to a single file and need only syntax.
+macro_rules! ctry {
+    ($expr:expr) => {
+        match $expr {
+            None => return Ok(None),
+            Some(it) => it,
+        }
+    };
+}
+
+mod completion;
+mod db;
+mod goto_defenition;
+mod imp;
+pub mod mock_analysis;
+mod runnables;
+mod symbol_index;
+
+mod extend_selection;
+mod hover;
+mod call_info;
+mod syntax_highlighting;
+
+use std::{fmt, sync::Arc};
+
+use ra_syntax::{SmolStr, SourceFile, TreePtr, SyntaxKind, TextRange, TextUnit};
+use ra_text_edit::TextEdit;
+use ra_db::{SyntaxDatabase, FilesDatabase, LocalSyntaxPtr};
+use rayon::prelude::*;
+use relative_path::RelativePathBuf;
+use rustc_hash::FxHashMap;
+use salsa::ParallelDatabase;
+
+use crate::{
+    symbol_index::{FileSymbol, SymbolIndex},
+    db::LineIndexDatabase,
+};
+
+pub use crate::{
+    completion::{CompletionItem, CompletionItemKind, InsertText},
+    runnables::{Runnable, RunnableKind},
+};
+pub use ra_ide_api_light::{
+    Fold, FoldKind, HighlightedRange, Severity, StructureNode,
+    LineIndex, LineCol, translate_offset_with_edit,
+};
+pub use ra_db::{
+    Cancelable, Canceled, CrateGraph, CrateId, FileId, FilePosition, FileRange, SourceRootId
+};
+
+#[derive(Default)]
+pub struct AnalysisChange {
+    new_roots: Vec<(SourceRootId, bool)>,
+    roots_changed: FxHashMap<SourceRootId, RootChange>,
+    files_changed: Vec<(FileId, Arc<String>)>,
+    libraries_added: Vec<LibraryData>,
+    crate_graph: Option<CrateGraph>,
+}
+
+#[derive(Default)]
+struct RootChange {
+    added: Vec<AddFile>,
+    removed: Vec<RemoveFile>,
+}
+
+#[derive(Debug)]
+struct AddFile {
+    file_id: FileId,
+    path: RelativePathBuf,
+    text: Arc<String>,
+}
+
+#[derive(Debug)]
+struct RemoveFile {
+    file_id: FileId,
+    path: RelativePathBuf,
+}
+
+impl fmt::Debug for AnalysisChange {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let mut d = fmt.debug_struct("AnalysisChange");
+        if !self.new_roots.is_empty() {
+            d.field("new_roots", &self.new_roots);
+        }
+        if !self.roots_changed.is_empty() {
+            d.field("roots_changed", &self.roots_changed);
+        }
+        if !self.files_changed.is_empty() {
+            d.field("files_changed", &self.files_changed.len());
+        }
+        if !self.libraries_added.is_empty() {
+            d.field("libraries_added", &self.libraries_added.len());
+        }
+        if !self.crate_graph.is_some() {
+            d.field("crate_graph", &self.crate_graph);
+        }
+        d.finish()
+    }
+}
+
+impl fmt::Debug for RootChange {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("AnalysisChange")
+            .field("added", &self.added.len())
+            .field("removed", &self.removed.len())
+            .finish()
+    }
+}
+
+impl AnalysisChange {
+    pub fn new() -> AnalysisChange {
+        AnalysisChange::default()
+    }
+    pub fn add_root(&mut self, root_id: SourceRootId, is_local: bool) {
+        self.new_roots.push((root_id, is_local));
+    }
+    pub fn add_file(
+        &mut self,
+        root_id: SourceRootId,
+        file_id: FileId,
+        path: RelativePathBuf,
+        text: Arc<String>,
+    ) {
+        let file = AddFile {
+            file_id,
+            path,
+            text,
+        };
+        self.roots_changed
+            .entry(root_id)
+            .or_default()
+            .added
+            .push(file);
+    }
+    pub fn change_file(&mut self, file_id: FileId, new_text: Arc<String>) {
+        self.files_changed.push((file_id, new_text))
+    }
+    pub fn remove_file(&mut self, root_id: SourceRootId, file_id: FileId, path: RelativePathBuf) {
+        let file = RemoveFile { file_id, path };
+        self.roots_changed
+            .entry(root_id)
+            .or_default()
+            .removed
+            .push(file);
+    }
+    pub fn add_library(&mut self, data: LibraryData) {
+        self.libraries_added.push(data)
+    }
+    pub fn set_crate_graph(&mut self, graph: CrateGraph) {
+        self.crate_graph = Some(graph);
+    }
+}
+
+#[derive(Debug)]
+pub struct SourceChange {
+    pub label: String,
+    pub source_file_edits: Vec<SourceFileEdit>,
+    pub file_system_edits: Vec<FileSystemEdit>,
+    pub cursor_position: Option<FilePosition>,
+}
+
+#[derive(Debug)]
+pub struct SourceFileEdit {
+    pub file_id: FileId,
+    pub edit: TextEdit,
+}
+
+#[derive(Debug)]
+pub enum FileSystemEdit {
+    CreateFile {
+        source_root: SourceRootId,
+        path: RelativePathBuf,
+    },
+    MoveFile {
+        src: FileId,
+        dst_source_root: SourceRootId,
+        dst_path: RelativePathBuf,
+    },
+}
+
+#[derive(Debug)]
+pub struct Diagnostic {
+    pub message: String,
+    pub range: TextRange,
+    pub fix: Option<SourceChange>,
+    pub severity: Severity,
+}
+
+#[derive(Debug)]
+pub struct Query {
+    query: String,
+    lowercased: String,
+    only_types: bool,
+    libs: bool,
+    exact: bool,
+    limit: usize,
+}
+
+impl Query {
+    pub fn new(query: String) -> Query {
+        let lowercased = query.to_lowercase();
+        Query {
+            query,
+            lowercased,
+            only_types: false,
+            libs: false,
+            exact: false,
+            limit: usize::max_value(),
+        }
+    }
+    pub fn only_types(&mut self) {
+        self.only_types = true;
+    }
+    pub fn libs(&mut self) {
+        self.libs = true;
+    }
+    pub fn exact(&mut self) {
+        self.exact = true;
+    }
+    pub fn limit(&mut self, limit: usize) {
+        self.limit = limit
+    }
+}
+
+/// `NavigationTarget` represents and element in the editor's UI whihc you can
+/// click on to navigate to a particular piece of code.
+///
+/// Typically, a `NavigationTarget` corresponds to some element in the source
+/// code, like a function or a struct, but this is not strictly required.
+#[derive(Debug, Clone)]
+pub struct NavigationTarget {
+    file_id: FileId,
+    name: SmolStr,
+    kind: SyntaxKind,
+    range: TextRange,
+    // Should be DefId ideally
+    ptr: Option<LocalSyntaxPtr>,
+}
+
+impl NavigationTarget {
+    fn from_symbol(symbol: FileSymbol) -> NavigationTarget {
+        NavigationTarget {
+            file_id: symbol.file_id,
+            name: symbol.name.clone(),
+            kind: symbol.ptr.kind(),
+            range: symbol.ptr.range(),
+            ptr: Some(symbol.ptr.clone()),
+        }
+    }
+    pub fn name(&self) -> &SmolStr {
+        &self.name
+    }
+    pub fn kind(&self) -> SyntaxKind {
+        self.kind
+    }
+    pub fn file_id(&self) -> FileId {
+        self.file_id
+    }
+    pub fn range(&self) -> TextRange {
+        self.range
+    }
+}
+
+#[derive(Debug)]
+pub struct RangeInfo<T> {
+    pub range: TextRange,
+    pub info: T,
+}
+
+impl<T> RangeInfo<T> {
+    fn new(range: TextRange, info: T) -> RangeInfo<T> {
+        RangeInfo { range, info }
+    }
+}
+
+#[derive(Debug)]
+pub struct CallInfo {
+    pub label: String,
+    pub doc: Option<String>,
+    pub parameters: Vec<String>,
+    pub active_parameter: Option<usize>,
+}
+
+/// `AnalysisHost` stores the current state of the world.
+#[derive(Debug, Default)]
+pub struct AnalysisHost {
+    db: db::RootDatabase,
+}
+
+impl AnalysisHost {
+    /// Returns a snapshot of the current state, which you can query for
+    /// semantic information.
+    pub fn analysis(&self) -> Analysis {
+        Analysis {
+            db: self.db.snapshot(),
+        }
+    }
+    /// Applies changes to the current state of the world. If there are
+    /// outstanding snapshots, they will be canceled.
+    pub fn apply_change(&mut self, change: AnalysisChange) {
+        self.db.apply_change(change)
+    }
+}
+
+/// Analysis is a snapshot of a world state at a moment in time. It is the main
+/// entry point for asking semantic information about the world. When the world
+/// state is advanced using `AnalysisHost::apply_change` method, all existing
+/// `Analysis` are canceled (most method return `Err(Canceled)`).
+#[derive(Debug)]
+pub struct Analysis {
+    db: salsa::Snapshot<db::RootDatabase>,
+}
+
+impl Analysis {
+    /// Gets the text of the source file.
+    pub fn file_text(&self, file_id: FileId) -> Arc<String> {
+        self.db.file_text(file_id)
+    }
+    /// Gets the syntax tree of the file.
+    pub fn file_syntax(&self, file_id: FileId) -> TreePtr<SourceFile> {
+        self.db.source_file(file_id).clone()
+    }
+    /// Gets the file's `LineIndex`: data structure to convert between absolute
+    /// offsets and line/column representation.
+    pub fn file_line_index(&self, file_id: FileId) -> Arc<LineIndex> {
+        self.db.line_index(file_id)
+    }
+    /// Selects the next syntactic nodes encopasing the range.
+    pub fn extend_selection(&self, frange: FileRange) -> TextRange {
+        extend_selection::extend_selection(&self.db, frange)
+    }
+    /// Returns position of the mathcing brace (all types of braces are
+    /// supported).
+    pub fn matching_brace(&self, file: &SourceFile, offset: TextUnit) -> Option<TextUnit> {
+        ra_ide_api_light::matching_brace(file, offset)
+    }
+    /// Returns a syntax tree represented as `String`, for debug purposes.
+    // FIXME: use a better name here.
+    pub fn syntax_tree(&self, file_id: FileId) -> String {
+        let file = self.db.source_file(file_id);
+        ra_ide_api_light::syntax_tree(&file)
+    }
+    /// Returns an edit to remove all newlines in the range, cleaning up minor
+    /// stuff like trailing commas.
+    pub fn join_lines(&self, frange: FileRange) -> SourceChange {
+        let file = self.db.source_file(frange.file_id);
+        SourceChange::from_local_edit(
+            frange.file_id,
+            ra_ide_api_light::join_lines(&file, frange.range),
+        )
+    }
+    /// Returns an edit which should be applied when opening a new line, fixing
+    /// up minor stuff like continuing the comment.
+    pub fn on_enter(&self, position: FilePosition) -> Option<SourceChange> {
+        let file = self.db.source_file(position.file_id);
+        let edit = ra_ide_api_light::on_enter(&file, position.offset)?;
+        Some(SourceChange::from_local_edit(position.file_id, edit))
+    }
+    /// Returns an edit which should be applied after `=` was typed. Primarily,
+    /// this works when adding `let =`.
+    // FIXME: use a snippet completion instead of this hack here.
+    pub fn on_eq_typed(&self, position: FilePosition) -> Option<SourceChange> {
+        let file = self.db.source_file(position.file_id);
+        let edit = ra_ide_api_light::on_eq_typed(&file, position.offset)?;
+        Some(SourceChange::from_local_edit(position.file_id, edit))
+    }
+    /// Returns an edit which should be applied when a dot ('.') is typed on a blank line, indenting the line appropriately.
+    pub fn on_dot_typed(&self, position: FilePosition) -> Option<SourceChange> {
+        let file = self.db.source_file(position.file_id);
+        let edit = ra_ide_api_light::on_dot_typed(&file, position.offset)?;
+        Some(SourceChange::from_local_edit(position.file_id, edit))
+    }
+    /// Returns a tree representation of symbols in the file. Useful to draw a
+    /// file outline.
+    pub fn file_structure(&self, file_id: FileId) -> Vec<StructureNode> {
+        let file = self.db.source_file(file_id);
+        ra_ide_api_light::file_structure(&file)
+    }
+    /// Returns the set of folding ranges.
+    pub fn folding_ranges(&self, file_id: FileId) -> Vec<Fold> {
+        let file = self.db.source_file(file_id);
+        ra_ide_api_light::folding_ranges(&file)
+    }
+    /// Fuzzy searches for a symbol.
+    pub fn symbol_search(&self, query: Query) -> Cancelable<Vec<NavigationTarget>> {
+        let res = symbol_index::world_symbols(&*self.db, query)?
+            .into_iter()
+            .map(NavigationTarget::from_symbol)
+            .collect();
+        Ok(res)
+    }
+    pub fn goto_defenition(
+        &self,
+        position: FilePosition,
+    ) -> Cancelable<Option<Vec<NavigationTarget>>> {
+        goto_defenition::goto_defenition(&*self.db, position)
+    }
+    /// Finds all usages of the reference at point.
+    pub fn find_all_refs(&self, position: FilePosition) -> Cancelable<Vec<(FileId, TextRange)>> {
+        self.db.find_all_refs(position)
+    }
+    /// Returns a short text descrbing element at position.
+    pub fn hover(&self, position: FilePosition) -> Cancelable<Option<RangeInfo<String>>> {
+        hover::hover(&*self.db, position)
+    }
+    /// Computes parameter information for the given call expression.
+    pub fn call_info(&self, position: FilePosition) -> Cancelable<Option<CallInfo>> {
+        call_info::call_info(&*self.db, position)
+    }
+    /// Returns a `mod name;` declaration which created the current module.
+    pub fn parent_module(&self, position: FilePosition) -> Cancelable<Vec<NavigationTarget>> {
+        self.db.parent_module(position)
+    }
+    /// Returns crates this file belongs too.
+    pub fn crate_for(&self, file_id: FileId) -> Cancelable<Vec<CrateId>> {
+        self.db.crate_for(file_id)
+    }
+    /// Returns the root file of the given crate.
+    pub fn crate_root(&self, crate_id: CrateId) -> Cancelable<FileId> {
+        Ok(self.db.crate_graph().crate_root(crate_id))
+    }
+    /// Returns the set of possible targets to run for the current file.
+    pub fn runnables(&self, file_id: FileId) -> Cancelable<Vec<Runnable>> {
+        runnables::runnables(&*self.db, file_id)
+    }
+    /// Computes syntax highlighting for the given file.
+    pub fn highlight(&self, file_id: FileId) -> Cancelable<Vec<HighlightedRange>> {
+        syntax_highlighting::highlight(&*self.db, file_id)
+    }
+    /// Computes completions at the given position.
+    pub fn completions(&self, position: FilePosition) -> Cancelable<Option<Vec<CompletionItem>>> {
+        let completions = completion::completions(&self.db, position)?;
+        Ok(completions.map(|it| it.into()))
+    }
+    /// Computes assists (aks code actons aka intentions) for the given
+    /// position.
+    pub fn assists(&self, frange: FileRange) -> Cancelable<Vec<SourceChange>> {
+        Ok(self.db.assists(frange))
+    }
+    /// Computes the set of diagnostics for the given file.
+    pub fn diagnostics(&self, file_id: FileId) -> Cancelable<Vec<Diagnostic>> {
+        self.db.diagnostics(file_id)
+    }
+    /// Computes the type of the expression at the given position.
+    pub fn type_of(&self, frange: FileRange) -> Cancelable<Option<String>> {
+        hover::type_of(&*self.db, frange)
+    }
+    /// Returns the edit required to rename reference at the position to the new
+    /// name.
+    pub fn rename(
+        &self,
+        position: FilePosition,
+        new_name: &str,
+    ) -> Cancelable<Vec<SourceFileEdit>> {
+        self.db.rename(position, new_name)
+    }
+}
+
+pub struct LibraryData {
+    root_id: SourceRootId,
+    root_change: RootChange,
+    symbol_index: SymbolIndex,
+}
+
+impl fmt::Debug for LibraryData {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("LibraryData")
+            .field("root_id", &self.root_id)
+            .field("root_change", &self.root_change)
+            .field("n_symbols", &self.symbol_index.len())
+            .finish()
+    }
+}
+
+impl LibraryData {
+    pub fn prepare(
+        root_id: SourceRootId,
+        files: Vec<(FileId, RelativePathBuf, Arc<String>)>,
+    ) -> LibraryData {
+        let symbol_index = SymbolIndex::for_files(files.par_iter().map(|(file_id, _, text)| {
+            let file = SourceFile::parse(text);
+            (*file_id, file)
+        }));
+        let mut root_change = RootChange::default();
+        root_change.added = files
+            .into_iter()
+            .map(|(file_id, path, text)| AddFile {
+                file_id,
+                path,
+                text,
+            })
+            .collect();
+        LibraryData {
+            root_id,
+            root_change,
+            symbol_index,
+        }
+    }
+}
+
+#[test]
+fn analysis_is_send() {
+    fn is_send<T: Send>() {}
+    is_send::<Analysis>();
+}
diff --git a/crates/ra_ide_api/src/mock_analysis.rs b/crates/ra_ide_api/src/mock_analysis.rs
new file mode 100644
index 000000000..846c76cfe
--- /dev/null
+++ b/crates/ra_ide_api/src/mock_analysis.rs
@@ -0,0 +1,135 @@
+use std::sync::Arc;
+
+use relative_path::RelativePathBuf;
+use test_utils::{extract_offset, extract_range, parse_fixture, CURSOR_MARKER};
+use ra_db::mock::FileMap;
+
+use crate::{Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, FilePosition, FileRange, SourceRootId};
+
+/// 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()
+    }
+    /// Creates `MockAnalysis` using a fixture data in the following format:
+    ///
+    /// ```notrust
+    /// //- /main.rs
+    /// mod foo;
+    /// fn main() {}
+    ///
+    /// //- /foo.rs
+    /// struct Baz;
+    /// ```
+    pub fn with_files(fixture: &str) -> MockAnalysis {
+        let mut res = MockAnalysis::new();
+        for entry in parse_fixture(fixture) {
+            res.add_file(&entry.meta, &entry.text);
+        }
+        res
+    }
+
+    /// Same as `with_files`, but requires that a single file contains a `<|>` marker,
+    /// whose position is also returned.
+    pub fn with_files_and_position(fixture: &str) -> (MockAnalysis, FilePosition) {
+        let mut position = None;
+        let mut res = MockAnalysis::new();
+        for entry in parse_fixture(fixture) {
+            if entry.text.contains(CURSOR_MARKER) {
+                assert!(
+                    position.is_none(),
+                    "only one marker (<|>) per fixture is allowed"
+                );
+                position = Some(res.add_file_with_position(&entry.meta, &entry.text));
+            } else {
+                res.add_file(&entry.meta, &entry.text);
+            }
+        }
+        let position = position.expect("expected a marker (<|>)");
+        (res, position)
+    }
+
+    pub fn add_file(&mut self, path: &str, text: &str) -> FileId {
+        let file_id = FileId((self.files.len() + 1) as u32);
+        self.files.push((path.to_string(), text.to_string()));
+        file_id
+    }
+    pub fn add_file_with_position(&mut self, path: &str, text: &str) -> FilePosition {
+        let (offset, text) = extract_offset(text);
+        let file_id = FileId((self.files.len() + 1) as u32);
+        self.files.push((path.to_string(), text.to_string()));
+        FilePosition { file_id, offset }
+    }
+    pub fn add_file_with_range(&mut self, path: &str, text: &str) -> FileRange {
+        let (range, text) = extract_range(text);
+        let file_id = FileId((self.files.len() + 1) as u32);
+        self.files.push((path.to_string(), text.to_string()));
+        FileRange { file_id, range }
+    }
+    pub fn id_of(&self, path: &str) -> FileId {
+        let (idx, _) = self
+            .files
+            .iter()
+            .enumerate()
+            .find(|(_, (p, _text))| path == p)
+            .expect("no file in this mock");
+        FileId(idx as u32 + 1)
+    }
+    pub fn analysis_host(self) -> AnalysisHost {
+        let mut host = AnalysisHost::default();
+        let mut file_map = FileMap::default();
+        let source_root = SourceRootId(0);
+        let mut change = AnalysisChange::new();
+        change.add_root(source_root, true);
+        let mut crate_graph = CrateGraph::default();
+        for (path, contents) in self.files.into_iter() {
+            assert!(path.starts_with('/'));
+            let path = RelativePathBuf::from_path(&path[1..]).unwrap();
+            let file_id = file_map.add(path.clone());
+            if path == "/lib.rs" || path == "/main.rs" {
+                crate_graph.add_crate_root(file_id);
+            }
+            change.add_file(source_root, file_id, path, Arc::new(contents));
+        }
+        change.set_crate_graph(crate_graph);
+        // change.set_file_resolver(Arc::new(file_map));
+        host.apply_change(change);
+        host
+    }
+    pub fn analysis(self) -> Analysis {
+        self.analysis_host().analysis()
+    }
+}
+
+/// Creates analysis from a multi-file fixture, returns positions marked with <|>.
+pub fn analysis_and_position(fixture: &str) -> (Analysis, FilePosition) {
+    let (mock, position) = MockAnalysis::with_files_and_position(fixture);
+    (mock.analysis(), position)
+}
+
+/// Creates analysis for a single file.
+pub fn single_file(code: &str) -> (Analysis, FileId) {
+    let mut mock = MockAnalysis::new();
+    let file_id = mock.add_file("/main.rs", code);
+    (mock.analysis(), file_id)
+}
+
+/// Creates analysis for a single file, returns position marked with <|>.
+pub fn single_file_with_position(code: &str) -> (Analysis, FilePosition) {
+    let mut mock = MockAnalysis::new();
+    let pos = mock.add_file_with_position("/main.rs", code);
+    (mock.analysis(), pos)
+}
+
+/// Creates analysis for a single file, returns range marked with a pair of <|>.
+pub fn single_file_with_range(code: &str) -> (Analysis, FileRange) {
+    let mut mock = MockAnalysis::new();
+    let pos = mock.add_file_with_range("/main.rs", code);
+    (mock.analysis(), pos)
+}
diff --git a/crates/ra_ide_api/src/runnables.rs b/crates/ra_ide_api/src/runnables.rs
new file mode 100644
index 000000000..98b1d2d55
--- /dev/null
+++ b/crates/ra_ide_api/src/runnables.rs
@@ -0,0 +1,89 @@
+use itertools::Itertools;
+use ra_syntax::{
+    TextRange, SyntaxNode,
+    ast::{self, AstNode, NameOwner, ModuleItemOwner},
+};
+use ra_db::{Cancelable, SyntaxDatabase};
+
+use crate::{db::RootDatabase, FileId};
+
+#[derive(Debug)]
+pub struct Runnable {
+    pub range: TextRange,
+    pub kind: RunnableKind,
+}
+
+#[derive(Debug)]
+pub enum RunnableKind {
+    Test { name: String },
+    TestMod { path: String },
+    Bin,
+}
+
+pub(crate) fn runnables(db: &RootDatabase, file_id: FileId) -> Cancelable<Vec<Runnable>> {
+    let source_file = db.source_file(file_id);
+    let res = source_file
+        .syntax()
+        .descendants()
+        .filter_map(|i| runnable(db, file_id, i))
+        .collect();
+    Ok(res)
+}
+
+fn runnable(db: &RootDatabase, file_id: FileId, item: &SyntaxNode) -> Option<Runnable> {
+    if let Some(fn_def) = ast::FnDef::cast(item) {
+        runnable_fn(fn_def)
+    } else if let Some(m) = ast::Module::cast(item) {
+        runnable_mod(db, file_id, m)
+    } else {
+        None
+    }
+}
+
+fn runnable_fn(fn_def: &ast::FnDef) -> Option<Runnable> {
+    let name = fn_def.name()?.text();
+    let kind = if name == "main" {
+        RunnableKind::Bin
+    } else if fn_def.has_atom_attr("test") {
+        RunnableKind::Test {
+            name: name.to_string(),
+        }
+    } else {
+        return None;
+    };
+    Some(Runnable {
+        range: fn_def.syntax().range(),
+        kind,
+    })
+}
+
+fn runnable_mod(db: &RootDatabase, file_id: FileId, module: &ast::Module) -> Option<Runnable> {
+    let has_test_function = module
+        .item_list()?
+        .items()
+        .filter_map(|it| match it.kind() {
+            ast::ModuleItemKind::FnDef(it) => Some(it),
+            _ => None,
+        })
+        .any(|f| f.has_atom_attr("test"));
+    if !has_test_function {
+        return None;
+    }
+    let range = module.syntax().range();
+    let module =
+        hir::source_binder::module_from_child_node(db, file_id, module.syntax()).ok()??;
+
+    // FIXME: thread cancellation instead of `.ok`ing
+    let path = module
+        .path_to_root(db)
+        .ok()?
+        .into_iter()
+        .rev()
+        .filter_map(|it| it.name(db).ok())
+        .filter_map(|it| it)
+        .join("::");
+    Some(Runnable {
+        range,
+        kind: RunnableKind::TestMod { path },
+    })
+}
diff --git a/crates/ra_ide_api/src/symbol_index.rs b/crates/ra_ide_api/src/symbol_index.rs
new file mode 100644
index 000000000..8dd15b40e
--- /dev/null
+++ b/crates/ra_ide_api/src/symbol_index.rs
@@ -0,0 +1,222 @@
+//! This module handles fuzzy-searching of functions, structs and other symbols
+//! by name across the whole workspace and dependencies.
+//!
+//! It works by building an incrementally-updated text-search index of all
+//! symbols. The backbone of the index is the **awesome** `fst` crate by
+//! @BurntSushi.
+//!
+//! In a nutshell, you give a set of strings to the `fst`, and it builds a
+//! finite state machine describing this set of strtings. The strings which
+//! could fuzzy-match a pattern can also be described by a finite state machine.
+//! What is freakingly cool is that you can now traverse both state machines in
+//! lock-step to enumerate the strings which are both in the input set and
+//! fuzz-match the query. Or, more formally, given two langauges described by
+//! fsts, one can build an product fst which describes the intersection of the
+//! languages.
+//!
+//! `fst` does not support cheap updating of the index, but it supports unioning
+//! of state machines. So, to account for changing source code, we build an fst
+//! for each library (which is assumed to never change) and an fst for each rust
+//! file in the current workspace, and run a query aginst the union of all
+//! thouse fsts.
+use std::{
+    cmp::Ordering,
+    hash::{Hash, Hasher},
+    sync::Arc,
+};
+
+use fst::{self, Streamer};
+use ra_syntax::{
+    SyntaxNode, SourceFile, SmolStr, TreePtr, AstNode,
+    algo::{visit::{visitor, Visitor}, find_covering_node},
+    SyntaxKind::{self, *},
+    ast::{self, NameOwner},
+};
+use ra_db::{SourceRootId, FilesDatabase, LocalSyntaxPtr};
+use salsa::ParallelDatabase;
+use rayon::prelude::*;
+
+use crate::{
+    Cancelable, FileId, Query,
+    db::RootDatabase,
+};
+
+salsa::query_group! {
+    pub(crate) trait SymbolsDatabase: hir::db::HirDatabase {
+        fn file_symbols(file_id: FileId) -> Cancelable<Arc<SymbolIndex>> {
+            type FileSymbolsQuery;
+        }
+        fn library_symbols(id: SourceRootId) -> Arc<SymbolIndex> {
+            type LibrarySymbolsQuery;
+            storage input;
+        }
+    }
+}
+
+fn file_symbols(db: &impl SymbolsDatabase, file_id: FileId) -> Cancelable<Arc<SymbolIndex>> {
+    db.check_canceled()?;
+    let source_file = db.source_file(file_id);
+    let mut symbols = source_file
+        .syntax()
+        .descendants()
+        .filter_map(to_symbol)
+        .map(move |(name, ptr)| FileSymbol { name, ptr, file_id })
+        .collect::<Vec<_>>();
+
+    for (name, text_range) in hir::source_binder::macro_symbols(db, file_id)? {
+        let node = find_covering_node(source_file.syntax(), text_range);
+        let ptr = LocalSyntaxPtr::new(node);
+        symbols.push(FileSymbol { file_id, name, ptr })
+    }
+
+    Ok(Arc::new(SymbolIndex::new(symbols)))
+}
+
+pub(crate) fn world_symbols(db: &RootDatabase, query: Query) -> Cancelable<Vec<FileSymbol>> {
+    /// Need to wrap Snapshot to provide `Clone` impl for `map_with`
+    struct Snap(salsa::Snapshot<RootDatabase>);
+    impl Clone for Snap {
+        fn clone(&self) -> Snap {
+            Snap(self.0.snapshot())
+        }
+    }
+
+    let buf: Vec<Arc<SymbolIndex>> = if query.libs {
+        let snap = Snap(db.snapshot());
+        db.library_roots()
+            .par_iter()
+            .map_with(snap, |db, &lib_id| db.0.library_symbols(lib_id))
+            .collect()
+    } else {
+        let mut files = Vec::new();
+        for &root in db.local_roots().iter() {
+            let sr = db.source_root(root);
+            files.extend(sr.files.values().map(|&it| it))
+        }
+
+        let snap = Snap(db.snapshot());
+        files
+            .par_iter()
+            .map_with(snap, |db, &file_id| db.0.file_symbols(file_id))
+            .filter_map(|it| it.ok())
+            .collect()
+    };
+    Ok(query.search(&buf))
+}
+
+#[derive(Default, Debug)]
+pub(crate) struct SymbolIndex {
+    symbols: Vec<FileSymbol>,
+    map: fst::Map,
+}
+
+impl PartialEq for SymbolIndex {
+    fn eq(&self, other: &SymbolIndex) -> bool {
+        self.symbols == other.symbols
+    }
+}
+
+impl Eq for SymbolIndex {}
+
+impl Hash for SymbolIndex {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        self.symbols.hash(hasher)
+    }
+}
+
+impl SymbolIndex {
+    fn new(mut symbols: Vec<FileSymbol>) -> SymbolIndex {
+        fn cmp(s1: &FileSymbol, s2: &FileSymbol) -> Ordering {
+            unicase::Ascii::new(s1.name.as_str()).cmp(&unicase::Ascii::new(s2.name.as_str()))
+        }
+        symbols.par_sort_by(cmp);
+        symbols.dedup_by(|s1, s2| cmp(s1, s2) == Ordering::Equal);
+        let names = symbols.iter().map(|it| it.name.as_str().to_lowercase());
+        let map = fst::Map::from_iter(names.into_iter().zip(0u64..)).unwrap();
+        SymbolIndex { symbols, map }
+    }
+
+    pub(crate) fn len(&self) -> usize {
+        self.symbols.len()
+    }
+
+    pub(crate) fn for_files(
+        files: impl ParallelIterator<Item = (FileId, TreePtr<SourceFile>)>,
+    ) -> SymbolIndex {
+        let symbols = files
+            .flat_map(|(file_id, file)| {
+                file.syntax()
+                    .descendants()
+                    .filter_map(to_symbol)
+                    .map(move |(name, ptr)| FileSymbol { name, ptr, file_id })
+                    .collect::<Vec<_>>()
+            })
+            .collect::<Vec<_>>();
+        SymbolIndex::new(symbols)
+    }
+}
+
+impl Query {
+    pub(crate) fn search(self, indices: &[Arc<SymbolIndex>]) -> Vec<FileSymbol> {
+        let mut op = fst::map::OpBuilder::new();
+        for file_symbols in indices.iter() {
+            let automaton = fst::automaton::Subsequence::new(&self.lowercased);
+            op = op.add(file_symbols.map.search(automaton))
+        }
+        let mut stream = op.union();
+        let mut res = Vec::new();
+        while let Some((_, indexed_values)) = stream.next() {
+            if res.len() >= self.limit {
+                break;
+            }
+            for indexed_value in indexed_values {
+                let file_symbols = &indices[indexed_value.index];
+                let idx = indexed_value.value as usize;
+
+                let symbol = &file_symbols.symbols[idx];
+                if self.only_types && !is_type(symbol.ptr.kind()) {
+                    continue;
+                }
+                if self.exact && symbol.name != self.query {
+                    continue;
+                }
+                res.push(symbol.clone());
+            }
+        }
+        res
+    }
+}
+
+fn is_type(kind: SyntaxKind) -> bool {
+    match kind {
+        STRUCT_DEF | ENUM_DEF | TRAIT_DEF | TYPE_DEF => true,
+        _ => false,
+    }
+}
+
+/// The actual data that is stored in the index. It should be as compact as
+/// possible.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub(crate) struct FileSymbol {
+    pub(crate) file_id: FileId,
+    pub(crate) name: SmolStr,
+    pub(crate) ptr: LocalSyntaxPtr,
+}
+
+fn to_symbol(node: &SyntaxNode) -> Option<(SmolStr, LocalSyntaxPtr)> {
+    fn decl<N: NameOwner>(node: &N) -> Option<(SmolStr, LocalSyntaxPtr)> {
+        let name = node.name()?.text().clone();
+        let ptr = LocalSyntaxPtr::new(node.syntax());
+        Some((name, ptr))
+    }
+    visitor()
+        .visit(decl::<ast::FnDef>)
+        .visit(decl::<ast::StructDef>)
+        .visit(decl::<ast::EnumDef>)
+        .visit(decl::<ast::TraitDef>)
+        .visit(decl::<ast::Module>)
+        .visit(decl::<ast::TypeDef>)
+        .visit(decl::<ast::ConstDef>)
+        .visit(decl::<ast::StaticDef>)
+        .accept(node)?
+}
diff --git a/crates/ra_ide_api/src/syntax_highlighting.rs b/crates/ra_ide_api/src/syntax_highlighting.rs
new file mode 100644
index 000000000..cb19e9515
--- /dev/null
+++ b/crates/ra_ide_api/src/syntax_highlighting.rs
@@ -0,0 +1,92 @@
+use ra_syntax::{ast, AstNode,};
+use ra_db::SyntaxDatabase;
+
+use crate::{
+    FileId, Cancelable, HighlightedRange,
+    db::RootDatabase,
+};
+
+pub(crate) fn highlight(db: &RootDatabase, file_id: FileId) -> Cancelable<Vec<HighlightedRange>> {
+    let source_file = db.source_file(file_id);
+    let mut res = ra_ide_api_light::highlight(source_file.syntax());
+    for macro_call in source_file
+        .syntax()
+        .descendants()
+        .filter_map(ast::MacroCall::cast)
+    {
+        if let Some((off, exp)) = hir::MacroDef::ast_expand(macro_call) {
+            let mapped_ranges = ra_ide_api_light::highlight(&exp.syntax())
+                .into_iter()
+                .filter_map(|r| {
+                    let mapped_range = exp.map_range_back(r.range)?;
+                    let res = HighlightedRange {
+                        range: mapped_range + off,
+                        tag: r.tag,
+                    };
+                    Some(res)
+                });
+            res.extend(mapped_ranges);
+        }
+    }
+    Ok(res)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::mock_analysis::single_file;
+    use test_utils::assert_eq_dbg;
+
+    #[test]
+    fn highlights_code_inside_macros() {
+        let (analysis, file_id) = single_file(
+            "
+            fn main() {
+                ctry!({ let x = 92; x});
+                vec![{ let x = 92; x}];
+            }
+            ",
+        );
+        let highlights = analysis.highlight(file_id).unwrap();
+        assert_eq_dbg(
+            r#"[HighlightedRange { range: [13; 15), tag: "keyword" },
+                HighlightedRange { range: [16; 20), tag: "function" },
+                HighlightedRange { range: [41; 46), tag: "macro" },
+                HighlightedRange { range: [49; 52), tag: "keyword" },
+                HighlightedRange { range: [57; 59), tag: "literal" },
+                HighlightedRange { range: [82; 86), tag: "macro" },
+                HighlightedRange { range: [89; 92), tag: "keyword" },
+                HighlightedRange { range: [97; 99), tag: "literal" },
+                HighlightedRange { range: [49; 52), tag: "keyword" },
+                HighlightedRange { range: [53; 54), tag: "function" },
+                HighlightedRange { range: [57; 59), tag: "literal" },
+                HighlightedRange { range: [61; 62), tag: "text" },
+                HighlightedRange { range: [89; 92), tag: "keyword" },
+                HighlightedRange { range: [93; 94), tag: "function" },
+                HighlightedRange { range: [97; 99), tag: "literal" },
+                HighlightedRange { range: [101; 102), tag: "text" }]"#,
+            &highlights,
+        )
+    }
+
+    // FIXME: this test is not really necessary: artifact of the inital hacky
+    // macros implementation.
+    #[test]
+    fn highlight_query_group_macro() {
+        let (analysis, file_id) = single_file(
+            "
+            salsa::query_group! {
+                pub trait HirDatabase: SyntaxDatabase {}
+            }
+            ",
+        );
+        let highlights = analysis.highlight(file_id).unwrap();
+        assert_eq_dbg(
+            r#"[HighlightedRange { range: [20; 32), tag: "macro" },
+                HighlightedRange { range: [13; 18), tag: "text" },
+                HighlightedRange { range: [51; 54), tag: "keyword" },
+                HighlightedRange { range: [55; 60), tag: "keyword" },
+                HighlightedRange { range: [61; 72), tag: "function" }]"#,
+            &highlights,
+        )
+    }
+}
diff --git a/crates/ra_ide_api/tests/test/main.rs b/crates/ra_ide_api/tests/test/main.rs
new file mode 100644
index 000000000..d1dc07e5b
--- /dev/null
+++ b/crates/ra_ide_api/tests/test/main.rs
@@ -0,0 +1,249 @@
+mod runnables;
+
+use ra_syntax::TextRange;
+use test_utils::{assert_eq_dbg, assert_eq_text};
+
+use ra_ide_api::{
+    mock_analysis::{analysis_and_position, single_file, single_file_with_position, MockAnalysis},
+    AnalysisChange, CrateGraph, FileId, Query
+};
+
+#[test]
+fn test_unresolved_module_diagnostic() {
+    let (analysis, file_id) = single_file("mod foo;");
+    let diagnostics = analysis.diagnostics(file_id).unwrap();
+    assert_eq_dbg(
+        r#"[Diagnostic {
+            message: "unresolved module",
+            range: [4; 7),
+            fix: Some(SourceChange {
+                label: "create module",
+                source_file_edits: [],
+                file_system_edits: [CreateFile { source_root: SourceRootId(0), path: "foo.rs" }],
+                cursor_position: None }),
+                severity: Error }]"#,
+        &diagnostics,
+    );
+}
+
+// FIXME: move this test to hir
+#[test]
+fn test_unresolved_module_diagnostic_no_diag_for_inline_mode() {
+    let (analysis, file_id) = single_file("mod foo {}");
+    let diagnostics = analysis.diagnostics(file_id).unwrap();
+    assert_eq_dbg(r#"[]"#, &diagnostics);
+}
+
+#[test]
+fn test_resolve_parent_module() {
+    let (analysis, pos) = analysis_and_position(
+        "
+        //- /lib.rs
+        mod foo;
+        //- /foo.rs
+        <|>// empty
+    ",
+    );
+    let symbols = analysis.parent_module(pos).unwrap();
+    assert_eq_dbg(
+        r#"[NavigationTarget { file_id: FileId(1), name: "foo", kind: MODULE, range: [4; 7), ptr: None }]"#,
+        &symbols,
+    );
+}
+
+#[test]
+fn test_resolve_parent_module_for_inline() {
+    let (analysis, pos) = analysis_and_position(
+        "
+        //- /lib.rs
+        mod foo {
+            mod bar {
+                mod baz { <|> }
+            }
+        }
+    ",
+    );
+    let symbols = analysis.parent_module(pos).unwrap();
+    assert_eq_dbg(
+        r#"[NavigationTarget { file_id: FileId(1), name: "baz", kind: MODULE, range: [36; 39), ptr: None }]"#,
+        &symbols,
+    );
+}
+
+#[test]
+fn test_resolve_crate_root() {
+    let mock = MockAnalysis::with_files(
+        "
+        //- /bar.rs
+        mod foo;
+        //- /bar/foo.rs
+        // emtpy <|>
+    ",
+    );
+    let root_file = mock.id_of("/bar.rs");
+    let mod_file = mock.id_of("/bar/foo.rs");
+    let mut host = mock.analysis_host();
+    assert!(host.analysis().crate_for(mod_file).unwrap().is_empty());
+
+    let mut crate_graph = CrateGraph::default();
+    let crate_id = crate_graph.add_crate_root(root_file);
+    let mut change = AnalysisChange::new();
+    change.set_crate_graph(crate_graph);
+    host.apply_change(change);
+
+    assert_eq!(host.analysis().crate_for(mod_file).unwrap(), vec![crate_id]);
+}
+
+fn get_all_refs(text: &str) -> Vec<(FileId, TextRange)> {
+    let (analysis, position) = single_file_with_position(text);
+    analysis.find_all_refs(position).unwrap()
+}
+
+#[test]
+fn test_find_all_refs_for_local() {
+    let code = r#"
+    fn main() {
+        let mut i = 1;
+        let j = 1;
+        i = i<|> + j;
+
+        {
+            i = 0;
+        }
+
+        i = 5;
+    }"#;
+
+    let refs = get_all_refs(code);
+    assert_eq!(refs.len(), 5);
+}
+
+#[test]
+fn test_find_all_refs_for_param_inside() {
+    let code = r#"
+    fn foo(i : u32) -> u32 {
+        i<|>
+    }"#;
+
+    let refs = get_all_refs(code);
+    assert_eq!(refs.len(), 2);
+}
+
+#[test]
+fn test_find_all_refs_for_fn_param() {
+    let code = r#"
+    fn foo(i<|> : u32) -> u32 {
+        i
+    }"#;
+
+    let refs = get_all_refs(code);
+    assert_eq!(refs.len(), 2);
+}
+#[test]
+fn test_rename_for_local() {
+    test_rename(
+        r#"
+    fn main() {
+        let mut i = 1;
+        let j = 1;
+        i = i<|> + j;
+
+        {
+            i = 0;
+        }
+
+        i = 5;
+    }"#,
+        "k",
+        r#"
+    fn main() {
+        let mut k = 1;
+        let j = 1;
+        k = k + j;
+
+        {
+            k = 0;
+        }
+
+        k = 5;
+    }"#,
+    );
+}
+
+#[test]
+fn test_rename_for_param_inside() {
+    test_rename(
+        r#"
+    fn foo(i : u32) -> u32 {
+        i<|>
+    }"#,
+        "j",
+        r#"
+    fn foo(j : u32) -> u32 {
+        j
+    }"#,
+    );
+}
+
+#[test]
+fn test_rename_refs_for_fn_param() {
+    test_rename(
+        r#"
+    fn foo(i<|> : u32) -> u32 {
+        i
+    }"#,
+        "new_name",
+        r#"
+    fn foo(new_name : u32) -> u32 {
+        new_name
+    }"#,
+    );
+}
+
+#[test]
+fn test_rename_for_mut_param() {
+    test_rename(
+        r#"
+    fn foo(mut i<|> : u32) -> u32 {
+        i
+    }"#,
+        "new_name",
+        r#"
+    fn foo(mut new_name : u32) -> u32 {
+        new_name
+    }"#,
+    );
+}
+
+fn test_rename(text: &str, new_name: &str, expected: &str) {
+    let (analysis, position) = single_file_with_position(text);
+    let edits = analysis.rename(position, new_name).unwrap();
+    let mut text_edit_bulder = ra_text_edit::TextEditBuilder::default();
+    let mut file_id: Option<FileId> = None;
+    for edit in edits {
+        file_id = Some(edit.file_id);
+        for atom in edit.edit.as_atoms() {
+            text_edit_bulder.replace(atom.delete, atom.insert.clone());
+        }
+    }
+    let result = text_edit_bulder
+        .finish()
+        .apply(&*analysis.file_text(file_id.unwrap()));
+    assert_eq_text!(expected, &*result);
+}
+
+#[test]
+fn world_symbols_include_stuff_from_macros() {
+    let (analysis, _) = single_file(
+        "
+salsa::query_group! {
+pub trait HirDatabase: SyntaxDatabase {}
+}
+    ",
+    );
+
+    let mut symbols = analysis.symbol_search(Query::new("Hir".into())).unwrap();
+    let s = symbols.pop().unwrap();
+    assert_eq!(s.name(), "HirDatabase");
+    assert_eq!(s.range(), TextRange::from_to(33.into(), 44.into()));
+}
diff --git a/crates/ra_ide_api/tests/test/runnables.rs b/crates/ra_ide_api/tests/test/runnables.rs
new file mode 100644
index 000000000..da8d5e0d5
--- /dev/null
+++ b/crates/ra_ide_api/tests/test/runnables.rs
@@ -0,0 +1,109 @@
+use test_utils::assert_eq_dbg;
+
+use ra_ide_api::mock_analysis::analysis_and_position;
+
+#[test]
+fn test_runnables() {
+    let (analysis, pos) = analysis_and_position(
+        r#"
+        //- /lib.rs
+        <|> //empty
+        fn main() {}
+
+        #[test]
+        fn test_foo() {}
+
+        #[test]
+        #[ignore]
+        fn test_foo() {}
+        "#,
+    );
+    let runnables = analysis.runnables(pos.file_id).unwrap();
+    assert_eq_dbg(
+        r#"[Runnable { range: [1; 21), kind: Bin },
+                Runnable { range: [22; 46), kind: Test { name: "test_foo" } },
+                Runnable { range: [47; 81), kind: Test { name: "test_foo" } }]"#,
+        &runnables,
+    )
+}
+
+#[test]
+fn test_runnables_module() {
+    let (analysis, pos) = analysis_and_position(
+        r#"
+        //- /lib.rs
+        <|> //empty
+        mod test_mod {
+            #[test]
+            fn test_foo1() {}
+        }
+        "#,
+    );
+    let runnables = analysis.runnables(pos.file_id).unwrap();
+    assert_eq_dbg(
+        r#"[Runnable { range: [1; 59), kind: TestMod { path: "test_mod" } },
+                Runnable { range: [28; 57), kind: Test { name: "test_foo1" } }]"#,
+        &runnables,
+    )
+}
+
+#[test]
+fn test_runnables_one_depth_layer_module() {
+    let (analysis, pos) = analysis_and_position(
+        r#"
+        //- /lib.rs
+        <|> //empty
+        mod foo {
+            mod test_mod {
+                #[test]
+                fn test_foo1() {}
+            }
+        }
+        "#,
+    );
+    let runnables = analysis.runnables(pos.file_id).unwrap();
+    assert_eq_dbg(
+        r#"[Runnable { range: [23; 85), kind: TestMod { path: "foo::test_mod" } },
+                Runnable { range: [46; 79), kind: Test { name: "test_foo1" } }]"#,
+        &runnables,
+    )
+}
+
+#[test]
+fn test_runnables_multiple_depth_module() {
+    let (analysis, pos) = analysis_and_position(
+        r#"
+        //- /lib.rs
+        <|> //empty
+        mod foo {
+            mod bar {
+                mod test_mod {
+                    #[test]
+                    fn test_foo1() {}
+                }
+            }
+        }
+        "#,
+    );
+    let runnables = analysis.runnables(pos.file_id).unwrap();
+    assert_eq_dbg(
+        r#"[Runnable { range: [41; 115), kind: TestMod { path: "foo::bar::test_mod" } },
+                Runnable { range: [68; 105), kind: Test { name: "test_foo1" } }]"#,
+        &runnables,
+    )
+}
+
+#[test]
+fn test_runnables_no_test_function_in_module() {
+    let (analysis, pos) = analysis_and_position(
+        r#"
+        //- /lib.rs
+        <|> //empty
+        mod test_mod {
+            fn foo1() {}
+        }
+        "#,
+    );
+    let runnables = analysis.runnables(pos.file_id).unwrap();
+    assert_eq_dbg(r#"[]"#, &runnables)
+}