8 files changed, 1017 insertions, 294 deletions

diff --git a/crates/ra_analysis/src/completion/complete_fn_param.rs b/crates/ra_analysis/src/completion/complete_fn_param.rs
new file mode 100644
index 000000000..bb5fdfda0
--- /dev/null
+++ b/crates/ra_analysis/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<'a>>(
+        node: N,
+        params: &mut FxHashMap<String, (u32, ast::Param<'a>)>,
+    ) {
+        node.functions()
+            .filter_map(|it| it.param_list())
+            .flat_map(|it| it.params())
+            .for_each(|param| {
+                let text = param.syntax().text().to_string();
+                params.entry(text).or_insert((0, param)).0 += 1;
+            })
+    }
+}
+
+#[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_analysis/src/completion/complete_keyword.rs b/crates/ra_analysis/src/completion/complete_keyword.rs
new file mode 100644
index 000000000..5427fcb11
--- /dev/null
+++ b/crates/ra_analysis/src/completion/complete_keyword.rs
@@ -0,0 +1,204 @@
+use ra_syntax::{
+    algo::visit::{visitor, Visitor},
+    AstNode,
+    ast::{self, LoopBodyOwner},
+    SyntaxKind::*, SyntaxNodeRef,
+};
+
+use crate::completion::{CompletionContext, CompletionItem, Completions, CompletionKind, CompletionItemKind};
+
+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.enclosing_fn {
+        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) {
+        acc.add(keyword("continue", "continue"));
+        acc.add(keyword("break", "break"));
+    }
+    acc.add_all(complete_return(fn_def, ctx.is_stmt));
+}
+
+fn is_in_loop_body(leaf: SyntaxNodeRef) -> 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, is_stmt: bool) -> Option<CompletionItem> {
+    let snip = match (is_stmt, fn_def.ret_type().is_some()) {
+        (true, true) => "return $0;",
+        (true, false) => "return;",
+        (false, true) => "return $0",
+        (false, false) => "return",
+    };
+    Some(keyword("return", snip))
+}
+
+#[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 test_completion_kewords() {
+        check_keyword_completion(
+            r"
+            fn quux() {
+                <|>
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return"
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_completion_else() {
+        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 test_completion_return_no_stmt() {
+        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 test_continue_break_completion() {
+        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"
+            "#,
+        );
+        check_keyword_completion(
+            r"
+            fn quux() -> i32 {
+                loop { || { <|> } }
+            }
+            ",
+            r#"
+            if "if $0 {}"
+            match "match $0 {}"
+            while "while $0 {}"
+            loop "loop {$0}"
+            return "return $0"
+            "#,
+        );
+    }
+}
diff --git a/crates/ra_analysis/src/completion/complete_path.rs b/crates/ra_analysis/src/completion/complete_path.rs
new file mode 100644
index 000000000..ad4d68a33
--- /dev/null
+++ b/crates/ra_analysis/src/completion/complete_path.rs
@@ -0,0 +1,95 @@
+use crate::{
+    Cancelable,
+    completion::{CompletionItem, 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)? {
+        Some(it) => it,
+        None => return Ok(()),
+    };
+    let target_module = match def_id.resolve(ctx.db)? {
+        hir::Def::Module(it) => it,
+        _ => return Ok(()),
+    };
+    let module_scope = target_module.scope(ctx.db)?;
+    module_scope.entries().for_each(|(name, res)| {
+        CompletionItem::new(CompletionKind::Reference, name.to_string())
+            .from_resolution(ctx.db, res)
+            .add_to(acc)
+    });
+    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",
+        );
+    }
+}
diff --git a/crates/ra_analysis/src/completion/complete_scope.rs b/crates/ra_analysis/src/completion/complete_scope.rs
new file mode 100644
index 000000000..a57670e3b
--- /dev/null
+++ b/crates/ra_analysis/src/completion/complete_scope.rs
@@ -0,0 +1,173 @@
+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(fn_def) = ctx.enclosing_fn {
+        let function = hir::source_binder::function_from_module(ctx.db, module, fn_def);
+        let scopes = function.scopes(ctx.db);
+        complete_fn(acc, &scopes, ctx.offset);
+    }
+
+    let module_scope = module.scope(ctx.db)?;
+    module_scope
+        .entries()
+        .filter(|(_name, res)| {
+            // Don't expose this item
+            match res.import {
+                None => true,
+                Some(import) => {
+                    let range = import.range(ctx.db, module.source().file_id());
+                    !range.is_subrange(&ctx.leaf.range())
+                }
+            }
+        })
+        .for_each(|(name, res)| {
+            CompletionItem::new(CompletionKind::Reference, name.to_string())
+                .from_resolution(ctx.db, res)
+                .add_to(acc)
+        });
+    Ok(())
+}
+
+fn complete_fn(acc: &mut Completions, scopes: &hir::FnScopes, offset: TextUnit) {
+    let mut shadowed = FxHashSet::default();
+    scopes
+        .scope_chain_for_offset(offset)
+        .flat_map(|scope| 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)
+        });
+    if scopes.self_param.is_some() {
+        CompletionItem::new(CompletionKind::Reference, "self").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 = ();
+            }
+            ",
+            "y;x;quux",
+        );
+    }
+
+    #[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 + <|>
+                }
+            }
+            ",
+            "b;a;quux",
+        );
+    }
+
+    #[test]
+    fn completes_bindings_from_for() {
+        check_reference_completion(
+            r"
+            fn quux() {
+                for x in &[1, 2, 3] {
+                    <|>
+                }
+            }
+            ",
+            "x;quux",
+        );
+    }
+
+    #[test]
+    fn completes_module_items() {
+        check_reference_completion(
+            r"
+            struct Foo;
+            enum Baz {}
+            fn quux() {
+                <|>
+            }
+            ",
+            "quux;Foo;Baz",
+        );
+    }
+
+    #[test]
+    fn completes_module_items_in_nested_modules() {
+        check_reference_completion(
+            r"
+            struct Foo;
+            mod m {
+                struct Bar;
+                fn quux() { <|> }
+            }
+            ",
+            "quux;Bar",
+        );
+    }
+
+    #[test]
+    fn completes_return_type() {
+        check_reference_completion(
+            r"
+            struct Foo;
+            fn x() -> <|>
+            ",
+            "Foo;x",
+        )
+    }
+
+    #[test]
+    fn dont_show_to_completions_for_shadowing() {
+        check_reference_completion(
+            r"
+            fn foo() -> {
+                let bar = 92;
+                {
+                    let bar = 62;
+                    <|>
+                }
+            }
+            ",
+            "bar;foo",
+        )
+    }
+
+    #[test]
+    fn completes_self_in_methods() {
+        check_reference_completion(r"impl S { fn foo(&self) { <|> } }", "self")
+    }
+}
diff --git a/crates/ra_analysis/src/completion/complete_snippet.rs b/crates/ra_analysis/src/completion/complete_snippet.rs
new file mode 100644
index 000000000..fb9da0a4f
--- /dev/null
+++ b/crates/ra_analysis/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.enclosing_fn.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_analysis/src/completion/completion_context.rs b/crates/ra_analysis/src/completion/completion_context.rs
new file mode 100644
index 000000000..064fbc6f7
--- /dev/null
+++ b/crates/ra_analysis/src/completion/completion_context.rs
@@ -0,0 +1,156 @@
+use ra_editor::find_node_at_offset;
+use ra_text_edit::AtomTextEdit;
+use ra_syntax::{
+    algo::find_leaf_at_offset,
+    ast,
+    AstNode,
+    SyntaxNodeRef,
+    SourceFileNode,
+    TextUnit,
+    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: SyntaxNodeRef<'a>,
+    pub(super) module: Option<hir::Module>,
+    pub(super) enclosing_fn: Option<ast::FnDef<'a>>,
+    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,
+    pub(super) is_stmt: bool,
+    /// Something is typed at the "top" level, in module or impl/trait.
+    pub(super) is_new_item: bool,
+}
+
+impl<'a> CompletionContext<'a> {
+    pub(super) fn new(
+        db: &'a db::RootDatabase,
+        original_file: &'a SourceFileNode,
+        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,
+            enclosing_fn: None,
+            is_param: false,
+            is_trivial_path: false,
+            path_prefix: None,
+            after_if: false,
+            is_stmt: false,
+            is_new_item: false,
+        };
+        ctx.fill(original_file, position.offset);
+        Ok(Some(ctx))
+    }
+
+    fn fill(&mut self, original_file: &SourceFileNode, 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(&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, file: &SourceFileNode, 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;
+            }
+            _ => (),
+        }
+
+        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;
+                self.enclosing_fn = self
+                    .leaf
+                    .ancestors()
+                    .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
+                    .find_map(ast::FnDef::cast);
+
+                self.is_stmt = match name_ref
+                    .syntax()
+                    .ancestors()
+                    .filter_map(ast::ExprStmt::cast)
+                    .next()
+                {
+                    None => false,
+                    Some(expr_stmt) => expr_stmt.syntax().range() == name_ref.syntax().range(),
+                };
+
+                if let Some(off) = name_ref.syntax().range().start().checked_sub(2.into()) {
+                    if let Some(if_expr) = find_node_at_offset::<ast::IfExpr>(file.syntax(), off) {
+                        if if_expr.syntax().range().end() < name_ref.syntax().range().start() {
+                            self.after_if = true;
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn is_node<'a, N: AstNode<'a>>(node: SyntaxNodeRef<'a>) -> bool {
+    match node.ancestors().filter_map(N::cast).next() {
+        None => false,
+        Some(n) => n.syntax().range() == node.range(),
+    }
+}
diff --git a/crates/ra_analysis/src/completion/completion_item.rs b/crates/ra_analysis/src/completion/completion_item.rs
new file mode 100644
index 000000000..911f08468
--- /dev/null
+++ b/crates/ra_analysis/src/completion/completion_item.rs
@@ -0,0 +1,214 @@
+use crate::db;
+
+/// `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,
+    Binding,
+}
+
+#[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(crate) fn from_resolution(
+        mut self,
+        db: &db::RootDatabase,
+        resolution: &hir::Resolution,
+    ) -> Builder {
+        if let Some(def_id) = resolution.def_id {
+            if let Ok(def) = def_id.resolve(db) {
+                let kind = match def {
+                    hir::Def::Module(..) => CompletionItemKind::Module,
+                    hir::Def::Function(..) => CompletionItemKind::Function,
+                    _ => return self,
+                };
+                self.kind = Some(kind);
+            }
+        }
+        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_analysis/src/completion/reference_completion.rs b/crates/ra_analysis/src/completion/reference_completion.rs
deleted file mode 100644
index f483ed045..000000000
--- a/crates/ra_analysis/src/completion/reference_completion.rs
+++ /dev/null
@@ -1,294 +0,0 @@
-use rustc_hash::{FxHashSet};
-use ra_editor::find_node_at_offset;
-use ra_syntax::{
-    algo::visit::{visitor, Visitor},
-    SourceFileNode, AstNode,
-    ast::{self, LoopBodyOwner},
-    SyntaxKind::*,
-};
-use     hir::{
-        self,
-        FnScopes,
-        Def,
-        Path,
-};
-
-use crate::{
-    db::RootDatabase,
-    completion::CompletionItem,
-    Cancelable
-};
-
-pub(super) fn completions(
-    acc: &mut Vec<CompletionItem>,
-    db: &RootDatabase,
-    module: &hir::Module,
-    file: &SourceFileNode,
-    name_ref: ast::NameRef,
-) -> Cancelable<()> {
-    let kind = match classify_name_ref(name_ref) {
-        Some(it) => it,
-        None => return Ok(()),
-    };
-
-    match kind {
-        NameRefKind::LocalRef { enclosing_fn } => {
-            if let Some(fn_def) = enclosing_fn {
-                let scopes = FnScopes::new(fn_def);
-                complete_fn(name_ref, &scopes, acc);
-                complete_expr_keywords(&file, fn_def, name_ref, acc);
-                complete_expr_snippets(acc);
-            }
-
-            let module_scope = module.scope(db)?;
-            acc.extend(
-                module_scope
-                    .entries()
-                    .filter(|(_name, res)| {
-                        // Don't expose this item
-                        match res.import {
-                            None => true,
-                            Some(import) => {
-                                let range = import.range(db, module.source().file_id());
-                                !range.is_subrange(&name_ref.syntax().range())
-                            }
-                        }
-                    })
-                    .map(|(name, _res)| CompletionItem {
-                        label: name.to_string(),
-                        lookup: None,
-                        snippet: None,
-                    }),
-            );
-        }
-        NameRefKind::Path(path) => complete_path(acc, db, module, path)?,
-        NameRefKind::BareIdentInMod => {
-            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) => complete_mod_item_snippets(acc),
-                _ => (),
-            }
-        }
-    }
-    Ok(())
-}
-
-enum NameRefKind<'a> {
-    /// NameRef is a part of single-segment path, for example, a refernece to a
-    /// local variable.
-    LocalRef {
-        enclosing_fn: Option<ast::FnDef<'a>>,
-    },
-    /// NameRef is the last segment in some path
-    Path(Path),
-    /// NameRef is bare identifier at the module's root.
-    /// Used for keyword completion
-    BareIdentInMod,
-}
-
-fn classify_name_ref(name_ref: ast::NameRef) -> Option<NameRefKind> {
-    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) => return Some(NameRefKind::BareIdentInMod),
-        _ => (),
-    }
-
-    let parent = name_ref.syntax().parent()?;
-    if let Some(segment) = ast::PathSegment::cast(parent) {
-        let path = segment.parent_path();
-        if let Some(path) = Path::from_ast(path) {
-            if !path.is_ident() {
-                return Some(NameRefKind::Path(path));
-            }
-        }
-        if path.qualifier().is_none() {
-            let enclosing_fn = name_ref
-                .syntax()
-                .ancestors()
-                .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
-                .find_map(ast::FnDef::cast);
-            return Some(NameRefKind::LocalRef { enclosing_fn });
-        }
-    }
-    None
-}
-
-fn complete_fn(name_ref: ast::NameRef, scopes: &FnScopes, acc: &mut Vec<CompletionItem>) {
-    let mut shadowed = FxHashSet::default();
-    acc.extend(
-        scopes
-            .scope_chain(name_ref.syntax())
-            .flat_map(|scope| scopes.entries(scope).iter())
-            .filter(|entry| shadowed.insert(entry.name()))
-            .map(|entry| CompletionItem {
-                label: entry.name().to_string(),
-                lookup: None,
-                snippet: None,
-            }),
-    );
-    if scopes.self_param.is_some() {
-        acc.push(CompletionItem {
-            label: "self".to_string(),
-            lookup: None,
-            snippet: None,
-        })
-    }
-}
-
-fn complete_path(
-    acc: &mut Vec<CompletionItem>,
-    db: &RootDatabase,
-    module: &hir::Module,
-    mut path: Path,
-) -> Cancelable<()> {
-    if path.segments.is_empty() {
-        return Ok(());
-    }
-    path.segments.pop();
-    let def_id = match module.resolve_path(db, path)? {
-        None => return Ok(()),
-        Some(it) => it,
-    };
-    let target_module = match def_id.resolve(db)? {
-        Def::Module(it) => it,
-        _ => return Ok(()),
-    };
-    let module_scope = target_module.scope(db)?;
-    let completions = module_scope.entries().map(|(name, _res)| CompletionItem {
-        label: name.to_string(),
-        lookup: None,
-        snippet: None,
-    });
-    acc.extend(completions);
-    Ok(())
-}
-
-fn complete_mod_item_snippets(acc: &mut Vec<CompletionItem>) {
-    acc.push(CompletionItem {
-        label: "Test function".to_string(),
-        lookup: Some("tfn".to_string()),
-        snippet: Some(
-            "#[test]\n\
-             fn ${1:feature}() {\n\
-             $0\n\
-             }"
-            .to_string(),
-        ),
-    });
-    acc.push(CompletionItem {
-        label: "pub(crate)".to_string(),
-        lookup: None,
-        snippet: Some("pub(crate) $0".to_string()),
-    })
-}
-
-fn complete_expr_keywords(
-    file: &SourceFileNode,
-    fn_def: ast::FnDef,
-    name_ref: ast::NameRef,
-    acc: &mut Vec<CompletionItem>,
-) {
-    acc.push(keyword("if", "if $0 {}"));
-    acc.push(keyword("match", "match $0 {}"));
-    acc.push(keyword("while", "while $0 {}"));
-    acc.push(keyword("loop", "loop {$0}"));
-
-    if let Some(off) = name_ref.syntax().range().start().checked_sub(2.into()) {
-        if let Some(if_expr) = find_node_at_offset::<ast::IfExpr>(file.syntax(), off) {
-            if if_expr.syntax().range().end() < name_ref.syntax().range().start() {
-                acc.push(keyword("else", "else {$0}"));
-                acc.push(keyword("else if", "else if $0 {}"));
-            }
-        }
-    }
-    if is_in_loop_body(name_ref) {
-        acc.push(keyword("continue", "continue"));
-        acc.push(keyword("break", "break"));
-    }
-    acc.extend(complete_return(fn_def, name_ref));
-}
-
-fn is_in_loop_body(name_ref: ast::NameRef) -> bool {
-    for node in name_ref.syntax().ancestors() {
-        if node.kind() == FN_DEF || node.kind() == LAMBDA_EXPR {
-            break;
-        }
-        let loop_body = visitor()
-            .visit::<ast::ForExpr, _>(LoopBodyOwner::loop_body)
-            .visit::<ast::WhileExpr, _>(LoopBodyOwner::loop_body)
-            .visit::<ast::LoopExpr, _>(LoopBodyOwner::loop_body)
-            .accept(node);
-        if let Some(Some(body)) = loop_body {
-            if name_ref
-                .syntax()
-                .range()
-                .is_subrange(&body.syntax().range())
-            {
-                return true;
-            }
-        }
-    }
-    false
-}
-
-fn complete_return(fn_def: ast::FnDef, name_ref: ast::NameRef) -> Option<CompletionItem> {
-    // let is_last_in_block = name_ref.syntax().ancestors().filter_map(ast::Expr::cast)
-    //     .next()
-    //     .and_then(|it| it.syntax().parent())
-    //     .and_then(ast::Block::cast)
-    //     .is_some();
-
-    // if is_last_in_block {
-    //     return None;
-    // }
-
-    let is_stmt = match name_ref
-        .syntax()
-        .ancestors()
-        .filter_map(ast::ExprStmt::cast)
-        .next()
-    {
-        None => false,
-        Some(expr_stmt) => expr_stmt.syntax().range() == name_ref.syntax().range(),
-    };
-    let snip = match (is_stmt, fn_def.ret_type().is_some()) {
-        (true, true) => "return $0;",
-        (true, false) => "return;",
-        (false, true) => "return $0",
-        (false, false) => "return",
-    };
-    Some(keyword("return", snip))
-}
-
-fn keyword(kw: &str, snip: &str) -> CompletionItem {
-    CompletionItem {
-        label: kw.to_string(),
-        lookup: None,
-        snippet: Some(snip.to_string()),
-    }
-}
-
-fn complete_expr_snippets(acc: &mut Vec<CompletionItem>) {
-    acc.push(CompletionItem {
-        label: "pd".to_string(),
-        lookup: None,
-        snippet: Some("eprintln!(\"$0 = {:?}\", $0);".to_string()),
-    });
-    acc.push(CompletionItem {
-        label: "ppd".to_string(),
-        lookup: None,
-        snippet: Some("eprintln!(\"$0 = {:#?}\", $0);".to_string()),
-    });
-}