41 files changed, 1862 insertions, 324 deletions

diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index 0848ab6bc..64444ee3a 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -59,6 +59,33 @@ fn main() {
 }
 
 #[test]
+fn doctest_add_function() {
+    check(
+        "add_function",
+        r#####"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+     bar<|>("", baz());
+}
+
+"#####,
+        r#####"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+     bar("", baz());
+}
+
+fn bar(arg: &str, baz: Baz) {
+    unimplemented!()
+}
+
+"#####,
+    )
+}
+
+#[test]
 fn doctest_add_hash() {
     check(
         "add_hash",
diff --git a/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs b/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs
new file mode 100644
index 000000000..864373aa5
--- /dev/null
+++ b/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs
@@ -0,0 +1,206 @@
+use ra_syntax::{
+    ast::{self, AstNode, NameOwner},
+    TextUnit,
+};
+use stdx::format_to;
+
+use crate::{Assist, AssistCtx, AssistId};
+use ra_ide_db::RootDatabase;
+
+// Assist add_from_impl_for_enum
+//
+// Adds a From impl for an enum variant with one tuple field
+//
+// ```
+// enum A { <|>One(u32) }
+// ```
+// ->
+// ```
+// enum A { One(u32) }
+//
+// impl From<u32> for A {
+//     fn from(v: u32) -> Self {
+//         A::One(v)
+//     }
+// }
+// ```
+pub(crate) fn add_from_impl_for_enum(ctx: AssistCtx) -> Option<Assist> {
+    let variant = ctx.find_node_at_offset::<ast::EnumVariant>()?;
+    let variant_name = variant.name()?;
+    let enum_name = variant.parent_enum().name()?;
+    let field_list = match variant.kind() {
+        ast::StructKind::Tuple(field_list) => field_list,
+        _ => return None,
+    };
+    if field_list.fields().count() != 1 {
+        return None;
+    }
+    let field_type = field_list.fields().next()?.type_ref()?;
+    let path = match field_type {
+        ast::TypeRef::PathType(p) => p,
+        _ => return None,
+    };
+
+    if already_has_from_impl(ctx.sema, &variant) {
+        return None;
+    }
+
+    ctx.add_assist(
+        AssistId("add_from_impl_for_enum"),
+        "Add From impl for this enum variant",
+        |edit| {
+            let start_offset = variant.parent_enum().syntax().text_range().end();
+            let mut buf = String::new();
+            format_to!(
+                buf,
+                r#"
+
+impl From<{0}> for {1} {{
+    fn from(v: {0}) -> Self {{
+        {1}::{2}(v)
+    }}
+}}"#,
+                path.syntax(),
+                enum_name,
+                variant_name
+            );
+            edit.insert(start_offset, buf);
+            edit.set_cursor(start_offset + TextUnit::of_str("\n\n"));
+        },
+    )
+}
+
+fn already_has_from_impl(
+    sema: &'_ hir::Semantics<'_, RootDatabase>,
+    variant: &ast::EnumVariant,
+) -> bool {
+    let scope = sema.scope(&variant.syntax());
+
+    let from_path = ast::make::path_from_text("From");
+    let from_hir_path = match hir::Path::from_ast(from_path) {
+        Some(p) => p,
+        None => return false,
+    };
+    let from_trait = match scope.resolve_hir_path(&from_hir_path) {
+        Some(hir::PathResolution::Def(hir::ModuleDef::Trait(t))) => t,
+        _ => return false,
+    };
+
+    let e: hir::Enum = match sema.to_def(&variant.parent_enum()) {
+        Some(e) => e,
+        None => return false,
+    };
+    let e_ty = e.ty(sema.db);
+
+    let hir_enum_var: hir::EnumVariant = match sema.to_def(variant) {
+        Some(ev) => ev,
+        None => return false,
+    };
+    let var_ty = hir_enum_var.fields(sema.db)[0].signature_ty(sema.db);
+
+    e_ty.impls_trait(sema.db, from_trait, &[var_ty.clone()])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn test_add_from_impl_for_enum() {
+        check_assist(
+            add_from_impl_for_enum,
+            "enum A { <|>One(u32) }",
+            r#"enum A { One(u32) }
+
+<|>impl From<u32> for A {
+    fn from(v: u32) -> Self {
+        A::One(v)
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_add_from_impl_for_enum_complicated_path() {
+        check_assist(
+            add_from_impl_for_enum,
+            "enum A { <|>One(foo::bar::baz::Boo) }",
+            r#"enum A { One(foo::bar::baz::Boo) }
+
+<|>impl From<foo::bar::baz::Boo> for A {
+    fn from(v: foo::bar::baz::Boo) -> Self {
+        A::One(v)
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_add_from_impl_no_element() {
+        check_assist_not_applicable(add_from_impl_for_enum, "enum A { <|>One }");
+    }
+
+    #[test]
+    fn test_add_from_impl_more_than_one_element_in_tuple() {
+        check_assist_not_applicable(add_from_impl_for_enum, "enum A { <|>One(u32, String) }");
+    }
+
+    #[test]
+    fn test_add_from_impl_struct_variant() {
+        check_assist_not_applicable(add_from_impl_for_enum, "enum A { <|>One { x: u32 } }");
+    }
+
+    #[test]
+    fn test_add_from_impl_already_exists() {
+        check_assist_not_applicable(
+            add_from_impl_for_enum,
+            r#"enum A { <|>One(u32), }
+
+impl From<u32> for A {
+    fn from(v: u32) -> Self {
+        A::One(v)
+    }
+}
+
+pub trait From<T> {
+    fn from(T) -> Self;
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_add_from_impl_different_variant_impl_exists() {
+        check_assist(
+            add_from_impl_for_enum,
+            r#"enum A { <|>One(u32), Two(String), }
+
+impl From<String> for A {
+    fn from(v: String) -> Self {
+        A::Two(v)
+    }
+}
+
+pub trait From<T> {
+    fn from(T) -> Self;
+}"#,
+            r#"enum A { One(u32), Two(String), }
+
+<|>impl From<u32> for A {
+    fn from(v: u32) -> Self {
+        A::One(v)
+    }
+}
+
+impl From<String> for A {
+    fn from(v: String) -> Self {
+        A::Two(v)
+    }
+}
+
+pub trait From<T> {
+    fn from(T) -> Self;
+}"#,
+        );
+    }
+}
diff --git a/crates/ra_assists/src/handlers/add_function.rs b/crates/ra_assists/src/handlers/add_function.rs
new file mode 100644
index 000000000..488bae08f
--- /dev/null
+++ b/crates/ra_assists/src/handlers/add_function.rs
@@ -0,0 +1,788 @@
+use ra_syntax::{
+    ast::{self, AstNode},
+    SyntaxKind, SyntaxNode, TextUnit,
+};
+
+use crate::{Assist, AssistCtx, AssistId};
+use ast::{edit::IndentLevel, ArgListOwner, CallExpr, Expr};
+use hir::HirDisplay;
+use rustc_hash::{FxHashMap, FxHashSet};
+
+// Assist: add_function
+//
+// Adds a stub function with a signature matching the function under the cursor.
+//
+// ```
+// struct Baz;
+// fn baz() -> Baz { Baz }
+// fn foo() {
+//      bar<|>("", baz());
+// }
+//
+// ```
+// ->
+// ```
+// struct Baz;
+// fn baz() -> Baz { Baz }
+// fn foo() {
+//      bar("", baz());
+// }
+//
+// fn bar(arg: &str, baz: Baz) {
+//     unimplemented!()
+// }
+//
+// ```
+pub(crate) fn add_function(ctx: AssistCtx) -> Option<Assist> {
+    let path_expr: ast::PathExpr = ctx.find_node_at_offset()?;
+    let call = path_expr.syntax().parent().and_then(ast::CallExpr::cast)?;
+    let path = path_expr.path()?;
+
+    if path.qualifier().is_some() {
+        return None;
+    }
+
+    if ctx.sema.resolve_path(&path).is_some() {
+        // The function call already resolves, no need to add a function
+        return None;
+    }
+
+    let function_builder = FunctionBuilder::from_call(&ctx, &call)?;
+
+    ctx.add_assist(AssistId("add_function"), "Add function", |edit| {
+        edit.target(call.syntax().text_range());
+
+        if let Some(function_template) = function_builder.render() {
+            edit.set_cursor(function_template.cursor_offset);
+            edit.insert(function_template.insert_offset, function_template.fn_def.to_string());
+        }
+    })
+}
+
+struct FunctionTemplate {
+    insert_offset: TextUnit,
+    cursor_offset: TextUnit,
+    fn_def: ast::SourceFile,
+}
+
+struct FunctionBuilder {
+    append_fn_at: SyntaxNode,
+    fn_name: ast::Name,
+    type_params: Option<ast::TypeParamList>,
+    params: ast::ParamList,
+}
+
+impl FunctionBuilder {
+    fn from_call(ctx: &AssistCtx, call: &ast::CallExpr) -> Option<Self> {
+        let append_fn_at = next_space_for_fn(&call)?;
+        let fn_name = fn_name(&call)?;
+        let (type_params, params) = fn_args(ctx, &call)?;
+        Some(Self { append_fn_at, fn_name, type_params, params })
+    }
+    fn render(self) -> Option<FunctionTemplate> {
+        let placeholder_expr = ast::make::expr_unimplemented();
+        let fn_body = ast::make::block_expr(vec![], Some(placeholder_expr));
+        let fn_def = ast::make::fn_def(self.fn_name, self.type_params, self.params, fn_body);
+        let fn_def = ast::make::add_newlines(2, fn_def);
+        let fn_def = IndentLevel::from_node(&self.append_fn_at).increase_indent(fn_def);
+        let insert_offset = self.append_fn_at.text_range().end();
+        let cursor_offset_from_fn_start = fn_def
+            .syntax()
+            .descendants()
+            .find_map(ast::MacroCall::cast)?
+            .syntax()
+            .text_range()
+            .start();
+        let cursor_offset = insert_offset + cursor_offset_from_fn_start;
+        Some(FunctionTemplate { insert_offset, cursor_offset, fn_def })
+    }
+}
+
+fn fn_name(call: &CallExpr) -> Option<ast::Name> {
+    let name = call.expr()?.syntax().to_string();
+    Some(ast::make::name(&name))
+}
+
+/// Computes the type variables and arguments required for the generated function
+fn fn_args(
+    ctx: &AssistCtx,
+    call: &CallExpr,
+) -> Option<(Option<ast::TypeParamList>, ast::ParamList)> {
+    let mut arg_names = Vec::new();
+    let mut arg_types = Vec::new();
+    for arg in call.arg_list()?.args() {
+        let arg_name = match fn_arg_name(&arg) {
+            Some(name) => name,
+            None => String::from("arg"),
+        };
+        arg_names.push(arg_name);
+        arg_types.push(match fn_arg_type(ctx, &arg) {
+            Some(ty) => ty,
+            None => String::from("()"),
+        });
+    }
+    deduplicate_arg_names(&mut arg_names);
+    let params = arg_names.into_iter().zip(arg_types).map(|(name, ty)| ast::make::param(name, ty));
+    Some((None, ast::make::param_list(params)))
+}
+
+/// Makes duplicate argument names unique by appending incrementing numbers.
+///
+/// ```
+/// let mut names: Vec<String> =
+///     vec!["foo".into(), "foo".into(), "bar".into(), "baz".into(), "bar".into()];
+/// deduplicate_arg_names(&mut names);
+/// let expected: Vec<String> =
+///     vec!["foo_1".into(), "foo_2".into(), "bar_1".into(), "baz".into(), "bar_2".into()];
+/// assert_eq!(names, expected);
+/// ```
+fn deduplicate_arg_names(arg_names: &mut Vec<String>) {
+    let arg_name_counts = arg_names.iter().fold(FxHashMap::default(), |mut m, name| {
+        *m.entry(name).or_insert(0) += 1;
+        m
+    });
+    let duplicate_arg_names: FxHashSet<String> = arg_name_counts
+        .into_iter()
+        .filter(|(_, count)| *count >= 2)
+        .map(|(name, _)| name.clone())
+        .collect();
+
+    let mut counter_per_name = FxHashMap::default();
+    for arg_name in arg_names.iter_mut() {
+        if duplicate_arg_names.contains(arg_name) {
+            let counter = counter_per_name.entry(arg_name.clone()).or_insert(1);
+            arg_name.push('_');
+            arg_name.push_str(&counter.to_string());
+            *counter += 1;
+        }
+    }
+}
+
+fn fn_arg_name(fn_arg: &Expr) -> Option<String> {
+    match fn_arg {
+        Expr::CastExpr(cast_expr) => fn_arg_name(&cast_expr.expr()?),
+        _ => Some(
+            fn_arg
+                .syntax()
+                .descendants()
+                .filter(|d| ast::NameRef::can_cast(d.kind()))
+                .last()?
+                .to_string(),
+        ),
+    }
+}
+
+fn fn_arg_type(ctx: &AssistCtx, fn_arg: &Expr) -> Option<String> {
+    let ty = ctx.sema.type_of_expr(fn_arg)?;
+    if ty.is_unknown() {
+        return None;
+    }
+    Some(ty.display(ctx.sema.db).to_string())
+}
+
+/// Returns the position inside the current mod or file
+/// directly after the current block
+/// We want to write the generated function directly after
+/// fns, impls or macro calls, but inside mods
+fn next_space_for_fn(expr: &CallExpr) -> Option<SyntaxNode> {
+    let mut ancestors = expr.syntax().ancestors().peekable();
+    let mut last_ancestor: Option<SyntaxNode> = None;
+    while let Some(next_ancestor) = ancestors.next() {
+        match next_ancestor.kind() {
+            SyntaxKind::SOURCE_FILE => {
+                break;
+            }
+            SyntaxKind::ITEM_LIST => {
+                if ancestors.peek().map(|a| a.kind()) == Some(SyntaxKind::MODULE) {
+                    break;
+                }
+            }
+            _ => {}
+        }
+        last_ancestor = Some(next_ancestor);
+    }
+    last_ancestor
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn add_function_with_no_args() {
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    bar<|>();
+}
+",
+            r"
+fn foo() {
+    bar();
+}
+
+fn bar() {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_from_method() {
+        // This ensures that the function is correctly generated
+        // in the next outer mod or file
+        check_assist(
+            add_function,
+            r"
+impl Foo {
+    fn foo() {
+        bar<|>();
+    }
+}
+",
+            r"
+impl Foo {
+    fn foo() {
+        bar();
+    }
+}
+
+fn bar() {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_directly_after_current_block() {
+        // The new fn should not be created at the end of the file or module
+        check_assist(
+            add_function,
+            r"
+fn foo1() {
+    bar<|>();
+}
+
+fn foo2() {}
+",
+            r"
+fn foo1() {
+    bar();
+}
+
+fn bar() {
+    <|>unimplemented!()
+}
+
+fn foo2() {}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_with_no_args_in_same_module() {
+        check_assist(
+            add_function,
+            r"
+mod baz {
+    fn foo() {
+        bar<|>();
+    }
+}
+",
+            r"
+mod baz {
+    fn foo() {
+        bar();
+    }
+
+    fn bar() {
+        <|>unimplemented!()
+    }
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_with_function_call_arg() {
+        check_assist(
+            add_function,
+            r"
+struct Baz;
+fn baz() -> Baz { unimplemented!() }
+fn foo() {
+    bar<|>(baz());
+}
+",
+            r"
+struct Baz;
+fn baz() -> Baz { unimplemented!() }
+fn foo() {
+    bar(baz());
+}
+
+fn bar(baz: Baz) {
+    <|>unimplemented!()
+}
+",
+        );
+    }
+
+    #[test]
+    fn add_function_with_method_call_arg() {
+        check_assist(
+            add_function,
+            r"
+struct Baz;
+impl Baz {
+    fn foo(&self) -> Baz {
+        ba<|>r(self.baz())
+    }
+    fn baz(&self) -> Baz {
+        Baz
+    }
+}
+",
+            r"
+struct Baz;
+impl Baz {
+    fn foo(&self) -> Baz {
+        bar(self.baz())
+    }
+    fn baz(&self) -> Baz {
+        Baz
+    }
+}
+
+fn bar(baz: Baz) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_with_string_literal_arg() {
+        check_assist(
+            add_function,
+            r#"
+fn foo() {
+    <|>bar("bar")
+}
+"#,
+            r#"
+fn foo() {
+    bar("bar")
+}
+
+fn bar(arg: &str) {
+    <|>unimplemented!()
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_function_with_char_literal_arg() {
+        check_assist(
+            add_function,
+            r#"
+fn foo() {
+    <|>bar('x')
+}
+"#,
+            r#"
+fn foo() {
+    bar('x')
+}
+
+fn bar(arg: char) {
+    <|>unimplemented!()
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_function_with_int_literal_arg() {
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    <|>bar(42)
+}
+",
+            r"
+fn foo() {
+    bar(42)
+}
+
+fn bar(arg: i32) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_with_cast_int_literal_arg() {
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    <|>bar(42 as u8)
+}
+",
+            r"
+fn foo() {
+    bar(42 as u8)
+}
+
+fn bar(arg: u8) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn name_of_cast_variable_is_used() {
+        // Ensures that the name of the cast type isn't used
+        // in the generated function signature.
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    let x = 42;
+    bar<|>(x as u8)
+}
+",
+            r"
+fn foo() {
+    let x = 42;
+    bar(x as u8)
+}
+
+fn bar(x: u8) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_with_variable_arg() {
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    let worble = ();
+    <|>bar(worble)
+}
+",
+            r"
+fn foo() {
+    let worble = ();
+    bar(worble)
+}
+
+fn bar(worble: ()) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_with_impl_trait_arg() {
+        check_assist(
+            add_function,
+            r"
+trait Foo {}
+fn foo() -> impl Foo {
+    unimplemented!()
+}
+fn baz() {
+    <|>bar(foo())
+}
+",
+            r"
+trait Foo {}
+fn foo() -> impl Foo {
+    unimplemented!()
+}
+fn baz() {
+    bar(foo())
+}
+
+fn bar(foo: impl Foo) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    #[ignore]
+    // FIXME print paths properly to make this test pass
+    fn add_function_with_qualified_path_arg() {
+        check_assist(
+            add_function,
+            r"
+mod Baz {
+    pub struct Bof;
+    pub fn baz() -> Bof { Bof }
+}
+mod Foo {
+    fn foo() {
+        <|>bar(super::Baz::baz())
+    }
+}
+",
+            r"
+mod Baz {
+    pub struct Bof;
+    pub fn baz() -> Bof { Bof }
+}
+mod Foo {
+    fn foo() {
+        bar(super::Baz::baz())
+    }
+
+    fn bar(baz: super::Baz::Bof) {
+        <|>unimplemented!()
+    }
+}
+",
+        )
+    }
+
+    #[test]
+    #[ignore]
+    // FIXME fix printing the generics of a `Ty` to make this test pass
+    fn add_function_with_generic_arg() {
+        check_assist(
+            add_function,
+            r"
+fn foo<T>(t: T) {
+    <|>bar(t)
+}
+",
+            r"
+fn foo<T>(t: T) {
+    bar(t)
+}
+
+fn bar<T>(t: T) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    #[ignore]
+    // FIXME Fix function type printing to make this test pass
+    fn add_function_with_fn_arg() {
+        check_assist(
+            add_function,
+            r"
+struct Baz;
+impl Baz {
+    fn new() -> Self { Baz }
+}
+fn foo() {
+    <|>bar(Baz::new);
+}
+",
+            r"
+struct Baz;
+impl Baz {
+    fn new() -> Self { Baz }
+}
+fn foo() {
+    bar(Baz::new);
+}
+
+fn bar(arg: fn() -> Baz) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    #[ignore]
+    // FIXME Fix closure type printing to make this test pass
+    fn add_function_with_closure_arg() {
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    let closure = |x: i64| x - 1;
+    <|>bar(closure)
+}
+",
+            r"
+fn foo() {
+    let closure = |x: i64| x - 1;
+    bar(closure)
+}
+
+fn bar(closure: impl Fn(i64) -> i64) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn unresolveable_types_default_to_unit() {
+        check_assist(
+            add_function,
+            r"
+fn foo() {
+    <|>bar(baz)
+}
+",
+            r"
+fn foo() {
+    bar(baz)
+}
+
+fn bar(baz: ()) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn arg_names_dont_overlap() {
+        check_assist(
+            add_function,
+            r"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+    <|>bar(baz(), baz())
+}
+",
+            r"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+    bar(baz(), baz())
+}
+
+fn bar(baz_1: Baz, baz_2: Baz) {
+    <|>unimplemented!()
+}
+",
+        )
+    }
+
+    #[test]
+    fn arg_name_counters_start_at_1_per_name() {
+        check_assist(
+            add_function,
+            r#"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+    <|>bar(baz(), baz(), "foo", "bar")
+}
+"#,
+            r#"
+struct Baz;
+fn baz() -> Baz { Baz }
+fn foo() {
+    bar(baz(), baz(), "foo", "bar")
+}
+
+fn bar(baz_1: Baz, baz_2: Baz, arg_1: &str, arg_2: &str) {
+    <|>unimplemented!()
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn add_function_not_applicable_if_function_already_exists() {
+        check_assist_not_applicable(
+            add_function,
+            r"
+fn foo() {
+    bar<|>();
+}
+
+fn bar() {}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_not_applicable_if_unresolved_variable_in_call_is_selected() {
+        check_assist_not_applicable(
+            // bar is resolved, but baz isn't.
+            // The assist is only active if the cursor is on an unresolved path,
+            // but the assist should only be offered if the path is a function call.
+            add_function,
+            r"
+fn foo() {
+    bar(b<|>az);
+}
+
+fn bar(baz: ()) {}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_not_applicable_if_function_path_not_singleton() {
+        // In the future this assist could be extended to generate functions
+        // if the path is in the same crate (or even the same workspace).
+        // For the beginning, I think this is fine.
+        check_assist_not_applicable(
+            add_function,
+            r"
+fn foo() {
+    other_crate::bar<|>();
+}
+        ",
+        )
+    }
+
+    #[test]
+    #[ignore]
+    fn create_method_with_no_args() {
+        check_assist(
+            add_function,
+            r"
+struct Foo;
+impl Foo {
+    fn foo(&self) {
+        self.bar()<|>;
+    }
+}
+        ",
+            r"
+struct Foo;
+impl Foo {
+    fn foo(&self) {
+        self.bar();
+    }
+    fn bar(&self) {
+        unimplemented!();
+    }
+}
+        ",
+        )
+    }
+}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index fa1f3dd26..fa3d3913f 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -96,6 +96,7 @@ mod handlers {
     mod add_custom_impl;
     mod add_derive;
     mod add_explicit_type;
+    mod add_function;
     mod add_impl;
     mod add_missing_impl_members;
     mod add_new;
@@ -122,12 +123,14 @@ mod handlers {
     mod replace_qualified_name_with_use;
     mod replace_unwrap_with_match;
     mod split_import;
+    mod add_from_impl_for_enum;
 
     pub(crate) fn all() -> &'static [AssistHandler] {
         &[
             add_custom_impl::add_custom_impl,
             add_derive::add_derive,
             add_explicit_type::add_explicit_type,
+            add_function::add_function,
             add_impl::add_impl,
             add_missing_impl_members::add_missing_default_members,
             add_missing_impl_members::add_missing_impl_members,
@@ -159,6 +162,7 @@ mod handlers {
             replace_qualified_name_with_use::replace_qualified_name_with_use,
             replace_unwrap_with_match::replace_unwrap_with_match,
             split_import::split_import,
+            add_from_impl_for_enum::add_from_impl_for_enum,
         ]
     }
 }
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index cd2a8fc62..c6f3bdb8e 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -1084,6 +1084,26 @@ impl Type {
         )
     }
 
+    pub fn impls_trait(&self, db: &dyn HirDatabase, trait_: Trait, args: &[Type]) -> bool {
+        let trait_ref = hir_ty::TraitRef {
+            trait_: trait_.id,
+            substs: Substs::build_for_def(db, trait_.id)
+                .push(self.ty.value.clone())
+                .fill(args.iter().map(|t| t.ty.value.clone()))
+                .build(),
+        };
+
+        let goal = Canonical {
+            value: hir_ty::InEnvironment::new(
+                self.ty.environment.clone(),
+                hir_ty::Obligation::Trait(trait_ref),
+            ),
+            num_vars: 0,
+        };
+
+        db.trait_solve(self.krate, goal).is_some()
+    }
+
     // FIXME: this method is broken, as it doesn't take closures into account.
     pub fn as_callable(&self) -> Option<CallableDef> {
         Some(self.ty.value.as_callable()?.0)
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 28c570c76..8d4b8b0f0 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -672,8 +672,7 @@ impl ExprCollector<'_> {
             }
 
             // FIXME: implement
-            ast::Pat::BoxPat(_) => Pat::Missing,
-            ast::Pat::RangePat(_) => Pat::Missing,
+            ast::Pat::BoxPat(_) | ast::Pat::RangePat(_) | ast::Pat::MacroPat(_) => Pat::Missing,
         };
         let ptr = AstPtr::new(&pat);
         self.alloc_pat(pattern, Either::Left(ptr))
diff --git a/crates/ra_hir_def/src/type_ref.rs b/crates/ra_hir_def/src/type_ref.rs
index 102fdb13d..01cc392db 100644
--- a/crates/ra_hir_def/src/type_ref.rs
+++ b/crates/ra_hir_def/src/type_ref.rs
@@ -93,7 +93,11 @@ impl TypeRef {
             }
             ast::TypeRef::PlaceholderType(_inner) => TypeRef::Placeholder,
             ast::TypeRef::FnPointerType(inner) => {
-                let ret_ty = TypeRef::from_ast_opt(inner.ret_type().and_then(|rt| rt.type_ref()));
+                let ret_ty = inner
+                    .ret_type()
+                    .and_then(|rt| rt.type_ref())
+                    .map(TypeRef::from_ast)
+                    .unwrap_or_else(|| TypeRef::Tuple(Vec::new()));
                 let mut params = if let Some(pl) = inner.param_list() {
                     pl.params().map(|p| p.ascribed_type()).map(TypeRef::from_ast_opt).collect()
                 } else {
diff --git a/crates/ra_hir_ty/Cargo.toml b/crates/ra_hir_ty/Cargo.toml
index 5a58d70cf..45be08430 100644
--- a/crates/ra_hir_ty/Cargo.toml
+++ b/crates/ra_hir_ty/Cargo.toml
@@ -23,9 +23,9 @@ ra_prof = { path = "../ra_prof" }
 ra_syntax = { path = "../ra_syntax" }
 test_utils = { path = "../test_utils" }
 
-chalk-solve =   { git = "https://github.com/rust-lang/chalk.git", rev = "177d71340acc7a7204a33115fc63075d86452179" }
-chalk-rust-ir = { git = "https://github.com/rust-lang/chalk.git", rev = "177d71340acc7a7204a33115fc63075d86452179" }
-chalk-ir =      { git = "https://github.com/rust-lang/chalk.git", rev = "177d71340acc7a7204a33115fc63075d86452179" }
+chalk-solve =   { git = "https://github.com/rust-lang/chalk.git", rev = "039fc904a05f8cb3d0c682c9a57a63dda7a35356" }
+chalk-rust-ir = { git = "https://github.com/rust-lang/chalk.git", rev = "039fc904a05f8cb3d0c682c9a57a63dda7a35356" }
+chalk-ir =      { git = "https://github.com/rust-lang/chalk.git", rev = "039fc904a05f8cb3d0c682c9a57a63dda7a35356" }
 
 [dev-dependencies]
 insta = "0.15.0"
diff --git a/crates/ra_hir_ty/src/autoderef.rs b/crates/ra_hir_ty/src/autoderef.rs
index 53e81e85d..d91c21e24 100644
--- a/crates/ra_hir_ty/src/autoderef.rs
+++ b/crates/ra_hir_ty/src/autoderef.rs
@@ -14,7 +14,7 @@ use crate::{
     db::HirDatabase,
     traits::{InEnvironment, Solution},
     utils::generics,
-    Canonical, Substs, Ty, TypeWalk,
+    BoundVar, Canonical, DebruijnIndex, Substs, Ty,
 };
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
@@ -61,14 +61,13 @@ fn deref_by_trait(
         return None;
     }
 
-    // FIXME make the Canonical handling nicer
+    // FIXME make the Canonical / bound var handling nicer
 
-    let parameters = Substs::build_for_generics(&generic_params)
-        .push(ty.value.value.clone().shift_bound_vars(1))
-        .build();
+    let parameters =
+        Substs::build_for_generics(&generic_params).push(ty.value.value.clone()).build();
 
     let projection = super::traits::ProjectionPredicate {
-        ty: Ty::Bound(0),
+        ty: Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, ty.value.num_vars)),
         projection_ty: super::ProjectionTy { associated_ty: target, parameters },
     };
 
@@ -93,12 +92,16 @@ fn deref_by_trait(
             // we have `impl<T> Deref for Foo<T> { Target = T }`, that should be
             // the case.
             for i in 1..vars.0.num_vars {
-                if vars.0.value[i] != Ty::Bound((i - 1) as u32) {
+                if vars.0.value[i - 1] != Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, i - 1))
+                {
                     warn!("complex solution for derefing {:?}: {:?}, ignoring", ty.value, solution);
                     return None;
                 }
             }
-            Some(Canonical { value: vars.0.value[0].clone(), num_vars: vars.0.num_vars })
+            Some(Canonical {
+                value: vars.0.value[vars.0.value.len() - 1].clone(),
+                num_vars: vars.0.num_vars,
+            })
         }
         Solution::Ambig(_) => {
             info!("Ambiguous solution for derefing {:?}: {:?}", ty.value, solution);
diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index 13ecd537a..0e9313aa1 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/crates/ra_hir_ty/src/display.rs
@@ -155,7 +155,11 @@ impl HirDisplay for ApplicationTy {
                 let sig = FnSig::from_fn_ptr_substs(&self.parameters);
                 write!(f, "fn(")?;
                 f.write_joined(sig.params(), ", ")?;
-                write!(f, ") -> {}", sig.ret().display(f.db))?;
+                write!(f, ")")?;
+                let ret = sig.ret();
+                if *ret != Ty::unit() {
+                    write!(f, " -> {}", ret.display(f.db))?;
+                }
             }
             TypeCtor::FnDef(def) => {
                 let sig = f.db.callable_item_signature(def).subst(&self.parameters);
@@ -180,7 +184,11 @@ impl HirDisplay for ApplicationTy {
                 }
                 write!(f, "(")?;
                 f.write_joined(sig.params(), ", ")?;
-                write!(f, ") -> {}", sig.ret().display(f.db))?;
+                write!(f, ")")?;
+                let ret = sig.ret();
+                if *ret != Ty::unit() {
+                    write!(f, " -> {}", ret.display(f.db))?;
+                }
             }
             TypeCtor::Adt(def_id) => {
                 let name = match def_id {
@@ -242,16 +250,16 @@ impl HirDisplay for ApplicationTy {
                 let sig = self.parameters[0]
                     .callable_sig(f.db)
                     .expect("first closure parameter should contain signature");
-                let return_type_hint = sig.ret().display(f.db);
                 if sig.params().is_empty() {
-                    write!(f, "|| -> {}", return_type_hint)?;
+                    write!(f, "||")?;
                 } else if f.omit_verbose_types() {
-                    write!(f, "|{}| -> {}", TYPE_HINT_TRUNCATION, return_type_hint)?;
+                    write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
                 } else {
                     write!(f, "|")?;
                     f.write_joined(sig.params(), ", ")?;
-                    write!(f, "| -> {}", return_type_hint)?;
+                    write!(f, "|")?;
                 };
+                write!(f, " -> {}", sig.ret().display(f.db))?;
             }
         }
         Ok(())
@@ -303,7 +311,7 @@ impl HirDisplay for Ty {
                     }
                 }
             }
-            Ty::Bound(idx) => write!(f, "?{}", idx)?,
+            Ty::Bound(idx) => write!(f, "?{}.{}", idx.debruijn.depth(), idx.index)?,
             Ty::Dyn(predicates) | Ty::Opaque(predicates) => {
                 match self {
                     Ty::Dyn(_) => write!(f, "dyn ")?,
diff --git a/crates/ra_hir_ty/src/infer/unify.rs b/crates/ra_hir_ty/src/infer/unify.rs
index 0bf8fbd63..ac25f8a80 100644
--- a/crates/ra_hir_ty/src/infer/unify.rs
+++ b/crates/ra_hir_ty/src/infer/unify.rs
@@ -7,7 +7,9 @@ use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
 use test_utils::tested_by;
 
 use super::{InferenceContext, Obligation};
-use crate::{Canonical, InEnvironment, InferTy, Substs, Ty, TypeCtor, TypeWalk};
+use crate::{
+    BoundVar, Canonical, DebruijnIndex, InEnvironment, InferTy, Substs, Ty, TypeCtor, TypeWalk,
+};
 
 impl<'a> InferenceContext<'a> {
     pub(super) fn canonicalizer<'b>(&'b mut self) -> Canonicalizer<'a, 'b>
@@ -47,7 +49,7 @@ where
         })
     }
 
-    fn do_canonicalize<T: TypeWalk>(&mut self, t: T, binders: usize) -> T {
+    fn do_canonicalize<T: TypeWalk>(&mut self, t: T, binders: DebruijnIndex) -> T {
         t.fold_binders(
             &mut |ty, binders| match ty {
                 Ty::Infer(tv) => {
@@ -72,7 +74,7 @@ where
                             InferTy::MaybeNeverTypeVar(_) => InferTy::MaybeNeverTypeVar(root),
                         };
                         let position = self.add(free_var);
-                        Ty::Bound((position + binders) as u32)
+                        Ty::Bound(BoundVar::new(binders, position))
                     }
                 }
                 _ => ty,
@@ -89,7 +91,7 @@ where
     }
 
     pub(crate) fn canonicalize_ty(mut self, ty: Ty) -> Canonicalized<Ty> {
-        let result = self.do_canonicalize(ty, 0);
+        let result = self.do_canonicalize(ty, DebruijnIndex::INNERMOST);
         self.into_canonicalized(result)
     }
 
@@ -98,8 +100,12 @@ where
         obligation: InEnvironment<Obligation>,
     ) -> Canonicalized<InEnvironment<Obligation>> {
         let result = match obligation.value {
-            Obligation::Trait(tr) => Obligation::Trait(self.do_canonicalize(tr, 0)),
-            Obligation::Projection(pr) => Obligation::Projection(self.do_canonicalize(pr, 0)),
+            Obligation::Trait(tr) => {
+                Obligation::Trait(self.do_canonicalize(tr, DebruijnIndex::INNERMOST))
+            }
+            Obligation::Projection(pr) => {
+                Obligation::Projection(self.do_canonicalize(pr, DebruijnIndex::INNERMOST))
+            }
         };
         self.into_canonicalized(InEnvironment {
             value: result,
@@ -112,13 +118,13 @@ impl<T> Canonicalized<T> {
     pub fn decanonicalize_ty(&self, mut ty: Ty) -> Ty {
         ty.walk_mut_binders(
             &mut |ty, binders| {
-                if let &mut Ty::Bound(idx) = ty {
-                    if idx as usize >= binders && (idx as usize - binders) < self.free_vars.len() {
-                        *ty = Ty::Infer(self.free_vars[idx as usize - binders]);
+                if let &mut Ty::Bound(bound) = ty {
+                    if bound.debruijn >= binders {
+                        *ty = Ty::Infer(self.free_vars[bound.index]);
                     }
                 }
             },
-            0,
+            DebruijnIndex::INNERMOST,
         );
         ty
     }
@@ -150,7 +156,7 @@ pub fn unify(ty1: &Canonical<Ty>, ty2: &Canonical<Ty>) -> Option<Substs> {
     // (kind of hacky)
     for (i, var) in vars.iter().enumerate() {
         if &*table.resolve_ty_shallow(var) == var {
-            table.unify(var, &Ty::Bound(i as u32));
+            table.unify(var, &Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, i)));
         }
     }
     Some(
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 6c5469ecd..a9022dee7 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -64,6 +64,8 @@ pub use lower::{
 };
 pub use traits::{InEnvironment, Obligation, ProjectionPredicate, TraitEnvironment};
 
+pub use chalk_ir::{BoundVar, DebruijnIndex};
+
 /// A type constructor or type name: this might be something like the primitive
 /// type `bool`, a struct like `Vec`, or things like function pointers or
 /// tuples.
@@ -265,7 +267,11 @@ impl TypeWalk for ProjectionTy {
         self.parameters.walk(f);
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         self.parameters.walk_mut_binders(f, binders);
     }
 }
@@ -299,7 +305,7 @@ pub enum Ty {
     /// parameters get turned into variables; during trait resolution, inference
     /// variables get turned into bound variables and back; and in `Dyn` the
     /// `Self` type is represented with a bound variable as well.
-    Bound(u32),
+    Bound(BoundVar),
 
     /// A type variable used during type checking.
     Infer(InferTy),
@@ -337,7 +343,11 @@ impl TypeWalk for Substs {
         }
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         for t in make_mut_slice(&mut self.0) {
             t.walk_mut_binders(f, binders);
         }
@@ -381,7 +391,13 @@ impl Substs {
 
     /// Return Substs that replace each parameter by a bound variable.
     pub(crate) fn bound_vars(generic_params: &Generics) -> Substs {
-        Substs(generic_params.iter().enumerate().map(|(idx, _)| Ty::Bound(idx as u32)).collect())
+        Substs(
+            generic_params
+                .iter()
+                .enumerate()
+                .map(|(idx, _)| Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, idx)))
+                .collect(),
+        )
     }
 
     pub fn build_for_def(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> SubstsBuilder {
@@ -425,8 +441,8 @@ impl SubstsBuilder {
         self.param_count - self.vec.len()
     }
 
-    pub fn fill_with_bound_vars(self, starting_from: u32) -> Self {
-        self.fill((starting_from..).map(Ty::Bound))
+    pub fn fill_with_bound_vars(self, debruijn: DebruijnIndex, starting_from: usize) -> Self {
+        self.fill((starting_from..).map(|idx| Ty::Bound(BoundVar::new(debruijn, idx))))
     }
 
     pub fn fill_with_unknown(self) -> Self {
@@ -507,7 +523,11 @@ impl TypeWalk for TraitRef {
         self.substs.walk(f);
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         self.substs.walk_mut_binders(f, binders);
     }
 }
@@ -558,7 +578,11 @@ impl TypeWalk for GenericPredicate {
         }
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         match self {
             GenericPredicate::Implemented(trait_ref) => trait_ref.walk_mut_binders(f, binders),
             GenericPredicate::Projection(projection_pred) => {
@@ -616,7 +640,11 @@ impl TypeWalk for FnSig {
         }
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         for t in make_mut_slice(&mut self.params_and_return) {
             t.walk_mut_binders(f, binders);
         }
@@ -755,7 +783,7 @@ impl Ty {
 pub trait TypeWalk {
     fn walk(&self, f: &mut impl FnMut(&Ty));
     fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
-        self.walk_mut_binders(&mut |ty, _binders| f(ty), 0);
+        self.walk_mut_binders(&mut |ty, _binders| f(ty), DebruijnIndex::INNERMOST);
     }
     /// Walk the type, counting entered binders.
     ///
@@ -767,9 +795,17 @@ pub trait TypeWalk {
     /// that. Currently, the only thing that introduces bound variables on our
     /// side are `Ty::Dyn` and `Ty::Opaque`, which each introduce a bound
     /// variable for the self type.
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize);
-
-    fn fold_binders(mut self, f: &mut impl FnMut(Ty, usize) -> Ty, binders: usize) -> Self
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    );
+
+    fn fold_binders(
+        mut self,
+        f: &mut impl FnMut(Ty, DebruijnIndex) -> Ty,
+        binders: DebruijnIndex,
+    ) -> Self
     where
         Self: Sized,
     {
@@ -795,40 +831,43 @@ pub trait TypeWalk {
     }
 
     /// Substitutes `Ty::Bound` vars with the given substitution.
-    fn subst_bound_vars(mut self, substs: &Substs) -> Self
+    fn subst_bound_vars(self, substs: &Substs) -> Self
+    where
+        Self: Sized,
+    {
+        self.subst_bound_vars_at_depth(substs, DebruijnIndex::INNERMOST)
+    }
+
+    /// Substitutes `Ty::Bound` vars with the given substitution.
+    fn subst_bound_vars_at_depth(mut self, substs: &Substs, depth: DebruijnIndex) -> Self
     where
         Self: Sized,
     {
         self.walk_mut_binders(
             &mut |ty, binders| {
-                if let &mut Ty::Bound(idx) = ty {
-                    if idx as usize >= binders && (idx as usize - binders) < substs.len() {
-                        *ty = substs.0[idx as usize - binders].clone();
-                    } else if idx as usize >= binders + substs.len() {
-                        // shift free binders
-                        *ty = Ty::Bound(idx - substs.len() as u32);
+                if let &mut Ty::Bound(bound) = ty {
+                    if bound.debruijn >= binders {
+                        *ty = substs.0[bound.index].clone();
                     }
                 }
             },
-            0,
+            depth,
         );
         self
     }
-
-    /// Shifts up `Ty::Bound` vars by `n`.
-    fn shift_bound_vars(self, n: i32) -> Self
+    // /// Shifts up debruijn indices of `Ty::Bound` vars by `n`.
+    fn shift_bound_vars(self, n: DebruijnIndex) -> Self
     where
         Self: Sized,
     {
         self.fold_binders(
             &mut |ty, binders| match ty {
-                Ty::Bound(idx) if idx as usize >= binders => {
-                    assert!(idx as i32 >= -n);
-                    Ty::Bound((idx as i32 + n) as u32)
+                Ty::Bound(bound) if bound.debruijn >= binders => {
+                    Ty::Bound(bound.shifted_in_from(n))
                 }
                 ty => ty,
             },
-            0,
+            DebruijnIndex::INNERMOST,
         )
     }
 }
@@ -856,7 +895,11 @@ impl TypeWalk for Ty {
         f(self);
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         match self {
             Ty::Apply(a_ty) => {
                 a_ty.parameters.walk_mut_binders(f, binders);
@@ -866,7 +909,7 @@ impl TypeWalk for Ty {
             }
             Ty::Dyn(predicates) | Ty::Opaque(predicates) => {
                 for p in make_mut_slice(predicates) {
-                    p.walk_mut_binders(f, binders + 1);
+                    p.walk_mut_binders(f, binders.shifted_in());
                 }
             }
             Ty::Placeholder { .. } | Ty::Bound(_) | Ty::Infer(_) | Ty::Unknown => {}
diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index d7f250783..6c7bbc448 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -29,8 +29,8 @@ use crate::{
         all_super_traits, associated_type_by_name_including_super_traits, generics, make_mut_slice,
         variant_data,
     },
-    Binders, FnSig, GenericPredicate, PolyFnSig, ProjectionPredicate, ProjectionTy, Substs,
-    TraitEnvironment, TraitRef, Ty, TypeCtor,
+    Binders, BoundVar, DebruijnIndex, FnSig, GenericPredicate, PolyFnSig, ProjectionPredicate,
+    ProjectionTy, Substs, TraitEnvironment, TraitRef, Ty, TypeCtor,
 };
 
 #[derive(Debug)]
@@ -131,7 +131,7 @@ impl Ty {
                 Ty::apply(TypeCtor::FnPtr { num_args: sig.len() as u16 - 1 }, sig)
             }
             TypeRef::DynTrait(bounds) => {
-                let self_ty = Ty::Bound(0);
+                let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
                 let predicates = bounds
                     .iter()
                     .flat_map(|b| GenericPredicate::from_type_bound(ctx, b, self_ty.clone()))
@@ -141,7 +141,7 @@ impl Ty {
             TypeRef::ImplTrait(bounds) => {
                 match ctx.impl_trait_mode {
                     ImplTraitLoweringMode::Opaque => {
-                        let self_ty = Ty::Bound(0);
+                        let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
                         let predicates = bounds
                             .iter()
                             .flat_map(|b| {
@@ -177,12 +177,10 @@ impl Ty {
                             } else {
                                 (0, 0, 0, 0)
                             };
-                        Ty::Bound(
-                            idx as u32
-                                + parent_params as u32
-                                + self_params as u32
-                                + list_params as u32,
-                        )
+                        Ty::Bound(BoundVar::new(
+                            DebruijnIndex::INNERMOST,
+                            idx as usize + parent_params + self_params + list_params,
+                        ))
                     }
                     ImplTraitLoweringMode::Disallowed => {
                         // FIXME: report error
@@ -249,7 +247,11 @@ impl Ty {
         let ty = match resolution {
             TypeNs::TraitId(trait_) => {
                 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
-                let self_ty = if remaining_segments.len() == 0 { Some(Ty::Bound(0)) } else { None };
+                let self_ty = if remaining_segments.len() == 0 {
+                    Some(Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
+                } else {
+                    None
+                };
                 let trait_ref =
                     TraitRef::from_resolved_path(ctx, trait_, resolved_segment, self_ty);
                 let ty = if remaining_segments.len() == 1 {
@@ -289,7 +291,7 @@ impl Ty {
                     TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
                     TypeParamLoweringMode::Variable => {
                         let idx = generics.param_idx(param_id).expect("matching generics");
-                        Ty::Bound(idx)
+                        Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, idx))
                     }
                 }
             }
@@ -558,7 +560,7 @@ impl GenericPredicate {
                     TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
                     TypeParamLoweringMode::Variable => {
                         let idx = generics.param_idx(param_id).expect("matching generics");
-                        Ty::Bound(idx)
+                        Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, idx))
                     }
                 }
             }
diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index 533c6ccfb..74a0bc7db 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -20,7 +20,8 @@ use crate::{
     db::HirDatabase,
     primitive::{FloatBitness, Uncertain},
     utils::all_super_traits,
-    ApplicationTy, Canonical, InEnvironment, TraitEnvironment, TraitRef, Ty, TypeCtor, TypeWalk,
+    ApplicationTy, Canonical, DebruijnIndex, InEnvironment, TraitEnvironment, TraitRef, Ty,
+    TypeCtor, TypeWalk,
 };
 
 /// This is used as a key for indexing impls.
@@ -507,8 +508,9 @@ pub(crate) fn inherent_impl_substs(
 ) -> Option<Substs> {
     // we create a var for each type parameter of the impl; we need to keep in
     // mind here that `self_ty` might have vars of its own
-    let vars =
-        Substs::build_for_def(db, impl_id).fill_with_bound_vars(self_ty.num_vars as u32).build();
+    let vars = Substs::build_for_def(db, impl_id)
+        .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty.num_vars)
+        .build();
     let self_ty_with_vars = db.impl_self_ty(impl_id).subst(&vars);
     let self_ty_with_vars =
         Canonical { num_vars: vars.len() + self_ty.num_vars, value: self_ty_with_vars };
@@ -526,8 +528,8 @@ pub(crate) fn inherent_impl_substs(
 fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs {
     s.fold_binders(
         &mut |ty, binders| {
-            if let Ty::Bound(idx) = &ty {
-                if *idx >= binders as u32 {
+            if let Ty::Bound(bound) = &ty {
+                if bound.index >= num_vars_to_keep && bound.debruijn >= binders {
                     Ty::Unknown
                 } else {
                     ty
@@ -536,7 +538,7 @@ fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs {
                 ty
             }
         },
-        num_vars_to_keep,
+        DebruijnIndex::INNERMOST,
     )
 }
 
@@ -586,7 +588,7 @@ fn generic_implements_goal(
     let num_vars = self_ty.num_vars;
     let substs = super::Substs::build_for_def(db, trait_)
         .push(self_ty.value)
-        .fill_with_bound_vars(num_vars as u32)
+        .fill_with_bound_vars(DebruijnIndex::INNERMOST, num_vars)
         .build();
     let num_vars = substs.len() - 1 + self_ty.num_vars;
     let trait_ref = TraitRef { trait_, substs };
diff --git a/crates/ra_hir_ty/src/tests/coercion.rs b/crates/ra_hir_ty/src/tests/coercion.rs
index 3e3d55c04..b2c971f02 100644
--- a/crates/ra_hir_ty/src/tests/coercion.rs
+++ b/crates/ra_hir_ty/src/tests/coercion.rs
@@ -407,16 +407,16 @@ fn test() {
     [30; 31) 'x': &Foo
     [39; 41) '{}': ()
     [52; 133) '{     ...oo); }': ()
-    [58; 71) 'takes_ref_foo': fn takes_ref_foo(&Foo) -> ()
+    [58; 71) 'takes_ref_foo': fn takes_ref_foo(&Foo)
     [58; 77) 'takes_...(&Foo)': ()
     [72; 76) '&Foo': &Foo
     [73; 76) 'Foo': Foo
-    [83; 96) 'takes_ref_foo': fn takes_ref_foo(&Foo) -> ()
+    [83; 96) 'takes_ref_foo': fn takes_ref_foo(&Foo)
     [83; 103) 'takes_...&&Foo)': ()
     [97; 102) '&&Foo': &&Foo
     [98; 102) '&Foo': &Foo
     [99; 102) 'Foo': Foo
-    [109; 122) 'takes_ref_foo': fn takes_ref_foo(&Foo) -> ()
+    [109; 122) 'takes_ref_foo': fn takes_ref_foo(&Foo)
     [109; 130) 'takes_...&&Foo)': ()
     [123; 129) '&&&Foo': &&&Foo
     [124; 129) '&&Foo': &&Foo
@@ -484,7 +484,7 @@ fn test() {
     [171; 178) 'loop {}': !
     [176; 178) '{}': ()
     [191; 236) '{     ... }); }': ()
-    [197; 210) 'takes_ref_str': fn takes_ref_str(&str) -> ()
+    [197; 210) 'takes_ref_str': fn takes_ref_str(&str)
     [197; 233) 'takes_...g() })': ()
     [211; 232) '&{ ret...ng() }': &String
     [212; 232) '{ retu...ng() }': String
diff --git a/crates/ra_hir_ty/src/tests/macros.rs b/crates/ra_hir_ty/src/tests/macros.rs
index eb97288f1..ff4599b71 100644
--- a/crates/ra_hir_ty/src/tests/macros.rs
+++ b/crates/ra_hir_ty/src/tests/macros.rs
@@ -1,8 +1,10 @@
-use super::{infer, type_at, type_at_pos};
-use crate::test_db::TestDB;
 use insta::assert_snapshot;
 use ra_db::fixture::WithFixture;
 
+use super::{infer, type_at, type_at_pos};
+
+use crate::test_db::TestDB;
+
 #[test]
 fn cfg_impl_def() {
     let (db, pos) = TestDB::with_position(
@@ -658,3 +660,28 @@ fn test() {
     );
     assert_eq!("S", type_at_pos(&db, pos));
 }
+
+#[test]
+fn macro_in_arm() {
+    assert_snapshot!(
+        infer(r#"
+macro_rules! unit {
+    () => { () };
+}
+
+fn main() {
+    let x = match () {
+        unit!() => 92u32,
+    };
+}
+"#),
+        @r###"
+    [52; 111) '{     ...  }; }': ()
+    [62; 63) 'x': u32
+    [66; 108) 'match ...     }': u32
+    [72; 74) '()': ()
+    [85; 92) 'unit!()': ()
+    [96; 101) '92u32': u32
+    "###
+    );
+}
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index 2ee9b8f10..3402e0cb5 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -376,7 +376,7 @@ fn issue_2669() {
         ),
         @r###"
     [147; 262) '{     ...     }': ()
-    [161; 164) 'end': fn end<{unknown}>() -> ()
+    [161; 164) 'end': fn end<{unknown}>()
     [161; 166) 'end()': ()
     [199; 252) '{     ...     }': ()
     [221; 223) '_x': !
diff --git a/crates/ra_hir_ty/src/tests/simple.rs b/crates/ra_hir_ty/src/tests/simple.rs
index a600b947d..c2f1ded2f 100644
--- a/crates/ra_hir_ty/src/tests/simple.rs
+++ b/crates/ra_hir_ty/src/tests/simple.rs
@@ -521,7 +521,7 @@ fn test() -> &mut &f64 {
     [88; 89) 'a': u32
     [92; 108) 'unknow...nction': {unknown}
     [92; 110) 'unknow...tion()': u32
-    [116; 125) 'takes_u32': fn takes_u32(u32) -> ()
+    [116; 125) 'takes_u32': fn takes_u32(u32)
     [116; 128) 'takes_u32(a)': ()
     [126; 127) 'a': u32
     [138; 139) 'b': i32
@@ -1729,3 +1729,29 @@ fn foo() -> u32 {
     "###
     );
 }
+
+#[test]
+fn fn_pointer_return() {
+    assert_snapshot!(
+        infer(r#"
+struct Vtable {
+    method: fn(),
+}
+
+fn main() {
+    let vtable = Vtable { method: || {} };
+    let m = vtable.method;
+}
+"#),
+        @r###"
+    [48; 121) '{     ...hod; }': ()
+    [58; 64) 'vtable': Vtable
+    [67; 91) 'Vtable...| {} }': Vtable
+    [84; 89) '|| {}': || -> ()
+    [87; 89) '{}': ()
+    [101; 102) 'm': fn()
+    [105; 111) 'vtable': Vtable
+    [105; 118) 'vtable.method': fn()
+    "###
+    );
+}
diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
index f009a708c..081aa943a 100644
--- a/crates/ra_hir_ty/src/tests/traits.rs
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -263,7 +263,7 @@ fn test() {
     [119; 120) 'S': S<u32>(u32) -> S<u32>
     [119; 129) 'S(unknown)': S<u32>
     [121; 128) 'unknown': u32
-    [135; 138) 'foo': fn foo<S<u32>>(S<u32>) -> ()
+    [135; 138) 'foo': fn foo<S<u32>>(S<u32>)
     [135; 141) 'foo(s)': ()
     [139; 140) 's': S<u32>
     "###
@@ -962,7 +962,7 @@ fn test(x: impl Trait<u64>, y: &impl Trait<u32>) {
     [224; 225) 'S': S<u16>(u16) -> S<u16>
     [224; 228) 'S(1)': S<u16>
     [226; 227) '1': u16
-    [234; 237) 'bar': fn bar(S<u16>) -> ()
+    [234; 237) 'bar': fn bar(S<u16>)
     [234; 240) 'bar(z)': ()
     [238; 239) 'z': S<u16>
     [246; 247) 'x': impl Trait<u64>
@@ -1108,8 +1108,8 @@ fn test() {
     [40; 47) 'loop {}': !
     [45; 47) '{}': ()
     [91; 124) '{     ...foo; }': ()
-    [101; 102) 'f': fn(S) -> ()
-    [118; 121) 'foo': fn foo(S) -> ()
+    [101; 102) 'f': fn(S)
+    [118; 121) 'foo': fn foo(S)
     "###
     );
 }
@@ -1962,7 +1962,7 @@ fn test() -> impl Trait<i32> {
     [229; 241) 'S(default())': S<u32>
     [231; 238) 'default': fn default<u32>() -> u32
     [231; 240) 'default()': u32
-    [247; 250) 'foo': fn foo(S<u32>) -> ()
+    [247; 250) 'foo': fn foo(S<u32>)
     [247; 254) 'foo(s1)': ()
     [251; 253) 's1': S<u32>
     [264; 265) 'x': i32
@@ -2012,7 +2012,7 @@ fn main() {
     [147; 149) '_v': F
     [192; 195) '{ }': ()
     [207; 238) '{     ... }); }': ()
-    [213; 223) 'f::<(), _>': fn f<(), |&()| -> ()>(|&()| -> ()) -> ()
+    [213; 223) 'f::<(), _>': fn f<(), |&()| -> ()>(|&()| -> ())
     [213; 235) 'f::<()... z; })': ()
     [224; 234) '|z| { z; }': |&()| -> ()
     [225; 226) 'z': &()
diff --git a/crates/ra_hir_ty/src/traits.rs b/crates/ra_hir_ty/src/traits.rs
index a1ca33c98..07854a062 100644
--- a/crates/ra_hir_ty/src/traits.rs
+++ b/crates/ra_hir_ty/src/traits.rs
@@ -7,7 +7,7 @@ use ra_db::{impl_intern_key, salsa, CrateId};
 use ra_prof::profile;
 use rustc_hash::FxHashSet;
 
-use crate::db::HirDatabase;
+use crate::{db::HirDatabase, DebruijnIndex};
 
 use super::{Canonical, GenericPredicate, HirDisplay, ProjectionTy, TraitRef, Ty, TypeWalk};
 
@@ -128,7 +128,11 @@ impl TypeWalk for ProjectionPredicate {
         self.ty.walk(f);
     }
 
-    fn walk_mut_binders(&mut self, f: &mut impl FnMut(&mut Ty, usize), binders: usize) {
+    fn walk_mut_binders(
+        &mut self,
+        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
+        binders: DebruijnIndex,
+    ) {
         self.projection_ty.walk_mut_binders(f, binders);
         self.ty.walk_mut_binders(f, binders);
     }
@@ -144,7 +148,7 @@ pub(crate) fn trait_solve_query(
         Obligation::Trait(it) => db.trait_data(it.trait_).name.to_string(),
         Obligation::Projection(_) => "projection".to_string(),
     });
-    log::debug!("trait_solve_query({})", goal.value.value.display(db));
+    eprintln!("trait_solve_query({})", goal.value.value.display(db));
 
     if let Obligation::Projection(pred) = &goal.value.value {
         if let Ty::Bound(_) = &pred.projection_ty.parameters[0] {
@@ -153,7 +157,7 @@ pub(crate) fn trait_solve_query(
         }
     }
 
-    let canonical = goal.to_chalk(db).cast();
+    let canonical = goal.to_chalk(db).cast(&Interner);
 
     // We currently don't deal with universes (I think / hope they're not yet
     // relevant for our use cases?)
@@ -194,8 +198,8 @@ fn solution_from_chalk(
     let convert_subst = |subst: chalk_ir::Canonical<chalk_ir::Substitution<Interner>>| {
         let value = subst
             .value
-            .into_iter()
-            .map(|p| match p.ty() {
+            .iter(&Interner)
+            .map(|p| match p.ty(&Interner) {
                 Some(ty) => from_chalk(db, ty.clone()),
                 None => unimplemented!(),
             })
diff --git a/crates/ra_hir_ty/src/traits/builtin.rs b/crates/ra_hir_ty/src/traits/builtin.rs
index 73e3c5c78..ccab246bf 100644
--- a/crates/ra_hir_ty/src/traits/builtin.rs
+++ b/crates/ra_hir_ty/src/traits/builtin.rs
@@ -8,7 +8,8 @@ use super::{AssocTyValue, Impl, UnsizeToSuperTraitObjectData};
 use crate::{
     db::HirDatabase,
     utils::{all_super_traits, generics},
-    ApplicationTy, Binders, GenericPredicate, Substs, TraitRef, Ty, TypeCtor,
+    ApplicationTy, Binders, BoundVar, DebruijnIndex, GenericPredicate, Substs, TraitRef, Ty,
+    TypeCtor, TypeWalk,
 };
 
 pub(super) struct BuiltinImplData {
@@ -164,11 +165,15 @@ fn closure_fn_trait_impl_datum(
 
     let arg_ty = Ty::apply(
         TypeCtor::Tuple { cardinality: num_args },
-        Substs::builder(num_args as usize).fill_with_bound_vars(0).build(),
+        Substs::builder(num_args as usize)
+            .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
+            .build(),
     );
     let sig_ty = Ty::apply(
         TypeCtor::FnPtr { num_args },
-        Substs::builder(num_args as usize + 1).fill_with_bound_vars(0).build(),
+        Substs::builder(num_args as usize + 1)
+            .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
+            .build(),
     );
 
     let self_ty = Ty::apply_one(TypeCtor::Closure { def: data.def, expr: data.expr }, sig_ty);
@@ -203,7 +208,7 @@ fn closure_fn_trait_output_assoc_ty_value(
         }
     };
 
-    let output_ty = Ty::Bound(num_args.into());
+    let output_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, num_args.into()));
 
     let fn_once_trait =
         get_fn_trait(db, krate, super::FnTrait::FnOnce).expect("assoc ty value should not exist");
@@ -241,7 +246,7 @@ fn array_unsize_impl_datum(db: &dyn HirDatabase, krate: CrateId) -> BuiltinImplD
         // the existence of the Unsize trait has been checked before
         .expect("Unsize trait missing");
 
-    let var = Ty::Bound(0);
+    let var = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
     let substs = Substs::builder(2)
         .push(Ty::apply_one(TypeCtor::Array, var.clone()))
         .push(Ty::apply_one(TypeCtor::Slice, var))
@@ -270,19 +275,18 @@ fn trait_object_unsize_impl_datum(
         // the existence of the Unsize trait has been checked before
         .expect("Unsize trait missing");
 
-    let self_ty = Ty::Bound(0);
+    let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
 
     let target_substs = Substs::build_for_def(db, trait_)
-        .push(Ty::Bound(0))
-        // starting from ^2 because we want to start with ^1 outside of the
-        // `dyn`, which is ^2 inside
-        .fill_with_bound_vars(2)
+        .push(Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
+        .fill_with_bound_vars(DebruijnIndex::ONE, 1)
         .build();
     let num_vars = target_substs.len();
     let target_trait_ref = TraitRef { trait_, substs: target_substs };
     let target_bounds = vec![GenericPredicate::Implemented(target_trait_ref)];
 
-    let self_substs = Substs::build_for_def(db, trait_).fill_with_bound_vars(0).build();
+    let self_substs =
+        Substs::build_for_def(db, trait_).fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
     let self_trait_ref = TraitRef { trait_, substs: self_substs };
     let where_clauses = vec![GenericPredicate::Implemented(self_trait_ref)];
 
@@ -305,24 +309,26 @@ fn super_trait_object_unsize_impl_datum(
         // the existence of the Unsize trait has been checked before
         .expect("Unsize trait missing");
 
-    let self_substs = Substs::build_for_def(db, data.trait_).fill_with_bound_vars(0).build();
+    let self_substs = Substs::build_for_def(db, data.trait_)
+        .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
+        .build();
+    let self_trait_ref = TraitRef { trait_: data.trait_, substs: self_substs.clone() };
 
     let num_vars = self_substs.len() - 1;
 
-    let self_trait_ref = TraitRef { trait_: data.trait_, substs: self_substs.clone() };
-    let self_bounds = vec![GenericPredicate::Implemented(self_trait_ref.clone())];
-
     // we need to go from our trait to the super trait, substituting type parameters
     let path = crate::utils::find_super_trait_path(db.upcast(), data.trait_, data.super_trait);
 
-    let mut current_trait_ref = self_trait_ref;
+    let mut current_trait_ref = self_trait_ref.clone();
     for t in path.into_iter().skip(1) {
         let bounds = db.generic_predicates(current_trait_ref.trait_.into());
         let super_trait_ref = bounds
             .iter()
             .find_map(|b| match &b.value {
                 GenericPredicate::Implemented(tr)
-                    if tr.trait_ == t && tr.substs[0] == Ty::Bound(0) =>
+                    if tr.trait_ == t
+                        && tr.substs[0]
+                            == Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)) =>
                 {
                     Some(Binders { value: tr, num_binders: b.num_binders })
                 }
@@ -332,7 +338,18 @@ fn super_trait_object_unsize_impl_datum(
         current_trait_ref = super_trait_ref.cloned().subst(&current_trait_ref.substs);
     }
 
-    let super_bounds = vec![GenericPredicate::Implemented(current_trait_ref)];
+    // We need to renumber the variables a bit now: from ^0.0, ^0.1, ^0.2, ...
+    // to ^0.0, ^1.0, ^1.1. The reason for this is that the first variable comes
+    // from the dyn Trait binder, while the other variables come from the impl.
+    let new_substs = Substs::builder(num_vars + 1)
+        .push(Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
+        .fill_with_bound_vars(DebruijnIndex::ONE, 0)
+        .build();
+
+    let self_bounds =
+        vec![GenericPredicate::Implemented(self_trait_ref.subst_bound_vars(&new_substs))];
+    let super_bounds =
+        vec![GenericPredicate::Implemented(current_trait_ref.subst_bound_vars(&new_substs))];
 
     let substs = Substs::builder(2)
         .push(Ty::Dyn(self_bounds.into()))
diff --git a/crates/ra_hir_ty/src/traits/chalk.rs b/crates/ra_hir_ty/src/traits/chalk.rs
index 943d5f125..53ce362ea 100644
--- a/crates/ra_hir_ty/src/traits/chalk.rs
+++ b/crates/ra_hir_ty/src/traits/chalk.rs
@@ -3,7 +3,10 @@ use std::{fmt, sync::Arc};
 
 use log::debug;
 
-use chalk_ir::{cast::Cast, Goal, GoalData, Parameter, PlaceholderIndex, TypeName, UniverseIndex};
+use chalk_ir::{
+    cast::Cast, fold::shift::Shift, Goal, GoalData, Parameter, PlaceholderIndex, TypeName,
+    UniverseIndex,
+};
 
 use hir_def::{AssocContainerId, AssocItemId, GenericDefId, HasModule, Lookup, TypeAliasId};
 use ra_db::{
@@ -59,53 +62,126 @@ impl chalk_ir::interner::Interner for Interner {
         None
     }
 
+    fn debug_ty(_ty: &chalk_ir::Ty<Self>, _fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_lifetime(
+        _lifetime: &chalk_ir::Lifetime<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_parameter(
+        _parameter: &Parameter<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_goal(_goal: &Goal<Self>, _fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_goals(
+        _goals: &chalk_ir::Goals<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_program_clause_implication(
+        _pci: &chalk_ir::ProgramClauseImplication<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_application_ty(
+        _application_ty: &chalk_ir::ApplicationTy<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_substitution(
+        _substitution: &chalk_ir::Substitution<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
+    fn debug_separator_trait_ref(
+        _separator_trait_ref: &chalk_ir::SeparatorTraitRef<Self>,
+        _fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
+        None
+    }
+
     fn intern_ty(&self, ty: chalk_ir::TyData<Self>) -> Box<chalk_ir::TyData<Self>> {
         Box::new(ty)
     }
 
-    fn ty_data(ty: &Box<chalk_ir::TyData<Self>>) -> &chalk_ir::TyData<Self> {
+    fn ty_data<'a>(&self, ty: &'a Box<chalk_ir::TyData<Self>>) -> &'a chalk_ir::TyData<Self> {
         ty
     }
 
-    fn intern_lifetime(lifetime: chalk_ir::LifetimeData<Self>) -> chalk_ir::LifetimeData<Self> {
+    fn intern_lifetime(
+        &self,
+        lifetime: chalk_ir::LifetimeData<Self>,
+    ) -> chalk_ir::LifetimeData<Self> {
         lifetime
     }
 
-    fn lifetime_data(lifetime: &chalk_ir::LifetimeData<Self>) -> &chalk_ir::LifetimeData<Self> {
+    fn lifetime_data<'a>(
+        &self,
+        lifetime: &'a chalk_ir::LifetimeData<Self>,
+    ) -> &'a chalk_ir::LifetimeData<Self> {
         lifetime
     }
 
-    fn intern_parameter(parameter: chalk_ir::ParameterData<Self>) -> chalk_ir::ParameterData<Self> {
+    fn intern_parameter(
+        &self,
+        parameter: chalk_ir::ParameterData<Self>,
+    ) -> chalk_ir::ParameterData<Self> {
         parameter
     }
 
-    fn parameter_data(parameter: &chalk_ir::ParameterData<Self>) -> &chalk_ir::ParameterData<Self> {
+    fn parameter_data<'a>(
+        &self,
+        parameter: &'a chalk_ir::ParameterData<Self>,
+    ) -> &'a chalk_ir::ParameterData<Self> {
         parameter
     }
 
-    fn intern_goal(goal: GoalData<Self>) -> Arc<GoalData<Self>> {
+    fn intern_goal(&self, goal: GoalData<Self>) -> Arc<GoalData<Self>> {
         Arc::new(goal)
     }
 
-    fn intern_goals(data: impl IntoIterator<Item = Goal<Self>>) -> Self::InternedGoals {
+    fn intern_goals(&self, data: impl IntoIterator<Item = Goal<Self>>) -> Self::InternedGoals {
         data.into_iter().collect()
     }
 
-    fn goal_data(goal: &Arc<GoalData<Self>>) -> &GoalData<Self> {
+    fn goal_data<'a>(&self, goal: &'a Arc<GoalData<Self>>) -> &'a GoalData<Self> {
         goal
     }
 
-    fn goals_data(goals: &Vec<Goal<Interner>>) -> &[Goal<Interner>] {
+    fn goals_data<'a>(&self, goals: &'a Vec<Goal<Interner>>) -> &'a [Goal<Interner>] {
         goals
     }
 
     fn intern_substitution<E>(
+        &self,
         data: impl IntoIterator<Item = Result<Parameter<Self>, E>>,
     ) -> Result<Vec<Parameter<Self>>, E> {
         data.into_iter().collect()
     }
 
-    fn substitution_data(substitution: &Vec<Parameter<Self>>) -> &[Parameter<Self>] {
+    fn substitution_data<'a>(
+        &self,
+        substitution: &'a Vec<Parameter<Self>>,
+    ) -> &'a [Parameter<Self>] {
         substitution
     }
 }
@@ -145,12 +221,14 @@ impl ToChalk for Ty {
             Ty::Apply(apply_ty) => {
                 let name = apply_ty.ctor.to_chalk(db);
                 let substitution = apply_ty.parameters.to_chalk(db);
-                chalk_ir::ApplicationTy { name, substitution }.cast().intern(&Interner)
+                chalk_ir::ApplicationTy { name, substitution }.cast(&Interner).intern(&Interner)
             }
             Ty::Projection(proj_ty) => {
                 let associated_ty_id = proj_ty.associated_ty.to_chalk(db);
                 let substitution = proj_ty.parameters.to_chalk(db);
-                chalk_ir::AliasTy { associated_ty_id, substitution }.cast().intern(&Interner)
+                chalk_ir::AliasTy { associated_ty_id, substitution }
+                    .cast(&Interner)
+                    .intern(&Interner)
             }
             Ty::Placeholder(id) => {
                 let interned_id = db.intern_type_param_id(id);
@@ -160,7 +238,7 @@ impl ToChalk for Ty {
                 }
                 .to_ty::<Interner>(&Interner)
             }
-            Ty::Bound(idx) => chalk_ir::TyData::BoundVar(idx as usize).intern(&Interner),
+            Ty::Bound(idx) => chalk_ir::TyData::BoundVar(idx).intern(&Interner),
             Ty::Infer(_infer_ty) => panic!("uncanonicalized infer ty"),
             Ty::Dyn(predicates) => {
                 let where_clauses = predicates
@@ -173,14 +251,14 @@ impl ToChalk for Ty {
                 chalk_ir::TyData::Dyn(bounded_ty).intern(&Interner)
             }
             Ty::Opaque(_) | Ty::Unknown => {
-                let substitution = chalk_ir::Substitution::empty();
+                let substitution = chalk_ir::Substitution::empty(&Interner);
                 let name = TypeName::Error;
-                chalk_ir::ApplicationTy { name, substitution }.cast().intern(&Interner)
+                chalk_ir::ApplicationTy { name, substitution }.cast(&Interner).intern(&Interner)
             }
         }
     }
     fn from_chalk(db: &dyn HirDatabase, chalk: chalk_ir::Ty<Interner>) -> Self {
-        match chalk.data().clone() {
+        match chalk.data(&Interner).clone() {
             chalk_ir::TyData::Apply(apply_ty) => match apply_ty.name {
                 TypeName::Error => Ty::Unknown,
                 _ => {
@@ -202,7 +280,7 @@ impl ToChalk for Ty {
                 Ty::Projection(ProjectionTy { associated_ty, parameters })
             }
             chalk_ir::TyData::Function(_) => unimplemented!(),
-            chalk_ir::TyData::BoundVar(idx) => Ty::Bound(idx as u32),
+            chalk_ir::TyData::BoundVar(idx) => Ty::Bound(idx),
             chalk_ir::TyData::InferenceVar(_iv) => Ty::Unknown,
             chalk_ir::TyData::Dyn(where_clauses) => {
                 assert_eq!(where_clauses.bounds.binders.len(), 1);
@@ -218,13 +296,13 @@ impl ToChalk for Substs {
     type Chalk = chalk_ir::Substitution<Interner>;
 
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Substitution<Interner> {
-        chalk_ir::Substitution::from(self.iter().map(|ty| ty.clone().to_chalk(db)))
+        chalk_ir::Substitution::from(&Interner, self.iter().map(|ty| ty.clone().to_chalk(db)))
     }
 
     fn from_chalk(db: &dyn HirDatabase, parameters: chalk_ir::Substitution<Interner>) -> Substs {
         let tys = parameters
-            .into_iter()
-            .map(|p| match p.ty() {
+            .iter(&Interner)
+            .map(|p| match p.ty(&Interner) {
                 Some(ty) => from_chalk(db, ty.clone()),
                 None => unimplemented!(),
             })
@@ -332,15 +410,15 @@ impl ToChalk for GenericPredicate {
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::QuantifiedWhereClause<Interner> {
         match self {
             GenericPredicate::Implemented(trait_ref) => {
-                make_binders(chalk_ir::WhereClause::Implemented(trait_ref.to_chalk(db)), 0)
+                let chalk_trait_ref = trait_ref.to_chalk(db);
+                let chalk_trait_ref = chalk_trait_ref.shifted_in(&Interner);
+                make_binders(chalk_ir::WhereClause::Implemented(chalk_trait_ref), 0)
+            }
+            GenericPredicate::Projection(projection_pred) => {
+                let ty = projection_pred.ty.to_chalk(db).shifted_in(&Interner);
+                let alias = projection_pred.projection_ty.to_chalk(db).shifted_in(&Interner);
+                make_binders(chalk_ir::WhereClause::AliasEq(chalk_ir::AliasEq { alias, ty }), 0)
             }
-            GenericPredicate::Projection(projection_pred) => make_binders(
-                chalk_ir::WhereClause::AliasEq(chalk_ir::AliasEq {
-                    alias: projection_pred.projection_ty.to_chalk(db),
-                    ty: projection_pred.ty.to_chalk(db),
-                }),
-                0,
-            ),
             GenericPredicate::Error => panic!("tried passing GenericPredicate::Error to Chalk"),
         }
     }
@@ -400,8 +478,8 @@ impl ToChalk for Obligation {
 
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::DomainGoal<Interner> {
         match self {
-            Obligation::Trait(tr) => tr.to_chalk(db).cast(),
-            Obligation::Projection(pr) => pr.to_chalk(db).cast(),
+            Obligation::Trait(tr) => tr.to_chalk(db).cast(&Interner),
+            Obligation::Projection(pr) => pr.to_chalk(db).cast(&Interner),
         }
     }
 
@@ -438,8 +516,8 @@ impl ToChalk for Arc<super::TraitEnvironment> {
                 continue;
             }
             let program_clause: chalk_ir::ProgramClause<Interner> =
-                pred.clone().to_chalk(db).cast();
-            clauses.push(program_clause.into_from_env_clause());
+                pred.clone().to_chalk(db).cast(&Interner);
+            clauses.push(program_clause.into_from_env_clause(&Interner));
         }
         chalk_ir::Environment::new().add_clauses(clauses)
     }
@@ -504,7 +582,8 @@ impl ToChalk for builtin::BuiltinImplAssocTyValueData {
     type Chalk = AssociatedTyValue;
 
     fn to_chalk(self, db: &dyn HirDatabase) -> AssociatedTyValue {
-        let value_bound = chalk_rust_ir::AssociatedTyValueBound { ty: self.value.to_chalk(db) };
+        let ty = self.value.to_chalk(db);
+        let value_bound = chalk_rust_ir::AssociatedTyValueBound { ty };
 
         chalk_rust_ir::AssociatedTyValue {
             associated_ty_id: self.assoc_ty_id.to_chalk(db),
@@ -578,9 +657,9 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
             .map(|impl_| impl_.to_chalk(self.db))
             .collect();
 
-        let ty: Ty = from_chalk(self.db, parameters[0].assert_ty_ref().clone());
+        let ty: Ty = from_chalk(self.db, parameters[0].assert_ty_ref(&Interner).clone());
         let arg: Option<Ty> =
-            parameters.get(1).map(|p| from_chalk(self.db, p.assert_ty_ref().clone()));
+            parameters.get(1).map(|p| from_chalk(self.db, p.assert_ty_ref(&Interner).clone()));
 
         builtin::get_builtin_impls(self.db, self.krate, &ty, &arg, trait_, |i| {
             result.push(i.to_chalk(self.db))
@@ -663,11 +742,13 @@ pub(crate) fn trait_datum_query(
     let associated_ty_ids =
         trait_data.associated_types().map(|type_alias| type_alias.to_chalk(db)).collect();
     let trait_datum_bound = chalk_rust_ir::TraitDatumBound { where_clauses };
+    let well_known = None; // FIXME set this (depending on lang items)
     let trait_datum = TraitDatum {
         id: trait_id,
         binders: make_binders(trait_datum_bound, bound_vars.len()),
         flags,
         associated_ty_ids,
+        well_known,
     };
     Arc::new(trait_datum)
 }
diff --git a/crates/ra_hir_ty/src/utils.rs b/crates/ra_hir_ty/src/utils.rs
index b40d4eb73..1e5022fa4 100644
--- a/crates/ra_hir_ty/src/utils.rs
+++ b/crates/ra_hir_ty/src/utils.rs
@@ -201,11 +201,11 @@ impl Generics {
         (parent, self_params, list_params, impl_trait_params)
     }
 
-    pub(crate) fn param_idx(&self, param: TypeParamId) -> Option<u32> {
+    pub(crate) fn param_idx(&self, param: TypeParamId) -> Option<usize> {
         Some(self.find_param(param)?.0)
     }
 
-    fn find_param(&self, param: TypeParamId) -> Option<(u32, &TypeParamData)> {
+    fn find_param(&self, param: TypeParamId) -> Option<(usize, &TypeParamData)> {
         if param.parent == self.def {
             let (idx, (_local_id, data)) = self
                 .params
@@ -215,7 +215,7 @@ impl Generics {
                 .find(|(_, (idx, _))| *idx == param.local_id)
                 .unwrap();
             let (_total, parent_len, _child) = self.len_split();
-            Some(((parent_len + idx) as u32, data))
+            Some((parent_len + idx, data))
         } else {
             self.parent_generics.as_ref().and_then(|g| g.find_param(param))
         }
diff --git a/crates/ra_ide/src/completion/complete_dot.rs b/crates/ra_ide/src/completion/complete_dot.rs
index 82ec16913..f433faef3 100644
--- a/crates/ra_ide/src/completion/complete_dot.rs
+++ b/crates/ra_ide/src/completion/complete_dot.rs
@@ -61,7 +61,7 @@ fn complete_methods(acc: &mut Completions, ctx: &CompletionContext, receiver: &T
                 && ctx.scope().module().map_or(true, |m| func.is_visible_from(ctx.db, m))
                 && seen_methods.insert(func.name(ctx.db))
             {
-                acc.add_function(ctx, func);
+                acc.add_function(ctx, func, None);
             }
             None::<()>
         });
diff --git a/crates/ra_ide/src/completion/complete_path.rs b/crates/ra_ide/src/completion/complete_path.rs
index 3db17f15f..3ed2ae2b6 100644
--- a/crates/ra_ide/src/completion/complete_path.rs
+++ b/crates/ra_ide/src/completion/complete_path.rs
@@ -38,7 +38,7 @@ pub(super) fn complete_path(acc: &mut Completions, ctx: &CompletionContext) {
         hir::ModuleDef::Adt(_) | hir::ModuleDef::TypeAlias(_) => {
             if let hir::ModuleDef::Adt(Adt::Enum(e)) = def {
                 for variant in e.variants(ctx.db) {
-                    acc.add_enum_variant(ctx, variant);
+                    acc.add_enum_variant(ctx, variant, None);
                 }
             }
             let ty = match def {
@@ -58,7 +58,7 @@ pub(super) fn complete_path(acc: &mut Completions, ctx: &CompletionContext) {
                     match item {
                         hir::AssocItem::Function(func) => {
                             if !func.has_self_param(ctx.db) {
-                                acc.add_function(ctx, func);
+                                acc.add_function(ctx, func, None);
                             }
                         }
                         hir::AssocItem::Const(ct) => acc.add_const(ctx, ct),
@@ -87,7 +87,7 @@ pub(super) fn complete_path(acc: &mut Completions, ctx: &CompletionContext) {
                 match item {
                     hir::AssocItem::Function(func) => {
                         if !func.has_self_param(ctx.db) {
-                            acc.add_function(ctx, func);
+                            acc.add_function(ctx, func, None);
                         }
                     }
                     hir::AssocItem::Const(ct) => acc.add_const(ctx, ct),
@@ -355,15 +355,17 @@ mod tests {
             @r###"
         [
             CompletionItem {
-                label: "Bar",
+                label: "Bar(…)",
                 source_range: [116; 116),
                 delete: [116; 116),
-                insert: "Bar",
+                insert: "Bar($0)",
                 kind: EnumVariant,
+                lookup: "Bar",
                 detail: "(i32)",
                 documentation: Documentation(
                     "Bar Variant with i32",
                 ),
+                trigger_call_info: true,
             },
             CompletionItem {
                 label: "Foo",
@@ -403,15 +405,17 @@ mod tests {
             @r###"
         [
             CompletionItem {
-                label: "Bar",
+                label: "Bar(…)",
                 source_range: [180; 180),
                 delete: [180; 180),
-                insert: "Bar",
+                insert: "Bar($0)",
                 kind: EnumVariant,
+                lookup: "Bar",
                 detail: "(i32, u32)",
                 documentation: Documentation(
                     "Bar Variant with i32 and u32",
                 ),
+                trigger_call_info: true,
             },
             CompletionItem {
                 label: "Foo",
@@ -425,15 +429,17 @@ mod tests {
                 ),
             },
             CompletionItem {
-                label: "S",
+                label: "S(…)",
                 source_range: [180; 180),
                 delete: [180; 180),
-                insert: "S",
+                insert: "S($0)",
                 kind: EnumVariant,
+                lookup: "S",
                 detail: "(S)",
                 documentation: Documentation(
                     "",
                 ),
+                trigger_call_info: true,
             },
         ]
         "###
diff --git a/crates/ra_ide/src/completion/complete_pattern.rs b/crates/ra_ide/src/completion/complete_pattern.rs
index bc8fade6f..1b7d3122f 100644
--- a/crates/ra_ide/src/completion/complete_pattern.rs
+++ b/crates/ra_ide/src/completion/complete_pattern.rs
@@ -4,23 +4,25 @@ use crate::completion::{CompletionContext, Completions};
 
 /// Completes constats and paths in patterns.
 pub(super) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
-    if !ctx.is_pat_binding {
+    if !ctx.is_pat_binding_or_const {
         return;
     }
     // FIXME: ideally, we should look at the type we are matching against and
     // suggest variants + auto-imports
     ctx.scope().process_all_names(&mut |name, res| {
-        let def = match &res {
-            hir::ScopeDef::ModuleDef(def) => def,
+        match &res {
+            hir::ScopeDef::ModuleDef(def) => match def {
+                hir::ModuleDef::Adt(hir::Adt::Enum(..))
+                | hir::ModuleDef::Adt(hir::Adt::Struct(..))
+                | hir::ModuleDef::EnumVariant(..)
+                | hir::ModuleDef::Const(..)
+                | hir::ModuleDef::Module(..) => (),
+                _ => return,
+            },
+            hir::ScopeDef::MacroDef(_) => (),
             _ => return,
         };
-        match def {
-            hir::ModuleDef::Adt(hir::Adt::Enum(..))
-            | hir::ModuleDef::EnumVariant(..)
-            | hir::ModuleDef::Const(..)
-            | hir::ModuleDef::Module(..) => (),
-            _ => return,
-        }
+
         acc.add_resolution(ctx, name.to_string(), &res)
     });
 }
@@ -70,32 +72,12 @@ mod tests {
                 kind: Enum,
             },
             CompletionItem {
-                label: "E",
-                source_range: [246; 246),
-                delete: [246; 246),
-                insert: "E",
-                kind: Enum,
-            },
-            CompletionItem {
                 label: "X",
                 source_range: [246; 246),
                 delete: [246; 246),
                 insert: "X",
                 kind: EnumVariant,
-            },
-            CompletionItem {
-                label: "X",
-                source_range: [246; 246),
-                delete: [246; 246),
-                insert: "X",
-                kind: EnumVariant,
-            },
-            CompletionItem {
-                label: "Z",
-                source_range: [246; 246),
-                delete: [246; 246),
-                insert: "Z",
-                kind: Const,
+                detail: "()",
             },
             CompletionItem {
                 label: "Z",
@@ -111,13 +93,6 @@ mod tests {
                 insert: "m",
                 kind: Module,
             },
-            CompletionItem {
-                label: "m",
-                source_range: [246; 246),
-                delete: [246; 246),
-                insert: "m",
-                kind: Module,
-            },
         ]
         "###);
     }
@@ -146,13 +121,6 @@ mod tests {
                 kind: Enum,
             },
             CompletionItem {
-                label: "E",
-                source_range: [151; 151),
-                delete: [151; 151),
-                insert: "E",
-                kind: Enum,
-            },
-            CompletionItem {
                 label: "m!",
                 source_range: [151; 151),
                 delete: [151; 151),
diff --git a/crates/ra_ide/src/completion/complete_scope.rs b/crates/ra_ide/src/completion/complete_scope.rs
index 2ca552733..665597e4c 100644
--- a/crates/ra_ide/src/completion/complete_scope.rs
+++ b/crates/ra_ide/src/completion/complete_scope.rs
@@ -1,19 +1,13 @@
 //! Completion of names from the current scope, e.g. locals and imported items.
 
 use crate::completion::{CompletionContext, Completions};
-use hir::{ModuleDef, ScopeDef};
 
 pub(super) fn complete_scope(acc: &mut Completions, ctx: &CompletionContext) {
-    if !ctx.is_trivial_path && !ctx.is_pat_binding_and_path {
+    if !(ctx.is_trivial_path && !ctx.is_pat_binding_or_const) {
         return;
     }
 
-    ctx.scope().process_all_names(&mut |name, res| match (ctx.is_pat_binding_and_path, &res) {
-        (true, ScopeDef::ModuleDef(ModuleDef::Function(..))) => (),
-        (true, ScopeDef::ModuleDef(ModuleDef::Static(..))) => (),
-        (true, ScopeDef::Local(..)) => (),
-        _ => acc.add_resolution(ctx, name.to_string(), &res),
-    });
+    ctx.scope().process_all_names(&mut |name, res| acc.add_resolution(ctx, name.to_string(), &res));
 }
 
 #[cfg(test)]
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index fdc0da2c5..b8213d62f 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -35,10 +35,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) is_param: bool,
     /// If a name-binding or reference to a const in a pattern.
     /// Irrefutable patterns (like let) are excluded.
-    pub(super) is_pat_binding: bool,
-    // A bind battern which may also be part of a path.
-    // if let Some(En<|>) = Some(Enum::A)
-    pub(super) is_pat_binding_and_path: bool,
+    pub(super) is_pat_binding_or_const: bool,
     /// A single-indent path, like `foo`. `::foo` should not be considered a trivial path.
     pub(super) is_trivial_path: bool,
     /// If not a trivial path, the prefix (qualifier).
@@ -97,8 +94,7 @@ impl<'a> CompletionContext<'a> {
             record_lit_pat: None,
             impl_def: None,
             is_param: false,
-            is_pat_binding: false,
-            is_pat_binding_and_path: false,
+            is_pat_binding_or_const: false,
             is_trivial_path: false,
             path_prefix: None,
             after_if: false,
@@ -190,18 +186,19 @@ impl<'a> CompletionContext<'a> {
         // suggest declaration names, see `CompletionKind::Magic`.
         if let Some(name) = find_node_at_offset::<ast::Name>(&file_with_fake_ident, offset) {
             if let Some(bind_pat) = name.syntax().ancestors().find_map(ast::BindPat::cast) {
-                let parent = bind_pat.syntax().parent();
-                if parent.clone().and_then(ast::MatchArm::cast).is_some()
-                    || parent.clone().and_then(ast::Condition::cast).is_some()
-                {
-                    self.is_pat_binding = true;
+                self.is_pat_binding_or_const = true;
+                if bind_pat.has_at() || bind_pat.is_ref() || bind_pat.is_mutable() {
+                    self.is_pat_binding_or_const = false;
                 }
-
-                if parent.and_then(ast::RecordFieldPatList::cast).is_none()
-                    && bind_pat.pat().is_none()
-                    && !bind_pat.is_ref()
-                {
-                    self.is_pat_binding_and_path = true;
+                if bind_pat.syntax().parent().and_then(ast::RecordFieldPatList::cast).is_some() {
+                    self.is_pat_binding_or_const = false;
+                }
+                if let Some(let_stmt) = bind_pat.syntax().ancestors().find_map(ast::LetStmt::cast) {
+                    if let Some(pat) = let_stmt.pat() {
+                        if bind_pat.syntax().text_range().is_subrange(&pat.syntax().text_range()) {
+                            self.is_pat_binding_or_const = false;
+                        }
+                    }
                 }
             }
             if is_node::<ast::Param>(name.syntax()) {
diff --git a/crates/ra_ide/src/completion/presentation.rs b/crates/ra_ide/src/completion/presentation.rs
index 1c7c0924d..cdfd7bc32 100644
--- a/crates/ra_ide/src/completion/presentation.rs
+++ b/crates/ra_ide/src/completion/presentation.rs
@@ -7,7 +7,8 @@ use test_utils::tested_by;
 
 use crate::{
     completion::{
-        CompletionContext, CompletionItem, CompletionItemKind, CompletionKind, Completions,
+        completion_item::Builder, CompletionContext, CompletionItem, CompletionItemKind,
+        CompletionKind, Completions,
     },
     display::{const_label, macro_label, type_label, FunctionSignature},
     RootDatabase,
@@ -56,14 +57,16 @@ impl Completions {
         let kind = match resolution {
             ScopeDef::ModuleDef(Module(..)) => CompletionItemKind::Module,
             ScopeDef::ModuleDef(Function(func)) => {
-                return self.add_function_with_name(ctx, Some(local_name), *func);
+                return self.add_function(ctx, *func, Some(local_name));
             }
             ScopeDef::ModuleDef(Adt(hir::Adt::Struct(_))) => CompletionItemKind::Struct,
             // FIXME: add CompletionItemKind::Union
             ScopeDef::ModuleDef(Adt(hir::Adt::Union(_))) => CompletionItemKind::Struct,
             ScopeDef::ModuleDef(Adt(hir::Adt::Enum(_))) => CompletionItemKind::Enum,
 
-            ScopeDef::ModuleDef(EnumVariant(..)) => CompletionItemKind::EnumVariant,
+            ScopeDef::ModuleDef(EnumVariant(var)) => {
+                return self.add_enum_variant(ctx, *var, Some(local_name));
+            }
             ScopeDef::ModuleDef(Const(..)) => CompletionItemKind::Const,
             ScopeDef::ModuleDef(Static(..)) => CompletionItemKind::Static,
             ScopeDef::ModuleDef(Trait(..)) => CompletionItemKind::Trait,
@@ -124,10 +127,6 @@ impl Completions {
         completion_item.kind(kind).set_documentation(docs).add_to(self)
     }
 
-    pub(crate) fn add_function(&mut self, ctx: &CompletionContext, func: hir::Function) {
-        self.add_function_with_name(ctx, None, func)
-    }
-
     fn guess_macro_braces(&self, macro_name: &str, docs: &str) -> &'static str {
         let mut votes = [0, 0, 0];
         for (idx, s) in docs.match_indices(&macro_name) {
@@ -186,16 +185,15 @@ impl Completions {
         self.add(builder);
     }
 
-    fn add_function_with_name(
+    pub(crate) fn add_function(
         &mut self,
         ctx: &CompletionContext,
-        name: Option<String>,
         func: hir::Function,
+        local_name: Option<String>,
     ) {
         let has_self_param = func.has_self_param(ctx.db);
-        let params = func.params(ctx.db);
 
-        let name = name.unwrap_or_else(|| func.name(ctx.db).to_string());
+        let name = local_name.unwrap_or_else(|| func.name(ctx.db).to_string());
         let ast_node = func.source(ctx.db).value;
         let function_signature = FunctionSignature::from(&ast_node);
 
@@ -210,32 +208,14 @@ impl Completions {
                 .set_deprecated(is_deprecated(func, ctx.db))
                 .detail(function_signature.to_string());
 
-        // If not an import, add parenthesis automatically.
-        if ctx.use_item_syntax.is_none() && !ctx.is_call && ctx.config.add_call_parenthesis {
-            tested_by!(inserts_parens_for_function_calls);
-
-            let (snippet, label) = if params.is_empty() || has_self_param && params.len() == 1 {
-                (format!("{}()$0", name), format!("{}()", name))
-            } else {
-                builder = builder.trigger_call_info();
-                let snippet = if ctx.config.add_call_argument_snippets {
-                    let to_skip = if has_self_param { 1 } else { 0 };
-                    let function_params_snippet = function_signature
-                        .parameter_names
-                        .iter()
-                        .skip(to_skip)
-                        .enumerate()
-                        .map(|(index, param_name)| format!("${{{}:{}}}", index + 1, param_name))
-                        .sep_by(", ");
-                    format!("{}({})$0", name, function_params_snippet)
-                } else {
-                    format!("{}($0)", name)
-                };
+        let params = function_signature
+            .parameter_names
+            .iter()
+            .skip(if function_signature.has_self_param { 1 } else { 0 })
+            .cloned()
+            .collect();
 
-                (snippet, format!("{}(…)", name))
-            };
-            builder = builder.lookup_by(name).label(label).insert_snippet(snippet);
-        }
+        builder = builder.add_call_parens(ctx, name, Params::Named(params));
 
         self.add(builder)
     }
@@ -272,14 +252,20 @@ impl Completions {
             .add_to(self);
     }
 
-    pub(crate) fn add_enum_variant(&mut self, ctx: &CompletionContext, variant: hir::EnumVariant) {
+    pub(crate) fn add_enum_variant(
+        &mut self,
+        ctx: &CompletionContext,
+        variant: hir::EnumVariant,
+        local_name: Option<String>,
+    ) {
         let is_deprecated = is_deprecated(variant, ctx.db);
-        let name = variant.name(ctx.db);
+        let name = local_name.unwrap_or_else(|| variant.name(ctx.db).to_string());
         let detail_types = variant
             .fields(ctx.db)
             .into_iter()
             .map(|field| (field.name(ctx.db), field.signature_ty(ctx.db)));
-        let detail = match variant.kind(ctx.db) {
+        let variant_kind = variant.kind(ctx.db);
+        let detail = match variant_kind {
             StructKind::Tuple | StructKind::Unit => detail_types
                 .map(|(_, t)| t.display(ctx.db).to_string())
                 .sep_by(", ")
@@ -291,12 +277,70 @@ impl Completions {
                 .surround_with("{ ", " }")
                 .to_string(),
         };
-        CompletionItem::new(CompletionKind::Reference, ctx.source_range(), name.to_string())
-            .kind(CompletionItemKind::EnumVariant)
-            .set_documentation(variant.docs(ctx.db))
-            .set_deprecated(is_deprecated)
-            .detail(detail)
-            .add_to(self);
+        let mut res =
+            CompletionItem::new(CompletionKind::Reference, ctx.source_range(), name.clone())
+                .kind(CompletionItemKind::EnumVariant)
+                .set_documentation(variant.docs(ctx.db))
+                .set_deprecated(is_deprecated)
+                .detail(detail);
+
+        if variant_kind == StructKind::Tuple {
+            let params = Params::Anonymous(variant.fields(ctx.db).len());
+            res = res.add_call_parens(ctx, name, params)
+        }
+
+        res.add_to(self);
+    }
+}
+
+enum Params {
+    Named(Vec<String>),
+    Anonymous(usize),
+}
+
+impl Params {
+    fn len(&self) -> usize {
+        match self {
+            Params::Named(xs) => xs.len(),
+            Params::Anonymous(len) => *len,
+        }
+    }
+
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+
+impl Builder {
+    fn add_call_parens(mut self, ctx: &CompletionContext, name: String, params: Params) -> Builder {
+        if !ctx.config.add_call_parenthesis {
+            return self;
+        }
+        if ctx.use_item_syntax.is_some() || ctx.is_call {
+            return self;
+        }
+        // If not an import, add parenthesis automatically.
+        tested_by!(inserts_parens_for_function_calls);
+
+        let (snippet, label) = if params.is_empty() {
+            (format!("{}()$0", name), format!("{}()", name))
+        } else {
+            self = self.trigger_call_info();
+            let snippet = match (ctx.config.add_call_argument_snippets, params) {
+                (true, Params::Named(params)) => {
+                    let function_params_snippet = params
+                        .iter()
+                        .enumerate()
+                        .map(|(index, param_name)| format!("${{{}:{}}}", index + 1, param_name))
+                        .sep_by(", ");
+                    format!("{}({})$0", name, function_params_snippet)
+                }
+                _ => format!("{}($0)", name),
+            };
+
+            (snippet, format!("{}(…)", name))
+        };
+        self.lookup_by(name).label(label).insert_snippet(snippet)
     }
 }
 
@@ -366,12 +410,14 @@ mod tests {
         @r###"
         [
             CompletionItem {
-                label: "Foo",
+                label: "Foo(…)",
                 source_range: [115; 117),
                 delete: [115; 117),
-                insert: "Foo",
+                insert: "Foo($0)",
                 kind: EnumVariant,
+                lookup: "Foo",
                 detail: "(i32, i32)",
+                trigger_call_info: true,
             },
         ]"###
         );
@@ -546,6 +592,101 @@ mod tests {
     }
 
     #[test]
+    fn inserts_parens_for_tuple_enums() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                enum Option<T> { Some(T), None }
+                use Option::*;
+                fn main() -> Option<i32> {
+                    Som<|>
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "None",
+                source_range: [144; 147),
+                delete: [144; 147),
+                insert: "None",
+                kind: EnumVariant,
+                detail: "()",
+            },
+            CompletionItem {
+                label: "Option",
+                source_range: [144; 147),
+                delete: [144; 147),
+                insert: "Option",
+                kind: Enum,
+            },
+            CompletionItem {
+                label: "Some(…)",
+                source_range: [144; 147),
+                delete: [144; 147),
+                insert: "Some($0)",
+                kind: EnumVariant,
+                lookup: "Some",
+                detail: "(T)",
+                trigger_call_info: true,
+            },
+            CompletionItem {
+                label: "main()",
+                source_range: [144; 147),
+                delete: [144; 147),
+                insert: "main()$0",
+                kind: Function,
+                lookup: "main",
+                detail: "fn main() -> Option<i32>",
+            },
+        ]
+        "###
+        );
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                enum Option<T> { Some(T), None }
+                use Option::*;
+                fn main(value: Option<i32>) {
+                    match value {
+                        Som<|>
+                    }
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "None",
+                source_range: [185; 188),
+                delete: [185; 188),
+                insert: "None",
+                kind: EnumVariant,
+                detail: "()",
+            },
+            CompletionItem {
+                label: "Option",
+                source_range: [185; 188),
+                delete: [185; 188),
+                insert: "Option",
+                kind: Enum,
+            },
+            CompletionItem {
+                label: "Some(…)",
+                source_range: [185; 188),
+                delete: [185; 188),
+                insert: "Some($0)",
+                kind: EnumVariant,
+                lookup: "Some",
+                detail: "(T)",
+                trigger_call_info: true,
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
     fn arg_snippets_for_method_call() {
         assert_debug_snapshot!(
             do_reference_completion(
diff --git a/crates/ra_parser/src/grammar/expressions.rs b/crates/ra_parser/src/grammar/expressions.rs
index 0c170ac5e..c486c0211 100644
--- a/crates/ra_parser/src/grammar/expressions.rs
+++ b/crates/ra_parser/src/grammar/expressions.rs
@@ -79,8 +79,6 @@ fn is_expr_stmt_attr_allowed(kind: SyntaxKind) -> bool {
 }
 
 pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi) {
-    // test block_items
-    // fn a() { fn b() {} }
     let m = p.start();
     // test attr_on_expr_stmt
     // fn foo() {
@@ -97,6 +95,8 @@ pub(super) fn stmt(p: &mut Parser, with_semi: StmtWithSemi) {
         return;
     }
 
+    // test block_items
+    // fn a() { fn b() {} }
     let m = match items::maybe_item(p, m, items::ItemFlavor::Mod) {
         Ok(()) => return,
         Err(m) => m,
diff --git a/crates/ra_parser/src/grammar/patterns.rs b/crates/ra_parser/src/grammar/patterns.rs
index 3afbaa82b..936d27575 100644
--- a/crates/ra_parser/src/grammar/patterns.rs
+++ b/crates/ra_parser/src/grammar/patterns.rs
@@ -70,15 +70,6 @@ fn pattern_single_r(p: &mut Parser, recovery_set: TokenSet) {
                 return;
             }
         }
-        // test marco_pat
-        // fn main() {
-        //     let m!(x) = 0;
-        // }
-        if lhs.kind() == PATH_PAT && p.at(T![!]) {
-            let m = lhs.undo_completion(p);
-            items::macro_call_after_excl(p);
-            m.complete(p, MACRO_CALL);
-        }
     }
 }
 
@@ -92,12 +83,12 @@ fn atom_pat(p: &mut Parser, recovery_set: TokenSet) -> Option<CompletedMarker> {
         IDENT => match p.nth(1) {
             // Checks the token after an IDENT to see if a pattern is a path (Struct { .. }) or macro
             // (T![x]).
-            T!['('] | T!['{'] | T![!] => path_pat(p),
-            T![:] if p.nth_at(1, T![::]) => path_pat(p),
+            T!['('] | T!['{'] | T![!] => path_or_macro_pat(p),
+            T![:] if p.nth_at(1, T![::]) => path_or_macro_pat(p),
             _ => bind_pat(p, true),
         },
 
-        _ if paths::is_use_path_start(p) => path_pat(p),
+        _ if paths::is_use_path_start(p) => path_or_macro_pat(p),
         _ if is_literal_pat_start(p) => literal_pat(p),
 
         T![.] if p.at(T![..]) => dot_dot_pat(p),
@@ -146,7 +137,7 @@ fn literal_pat(p: &mut Parser) -> CompletedMarker {
 //     let Bar { .. } = ();
 //     let Bar(..) = ();
 // }
-fn path_pat(p: &mut Parser) -> CompletedMarker {
+fn path_or_macro_pat(p: &mut Parser) -> CompletedMarker {
     assert!(paths::is_use_path_start(p));
     let m = p.start();
     paths::expr_path(p);
@@ -159,6 +150,14 @@ fn path_pat(p: &mut Parser) -> CompletedMarker {
             record_field_pat_list(p);
             RECORD_PAT
         }
+        // test marco_pat
+        // fn main() {
+        //     let m!(x) = 0;
+        // }
+        T![!] => {
+            items::macro_call_after_excl(p);
+            return m.complete(p, MACRO_CALL).precede(p).complete(p, MACRO_PAT);
+        }
         _ => PATH_PAT,
     };
     m.complete(p, kind)
diff --git a/crates/ra_parser/src/syntax_kind/generated.rs b/crates/ra_parser/src/syntax_kind/generated.rs
index dfc30d727..4c16cf1cd 100644
--- a/crates/ra_parser/src/syntax_kind/generated.rs
+++ b/crates/ra_parser/src/syntax_kind/generated.rs
@@ -167,6 +167,7 @@ pub enum SyntaxKind {
     SLICE_PAT,
     RANGE_PAT,
     LITERAL_PAT,
+    MACRO_PAT,
     TUPLE_EXPR,
     ARRAY_EXPR,
     PAREN_EXPR,
diff --git a/crates/ra_proc_macro/src/lib.rs b/crates/ra_proc_macro/src/lib.rs
index 51fbb046a..63da9f1b4 100644
--- a/crates/ra_proc_macro/src/lib.rs
+++ b/crates/ra_proc_macro/src/lib.rs
@@ -11,13 +11,12 @@ pub mod msg;
 
 use process::{ProcMacroProcessSrv, ProcMacroProcessThread};
 use ra_tt::{SmolStr, Subtree};
-use rpc::ProcMacroKind;
 use std::{
     path::{Path, PathBuf},
     sync::Arc,
 };
 
-pub use rpc::{ExpansionResult, ExpansionTask};
+pub use rpc::{ExpansionResult, ExpansionTask, ListMacrosResult, ListMacrosTask, ProcMacroKind};
 
 #[derive(Debug, Clone)]
 pub struct ProcMacroProcessExpander {
diff --git a/crates/ra_proc_macro_srv/Cargo.toml b/crates/ra_proc_macro_srv/Cargo.toml
new file mode 100644
index 000000000..315191cc5
--- /dev/null
+++ b/crates/ra_proc_macro_srv/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+edition = "2018"
+name = "ra_proc_macro_srv"
+version = "0.1.0"
+authors = ["rust-analyzer developers"]
+publish = false
+
+[lib]
+doctest = false
+
+[dependencies]
+ra_tt = { path = "../ra_tt" }
+ra_proc_macro = { path = "../ra_proc_macro" }
+
+serde_derive = "1.0.104"
+serde = "1.0.104"
+serde_json = "1.0.48"
+
+[dev-dependencies]
+cargo_metadata = "0.9.1"
+difference = "2.0.0"
diff --git a/crates/ra_proc_macro_srv/src/lib.rs b/crates/ra_proc_macro_srv/src/lib.rs
new file mode 100644
index 000000000..f77be1475
--- /dev/null
+++ b/crates/ra_proc_macro_srv/src/lib.rs
@@ -0,0 +1,21 @@
+//! RA Proc Macro Server
+//!
+//! This library is able to call compiled Rust custom derive dynamic libraries on arbitrary code.
+//! The general idea here is based on https://github.com/fedochet/rust-proc-macro-expander.
+//!
+//! But we change some several design for fitting RA needs:
+//!
+//! * We use `ra_tt` for proc-macro `TokenStream` server, it is easy to manipute and interact with
+//!   RA then proc-macro2 token stream.
+//! * By **copying** the whole rustc `lib_proc_macro` code, we are able to build this with `stable`
+//!   rustc rather than `unstable`. (Although in gerenal ABI compatibility is still an issue)
+
+use ra_proc_macro::{ExpansionResult, ExpansionTask, ListMacrosResult, ListMacrosTask};
+
+pub fn expand_task(_task: &ExpansionTask) -> Result<ExpansionResult, String> {
+    unimplemented!()
+}
+
+pub fn list_macros(_task: &ListMacrosTask) -> Result<ListMacrosResult, String> {
+    unimplemented!()
+}
diff --git a/crates/ra_proc_macro_srv/src/main.rs b/crates/ra_proc_macro_srv/src/main.rs
new file mode 100644
index 000000000..70743c1f4
--- /dev/null
+++ b/crates/ra_proc_macro_srv/src/main.rs
@@ -0,0 +1,55 @@
+//! Driver for proc macro server
+
+use ra_proc_macro::msg::{self, Message};
+use ra_proc_macro_srv::{expand_task, list_macros};
+
+use std::io;
+
+fn read_request() -> Result<Option<msg::Request>, io::Error> {
+    let stdin = io::stdin();
+    let mut stdin = stdin.lock();
+    msg::Request::read(&mut stdin)
+}
+
+fn write_response(res: Result<msg::Response, String>) -> Result<(), io::Error> {
+    let msg: msg::Response = match res {
+        Ok(res) => res,
+        Err(err) => msg::Response::Error(msg::ResponseError {
+            code: msg::ErrorCode::ExpansionError,
+            message: err,
+        }),
+    };
+
+    let stdout = io::stdout();
+    let mut stdout = stdout.lock();
+    msg.write(&mut stdout)
+}
+fn main() {
+    loop {
+        let req = match read_request() {
+            Err(err) => {
+                eprintln!("Read message error on ra_proc_macro_srv: {}", err.to_string());
+                continue;
+            }
+            Ok(None) => continue,
+            Ok(Some(req)) => req,
+        };
+
+        match req {
+            msg::Request::ListMacro(task) => {
+                if let Err(err) =
+                    write_response(list_macros(&task).map(|it| msg::Response::ListMacro(it)))
+                {
+                    eprintln!("Write message error on list macro: {}", err);
+                }
+            }
+            msg::Request::ExpansionMacro(task) => {
+                if let Err(err) =
+                    write_response(expand_task(&task).map(|it| msg::Response::ExpansionMacro(it)))
+                {
+                    eprintln!("Write message error on expansion macro: {}", err);
+                }
+            }
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index 392731dac..bf7d137be 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -325,6 +325,9 @@ impl ast::BindPat {
     pub fn is_ref(&self) -> bool {
         self.syntax().children_with_tokens().any(|n| n.kind() == T![ref])
     }
+    pub fn has_at(&self) -> bool {
+        self.syntax().children_with_tokens().any(|it| it.kind() == T![@])
+    }
 }
 
 pub struct SlicePatComponents {
diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index 7204ca5b1..0c339b987 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -2563,6 +2563,38 @@ impl LiteralPat {
     }
 }
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct MacroPat {
+    pub(crate) syntax: SyntaxNode,
+}
+impl std::fmt::Display for MacroPat {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        std::fmt::Display::fmt(self.syntax(), f)
+    }
+}
+impl AstNode for MacroPat {
+    fn can_cast(kind: SyntaxKind) -> bool {
+        match kind {
+            MACRO_PAT => true,
+            _ => false,
+        }
+    }
+    fn cast(syntax: SyntaxNode) -> Option<Self> {
+        if Self::can_cast(syntax.kind()) {
+            Some(Self { syntax })
+        } else {
+            None
+        }
+    }
+    fn syntax(&self) -> &SyntaxNode {
+        &self.syntax
+    }
+}
+impl MacroPat {
+    pub fn macro_call(&self) -> Option<MacroCall> {
+        AstChildren::new(&self.syntax).next()
+    }
+}
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct RecordPat {
     pub(crate) syntax: SyntaxNode,
 }
@@ -4600,6 +4632,7 @@ pub enum Pat {
     SlicePat(SlicePat),
     RangePat(RangePat),
     LiteralPat(LiteralPat),
+    MacroPat(MacroPat),
 }
 impl From<OrPat> for Pat {
     fn from(node: OrPat) -> Pat {
@@ -4671,6 +4704,11 @@ impl From<LiteralPat> for Pat {
         Pat::LiteralPat(node)
     }
 }
+impl From<MacroPat> for Pat {
+    fn from(node: MacroPat) -> Pat {
+        Pat::MacroPat(node)
+    }
+}
 impl std::fmt::Display for Pat {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         std::fmt::Display::fmt(self.syntax(), f)
@@ -4681,7 +4719,7 @@ impl AstNode for Pat {
         match kind {
             OR_PAT | PAREN_PAT | REF_PAT | BOX_PAT | BIND_PAT | PLACEHOLDER_PAT | DOT_DOT_PAT
             | PATH_PAT | RECORD_PAT | TUPLE_STRUCT_PAT | TUPLE_PAT | SLICE_PAT | RANGE_PAT
-            | LITERAL_PAT => true,
+            | LITERAL_PAT | MACRO_PAT => true,
             _ => false,
         }
     }
@@ -4701,6 +4739,7 @@ impl AstNode for Pat {
             SLICE_PAT => Pat::SlicePat(SlicePat { syntax }),
             RANGE_PAT => Pat::RangePat(RangePat { syntax }),
             LITERAL_PAT => Pat::LiteralPat(LiteralPat { syntax }),
+            MACRO_PAT => Pat::MacroPat(MacroPat { syntax }),
             _ => return None,
         };
         Some(res)
@@ -4721,6 +4760,7 @@ impl AstNode for Pat {
             Pat::SlicePat(it) => &it.syntax,
             Pat::RangePat(it) => &it.syntax,
             Pat::LiteralPat(it) => &it.syntax,
+            Pat::MacroPat(it) => &it.syntax,
         }
     }
 }
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index 0c908573d..f39559e9e 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -22,7 +22,8 @@ pub fn path_unqualified(segment: ast::PathSegment) -> ast::Path {
 pub fn path_qualified(qual: ast::Path, segment: ast::PathSegment) -> ast::Path {
     path_from_text(&format!("{}::{}", qual, segment))
 }
-fn path_from_text(text: &str) -> ast::Path {
+
+pub fn path_from_text(text: &str) -> ast::Path {
     ast_from_text(text)
 }
 
@@ -269,6 +270,31 @@ pub fn unreachable_macro_call() -> ast::MacroCall {
     ast_from_text(&format!("unreachable!()"))
 }
 
+pub fn param(name: String, ty: String) -> ast::Param {
+    ast_from_text(&format!("fn f({}: {}) {{ }}", name, ty))
+}
+
+pub fn param_list(pats: impl IntoIterator<Item = ast::Param>) -> ast::ParamList {
+    let args = pats.into_iter().join(", ");
+    ast_from_text(&format!("fn f({}) {{ }}", args))
+}
+
+pub fn fn_def(
+    fn_name: ast::Name,
+    type_params: Option<ast::TypeParamList>,
+    params: ast::ParamList,
+    body: ast::BlockExpr,
+) -> ast::FnDef {
+    let type_params =
+        if let Some(type_params) = type_params { format!("<{}>", type_params) } else { "".into() };
+    ast_from_text(&format!("fn {}{}{} {}", fn_name, type_params, params, body))
+}
+
+pub fn add_newlines(amount_of_newlines: usize, t: impl AstNode) -> ast::SourceFile {
+    let newlines = "\n".repeat(amount_of_newlines);
+    ast_from_text(&format!("{}{}", newlines, t.syntax()))
+}
+
 fn ast_from_text<N: AstNode>(text: &str) -> N {
     let parse = SourceFile::parse(text);
     let node = parse.tree().syntax().descendants().find_map(N::cast).unwrap();
diff --git a/crates/ra_syntax/test_data/parser/inline/ok/0129_marco_pat.txt b/crates/ra_syntax/test_data/parser/inline/ok/0129_marco_pat.txt
index b05ccc0ed..36d8f4a5f 100644
--- a/crates/ra_syntax/test_data/parser/inline/ok/0129_marco_pat.txt
+++ b/crates/ra_syntax/test_data/parser/inline/ok/0129_marco_pat.txt
@@ -15,16 +15,17 @@ SOURCE_FILE@[0; 33)
         LET_STMT@[16; 30)
           LET_KW@[16; 19) "let"
           WHITESPACE@[19; 20) " "
-          MACRO_CALL@[20; 25)
-            PATH@[20; 21)
-              PATH_SEGMENT@[20; 21)
-                NAME_REF@[20; 21)
-                  IDENT@[20; 21) "m"
-            EXCL@[21; 22) "!"
-            TOKEN_TREE@[22; 25)
-              L_PAREN@[22; 23) "("
-              IDENT@[23; 24) "x"
-              R_PAREN@[24; 25) ")"
+          MACRO_PAT@[20; 25)
+            MACRO_CALL@[20; 25)
+              PATH@[20; 21)
+                PATH_SEGMENT@[20; 21)
+                  NAME_REF@[20; 21)
+                    IDENT@[20; 21) "m"
+              EXCL@[21; 22) "!"
+              TOKEN_TREE@[22; 25)
+                L_PAREN@[22; 23) "("
+                IDENT@[23; 24) "x"
+                R_PAREN@[24; 25) ")"
           WHITESPACE@[25; 26) " "
           EQ@[26; 27) "="
           WHITESPACE@[27; 28) " "
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 04f5bb473..b6a015790 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -120,12 +120,10 @@ impl Config {
         set(value, "/withSysroot", &mut self.with_sysroot);
         set(value, "/featureFlags/lsp.diagnostics", &mut self.publish_diagnostics);
         set(value, "/lruCapacity", &mut self.lru_capacity);
-        if let Some(watcher) =  get::<String>(value, "/files/watcher") {
-            self.files.watcher = match watcher.as_str() {
-                "client" => FilesWatcher::Client,
-                "notify"| _ => FilesWatcher::Notify,
-            }
-        }
+        self.files.watcher = match get(value, "/files/watcher") {
+            Some("client") => FilesWatcher::Client,
+            Some("notify") | _ => FilesWatcher::Notify
+        };
         set(value, "/notifications/workspaceLoaded", &mut self.notifications.workspace_loaded);
         set(value, "/notifications/cargoTomlNotFound", &mut self.notifications.cargo_toml_not_found);
 
@@ -144,8 +142,9 @@ impl Config {
         } else if let RustfmtConfig::Rustfmt { extra_args } = &mut self.rustfmt {
             set(value, "/rustfmt/extraArgs", extra_args);
         }
+
         if let Some(false) = get(value, "/checkOnSave/enable") {
-            self.check = None
+            self.check = None;
         } else {
             if let Some(mut args) = get::<Vec<String>>(value, "/checkOnSave/overrideCommand") {
                 if !args.is_empty() {
@@ -153,7 +152,7 @@ impl Config {
                     self.check = Some(FlycheckConfig::CustomCommand {
                         command,
                         args,
-                    })
+                    });
                 }
 
             } else if let Some(FlycheckConfig::CargoCommand { command, extra_args, all_targets }) = &mut self.check
@@ -179,7 +178,7 @@ impl Config {
             value.pointer(pointer).and_then(|it| T::deserialize(it).ok())
         }
 
-        fn set<'a, T: Deserialize<'a> + std::fmt::Debug>(value: &'a serde_json::Value, pointer: &str, slot: &mut T) {
+        fn set<'a, T: Deserialize<'a>>(value: &'a serde_json::Value, pointer: &str, slot: &mut T) {
             if let Some(new_value) = get(value, pointer) {
                 *slot = new_value
             }