18 files changed, 476 insertions, 187 deletions

diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index 46680a08f..7cfea70f9 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -1,8 +1,9 @@
-pub mod visit;
+//! FIXME: write short doc here
 
 use std::ops::RangeInclusive;
 
 use itertools::Itertools;
+use ra_text_edit::TextEditBuilder;
 use rustc_hash::FxHashMap;
 
 use crate::{
@@ -63,6 +64,18 @@ pub enum InsertPosition<T> {
     After(T),
 }
 
+pub struct TreeDiff {
+    replacements: FxHashMap<SyntaxElement, SyntaxElement>,
+}
+
+impl TreeDiff {
+    pub fn into_text_edit(&self, builder: &mut TextEditBuilder) {
+        for (from, to) in self.replacements.iter() {
+            builder.replace(from.text_range(), to.to_string())
+        }
+    }
+}
+
 /// Finds minimal the diff, which, applied to `from`, will result in `to`.
 ///
 /// Specifically, returns a map whose keys are descendants of `from` and values
@@ -70,12 +83,12 @@ pub enum InsertPosition<T> {
 ///
 /// A trivial solution is a singletom map `{ from: to }`, but this function
 /// tries to find a more fine-grained diff.
-pub fn diff(from: &SyntaxNode, to: &SyntaxNode) -> FxHashMap<SyntaxElement, SyntaxElement> {
+pub fn diff(from: &SyntaxNode, to: &SyntaxNode) -> TreeDiff {
     let mut buf = FxHashMap::default();
     // FIXME: this is both horrible inefficient and gives larger than
     // necessary diff. I bet there's a cool algorithm to diff trees properly.
     go(&mut buf, from.clone().into(), to.clone().into());
-    return buf;
+    return TreeDiff { replacements: buf };
 
     fn go(
         buf: &mut FxHashMap<SyntaxElement, SyntaxElement>,
diff --git a/crates/ra_syntax/src/algo/visit.rs b/crates/ra_syntax/src/algo/visit.rs
deleted file mode 100644
index 87bd15cc0..000000000
--- a/crates/ra_syntax/src/algo/visit.rs
+++ /dev/null
@@ -1,110 +0,0 @@
-use crate::{AstNode, SyntaxNode};
-
-use std::marker::PhantomData;
-
-pub fn visitor<'a, T>() -> impl Visitor<'a, Output = T> {
-    EmptyVisitor { ph: PhantomData }
-}
-
-pub fn visitor_ctx<'a, T, C>(ctx: C) -> impl VisitorCtx<'a, Output = T, Ctx = C> {
-    EmptyVisitorCtx { ph: PhantomData, ctx }
-}
-
-pub trait Visitor<'a>: Sized {
-    type Output;
-    fn accept(self, node: &'a SyntaxNode) -> Option<Self::Output>;
-    fn visit<N, F>(self, f: F) -> Vis<Self, N, F>
-    where
-        N: AstNode + 'a,
-        F: FnOnce(N) -> Self::Output,
-    {
-        Vis { inner: self, f, ph: PhantomData }
-    }
-}
-
-pub trait VisitorCtx<'a>: Sized {
-    type Output;
-    type Ctx;
-    fn accept(self, node: &'a SyntaxNode) -> Result<Self::Output, Self::Ctx>;
-    fn visit<N, F>(self, f: F) -> VisCtx<Self, N, F>
-    where
-        N: AstNode + 'a,
-        F: FnOnce(N, Self::Ctx) -> Self::Output,
-    {
-        VisCtx { inner: self, f, ph: PhantomData }
-    }
-}
-
-#[derive(Debug)]
-struct EmptyVisitor<T> {
-    ph: PhantomData<fn() -> T>,
-}
-
-impl<'a, T> Visitor<'a> for EmptyVisitor<T> {
-    type Output = T;
-
-    fn accept(self, _node: &'a SyntaxNode) -> Option<T> {
-        None
-    }
-}
-
-#[derive(Debug)]
-struct EmptyVisitorCtx<T, C> {
-    ctx: C,
-    ph: PhantomData<fn() -> T>,
-}
-
-impl<'a, T, C> VisitorCtx<'a> for EmptyVisitorCtx<T, C> {
-    type Output = T;
-    type Ctx = C;
-
-    fn accept(self, _node: &'a SyntaxNode) -> Result<T, C> {
-        Err(self.ctx)
-    }
-}
-
-#[derive(Debug)]
-pub struct Vis<V, N, F> {
-    inner: V,
-    f: F,
-    ph: PhantomData<fn(N)>,
-}
-
-impl<'a, V, N, F> Visitor<'a> for Vis<V, N, F>
-where
-    V: Visitor<'a>,
-    N: AstNode + 'a,
-    F: FnOnce(N) -> <V as Visitor<'a>>::Output,
-{
-    type Output = <V as Visitor<'a>>::Output;
-
-    fn accept(self, node: &'a SyntaxNode) -> Option<Self::Output> {
-        let Vis { inner, f, .. } = self;
-        inner.accept(node).or_else(|| N::cast(node.clone()).map(f))
-    }
-}
-
-#[derive(Debug)]
-pub struct VisCtx<V, N, F> {
-    inner: V,
-    f: F,
-    ph: PhantomData<fn(N)>,
-}
-
-impl<'a, V, N, F> VisitorCtx<'a> for VisCtx<V, N, F>
-where
-    V: VisitorCtx<'a>,
-    N: AstNode + 'a,
-    F: FnOnce(N, <V as VisitorCtx<'a>>::Ctx) -> <V as VisitorCtx<'a>>::Output,
-{
-    type Output = <V as VisitorCtx<'a>>::Output;
-    type Ctx = <V as VisitorCtx<'a>>::Ctx;
-
-    fn accept(self, node: &'a SyntaxNode) -> Result<Self::Output, Self::Ctx> {
-        let VisCtx { inner, f, .. } = self;
-        inner.accept(node).or_else(|ctx| match N::cast(node.clone()) {
-            None => Err(ctx),
-            Some(node) => Ok(f(node, ctx)),
-        })
-    }
-}
diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index f464d6534..1b2ce921a 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -5,6 +5,7 @@ mod traits;
 mod tokens;
 mod extensions;
 mod expr_extensions;
+pub mod edit;
 pub mod make;
 
 use std::marker::PhantomData;
diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
new file mode 100644
index 000000000..03f3b5fbb
--- /dev/null
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -0,0 +1,271 @@
+//! This module contains functions for editing syntax trees. As the trees are
+//! immutable, all function here return a fresh copy of the tree, instead of
+//! doing an in-place modification.
+use std::{iter, ops::RangeInclusive};
+
+use arrayvec::ArrayVec;
+use rustc_hash::FxHashMap;
+
+use crate::{
+    algo,
+    ast::{
+        self,
+        make::{self, tokens},
+        AstNode, TypeBoundsOwner,
+    },
+    AstToken, Direction, InsertPosition, SmolStr, SyntaxElement,
+    SyntaxKind::{ATTR, COMMENT, WHITESPACE},
+    SyntaxNode, T,
+};
+
+impl ast::FnDef {
+    #[must_use]
+    pub fn with_body(&self, body: ast::Block) -> ast::FnDef {
+        let mut to_insert: ArrayVec<[SyntaxElement; 2]> = ArrayVec::new();
+        let old_body_or_semi: SyntaxElement = if let Some(old_body) = self.body() {
+            old_body.syntax().clone().into()
+        } else if let Some(semi) = self.semicolon_token() {
+            to_insert.push(make::tokens::single_space().into());
+            semi.into()
+        } else {
+            to_insert.push(make::tokens::single_space().into());
+            to_insert.push(body.syntax().clone().into());
+            return insert_children(self, InsertPosition::Last, to_insert.into_iter());
+        };
+        to_insert.push(body.syntax().clone().into());
+        let replace_range = RangeInclusive::new(old_body_or_semi.clone(), old_body_or_semi);
+        replace_children(self, replace_range, to_insert.into_iter())
+    }
+}
+
+impl ast::ItemList {
+    #[must_use]
+    pub fn append_items(&self, items: impl Iterator<Item = ast::ImplItem>) -> ast::ItemList {
+        let mut res = self.clone();
+        if !self.syntax().text().contains_char('\n') {
+            res = res.make_multiline();
+        }
+        items.for_each(|it| res = res.append_item(it));
+        res
+    }
+
+    #[must_use]
+    pub fn append_item(&self, item: ast::ImplItem) -> ast::ItemList {
+        let (indent, position) = match self.impl_items().last() {
+            Some(it) => (
+                leading_indent(it.syntax()).unwrap_or_default().to_string(),
+                InsertPosition::After(it.syntax().clone().into()),
+            ),
+            None => match self.l_curly() {
+                Some(it) => (
+                    "    ".to_string() + &leading_indent(self.syntax()).unwrap_or_default(),
+                    InsertPosition::After(it),
+                ),
+                None => return self.clone(),
+            },
+        };
+        let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
+        let to_insert: ArrayVec<[SyntaxElement; 2]> =
+            [ws.ws().into(), item.syntax().clone().into()].into();
+        insert_children(self, position, to_insert.into_iter())
+    }
+
+    fn l_curly(&self) -> Option<SyntaxElement> {
+        self.syntax().children_with_tokens().find(|it| it.kind() == T!['{'])
+    }
+
+    fn make_multiline(&self) -> ast::ItemList {
+        let l_curly = match self.syntax().children_with_tokens().find(|it| it.kind() == T!['{']) {
+            Some(it) => it,
+            None => return self.clone(),
+        };
+        let sibling = match l_curly.next_sibling_or_token() {
+            Some(it) => it,
+            None => return self.clone(),
+        };
+        let existing_ws = match sibling.as_token() {
+            None => None,
+            Some(tok) if tok.kind() != WHITESPACE => None,
+            Some(ws) => {
+                if ws.text().contains('\n') {
+                    return self.clone();
+                }
+                Some(ws.clone())
+            }
+        };
+
+        let indent = leading_indent(self.syntax()).unwrap_or("".into());
+        let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
+        let to_insert = iter::once(ws.ws().into());
+        match existing_ws {
+            None => insert_children(self, InsertPosition::After(l_curly), to_insert),
+            Some(ws) => {
+                replace_children(self, RangeInclusive::new(ws.clone().into(), ws.into()), to_insert)
+            }
+        }
+    }
+}
+
+impl ast::RecordFieldList {
+    #[must_use]
+    pub fn append_field(&self, field: &ast::RecordField) -> ast::RecordFieldList {
+        self.insert_field(InsertPosition::Last, field)
+    }
+
+    #[must_use]
+    pub fn insert_field(
+        &self,
+        position: InsertPosition<&'_ ast::RecordField>,
+        field: &ast::RecordField,
+    ) -> ast::RecordFieldList {
+        let is_multiline = self.syntax().text().contains_char('\n');
+        let ws;
+        let space = if is_multiline {
+            ws = tokens::WsBuilder::new(&format!(
+                "\n{}    ",
+                leading_indent(self.syntax()).unwrap_or("".into())
+            ));
+            ws.ws()
+        } else {
+            tokens::single_space()
+        };
+
+        let mut to_insert: ArrayVec<[SyntaxElement; 4]> = ArrayVec::new();
+        to_insert.push(space.into());
+        to_insert.push(field.syntax().clone().into());
+        to_insert.push(tokens::comma().into());
+
+        macro_rules! after_l_curly {
+            () => {{
+                let anchor = match self.l_curly() {
+                    Some(it) => it,
+                    None => return self.clone(),
+                };
+                InsertPosition::After(anchor)
+            }};
+        }
+
+        macro_rules! after_field {
+            ($anchor:expr) => {
+                if let Some(comma) = $anchor
+                    .syntax()
+                    .siblings_with_tokens(Direction::Next)
+                    .find(|it| it.kind() == T![,])
+                {
+                    InsertPosition::After(comma)
+                } else {
+                    to_insert.insert(0, tokens::comma().into());
+                    InsertPosition::After($anchor.syntax().clone().into())
+                }
+            };
+        };
+
+        let position = match position {
+            InsertPosition::First => after_l_curly!(),
+            InsertPosition::Last => {
+                if !is_multiline {
+                    // don't insert comma before curly
+                    to_insert.pop();
+                }
+                match self.fields().last() {
+                    Some(it) => after_field!(it),
+                    None => after_l_curly!(),
+                }
+            }
+            InsertPosition::Before(anchor) => {
+                InsertPosition::Before(anchor.syntax().clone().into())
+            }
+            InsertPosition::After(anchor) => after_field!(anchor),
+        };
+
+        insert_children(self, position, to_insert.iter().cloned())
+    }
+
+    fn l_curly(&self) -> Option<SyntaxElement> {
+        self.syntax().children_with_tokens().find(|it| it.kind() == T!['{'])
+    }
+}
+
+impl ast::TypeParam {
+    #[must_use]
+    pub fn remove_bounds(&self) -> ast::TypeParam {
+        let colon = match self.colon_token() {
+            Some(it) => it,
+            None => return self.clone(),
+        };
+        let end = match self.type_bound_list() {
+            Some(it) => it.syntax().clone().into(),
+            None => colon.clone().into(),
+        };
+        replace_children(self, RangeInclusive::new(colon.into(), end), iter::empty())
+    }
+}
+
+#[must_use]
+pub fn strip_attrs_and_docs<N: ast::AttrsOwner>(node: &N) -> N {
+    N::cast(strip_attrs_and_docs_inner(node.syntax().clone())).unwrap()
+}
+
+fn strip_attrs_and_docs_inner(mut node: SyntaxNode) -> SyntaxNode {
+    while let Some(start) =
+        node.children_with_tokens().find(|it| it.kind() == ATTR || it.kind() == COMMENT)
+    {
+        let end = match &start.next_sibling_or_token() {
+            Some(el) if el.kind() == WHITESPACE => el.clone(),
+            Some(_) | None => start.clone(),
+        };
+        node = algo::replace_children(&node, RangeInclusive::new(start, end), &mut iter::empty());
+    }
+    node
+}
+
+#[must_use]
+pub fn replace_descendants<N: AstNode, D: AstNode>(
+    parent: &N,
+    replacement_map: impl Iterator<Item = (D, D)>,
+) -> N {
+    let map = replacement_map
+        .map(|(from, to)| (from.syntax().clone().into(), to.syntax().clone().into()))
+        .collect::<FxHashMap<_, _>>();
+    let new_syntax = algo::replace_descendants(parent.syntax(), &map);
+    N::cast(new_syntax).unwrap()
+}
+
+// Note this is copy-pasted from fmt. It seems like fmt should be a separate
+// crate, but basic tree building should be this crate. However, tree building
+// might want to call into fmt...
+fn leading_indent(node: &SyntaxNode) -> Option<SmolStr> {
+    let prev_tokens = std::iter::successors(node.first_token(), |token| token.prev_token());
+    for token in prev_tokens {
+        if let Some(ws) = ast::Whitespace::cast(token.clone()) {
+            let ws_text = ws.text();
+            if let Some(pos) = ws_text.rfind('\n') {
+                return Some(ws_text[pos + 1..].into());
+            }
+        }
+        if token.text().contains('\n') {
+            break;
+        }
+    }
+    None
+}
+
+#[must_use]
+fn insert_children<N: AstNode>(
+    parent: &N,
+    position: InsertPosition<SyntaxElement>,
+    mut to_insert: impl Iterator<Item = SyntaxElement>,
+) -> N {
+    let new_syntax = algo::insert_children(parent.syntax(), position, &mut to_insert);
+    N::cast(new_syntax).unwrap()
+}
+
+#[must_use]
+fn replace_children<N: AstNode>(
+    parent: &N,
+    to_replace: RangeInclusive<SyntaxElement>,
+    mut to_insert: impl Iterator<Item = SyntaxElement>,
+) -> N {
+    let new_syntax = algo::replace_children(parent.syntax(), to_replace, &mut to_insert);
+    N::cast(new_syntax).unwrap()
+}
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index 5f7e9f5b1..cefc00402 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -1,10 +1,8 @@
 //! Various extension methods to ast Nodes, which are hard to code-generate.
 //! Extensions for various expressions live in a sibling `expr_extensions` module.
 
-use itertools::Itertools;
-
 use crate::{
-    ast::{self, child_opt, children, AstNode, SyntaxNode},
+    ast::{self, child_opt, children, AstChildren, AstNode, AttrInput, SyntaxNode},
     SmolStr, SyntaxElement,
     SyntaxKind::*,
     SyntaxToken, T,
@@ -21,6 +19,16 @@ impl ast::NameRef {
     pub fn text(&self) -> &SmolStr {
         text_of_first_token(self.syntax())
     }
+
+    pub fn as_tuple_field(&self) -> Option<usize> {
+        self.syntax().children_with_tokens().find_map(|c| {
+            if c.kind() == SyntaxKind::INT_NUMBER {
+                c.as_token().and_then(|tok| tok.text().as_str().parse().ok())
+            } else {
+                None
+            }
+        })
+    }
 }
 
 fn text_of_first_token(node: &SyntaxNode) -> &SmolStr {
@@ -28,62 +36,37 @@ fn text_of_first_token(node: &SyntaxNode) -> &SmolStr {
 }
 
 impl ast::Attr {
-    pub fn is_inner(&self) -> bool {
-        let tt = match self.value() {
-            None => return false,
-            Some(tt) => tt,
-        };
-
-        let prev = match tt.syntax().prev_sibling() {
-            None => return false,
-            Some(prev) => prev,
-        };
-
-        prev.kind() == T![!]
-    }
-
-    pub fn as_atom(&self) -> Option<SmolStr> {
-        let tt = self.value()?;
-        let (_bra, attr, _ket) = tt.syntax().children_with_tokens().collect_tuple()?;
-        if attr.kind() == IDENT {
-            Some(attr.as_token()?.text().clone())
-        } else {
-            None
+    pub fn as_simple_atom(&self) -> Option<SmolStr> {
+        match self.input() {
+            None => self.simple_name(),
+            Some(_) => None,
         }
     }
 
-    pub fn as_call(&self) -> Option<(SmolStr, ast::TokenTree)> {
-        let tt = self.value()?;
-        let (_bra, attr, args, _ket) = tt.syntax().children_with_tokens().collect_tuple()?;
-        let args = ast::TokenTree::cast(args.as_node()?.clone())?;
-        if attr.kind() == IDENT {
-            Some((attr.as_token()?.text().clone(), args))
-        } else {
-            None
+    pub fn as_simple_call(&self) -> Option<(SmolStr, ast::TokenTree)> {
+        match self.input() {
+            Some(AttrInput::TokenTree(tt)) => Some((self.simple_name()?, tt)),
+            _ => None,
         }
     }
 
-    pub fn as_named(&self) -> Option<SmolStr> {
-        let tt = self.value()?;
-        let attr = tt.syntax().children_with_tokens().nth(1)?;
-        if attr.kind() == IDENT {
-            Some(attr.as_token()?.text().clone())
-        } else {
-            None
+    pub fn as_simple_key_value(&self) -> Option<(SmolStr, SmolStr)> {
+        match self.input() {
+            Some(AttrInput::Literal(lit)) => {
+                let key = self.simple_name()?;
+                // FIXME: escape? raw string?
+                let value = lit.syntax().first_token()?.text().trim_matches('"').into();
+                Some((key, value))
+            }
+            _ => None,
         }
     }
 
-    pub fn as_key_value(&self) -> Option<(SmolStr, SmolStr)> {
-        let tt = self.value()?;
-        let tt_node = tt.syntax();
-        let attr = tt_node.children_with_tokens().nth(1)?;
-        if attr.kind() == IDENT {
-            let key = attr.as_token()?.text().clone();
-            let val_node = tt_node.children_with_tokens().find(|t| t.kind() == STRING)?;
-            let val = val_node.as_token()?.text().trim_start_matches('"').trim_end_matches('"');
-            Some((key, SmolStr::new(val)))
-        } else {
-            None
+    pub fn simple_name(&self) -> Option<SmolStr> {
+        let path = self.path()?;
+        match (path.segment(), path.qualifier()) {
+            (Some(segment), None) => Some(segment.syntax().first_token()?.text().clone()),
+            _ => None,
         }
     }
 }
@@ -193,6 +176,16 @@ impl ast::ImplBlock {
     }
 }
 
+impl ast::AttrsOwner for ast::ImplItem {
+    fn attrs(&self) -> AstChildren<ast::Attr> {
+        match self {
+            ast::ImplItem::FnDef(it) => it.attrs(),
+            ast::ImplItem::TypeAliasDef(it) => it.attrs(),
+            ast::ImplItem::ConstDef(it) => it.attrs(),
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum StructKind {
     Tuple(ast::TupleFieldDefList),
diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index dc1f8c82c..34b22c3e2 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -1,4 +1,4 @@
-// Generated file, do not edit by hand, see `crate/ra_tools/src/codegen`
+//! Generated file, do not edit by hand, see `crate/ra_tools/src/codegen`
 
 use crate::{
     ast::{self, AstChildren, AstNode},
@@ -166,11 +166,52 @@ impl AstNode for Attr {
     }
 }
 impl Attr {
-    pub fn value(&self) -> Option<TokenTree> {
+    pub fn path(&self) -> Option<Path> {
+        AstChildren::new(&self.syntax).next()
+    }
+    pub fn input(&self) -> Option<AttrInput> {
         AstChildren::new(&self.syntax).next()
     }
 }
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum AttrInput {
+    Literal(Literal),
+    TokenTree(TokenTree),
+}
+impl From<Literal> for AttrInput {
+    fn from(node: Literal) -> AttrInput {
+        AttrInput::Literal(node)
+    }
+}
+impl From<TokenTree> for AttrInput {
+    fn from(node: TokenTree) -> AttrInput {
+        AttrInput::TokenTree(node)
+    }
+}
+impl AstNode for AttrInput {
+    fn can_cast(kind: SyntaxKind) -> bool {
+        match kind {
+            LITERAL | TOKEN_TREE => true,
+            _ => false,
+        }
+    }
+    fn cast(syntax: SyntaxNode) -> Option<Self> {
+        let res = match syntax.kind() {
+            LITERAL => AttrInput::Literal(Literal { syntax }),
+            TOKEN_TREE => AttrInput::TokenTree(TokenTree { syntax }),
+            _ => return None,
+        };
+        Some(res)
+    }
+    fn syntax(&self) -> &SyntaxNode {
+        match self {
+            AttrInput::Literal(it) => &it.syntax,
+            AttrInput::TokenTree(it) => &it.syntax,
+        }
+    }
+}
+impl AttrInput {}
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct AwaitExpr {
     pub(crate) syntax: SyntaxNode,
 }
@@ -1921,6 +1962,7 @@ impl AstNode for ModuleItem {
         }
     }
 }
+impl ast::AttrsOwner for ModuleItem {}
 impl ModuleItem {}
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Name {
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index c06c62b3b..287a40bee 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -133,3 +133,51 @@ fn ast_from_text<N: AstNode>(text: &str) -> N {
     let res = parse.tree().syntax().descendants().find_map(N::cast).unwrap();
     res
 }
+
+pub mod tokens {
+    use crate::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
+    use once_cell::sync::Lazy;
+
+    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
+
+    pub fn comma() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == T![,])
+            .unwrap()
+    }
+
+    pub fn single_space() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == " ")
+            .unwrap()
+    }
+
+    pub fn single_newline() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == "\n")
+            .unwrap()
+    }
+
+    pub struct WsBuilder(SourceFile);
+
+    impl WsBuilder {
+        pub fn new(text: &str) -> WsBuilder {
+            WsBuilder(SourceFile::parse(text).ok().unwrap())
+        }
+        pub fn ws(&self) -> SyntaxToken {
+            self.0.syntax().first_child_or_token().unwrap().into_token().unwrap()
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/ast/traits.rs b/crates/ra_syntax/src/ast/traits.rs
index c3e676d4c..f275a4955 100644
--- a/crates/ra_syntax/src/ast/traits.rs
+++ b/crates/ra_syntax/src/ast/traits.rs
@@ -99,7 +99,7 @@ pub trait AttrsOwner: AstNode {
         children(self)
     }
     fn has_atom_attr(&self, atom: &str) -> bool {
-        self.attrs().filter_map(|x| x.as_atom()).any(|x| x == atom)
+        self.attrs().filter_map(|x| x.as_simple_atom()).any(|x| x == atom)
     }
 }
 
diff --git a/crates/ra_syntax/src/fuzz.rs b/crates/ra_syntax/src/fuzz.rs
index 698a624ec..7012df7f0 100644
--- a/crates/ra_syntax/src/fuzz.rs
+++ b/crates/ra_syntax/src/fuzz.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{validation, AstNode, SourceFile, TextRange, TextUnit};
 use ra_text_edit::AtomTextEdit;
 use std::str::{self, FromStr};
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 5f395501a..25e6f64ce 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -1,5 +1,5 @@
 // Stores definitions which must be used in multiple places
-// See `cargo gen-syntax` (defined in crates/tools/src/main.rs)
+// See `cargo gen-syntax` (defined in crates/ra_tools/src/main.rs)
 Grammar(
     punct: [
         (";", "SEMI"),
@@ -397,7 +397,8 @@ Grammar(
         ),
         "ModuleItem": (
             enum: ["StructDef", "EnumDef", "FnDef", "TraitDef", "TypeAliasDef", "ImplBlock",
-                   "UseItem", "ExternCrateItem", "ConstDef", "StaticDef", "Module" ]
+                   "UseItem", "ExternCrateItem", "ConstDef", "StaticDef", "Module" ],
+            traits: ["AttrsOwner"]
         ),
         "ImplItem": (
             enum: ["FnDef", "TypeAliasDef", "ConstDef"]
@@ -576,7 +577,8 @@ Grammar(
             traits: [ "NameOwner", "AttrsOwner","DocCommentsOwner" ],
             options: [ "TokenTree", "Path" ],
         ),
-        "Attr": ( options: [ ["value", "TokenTree"] ] ),
+        "AttrInput": ( enum: [ "Literal", "TokenTree" ] ),
+        "Attr": ( options: [ "Path", [ "input", "AttrInput" ] ] ),
         "TokenTree": (),
         "TypeParamList": (
             collections: [
diff --git a/crates/ra_syntax/src/lib.rs b/crates/ra_syntax/src/lib.rs
index edb6076bb..c315ba552 100644
--- a/crates/ra_syntax/src/lib.rs
+++ b/crates/ra_syntax/src/lib.rs
@@ -160,6 +160,17 @@ impl SourceFile {
     }
 }
 
+#[macro_export]
+macro_rules! match_ast {
+    (match $node:ident {
+        $( ast::$ast:ident($it:ident) => $res:block, )*
+        _ => $catch_all:expr,
+    }) => {{
+        $( if let Some($it) = ast::$ast::cast($node.clone()) $res else )*
+        { $catch_all }
+    }};
+}
+
 /// This test does not assert anything and instead just shows off the crate's
 /// API.
 #[test]
@@ -294,7 +305,7 @@ fn api_walkthrough() {
     // To recursively process the tree, there are three approaches:
     // 1. explicitly call getter methods on AST nodes.
     // 2. use descendants and `AstNode::cast`.
-    // 3. use descendants and the visitor.
+    // 3. use descendants and `match_ast!`.
     //
     // Here's how the first one looks like:
     let exprs_cast: Vec<String> = file
@@ -304,17 +315,17 @@ fn api_walkthrough() {
         .map(|expr| expr.syntax().text().to_string())
         .collect();
 
-    // An alternative is to use a visitor. The visitor does not do traversal
-    // automatically (so it's more akin to a generic lambda) and is constructed
-    // from closures. This seems more flexible than a single generated visitor
-    // trait.
-    use algo::visit::{visitor, Visitor};
+    // An alternative is to use a macro.
     let mut exprs_visit = Vec::new();
     for node in file.syntax().descendants() {
-        if let Some(result) =
-            visitor().visit::<ast::Expr, _>(|expr| expr.syntax().text().to_string()).accept(&node)
-        {
-            exprs_visit.push(result);
+        match_ast! {
+            match node {
+                ast::Expr(it) => {
+                    let res = it.syntax().text().to_string();
+                    exprs_visit.push(res);
+                },
+                _ => (),
+            }
         }
     }
     assert_eq!(exprs_cast, exprs_visit);
diff --git a/crates/ra_syntax/src/parsing/lexer.rs b/crates/ra_syntax/src/parsing/lexer.rs
index bdb01d40b..6d839208d 100644
--- a/crates/ra_syntax/src/parsing/lexer.rs
+++ b/crates/ra_syntax/src/parsing/lexer.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{
     SyntaxKind::{self, *},
     TextUnit,
diff --git a/crates/ra_syntax/src/parsing/text_token_source.rs b/crates/ra_syntax/src/parsing/text_token_source.rs
index 64cb20ae8..e793f93a4 100644
--- a/crates/ra_syntax/src/parsing/text_token_source.rs
+++ b/crates/ra_syntax/src/parsing/text_token_source.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use ra_parser::Token as PToken;
 use ra_parser::TokenSource;
 
diff --git a/crates/ra_syntax/src/parsing/text_tree_sink.rs b/crates/ra_syntax/src/parsing/text_tree_sink.rs
index be6e51780..142164316 100644
--- a/crates/ra_syntax/src/parsing/text_tree_sink.rs
+++ b/crates/ra_syntax/src/parsing/text_tree_sink.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::mem;
 
 use ra_parser::{ParseError, TreeSink};
diff --git a/crates/ra_syntax/src/ptr.rs b/crates/ra_syntax/src/ptr.rs
index 992034ef0..31167cada 100644
--- a/crates/ra_syntax/src/ptr.rs
+++ b/crates/ra_syntax/src/ptr.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::{iter::successors, marker::PhantomData};
 
 use crate::{AstNode, SyntaxKind, SyntaxNode, TextRange};
diff --git a/crates/ra_syntax/src/syntax_error.rs b/crates/ra_syntax/src/syntax_error.rs
index 5aefec768..d6eca2ad7 100644
--- a/crates/ra_syntax/src/syntax_error.rs
+++ b/crates/ra_syntax/src/syntax_error.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use std::fmt;
 
 use ra_parser::ParseError;
diff --git a/crates/ra_syntax/src/validation.rs b/crates/ra_syntax/src/validation.rs
index 16824f3c4..ab4f15908 100644
--- a/crates/ra_syntax/src/validation.rs
+++ b/crates/ra_syntax/src/validation.rs
@@ -1,10 +1,11 @@
+//! FIXME: write short doc here
+
 mod block;
 
 use rustc_lexer::unescape;
 
 use crate::{
-    algo::visit::{visitor_ctx, VisitorCtx},
-    ast, AstNode, SyntaxError, SyntaxErrorKind,
+    ast, match_ast, AstNode, SyntaxError, SyntaxErrorKind,
     SyntaxKind::{BYTE, BYTE_STRING, CHAR, INT_NUMBER, STRING},
     SyntaxNode, SyntaxToken, TextUnit, T,
 };
@@ -95,12 +96,15 @@ impl From<rustc_lexer::unescape::EscapeError> for SyntaxErrorKind {
 pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {
     let mut errors = Vec::new();
     for node in root.descendants() {
-        let _ = visitor_ctx(&mut errors)
-            .visit::<ast::Literal, _>(validate_literal)
-            .visit::<ast::BlockExpr, _>(block::validate_block_expr)
-            .visit::<ast::FieldExpr, _>(|it, errors| validate_numeric_name(it.name_ref(), errors))
-            .visit::<ast::RecordField, _>(|it, errors| validate_numeric_name(it.name_ref(), errors))
-            .accept(&node);
+        match_ast! {
+            match node {
+                ast::Literal(it) => { validate_literal(it, &mut errors) },
+                ast::BlockExpr(it) => { block::validate_block_expr(it, &mut errors) },
+                ast::FieldExpr(it) => { validate_numeric_name(it.name_ref(), &mut errors) },
+                ast::RecordField(it) => { validate_numeric_name(it.name_ref(), &mut errors) },
+                _ => (),
+            }
+        }
     }
     errors
 }
diff --git a/crates/ra_syntax/src/validation/block.rs b/crates/ra_syntax/src/validation/block.rs
index 3c9e96eb3..c85bbc1f4 100644
--- a/crates/ra_syntax/src/validation/block.rs
+++ b/crates/ra_syntax/src/validation/block.rs
@@ -1,3 +1,5 @@
+//! FIXME: write short doc here
+
 use crate::{
     ast::{self, AstNode, AttrsOwner},
     SyntaxError,