remove visitor module

crates/ra_assists/src/assists/split_import.rs

@@ -51,13 +51,13 @@ mod tests {
     fn split_import_works_with_trees() {
         check_assist(
             split_import,
-            "use algo:<|>:visitor::{Visitor, visit}",
-            "use algo::{<|>visitor::{Visitor, visit}}",
+            "use crate:<|>:db::{RootDatabase, FileSymbol}",
+            "use crate::{<|>db::{RootDatabase, FileSymbol}}",
         )
     }
 
     #[test]
     fn split_import_target() {
-        check_assist_target(split_import, "use algo::<|>visitor::{Visitor, visit}", "::");
+        check_assist_target(split_import, "use crate::<|>db::{RootDatabase, FileSymbol}", "::");
     }
 }

crates/ra_syntax/src/algo.rs

@@ -1,7 +1,5 @@
 //! FIXME: write short doc here
 
-pub mod visit;
-
 use std::ops::RangeInclusive;
 
 use itertools::Itertools;

crates/ra_syntax/src/algo/visit.rs

@@ -1,112 +0,0 @@
-//! FIXME: write short doc here
-
-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)),
-        })
-    }
-}

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]
@@ -294,8 +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.
-    // 4. use descendants and `match_ast!`.
+    // 3. use descendants and `match_ast!`.
     //
     // Here's how the first one looks like:
     let exprs_cast: Vec<String> = file
@@ -305,29 +315,18 @@ 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);
 }
-
-#[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 }
-    }};
-}

docs/dev/architecture.md

@@ -79,9 +79,7 @@ Rust syntax tree structure and parser. See
 - `grammar.ron` RON description of the grammar, which is used to
   generate `syntax_kinds` and `ast` modules, using `cargo gen-syntax` command.
 - `algo`: generic tree algorithms, including `walk` for O(1) stack
-  space tree traversal (this is cool) and `visit` for type-driven
-  visiting the nodes (this is double plus cool, if you understand how
-  `Visitor` works, you understand the design of syntax trees).
+  space tree traversal (this is cool).
 
 Tests for ra_syntax are mostly data-driven: `test_data/parser` contains subdirectories with a bunch of `.rs`
 (test vectors) and `.txt` files with corresponding syntax trees. During testing, we check

docs/user/features.md

@@ -367,9 +367,9 @@ impl VariantData {
 
 ```rust
 // before:
-use algo:<|>:visitor::{Visitor, visit};
+use crate:<|>:db::{RootDatabase, FileSymbol};
 // after:
-use algo::{<|>visitor::{Visitor, visit}};
+use crate::{<|>db::{RootDatabase, FileSymbol}};
 ```
 
 - Flip binary expression