Merge #1960

1960: Replace AST visitors with macro r=viorina a=viorina

Fixes #1672.

Co-authored-by: Ekaterina Babshukova <ekaterina.babshukova@yandex.ru>

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_ide_api/src/completion/complete_fn_param.rs

@@ -1,9 +1,6 @@
 //! FIXME: write short doc here
 
-use ra_syntax::{
-    algo::visit::{visitor_ctx, VisitorCtx},
-    ast, AstNode,
-};
+use ra_syntax::{ast, match_ast, AstNode};
 use rustc_hash::FxHashMap;
 
 use crate::completion::{CompletionContext, CompletionItem, CompletionKind, Completions};
@@ -19,10 +16,13 @@ pub(super) fn complete_fn_param(acc: &mut Completions, ctx: &CompletionContext)
 
     let mut params = FxHashMap::default();
     for node in ctx.token.parent().ancestors() {
-        let _ = visitor_ctx(&mut params)
-            .visit::<ast::SourceFile, _>(process)
-            .visit::<ast::ItemList, _>(process)
-            .accept(&node);
+        match_ast! {
+            match node {
+                ast::SourceFile(it) => { process(it, &mut params) },
+                ast::ItemList(it) => { process(it, &mut params) },
+                _ => (),
+            }
+        }
     }
     params
         .into_iter()

crates/ra_ide_api/src/completion/complete_keyword.rs

@@ -1,9 +1,8 @@
 //! FIXME: write short doc here
 
 use ra_syntax::{
-    algo::visit::{visitor, Visitor},
     ast::{self, LoopBodyOwner},
-    AstNode,
+    match_ast, AstNode,
     SyntaxKind::*,
     SyntaxToken,
 };
@@ -84,12 +83,15 @@ fn is_in_loop_body(leaf: &SyntaxToken) -> bool {
         if node.kind() == FN_DEF || node.kind() == LAMBDA_EXPR {
             break;
         }
-        let loop_body = visitor()
-            .visit::<ast::ForExpr, _>(|it| it.loop_body())
-            .visit::<ast::WhileExpr, _>(|it| it.loop_body())
-            .visit::<ast::LoopExpr, _>(|it| it.loop_body())
-            .accept(&node);
-        if let Some(Some(body)) = loop_body {
+        let loop_body = match_ast! {
+            match node {
+                ast::ForExpr(it) => { it.loop_body() },
+                ast::WhileExpr(it) => { it.loop_body() },
+                ast::LoopExpr(it) => { it.loop_body() },
+                _ => None,
+            }
+        };
+        if let Some(body) = loop_body {
             if leaf.text_range().is_subrange(&body.syntax().text_range()) {
                 return true;
             }

crates/ra_ide_api/src/display/navigation_target.rs

@@ -3,9 +3,8 @@
 use hir::{AssocItem, FieldSource, HasSource, ModuleSource};
 use ra_db::{FileId, SourceDatabase};
 use ra_syntax::{
-    algo::visit::{visitor, Visitor},
     ast::{self, DocCommentsOwner},
-    AstNode, AstPtr, SmolStr,
+    match_ast, AstNode, AstPtr, SmolStr,
     SyntaxKind::{self, NAME},
     SyntaxNode, TextRange,
 };
@@ -308,19 +307,22 @@ pub(crate) fn docs_from_symbol(db: &RootDatabase, symbol: &FileSymbol) -> Option
     let parse = db.parse(symbol.file_id);
     let node = symbol.ptr.to_node(parse.tree().syntax());
 
-    visitor()
-        .visit(|it: ast::FnDef| it.doc_comment_text())
-        .visit(|it: ast::StructDef| it.doc_comment_text())
-        .visit(|it: ast::EnumDef| it.doc_comment_text())
-        .visit(|it: ast::TraitDef| it.doc_comment_text())
-        .visit(|it: ast::Module| it.doc_comment_text())
-        .visit(|it: ast::TypeAliasDef| it.doc_comment_text())
-        .visit(|it: ast::ConstDef| it.doc_comment_text())
-        .visit(|it: ast::StaticDef| it.doc_comment_text())
-        .visit(|it: ast::RecordFieldDef| it.doc_comment_text())
-        .visit(|it: ast::EnumVariant| it.doc_comment_text())
-        .visit(|it: ast::MacroCall| it.doc_comment_text())
-        .accept(&node)?
+    match_ast! {
+        match node {
+            ast::FnDef(it) => { it.doc_comment_text() },
+            ast::StructDef(it) => { it.doc_comment_text() },
+            ast::EnumDef(it) => { it.doc_comment_text() },
+            ast::TraitDef(it) => { it.doc_comment_text() },
+            ast::Module(it) => { it.doc_comment_text() },
+            ast::TypeAliasDef(it) => { it.doc_comment_text() },
+            ast::ConstDef(it) => { it.doc_comment_text() },
+            ast::StaticDef(it) => { it.doc_comment_text() },
+            ast::RecordFieldDef(it) => { it.doc_comment_text() },
+            ast::EnumVariant(it) => { it.doc_comment_text() },
+            ast::MacroCall(it) => { it.doc_comment_text() },
+            _ => None,
+        }
+    }
 }
 
 /// Get a description of a symbol.
@@ -330,16 +332,19 @@ pub(crate) fn description_from_symbol(db: &RootDatabase, symbol: &FileSymbol) ->
     let parse = db.parse(symbol.file_id);
     let node = symbol.ptr.to_node(parse.tree().syntax());
 
-    visitor()
-        .visit(|node: ast::FnDef| node.short_label())
-        .visit(|node: ast::StructDef| node.short_label())
-        .visit(|node: ast::EnumDef| node.short_label())
-        .visit(|node: ast::TraitDef| node.short_label())
-        .visit(|node: ast::Module| node.short_label())
-        .visit(|node: ast::TypeAliasDef| node.short_label())
-        .visit(|node: ast::ConstDef| node.short_label())
-        .visit(|node: ast::StaticDef| node.short_label())
-        .visit(|node: ast::RecordFieldDef| node.short_label())
-        .visit(|node: ast::EnumVariant| node.short_label())
-        .accept(&node)?
+    match_ast! {
+        match node {
+            ast::FnDef(it) => { it.short_label() },
+            ast::StructDef(it) => { it.short_label() },
+            ast::EnumDef(it) => { it.short_label() },
+            ast::TraitDef(it) => { it.short_label() },
+            ast::Module(it) => { it.short_label() },
+            ast::TypeAliasDef(it) => { it.short_label() },
+            ast::ConstDef(it) => { it.short_label() },
+            ast::StaticDef(it) => { it.short_label() },
+            ast::RecordFieldDef(it) => { it.short_label() },
+            ast::EnumVariant(it) => { it.short_label() },
+            _ => None,
+        }
+    }
 }

crates/ra_ide_api/src/display/structure.rs

@@ -3,9 +3,8 @@
 use crate::TextRange;
 
 use ra_syntax::{
-    algo::visit::{visitor, Visitor},
     ast::{self, AttrsOwner, NameOwner, TypeAscriptionOwner, TypeParamsOwner},
-    AstNode, SourceFile, SyntaxKind, SyntaxNode, WalkEvent,
+    match_ast, AstNode, SourceFile, SyntaxKind, SyntaxNode, WalkEvent,
 };
 
 #[derive(Debug, Clone)]
@@ -101,63 +100,66 @@ fn structure_node(node: &SyntaxNode) -> Option<StructureNode> {
         })
     }
 
-    visitor()
-        .visit(|fn_def: ast::FnDef| {
-            let mut detail = String::from("fn");
-            if let Some(type_param_list) = fn_def.type_param_list() {
-                collapse_ws(type_param_list.syntax(), &mut detail);
-            }
-            if let Some(param_list) = fn_def.param_list() {
-                collapse_ws(param_list.syntax(), &mut detail);
-            }
-            if let Some(ret_type) = fn_def.ret_type() {
-                detail.push_str(" ");
-                collapse_ws(ret_type.syntax(), &mut detail);
-            }
-
-            decl_with_detail(fn_def, Some(detail))
-        })
-        .visit(decl::<ast::StructDef>)
-        .visit(decl::<ast::EnumDef>)
-        .visit(decl::<ast::EnumVariant>)
-        .visit(decl::<ast::TraitDef>)
-        .visit(decl::<ast::Module>)
-        .visit(|td: ast::TypeAliasDef| {
-            let ty = td.type_ref();
-            decl_with_type_ref(td, ty)
-        })
-        .visit(decl_with_ascription::<ast::RecordFieldDef>)
-        .visit(decl_with_ascription::<ast::ConstDef>)
-        .visit(decl_with_ascription::<ast::StaticDef>)
-        .visit(|im: ast::ImplBlock| {
-            let target_type = im.target_type()?;
-            let target_trait = im.target_trait();
-            let label = match target_trait {
-                None => format!("impl {}", target_type.syntax().text()),
-                Some(t) => {
-                    format!("impl {} for {}", t.syntax().text(), target_type.syntax().text(),)
+    match_ast! {
+        match node {
+            ast::FnDef(it) => {
+                let mut detail = String::from("fn");
+                if let Some(type_param_list) = it.type_param_list() {
+                    collapse_ws(type_param_list.syntax(), &mut detail);
+                }
+                if let Some(param_list) = it.param_list() {
+                    collapse_ws(param_list.syntax(), &mut detail);
+                }
+                if let Some(ret_type) = it.ret_type() {
+                    detail.push_str(" ");
+                    collapse_ws(ret_type.syntax(), &mut detail);
                 }
-            };
 
-            let node = StructureNode {
-                parent: None,
-                label,
-                navigation_range: target_type.syntax().text_range(),
-                node_range: im.syntax().text_range(),
-                kind: im.syntax().kind(),
-                detail: None,
-                deprecated: false,
-            };
-            Some(node)
-        })
-        .visit(|mc: ast::MacroCall| {
-            let first_token = mc.syntax().first_token().unwrap();
-            if first_token.text().as_str() != "macro_rules" {
-                return None;
-            }
-            decl(mc)
-        })
-        .accept(&node)?
+                decl_with_detail(it, Some(detail))
+            },
+            ast::StructDef(it) => { decl(it) },
+            ast::EnumDef(it) => { decl(it) },
+            ast::EnumVariant(it) => { decl(it) },
+            ast::TraitDef(it) => { decl(it) },
+            ast::Module(it) => { decl(it) },
+            ast::TypeAliasDef(it) => {
+                let ty = it.type_ref();
+                decl_with_type_ref(it, ty)
+            },
+            ast::RecordFieldDef(it) => { decl_with_ascription(it) },
+            ast::ConstDef(it) => { decl_with_ascription(it) },
+            ast::StaticDef(it) => { decl_with_ascription(it) },
+            ast::ImplBlock(it) => {
+                let target_type = it.target_type()?;
+                let target_trait = it.target_trait();
+                let label = match target_trait {
+                    None => format!("impl {}", target_type.syntax().text()),
+                    Some(t) => {
+                        format!("impl {} for {}", t.syntax().text(), target_type.syntax().text(),)
+                    }
+                };
+
+                let node = StructureNode {
+                    parent: None,
+                    label,
+                    navigation_range: target_type.syntax().text_range(),
+                    node_range: it.syntax().text_range(),
+                    kind: it.syntax().kind(),
+                    detail: None,
+                    deprecated: false,
+                };
+                Some(node)
+            },
+            ast::MacroCall(it) => {
+                let first_token = it.syntax().first_token().unwrap();
+                if first_token.text().as_str() != "macro_rules" {
+                    return None;
+                }
+                decl(it)
+            },
+            _ => None,
+        }
+    }
 }
 
 #[cfg(test)]

crates/ra_ide_api/src/goto_definition.rs

@@ -2,12 +2,9 @@
 
 use ra_db::{FileId, SourceDatabase};
 use ra_syntax::{
-    algo::{
-        find_node_at_offset,
-        visit::{visitor, Visitor},
-    },
+    algo::find_node_at_offset,
     ast::{self, DocCommentsOwner},
-    AstNode, SyntaxNode,
+    match_ast, AstNode, SyntaxNode,
 };
 
 use crate::{
@@ -114,91 +111,99 @@ pub(crate) fn name_definition(
 }
 
 fn named_target(file_id: FileId, node: &SyntaxNode) -> Option<NavigationTarget> {
-    visitor()
-        .visit(|node: ast::StructDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::EnumDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::EnumVariant| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::FnDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::TypeAliasDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::ConstDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::StaticDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::TraitDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::RecordFieldDef| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::Module| {
-            NavigationTarget::from_named(
-                file_id,
-                &node,
-                node.doc_comment_text(),
-                node.short_label(),
-            )
-        })
-        .visit(|node: ast::MacroCall| {
-            NavigationTarget::from_named(file_id, &node, node.doc_comment_text(), None)
-        })
-        .accept(node)
+    match_ast! {
+        match node {
+            ast::StructDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::EnumDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::EnumVariant(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::FnDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::TypeAliasDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::ConstDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::StaticDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::TraitDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::RecordFieldDef(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::Module(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    it.short_label(),
+                ))
+            },
+            ast::MacroCall(it) => {
+                Some(NavigationTarget::from_named(
+                    file_id,
+                    &it,
+                    it.doc_comment_text(),
+                    None,
+                ))
+            },
+            _ => None,
+        }
+    }
 }
 
 #[cfg(test)]

crates/ra_ide_api/src/hover.rs

@@ -3,12 +3,9 @@
 use hir::{Adt, HasSource, HirDisplay};
 use ra_db::SourceDatabase;
 use ra_syntax::{
-    algo::{
-        ancestors_at_offset, find_covering_element, find_node_at_offset,
-        visit::{visitor, Visitor},
-    },
+    algo::{ancestors_at_offset, find_covering_element, find_node_at_offset},
     ast::{self, DocCommentsOwner},
-    AstNode,
+    match_ast, AstNode,
 };
 
 use crate::{
@@ -178,37 +175,45 @@ pub(crate) fn hover(db: &RootDatabase, position: FilePosition) -> Option<RangeIn
         }
     } else if let Some(name) = find_node_at_offset::<ast::Name>(file.syntax(), position.offset) {
         if let Some(parent) = name.syntax().parent() {
-            let text = visitor()
-                .visit(|node: ast::StructDef| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::EnumDef| hover_text(node.doc_comment_text(), node.short_label()))
-                .visit(|node: ast::EnumVariant| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::FnDef| hover_text(node.doc_comment_text(), node.short_label()))
-                .visit(|node: ast::TypeAliasDef| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::ConstDef| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::StaticDef| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::TraitDef| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::RecordFieldDef| {
-                    hover_text(node.doc_comment_text(), node.short_label())
-                })
-                .visit(|node: ast::Module| hover_text(node.doc_comment_text(), node.short_label()))
-                .visit(|node: ast::MacroCall| hover_text(node.doc_comment_text(), None))
-                .accept(&parent);
-
-            if let Some(text) = text {
-                res.extend(text);
-            }
+            let text = match_ast! {
+                match parent {
+                    ast::StructDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::EnumDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::EnumVariant(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::FnDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::TypeAliasDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::ConstDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::StaticDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::TraitDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::RecordFieldDef(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::Module(it) => {
+                        hover_text(it.doc_comment_text(), it.short_label())
+                    },
+                    ast::MacroCall(it) => {
+                        hover_text(it.doc_comment_text(), None)
+                    },
+                    _ => None,
+                }
+            };
+            res.extend(text);
         }
 
         if !res.is_empty() && range.is_none() {

crates/ra_ide_api/src/inlay_hints.rs

@@ -3,9 +3,8 @@
 use crate::{db::RootDatabase, FileId};
 use hir::{HirDisplay, SourceAnalyzer, Ty};
 use ra_syntax::{
-    algo::visit::{visitor, Visitor},
     ast::{self, AstNode, TypeAscriptionOwner},
-    SmolStr, SourceFile, SyntaxKind, SyntaxNode, TextRange,
+    match_ast, SmolStr, SourceFile, SyntaxKind, SyntaxNode, TextRange,
 };
 
 #[derive(Debug, PartialEq, Eq)]
@@ -33,55 +32,58 @@ fn get_inlay_hints(
     file_id: FileId,
     node: &SyntaxNode,
 ) -> Option<Vec<InlayHint>> {
-    visitor()
-        .visit(|let_statement: ast::LetStmt| {
-            if let_statement.ascribed_type().is_some() {
-                return None;
-            }
-            let pat = let_statement.pat()?;
-            let analyzer = SourceAnalyzer::new(db, file_id, let_statement.syntax(), None);
-            Some(get_pat_type_hints(db, &analyzer, pat, false))
-        })
-        .visit(|closure_parameter: ast::LambdaExpr| {
-            let analyzer = SourceAnalyzer::new(db, file_id, closure_parameter.syntax(), None);
-            closure_parameter.param_list().map(|param_list| {
-                param_list
-                    .params()
-                    .filter(|closure_param| closure_param.ascribed_type().is_none())
-                    .filter_map(|closure_param| closure_param.pat())
-                    .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, false))
-                    .flatten()
-                    .collect()
-            })
-        })
-        .visit(|for_expression: ast::ForExpr| {
-            let pat = for_expression.pat()?;
-            let analyzer = SourceAnalyzer::new(db, file_id, for_expression.syntax(), None);
-            Some(get_pat_type_hints(db, &analyzer, pat, false))
-        })
-        .visit(|if_expr: ast::IfExpr| {
-            let pat = if_expr.condition()?.pat()?;
-            let analyzer = SourceAnalyzer::new(db, file_id, if_expr.syntax(), None);
-            Some(get_pat_type_hints(db, &analyzer, pat, true))
-        })
-        .visit(|while_expr: ast::WhileExpr| {
-            let pat = while_expr.condition()?.pat()?;
-            let analyzer = SourceAnalyzer::new(db, file_id, while_expr.syntax(), None);
-            Some(get_pat_type_hints(db, &analyzer, pat, true))
-        })
-        .visit(|match_arm_list: ast::MatchArmList| {
-            let analyzer = SourceAnalyzer::new(db, file_id, match_arm_list.syntax(), None);
-            Some(
-                match_arm_list
-                    .arms()
-                    .map(|match_arm| match_arm.pats())
-                    .flatten()
-                    .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, true))
-                    .flatten()
-                    .collect(),
-            )
-        })
-        .accept(&node)?
+    match_ast! {
+        match node {
+            ast::LetStmt(it) => {
+                if it.ascribed_type().is_some() {
+                    return None;
+                }
+                let pat = it.pat()?;
+                let analyzer = SourceAnalyzer::new(db, file_id, it.syntax(), None);
+                Some(get_pat_type_hints(db, &analyzer, pat, false))
+            },
+            ast::LambdaExpr(it) => {
+                let analyzer = SourceAnalyzer::new(db, file_id, it.syntax(), None);
+                it.param_list().map(|param_list| {
+                    param_list
+                        .params()
+                        .filter(|closure_param| closure_param.ascribed_type().is_none())
+                        .filter_map(|closure_param| closure_param.pat())
+                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, false))
+                        .flatten()
+                        .collect()
+                })
+            },
+            ast::ForExpr(it) => {
+                let pat = it.pat()?;
+                let analyzer = SourceAnalyzer::new(db, file_id, it.syntax(), None);
+                Some(get_pat_type_hints(db, &analyzer, pat, false))
+            },
+            ast::IfExpr(it) => {
+                let pat = it.condition()?.pat()?;
+                let analyzer = SourceAnalyzer::new(db, file_id, it.syntax(), None);
+                Some(get_pat_type_hints(db, &analyzer, pat, true))
+            },
+            ast::WhileExpr(it) => {
+                let pat = it.condition()?.pat()?;
+                let analyzer = SourceAnalyzer::new(db, file_id, it.syntax(), None);
+                Some(get_pat_type_hints(db, &analyzer, pat, true))
+            },
+            ast::MatchArmList(it) => {
+                let analyzer = SourceAnalyzer::new(db, file_id, it.syntax(), None);
+                Some(
+                    it
+                        .arms()
+                        .map(|match_arm| match_arm.pats())
+                        .flatten()
+                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, true))
+                        .flatten()
+                        .collect(),
+                )
+            },
+            _ => None,
+        }
+    }
 }
 
 fn get_pat_type_hints(

crates/ra_ide_api/src/symbol_index.rs

@@ -32,9 +32,8 @@ use ra_db::{
     SourceDatabase, SourceRootId,
 };
 use ra_syntax::{
-    algo::visit::{visitor, Visitor},
     ast::{self, NameOwner},
-    AstNode, Parse, SmolStr, SourceFile,
+    match_ast, AstNode, Parse, SmolStr, SourceFile,
     SyntaxKind::{self, *},
     SyntaxNode, SyntaxNodePtr, TextRange, WalkEvent,
 };
@@ -306,16 +305,19 @@ fn to_symbol(node: &SyntaxNode) -> Option<(SmolStr, SyntaxNodePtr, TextRange)> {
 
         Some((name, ptr, name_range))
     }
-    visitor()
-        .visit(decl::<ast::FnDef>)
-        .visit(decl::<ast::StructDef>)
-        .visit(decl::<ast::EnumDef>)
-        .visit(decl::<ast::TraitDef>)
-        .visit(decl::<ast::Module>)
-        .visit(decl::<ast::TypeAliasDef>)
-        .visit(decl::<ast::ConstDef>)
-        .visit(decl::<ast::StaticDef>)
-        .accept(node)?
+    match_ast! {
+        match node {
+            ast::FnDef(it) => { decl(it) },
+            ast::StructDef(it) => { decl(it) },
+            ast::EnumDef(it) => { decl(it) },
+            ast::TraitDef(it) => { decl(it) },
+            ast::Module(it) => { decl(it) },
+            ast::TypeAliasDef(it) => { decl(it) },
+            ast::ConstDef(it) => { decl(it) },
+            ast::StaticDef(it) => { decl(it) },
+            _ => None,
+        }
+    }
 }
 
 fn to_file_symbol(node: &SyntaxNode, file_id: FileId) -> Option<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]
@@ -294,7 +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);

crates/ra_syntax/src/validation.rs

@@ -5,8 +5,7 @@ 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,
 };
@@ -97,12 +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
 }

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