2 files changed, 22 insertions, 8 deletions

diff --git a/crates/ra_syntax/src/lib.rs b/crates/ra_syntax/src/lib.rs
index edb6076bb..09230ccb2 100644
--- a/crates/ra_syntax/src/lib.rs
+++ b/crates/ra_syntax/src/lib.rs
@@ -295,6 +295,7 @@ fn api_walkthrough() {
     // 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!`.
     //
     // Here's how the first one looks like:
     let exprs_cast: Vec<String> = file
@@ -319,3 +320,14 @@ fn api_walkthrough() {
     }
     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 }
+    }};
+}
diff --git a/crates/ra_syntax/src/validation.rs b/crates/ra_syntax/src/validation.rs
index 4f8935b2c..ab4f15908 100644
--- a/crates/ra_syntax/src/validation.rs
+++ b/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
 }