skip visit_type_definition in a @no_type_check context

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -723,6 +723,13 @@ impl<'a> Visitor<'a> for Checker<'a> {
                 // Visit the decorators and arguments, but avoid the body, which will be
                 // deferred.
                 for decorator in decorator_list {
+                    if decorator
+                        .expression
+                        .as_name_expr()
+                        .is_some_and(|name| name.id.as_str() == "no_type_check")
+                    {
+                        self.semantic.flags |= SemanticModelFlags::NO_TYPE_CHECK;
+                    }
                     self.visit_decorator(decorator);
                 }
 
@@ -1851,6 +1858,9 @@ impl<'a> Checker<'a> {
 
     /// Visit an [`Expr`], and treat it as a type definition.
     fn visit_type_definition(&mut self, expr: &'a Expr) {
+        if !(self.semantic.flags & SemanticModelFlags::NO_TYPE_CHECK).is_empty() {
+            return;
+        }
         let snapshot = self.semantic.flags;
         self.semantic.flags |= SemanticModelFlags::TYPE_DEFINITION;
         self.visit_expr(expr);

crates/ruff_python_semantic/src/model.rs

@@ -2222,6 +2222,8 @@ bitflags! {
         /// [PEP 257]: https://peps.python.org/pep-0257/#what-is-a-docstring
         const ATTRIBUTE_DOCSTRING = 1 << 25;
 
+        const NO_TYPE_CHECK = 1 << 26;
+
         /// The context is in any type annotation.
         const ANNOTATION = Self::TYPING_ONLY_ANNOTATION.bits() | Self::RUNTIME_EVALUATED_ANNOTATION.bits() | Self::RUNTIME_REQUIRED_ANNOTATION.bits();