Rust: fix duplicate asm! expressions

rust/schema/annotations.py

@@ -1404,17 +1404,25 @@ class _:
     """
 
 
-@annotate(MacroBlockExpr, replace_bases={AstNode: Expr}, cfg=True)
-@rust.doc_test_signature(None)
-class _:
+class MacroBlockExpr(Expr):
     """
     A sequence of statements generated by a `MacroCall`. For example:
     ```rust
-    fn main() {
-        println!("Hello, world!"); // This macro expands into a list of statements
+    macro_rules! my_macro {
+        () => {
+            let mut x = 40;
+            x += 2;
+            x
+        };
     }
+
+    my_macro!();  // this macro expands to a sequence of statements (and an expression)
     ```
     """
+    __cfg__ = True
+
+    statements: list[Stmt] | child
+    tail_expr: optional[Expr] | child
 
 
 @annotate(MacroTypeRepr)