Auto merge of #129346 - nnethercote:fix-double-handling-in-collect_tokens, r=petrochenkov

Fix double handling in `collect_tokens`

Double handling of AST nodes can occur in `collect_tokens`. This is when an inner call to `collect_tokens` produces an AST node, and then an outer call to `collect_tokens` produces the same AST node. This can happen in a few places, e.g. expression statements where the statement delegates `HasTokens` and `HasAttrs` to the expression. It will also happen more after #124141.

This PR fixes some double handling cases that cause problems, including #129166.

r? `@petrochenkov`

compiler/rustc_index/src/interval.rs

@@ -18,7 +18,7 @@ mod tests;
 #[derive(Debug, Clone)]
 pub struct IntervalSet<I> {
     // Start, end
-    map: SmallVec<[(u32, u32); 4]>,
+    map: SmallVec<[(u32, u32); 2]>,
     domain: usize,
     _data: PhantomData<I>,
 }