Rollup merge of #71572 - lcnr:type_length, r=Dylan-DPC

test iterator chain type length blowup

Adds a regression test. closes #58952

r? @Dylan-DPC

Author: Dylan-DPC

src/test/ui/iterators/issue-58952-filter-type-length.rs

@@ -0,0 +1,31 @@
+// run-pass
+//! This snippet causes the type length to blowup exponentially,
+//! so check that we don't accidentially exceed the type length limit.
+// FIXME: Once the size of iterator adaptors is further reduced,
+// increase the complexity of this test.
+
+fn main() {
+    let c = 2;
+    let bv = vec![2];
+    let b = bv
+        .iter()
+        .filter(|a| **a == c);
+
+    let _a = vec![1, 2, 3]
+        .into_iter()
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .filter(|a| b.clone().any(|b| *b == *a))
+        .collect::<Vec<_>>();
+}