1 files changed, 59 insertions, 0 deletions
diff --git a/src/test/ui/closures/issue-72408-nested-closures-exponential.rs b/src/test/ui/closures/issue-72408-nested-closures-exponential.rs
new file mode 100644
index 000000000..2d6ba9365
--- /dev/null
+++ b/src/test/ui/closures/issue-72408-nested-closures-exponential.rs
@@ -0,0 +1,59 @@
+// build-pass
+
+// Closures include captured types twice in a type tree.
+//
+// Wrapping one closure with another leads to doubling
+// the amount of types in the type tree.
+//
+// This test ensures that rust can handle
+// deeply nested type trees with a lot
+// of duplicated subtrees.
+
+fn dup(f: impl Fn(i32) -> i32) -> impl Fn(i32) -> i32 {
+    move |a| f(a * 2)
+}
+
+fn main() {
+    let f = |a| a;
+
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+
+    // Compiler dies around here if it tries
+    // to walk the tree exhaustively.
+
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+    let f = dup(f);
+
+    println!("Type size was at least {}", f(1));
+}