1 files changed, 42 insertions, 0 deletions
diff --git a/src/test/ui/mir/issue-100476-recursion-check-blewup.rs b/src/test/ui/mir/issue-100476-recursion-check-blewup.rs
new file mode 100644
index 000000000..bc2f32f4c
--- /dev/null
+++ b/src/test/ui/mir/issue-100476-recursion-check-blewup.rs
@@ -0,0 +1,42 @@
+// check-pass
+
+// compile-flags: --emit=mir,link -O
+
+// At one point the MIR inlining, when guarding against infinitely (or even just
+// excessive) recursion, was using `ty::Instance` as the basis for its history
+// check. The problem is that when you have polymorphic recursion, you can have
+// distinct instances of the same code (because you're inlining the same code
+// with differing substitutions), causing the amount of inlining to blow up
+// exponentially.
+//
+// This test illustrates an example of that filed in issue rust#100476.
+
+#![allow(unconditional_recursion)]
+#![feature(decl_macro)]
+
+macro emit($($m:ident)*) {$(
+    // Randomize `def_path_hash` by defining them under a module with
+    // different names
+    pub mod $m {
+    pub trait Tr {
+        type Next: Tr;
+    }
+
+    pub fn hoge<const N: usize, T: Tr>() {
+        inner::<N, T>();
+    }
+
+    #[inline(always)]
+    fn inner<const N: usize, T: Tr>() {
+        inner::<N, T::Next>();
+    }
+    }
+)*}
+
+// Increase the chance of triggering the bug
+emit!(
+    m00 m01 m02 m03 m04 m05 m06 m07 m08 m09
+    m10 m11 m12 m13 m14 m15 m16 m17 m18 m19
+);
+
+fn main() { }