regression tests for problems that are exposed by mir-inlining policy that we are reverting for 1.64-beta.

Author: pnkfelix

src/test/ui/issues/issue-100550-normalization-ice-exposed-by-mir-inlining.rs

@@ -0,0 +1,39 @@
+// check-pass
+
+// compile-flags: --emit=mir,link -O
+
+// There is an ICE somewhere in type normalization, and we are hitting it during
+// the MIR inlining pass on this code.
+//
+// Long term, we should fix that ICE and change the compile-flags for this test
+// to explicitly enable MIR inlining.
+//
+// Short term, we are diabling MIR inlining for Rust 1.64-beta, so that we avoid
+// this ICE in this instance.
+
+pub trait Trait {
+    type Associated;
+}
+impl<T> Trait for T {
+    type Associated = T;
+}
+
+pub struct Struct<T>(<T as Trait>::Associated);
+
+pub fn foo<T>() -> Struct<T>
+where
+    T: Trait,
+{
+    bar()
+}
+
+#[inline]
+fn bar<T>() -> Struct<T> {
+    Struct(baz())
+}
+
+fn baz<T>() -> T {
+    unimplemented!()
+}
+
+fn main() { }

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() { }