Add regression test for issue 22443.

Fix #22443.

Author: pnkfelix

src/test/compile-fail/dropck_no_diverge_on_nonregular_1.rs

@@ -0,0 +1,37 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Issue 22443: Reject code using non-regular types that would
+// otherwise cause dropck to loop infinitely.
+
+use std::marker::PhantomData;
+
+struct Digit<T> {
+    elem: T
+}
+
+struct Node<T:'static> { m: PhantomData<&'static T> }
+
+
+enum FingerTree<T:'static> {
+    Single(T),
+    // Bug report said Digit after Box would stack overflow (versus
+    // Digit before Box; see dropck_no_diverge_on_nonregular_2).
+    Deep(
+        Box<FingerTree<Node<T>>>,
+        Digit<T>,
+        )
+}
+
+fn main() {
+    let ft = //~ ERROR overflow while adding drop-check rules for FingerTree
+        FingerTree::Single(1);
+    //~^ ERROR overflow while adding drop-check rules for FingerTree
+}

src/test/compile-fail/dropck_no_diverge_on_nonregular_2.rs

@@ -0,0 +1,36 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Issue 22443: Reject code using non-regular types that would
+// otherwise cause dropck to loop infinitely.
+
+use std::marker::PhantomData;
+
+struct Digit<T> {
+    elem: T
+}
+
+struct Node<T:'static> { m: PhantomData<&'static T> }
+
+enum FingerTree<T:'static> {
+    Single(T),
+    // Bug report said Digit before Box would infinite loop (versus
+    // Digit after Box; see dropck_no_diverge_on_nonregular_1).
+    Deep(
+        Digit<T>,
+        Box<FingerTree<Node<T>>>,
+        )
+}
+
+fn main() {
+    let ft = //~ ERROR overflow while adding drop-check rules for FingerTree
+        FingerTree::Single(1);
+    //~^ ERROR overflow while adding drop-check rules for FingerTree
+}

src/test/compile-fail/dropck_no_diverge_on_nonregular_3.rs

@@ -0,0 +1,46 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Issue 22443: Reject code using non-regular types that would
+// otherwise cause dropck to loop infinitely.
+//
+// This version is just checking that we still sanely handle a trivial
+// wrapper around the non-regular type. (It also demonstrates how the
+// error messages will report different types depending on which type
+// dropck is analyzing.)
+
+use std::marker::PhantomData;
+
+struct Digit<T> {
+    elem: T
+}
+
+struct Node<T:'static> { m: PhantomData<&'static T> }
+
+enum FingerTree<T:'static> {
+    Single(T),
+    // According to the bug report, Digit before Box would infinite loop.
+    Deep(
+        Digit<T>,
+        Box<FingerTree<Node<T>>>,
+        )
+}
+
+enum Wrapper<T:'static> {
+    Simple,
+    Other(FingerTree<T>),
+}
+
+fn main() {
+    let w = //~ ERROR overflow while adding drop-check rules for core::option
+        Some(Wrapper::Simple::<u32>);
+    //~^ ERROR overflow while adding drop-check rules for core::option::Option
+    //~| ERROR overflow while adding drop-check rules for Wrapper
+}