Add test case for large number of closures within one codegen unit

src/test/run-pass/myriad-closures.rs

@@ -0,0 +1,48 @@
+// Copyright 2016 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.
+
+// This test case tests whether we can handle code bases that contain a high
+// number of closures, something that needs special handling in the MingGW
+// toolchain.
+// See https://github.com/rust-lang/rust/issues/34793 for more information.
+
+// Expand something exponentially
+macro_rules! go_bacterial {
+    ($mac:ident) => ($mac!());
+    ($mac:ident 1 $($t:tt)*) => (
+        go_bacterial!($mac $($t)*);
+        go_bacterial!($mac $($t)*);
+    )
+}
+
+macro_rules! mk_closure {
+    () => ({
+        let c = |a: u32| a + 4;
+        let _ = c(2);
+    })
+}
+
+macro_rules! mk_fn {
+    () => {
+        {
+            fn function() {
+                // Make 16 closures
+                go_bacterial!(mk_closure 1 1 1 1);
+            }
+            let _ = function();
+        }
+    }
+}
+
+fn main() {
+    // Make 2^12 functions, each containing 16 closures,
+    // resulting in 2^16 closures overall.
+    go_bacterial!(mk_fn 1 1 1 1  1 1 1 1  1 1 1 1);
+}