Add test for the bug I just caused

Author: amandasystems

tests/ui/borrowck/static-trait-bound-lost-closure.rs

@@ -0,0 +1,54 @@
+// This test is a reduced version of a bug introduced during work on type-tests for Polonius.
+// The underlying problem is that the 'static bound is lost for a closure that is threaded
+// deeply enough, causing an error.
+// The bug was first observed in exr-1.4.1/src/image/read/mod.rs:124:5 during perf test.
+
+//@ check-pass
+
+use std::marker::PhantomData;
+
+struct ReadAllLayers<ReadChannels> {
+    px: PhantomData<ReadChannels>,
+}
+
+trait ReadLayers<'s> {}
+
+impl<'s, C> ReadLayers<'s> for ReadAllLayers<C> where C: ReadChannels<'s> {}
+
+fn make_builder<A, Set, Pixels>(
+    _: Set,
+) -> ReadAllLayers<CollectPixels<A, Pixels, Set>>
+where
+    Set: Fn(&mut Pixels),
+{
+    todo!()
+}
+
+struct CollectPixels<Pixel, PixelStorage, SetPixel> {
+    px: PhantomData<(SetPixel, Pixel, PixelStorage)>,
+}
+
+impl<'s, PixelStorage, SetPixel: 's> ReadChannels<'s>
+    for CollectPixels<usize, PixelStorage, SetPixel>
+where
+    SetPixel: Fn(&mut PixelStorage),
+{
+}
+
+trait ReadChannels<'s> {}
+
+fn from_file<L>(_: L)
+where
+    for<'s> L: ReadLayers<'s>,
+{
+}
+
+pub fn read_all_rgba_layers_from_file<Set: 'static, Pixels: 'static>(
+    set_pixel: Set,
+) where
+    Set: Fn(&mut Pixels),
+{
+    from_file(make_builder(set_pixel)); // Error triggered.
+}
+
+pub fn main() {}