From 0eacf2cb240606343284a2d38b0f54b6028b134d Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Fri, 21 Dec 2018 15:08:33 +0100
Subject: [PATCH] Sidestep ICE in `FieldPlacement::count` by not calling it
 when count will not fit in host's usize.

---
 src/librustc/ty/layout.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index f4506c8e819..2bc352d1d99 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -1852,7 +1852,11 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
                 return Ok(None);
             }
         }
-        if let FieldPlacement::Array { .. } = layout.fields {
+        if let FieldPlacement::Array { count: original_64_bit_count, .. } = layout.fields {
+            // rust-lang/rust#57038: avoid ICE within FieldPlacement::count when count too big
+            if original_64_bit_count > usize::max_value() as u64 {
+                return Err(LayoutError::SizeOverflow(layout.ty));
+            }
             if layout.fields.count() > 0 {
                 return self.find_niche(layout.field(self, 0)?);
             } else {