Add StableHashingContextLike to HashStable_Generic derive.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 720ace90324..d11ef5fcab2 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -1562,3 +1562,8 @@ fn lookup_line(lines: &[BytePos], pos: BytePos) -> isize {
         Err(line) => line as isize - 1
     }
 }
+
+/// Requirements for a `StableHashingContext` to be used in this crate.
+/// This is a hack to allow using the `HashStable_Generic` derive macro
+/// instead of implementing everything in librustc.
+pub trait StableHashingContextLike {}