From e4883341f12556277dddffd7ca7aede3b71e5483 Mon Sep 17 00:00:00 2001
From: Johnathan Van Why <jrvanwhy@google.com>
Date: Thu, 8 Aug 2019 17:28:32 -0700
Subject: [PATCH 1/2] Pin serde to a specific version, to keep compatibility
 with libtock-rs' toolchain.

The latest version of serde requires a newer toolchain. This change allows the examples to keep building, un-breaking the Travil build.
---
 Cargo.toml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Cargo.toml b/Cargo.toml
index a2b98e5e..e49e6991 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,7 +10,9 @@ linked_list_allocator = "0.6.3"
 
 [dev-dependencies]
 corepack = { version = "0.4.0", default-features = false, features = ["alloc"] }
-serde = { version = "1.0.84", default-features = false, features = ["derive"] }
+# We pin the serde version because newer serde versions may not be compatible
+# with the nightly toolchain used by libtock-rs.
+serde = { version = "=1.0.84", default-features = false, features = ["derive"] }
 
 [profile.dev]
 panic = "abort"

From 8800af2ec0608ed71699e4199d110896082bfa93 Mon Sep 17 00:00:00 2001
From: Johnathan Van Why <jrvanwhy@google.com>
Date: Thu, 8 Aug 2019 16:43:21 -0700
Subject: [PATCH 2/2] Replace TockValue's auto-derived Debug implementation
 with a hand-written implementation optimized for size.

For Google's h1b_tests application, this saves 9440 bytes in .text. The caveat is that invoking Debug on a TockValue will not format the value contained in the TockValue::Expected().

I'm blocking serde updates so that the CI passes.
---
 src/result.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/result.rs b/src/result.rs
index cfc809ca..e00f3f09 100644
--- a/src/result.rs
+++ b/src/result.rs
@@ -1,9 +1,30 @@
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone)]
 pub enum TockValue<E> {
     Expected(E),
     Unexpected(isize),
 }
 
+// Size-optimized implementation of Debug.
+impl<E: core::fmt::Debug> core::fmt::Debug for TockValue<E> {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
+        match self {
+            // Printing out the value of E would cause TockResult::unwrap() to
+            // use a &dyn core::fmt::Debug, which defeats LLVM's
+            // devirtualization and prevents LTO from removing unused Debug
+            // implementations. Unfortunately, that generates too much code
+            // bloat (several kB), so we cannot display the value contained in
+            // this TockValue.
+            TockValue::Expected(_) => f.write_str("Expected(...)"),
+
+            TockValue::Unexpected(n) => {
+                f.write_str("Unexpected(")?;
+                n.fmt(f)?;
+                f.write_str(")")
+            }
+        }
+    }
+}
+
 pub type TockResult<T, E> = Result<T, TockValue<E>>;
 
 pub trait TockResultExt<T, E>: Sized {