[derive] Emit #[allow(deprecated)] in derived code

Makes progress on #553, although we still need to figure out how to
reproduce the bug that caused that issue in the first place, and add a
test that exercises the same behavior (ie, fails without this commit).

Cargo.toml

@@ -15,7 +15,7 @@
 [package]
 edition = "2021"
 name = "zerocopy"
-version = "0.7.15"
+version = "0.7.16"
 authors = ["Joshua Liebow-Feeser <[email protected]>"]
 description = "Utilities for zero-copy parsing and serialization"
 license = "BSD-2-Clause OR Apache-2.0 OR MIT"
@@ -45,7 +45,7 @@ simd-nightly = ["simd"]
 __internal_use_only_features_that_work_on_stable = ["alloc", "derive", "simd"]
 
 [dependencies]
-zerocopy-derive = { version = "=0.7.15", path = "zerocopy-derive", optional = true }
+zerocopy-derive = { version = "=0.7.16", path = "zerocopy-derive", optional = true }
 
 [dependencies.byteorder]
 version = "1.3"
@@ -56,7 +56,7 @@ optional = true
 # zerocopy-derive remain equal, even if the 'derive' feature isn't used.
 # See: https://github.com/matklad/macro-dep-test
 [target.'cfg(any())'.dependencies]
-zerocopy-derive = { version = "=0.7.15", path = "zerocopy-derive" }
+zerocopy-derive = { version = "=0.7.16", path = "zerocopy-derive" }
 
 [dev-dependencies]
 assert_matches = "1.5"
@@ -71,4 +71,4 @@ testutil = { path = "testutil" }
 # CI test failures.
 trybuild = { version = "=1.0.85", features = ["diff"] }
 # In tests, unlike in production, zerocopy-derive is not optional
-zerocopy-derive = { version = "=0.7.15", path = "zerocopy-derive" }
+zerocopy-derive = { version = "=0.7.16", path = "zerocopy-derive" }

zerocopy-derive/Cargo.toml

@@ -9,7 +9,7 @@
 [package]
 edition = "2021"
 name = "zerocopy-derive"
-version = "0.7.15"
+version = "0.7.16"
 authors = ["Joshua Liebow-Feeser <[email protected]>"]
 description = "Custom derive for traits from the zerocopy crate"
 license = "BSD-2-Clause OR Apache-2.0 OR MIT"

zerocopy-derive/src/lib.rs

@@ -617,6 +617,9 @@ fn impl_block<D: DataExt>(
     });
 
     quote! {
+        // TODO(#553): Add a test that generates a warning when
+        // `#[allow(deprecated)]` isn't present.
+        #[allow(deprecated)]
         unsafe impl < #(#params),* > zerocopy::#trait_ident for #type_ident < #(#param_idents),* >
         where
             #(#bounds,)*