Cargo.toml: warn on unnameable types

Such types should not appear anywhere - except for sealed traits.

Previous commits removed all occurrences of such types, so now we
can enable the lint.

The one legit occurrence - a sealed trait - is marked with `#[allow]`.

scylla-cql/Cargo.toml

@@ -55,4 +55,5 @@ full-serialization = [
 ]
 
 [lints.rust]
+unnameable_types = "warn"
 unreachable_pub = "warn"

scylla-macros/Cargo.toml

@@ -18,4 +18,5 @@ quote = "1.0"
 proc-macro2 = "1.0"
 
 [lints.rust]
+unnameable_types = "warn"
 unreachable_pub = "warn"

scylla/Cargo.toml

@@ -95,5 +95,6 @@ name = "benchmark"
 harness = false
 
 [lints.rust]
+unnameable_types = "warn"
 unreachable_pub = "warn"
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(scylla_cloud_tests)'] }

scylla/src/transport/session_builder.rs

@@ -29,6 +29,10 @@ use openssl::ssl::SslContext;
 use tracing::warn;
 
 mod sealed {
+    // This is a sealed trait - its whole purpose is to be unnameable.
+    // This means we need to disable the check.
+    #[allow(unknown_lints)] // Rust 1.66 doesn't know this lint
+    #[allow(unnameable_types)]
     pub trait Sealed {}
 }
 pub trait SessionBuilderKind: sealed::Sealed + Clone {}