feat(tvix/nix-compat-derive): Add deriver for NixDeserialize r/8586

This adds a nix-compat-derive derive crate that implements a deriver
for NixDeserialize implementations. This is to reduce the amount of
code needed to implement deserialization for all the types used by
the Nix daemon protocol.

Change-Id: I484724b550e8a1d5e9adad9555d9dc1374ae95c2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12022
Autosubmit: Brian Olsen <me@griff.name>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 32 insertions, 0 deletions

diff --git a/tvix/nix-compat-derive/src/internal/symbol.rs b/tvix/nix-compat-derive/src/internal/symbol.rs
new file mode 100644
index 000000000000..ed3fe304eb5d
--- /dev/null
+++ b/tvix/nix-compat-derive/src/internal/symbol.rs
@@ -0,0 +1,32 @@
+use std::fmt;
+
+use syn::Path;
+
+#[derive(Copy, Clone)]
+pub struct Symbol(&'static str);
+
+pub const NIX: Symbol = Symbol("nix");
+pub const VERSION: Symbol = Symbol("version");
+pub const DEFAULT: Symbol = Symbol("default");
+pub const FROM: Symbol = Symbol("from");
+pub const TRY_FROM: Symbol = Symbol("try_from");
+pub const FROM_STR: Symbol = Symbol("from_str");
+pub const CRATE: Symbol = Symbol("crate");
+
+impl PartialEq<Symbol> for Path {
+    fn eq(&self, word: &Symbol) -> bool {
+        self.is_ident(word.0)
+    }
+}
+
+impl<'a> PartialEq<Symbol> for &'a Path {
+    fn eq(&self, word: &Symbol) -> bool {
+        self.is_ident(word.0)
+    }
+}
+
+impl fmt::Display for Symbol {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(self.0)
+    }
+}