feat(tvix/eval): Record formals on lambda r/5153

In preparation for both implementing the `functionArgs` builtin and
adding support for validating closed formals, record information about
the formal arguments to a function *on the Lambda itself*. This may seem
a little odd for the purposes of just closed formal checking, but is
something we have to have anyway for builtins.functionArgs so I figured
I'd do it this way to kill both birds with one stone.

Change-Id: Ie3770a607bf352a1eb395c79ca29bb25d5978cd8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7001
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

1 files changed, 7 insertions, 0 deletions

diff --git a/tvix/eval/src/value/string.rs b/tvix/eval/src/value/string.rs
index d146ee4cec..4caef653f2 100644
--- a/tvix/eval/src/value/string.rs
+++ b/tvix/eval/src/value/string.rs
@@ -1,5 +1,6 @@
 //! This module implements Nix language strings and their different
 //! backing implementations.
+use rnix::ast;
 use smol_str::SmolStr;
 use std::ffi::OsStr;
 use std::hash::Hash;
@@ -55,6 +56,12 @@ impl From<SmolStr> for NixString {
     }
 }
 
+impl From<ast::Ident> for NixString {
+    fn from(ident: ast::Ident) -> Self {
+        ident.ident_token().unwrap().text().into()
+    }
+}
+
 impl Hash for NixString {
     fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
         self.as_str().hash(state)