1 files changed, 12 insertions, 1 deletions
diff --git a/tvix/eval/src/value/string.rs b/tvix/eval/src/value/string.rs
index 2649e00f0830..8ffbc2a5325c 100644
--- a/tvix/eval/src/value/string.rs
+++ b/tvix/eval/src/value/string.rs
@@ -135,7 +135,7 @@ impl NixString {
             // A borrowed string is unchanged and can be returned as
             // is.
             Cow::Borrowed(_) => {
-                if is_valid_nix_identifier(&escaped) {
+                if is_valid_nix_identifier(&escaped) && !is_keyword(&escaped) {
                     escaped
                 } else {
                     Cow::Owned(format!("\"{}\"", escaped))
@@ -171,6 +171,17 @@ fn nix_escape_char(ch: char, next: Option<&char>) -> Option<&'static str> {
     }
 }
 
+/// Return true if this string is a keyword -- character strings
+/// which lexically match the "identifier" production but are not
+/// parsed as identifiers.  See also cppnix commit
+/// b72bc4a972fe568744d98b89d63adcd504cb586c.
+fn is_keyword(s: &str) -> bool {
+    match s {
+        "if" | "then" | "else" | "assert" | "with" | "let" | "in" | "rec" | "inherit" => true,
+        _ => false,
+    }
+}
+
 /// Return true if this string can be used as an identifier in Nix.
 fn is_valid_nix_identifier(s: &str) -> bool {
     // adapted from rnix-parser's tokenizer.rs