From 93c0bb9ce225b191f4993114ab821c6091195863 Mon Sep 17 00:00:00 2001
From: NetterSilver <133535268+Silvertree2010@users.noreply.github.com>
Date: Thu, 22 Oct 2026 09:20:19 +0000
Subject: [PATCH] =?UTF-8?q?Keep=20`not=20<var>`=20from=20reading=20back=20?=
 =?UTF-8?q?as=20a=20variable=20named=20"not=20=E2=80=A6"?=
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Found while testing crates/doc/src/proto_expr.rs:172 (display writes `not {x}` with a bare var_ref) with crates/doc/src/proto_expr_parse.rs:262 (not() checks variable names before the `not` keyword)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 crates/doc/src/proto_expr.rs             |  7 ++++++-
 crates/doc/src/proto_expr_parse_tests.rs | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/crates/doc/src/proto_expr.rs b/crates/doc/src/proto_expr.rs
index f4404dc7..d5441b28 100644
--- a/crates/doc/src/proto_expr.rs
+++ b/crates/doc/src/proto_expr.rs
@@ -169,7 +169,12 @@ impl Expr {
                     })
                     .collect();
                 match (op, parts.as_slice()) {
-                    (ExprOp::Not, [x]) => format!("not {x}"),
+                    // `not done` reads as a variable named "not done" if there is one: then
+                    // `not (done)`.
+                    (ExprOp::Not, [x]) => {
+                        let bare = format!("not {x}");
+                        if x.starts_with('(') || Expr::parse(&bare, vars).is_ok_and(|e| e == *self) { bare } else { format!("not ({x})") }
+                    }
                     (ExprOp::Negate, [x]) => format!("-{x}"),
                     _ => parts.join(&format!(" {} ", op.symbol())),
                 }
diff --git a/crates/doc/src/proto_expr_parse_tests.rs b/crates/doc/src/proto_expr_parse_tests.rs
index e106121d..e2d4592a 100644
--- a/crates/doc/src/proto_expr_parse_tests.rs
+++ b/crates/doc/src/proto_expr_parse_tests.rs
@@ -195,3 +195,27 @@ fn names_that_look_like_literals_read_back_as_variables() {
     assert_eq!(parse("1"), n(1.0));
     assert_eq!(parse("\"q\""), Expr::Value(VariableValue::String("q".into())));
 }
+
+#[test]
+fn not_of_a_variable_reads_back_when_a_name_starts_with_not() {
+    use ExprOp::*;
+    let mut v = vars();
+    let b = v.variables.iter().find(|x| x.id == "b").unwrap().clone();
+    for (id, name) in [("done", "done"), ("nd", "not done")] {
+        let mut x = b.clone();
+        x.id = id.into();
+        x.name = name.into();
+        v.variables.push(x);
+    }
+    let not_done = Expr::op(Not, vec![Expr::var("done")]);
+    for e in [
+        not_done.clone(),
+        Expr::op(And, vec![Expr::var("b"), not_done.clone()]),
+        Expr::op(Equals, vec![not_done.clone(), Expr::Value(VariableValue::Boolean(true))]),
+        Expr::op(Not, vec![not_done.clone()]),
+    ] {
+        let shown = e.display(&v);
+        assert_eq!(Expr::parse(&shown, &v), Ok(e.clone()), "shown as {shown:?}");
+    }
+    assert_eq!(Expr::op(Not, vec![Expr::var("b")]).display(&vars()), "not b-name", "plain names stay bare");
+}