From 3c6b10c6b2777408beadee78df7a9a73c25e4ede Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20=C5=BD=C3=A1dn=C3=ADk?= <kubouch@gmail.com>
Date: Sat, 28 Jan 2023 19:55:29 +0200
Subject: [PATCH] Fix wrong VarId of $in variable (#7893)

Fixes https://github.com/nushell/nushell/issues/7872
---
 crates/nu-parser/src/parser.rs | 2 +-
 src/tests/test_engine.rs       | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/crates/nu-parser/src/parser.rs b/crates/nu-parser/src/parser.rs
index b715af9a44..c809a3d6f4 100644
--- a/crates/nu-parser/src/parser.rs
+++ b/crates/nu-parser/src/parser.rs
@@ -5995,7 +5995,7 @@ fn wrap_expr_with_collect(working_set: &mut StateWorkingSet, expr: &Expression)
     if let Some(decl_id) = working_set.find_decl(b"collect", &Type::Any) {
         let mut output = vec![];
 
-        let var_id = working_set.next_var_id();
+        let var_id = IN_VARIABLE_ID;
         let mut signature = Signature::new("");
         signature.required_positional.push(PositionalArg {
             var_id: Some(var_id),
diff --git a/src/tests/test_engine.rs b/src/tests/test_engine.rs
index dfed46dd7e..8da2be1b2c 100644
--- a/src/tests/test_engine.rs
+++ b/src/tests/test_engine.rs
@@ -365,3 +365,9 @@ fn better_operator_spans() -> TestResult {
 fn range_right_exclusive() -> TestResult {
     run_test(r#"[1, 4, 5, 8, 9] | range 1..<3 | math sum"#, "9")
 }
+
+/// Issue #7872
+#[test]
+fn assignment_to_in_var_no_panic() -> TestResult {
+    fail_test(r#"$in = 3"#, "needs to be a mutable variable")
+}