Don't leak set/set-env/source scopes via actions (#2849)

tests/shell/pipeline/commands/internal.rs

@@ -418,6 +418,18 @@ fn set_variable() {
     assert_eq!(actual.out, "17");
 }
 
+#[test]
+fn set_doesnt_leak() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        do { set x = 5 }; echo $x
+        "#
+    );
+
+    assert!(actual.err.contains("unknown variable"));
+}
+
 #[test]
 fn set_env_variable() {
     let actual = nu!(
@@ -431,6 +443,18 @@ fn set_env_variable() {
     assert_eq!(actual.out, "hello world");
 }
 
+#[test]
+fn set_env_doesnt_leak() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        do { set-env xyz = "my message" }; echo $nu.env.xyz
+        "#
+    );
+
+    assert!(actual.err.contains("did you mean"));
+}
+
 #[cfg(feature = "which")]
 #[test]
 fn argument_invocation_reports_errors() {