Add logical xor operator (#7242)

We already have the binary `bit-xor` and the shortcircuiting logical
`or`(`||`) and `and`(`&&`).
This introduces `xor` as a compact form for both brevity and clarity.
You can express the operation through `not`/`and`/`or` with a slight
risk of introducing bugs through typos.

Operator precedence

`and` > `xor` > `or`

Added logic and precedence tests.

src/tests/test_engine.rs

@@ -246,6 +246,11 @@ fn shortcircuiting_or() -> TestResult {
     run_test(r#"true || (5 / 0; false)"#, "true")
 }
 
+#[test]
+fn nonshortcircuiting_xor() -> TestResult {
+    run_test(r#"true xor (print "hello"; false) | ignore"#, "hello")
+}
+
 #[test]
 fn open_ended_range() -> TestResult {
     run_test(r#"1.. | first 100000 | length"#, "100000")

src/tests/test_math.rs

@@ -55,6 +55,16 @@ fn or() -> TestResult {
     run_test("true || false", "true")
 }
 
+#[test]
+fn xor_1() -> TestResult {
+    run_test("false xor true", "true")
+}
+
+#[test]
+fn xor_2() -> TestResult {
+    run_test("true xor true", "false")
+}
+
 #[test]
 fn bit_xor() -> TestResult {
     run_test("4 bit-xor 4", "0")

src/tests/test_parser.rs

@@ -430,3 +430,15 @@ fn date_literal() -> TestResult {
 fn and_and_or() -> TestResult {
     run_test(r#"true and false or true"#, "true")
 }
+
+#[test]
+fn and_and_xor() -> TestResult {
+    // Assumes the precedence NOT > AND > XOR > OR
+    run_test(r#"true and true xor true and false"#, "true")
+}
+
+#[test]
+fn or_and_xor() -> TestResult {
+    // Assumes the precedence NOT > AND > XOR > OR
+    run_test(r#"true or false xor true or false"#, "true")
+}