add test for local x = x

src/ast.rs

@@ -59,6 +59,13 @@ impl Location {
 	pub fn new_variable(name: impl Into<String>) -> Self {
 		Self::Variable { name: name.into() }
 	}
+
+	pub fn new_field(table: impl Into<Expression>, name: impl Into<String>) -> Self {
+		Self::Field {
+			table: Box::new(table.into()),
+			index: Box::new(Expression::new_constant(name.into())),
+		}
+	}
 }
 
 impl Expression {

src/twopass.rs

@@ -427,4 +427,36 @@ mod tests {
 		assert_eq!(ret, Some(3.into()));
 		assert_eq!(env.get("x".into()), Some(1.into()));
 	}
+
+	#[test]
+	fn test_self_assign() {
+		let testee = Function {
+			name: Some("testee".into()),
+			args: vec![],
+			body: vec![
+				Statement::Assign {
+					target: Location::new_variable("x"),
+					source: Box::new(Expression::new_constant(42)),
+				},
+				Statement::Local {
+					name: "x".into(),
+					init: Some(Box::new(Expression::new_variable("x"))),
+				},
+				Statement::Assign {
+					target: Location::new_field(Expression::new_variable("_ENV"), "x"),
+					source: Box::new(Expression::new_constant(666)),
+				},
+				Statement::Local {
+					name: "y".into(),
+					init: Some(Box::new(Expression::new_variable("x"))),
+				},
+			],
+			ret: Some(Box::new(Expression::new_variable("y"))),
+		};
+		let env = crate::types::Table::default();
+		let testee = build(&testee);
+		let ret = testee.call(Some(env.clone().into()), &[]);
+		assert_eq!(ret, Some(42.into()));
+		assert_eq!(env.get("x".into()), Some(666.into()));
+	}
 }