Refactor type variable counter to be shared

tests/repl.rs

@@ -0,0 +1,57 @@
+use myc::ast::environment::Environment;
+use myc::ast::types::Value;
+
+#[test]
+fn repl_preserves_variable_bindings() {
+    let env = Environment::new();
+
+    let r1 = env.run_script("(def x 42)");
+    assert!(r1.is_ok(), "def should succeed: {:?}", r1.err());
+
+    let r2 = env.run_script("(+ x 1)");
+    assert_eq!(r2.unwrap(), Value::Int(43));
+}
+
+#[test]
+fn repl_preserves_function_bindings() {
+    let env = Environment::new();
+
+    let r1 = env.run_script("(def double (fn [n] (* n 2)))");
+    assert!(r1.is_ok(), "def fn should succeed: {:?}", r1.err());
+
+    let r2 = env.run_script("(double 21)");
+    assert_eq!(r2.unwrap(), Value::Int(42));
+}
+
+#[test]
+fn repl_function_uses_prior_variable() {
+    let env = Environment::new();
+
+    env.run_script("(def x 10)").unwrap();
+    env.run_script("(def double (fn [n] (* n 2)))").unwrap();
+
+    let result = env.run_script("(double x)");
+    assert_eq!(result.unwrap(), Value::Int(20));
+}
+
+#[test]
+fn repl_reassign_variable() {
+    let env = Environment::new();
+
+    env.run_script("(def x 1)").unwrap();
+    env.run_script("(assign x 99)").unwrap();
+
+    let result = env.run_script("x");
+    assert_eq!(result.unwrap(), Value::Int(99));
+}
+
+#[test]
+fn repl_macro_from_prior_call() {
+    let env = Environment::new();
+
+    env.run_script("(macro unless [c body] `(if ~c ... ~body))")
+        .unwrap();
+
+    let result = env.run_script(r#"(unless false "yes")"#);
+    assert_eq!(result.unwrap(), Value::Text("yes".into()));
+}