added lox test files

lox.t/return/after_else.lox

@@ -0,0 +1,5 @@
+fun f() {
+  if (false) "no"; else return "ok";
+}
+
+print f(); // expect: ok

lox.t/return/after_if.lox

@@ -0,0 +1,5 @@
+fun f() {
+  if (true) return "ok";
+}
+
+print f(); // expect: ok

lox.t/return/after_while.lox

@@ -0,0 +1,5 @@
+fun f() {
+  while (true) return "ok";
+}
+
+print f(); // expect: ok

lox.t/return/at_top_level.lox

@@ -0,0 +1 @@
+return "wat"; // Error at 'return': Can't return from top-level code.

lox.t/return/in_function.lox

@@ -0,0 +1,6 @@
+fun f() {
+  return "ok";
+  print "bad";
+}
+
+print f(); // expect: ok

lox.t/return/in_method.lox

@@ -0,0 +1,8 @@
+class Foo {
+  method() {
+    return "ok";
+    print "bad";
+  }
+}
+
+print Foo().method(); // expect: ok

lox.t/return/return_nil_if_no_value.lox

@@ -0,0 +1,6 @@
+fun f() {
+  return;
+  print "bad";
+}
+
+print f(); // expect: nil