scanner: string interpolation with $var at the end

compiler/tests/string_interpolation_test.v

@@ -15,3 +15,15 @@ fn test_excape_dollar_in_string() {
   assert !'(\\\\${i})'.contains('i') && '(\\\\${i})'.contains('42') && '(\\\\${i})'.contains('\\\\')
   assert i==42
 }
+
+fn test_implicit_str() {
+  i := 42
+  assert 'int $i' == 'int 42'
+  assert '$i' == '42'
+
+  check := '$i' == '42'
+  assert check
+
+  text := '$i' + '42'
+  assert text == '4242'
+}