Tests for :let.  vim: set ft=vim ts=8 :

STARTTEST
:so small.vim
:set runtimepath+=./sautest
:" Test to not autoload when assigning.  It causes internal error.
:try
:  let Test104#numvar = function('tr')
:  $put ='OK: ' . string(Test104#numvar)
:catch
:  $put ='FAIL: ' . v:exception
:endtry
:let a = 1
:let b = 2
:for letargs in ['a b', '{0 == 1 ? "a" : "b"}', '{0 == 1 ? "a" : "b"} a', 'a {0 == 1 ? "a" : "b"}']
:  try
:    redir => messages
:    execute 'let' letargs
:    redir END
:    $put ='OK:'
:    $put =split(substitute(messages, '\n', '\0  ', 'g'), '\n')
:  catch
:    $put ='FAIL: ' . v:exception
:    redir END
:  endtry
:endfor
:/^Results/,$wq! test.out
ENDTEST

Results of test104: