not everything is an expression (most notably assignments)

hi, I've been using yuescript for a little bit now so I feel pretty familiar with the language. here are some example things that I thought should have worked:

-- parens not working
if (old_val = @v) != new_val
    @v = new_val

-- working
old_val = @v
if old_val != new_val
    @v = new_val

---

-- assignment not working
lala = (fn) ->
    print "fn:", fn
    fn(math.rand!)
lala listener = (val) -> print val -- left hand expression is not assignable
lala (listener = (val) -> print val) -- syntax error

-- working
lala = (fn) ->
    print "fn:", fn
    fn(math.rand!)
listener = (val) -> print val
lala listener

---

-- iter not returned
perm = (a) ->
    co = coroutine.create ->
        permgen a, #a
        return -- necessary cause no way to specify no return
    iter = ->
        code, res = coroutine.resume co
        res

-- working
perm = (a) ->
    co = coroutine.create ->
        permgen a, #a
        return -- necessary cause no way to specify no return
    iter = ->
        code, res = coroutine.resume co
        res
    iter

-- ideally, I'd like to write:
perm = (a) ->
    co = coroutine.create !->
        permgen a, #a
    iter = ->
        code, res = coroutine.resume co
        res

---

-- doesn't consider last expression of do-statement as module value
export default module = do
	{foo: true}

-- also, it doesn't think that the assignment is an expression
module = do
	lala = {foo: true}
export default module

-- working
module = do
	lala = {foo: true}
	lala
export default module

-- also works
export default do
	{foo: true}

---

---

in general I really like the language. I've got a lot of ideas as well for improvements to the language:

• if x isnt nil (is/isnt keywords)
• type val is "function" (compiles to type(val) == "function" instead of type(val == "function"))
• type val is \function (single backslash is single word text)
• !(var) -> ... (no return)
• !-> ... (no return)
• comma on next line extends function:

  lala (v1, v1) ->
      print v1, v2
  , var1
  , var2
  

---

lastly, the online compiler is quite valuable for seeing what yue compiles to and I really like it.
however, the text area only allows me to click on the top.
this can easily be fixed by setting prism-editor__container to have min-height: 100%. (seen below)
edit: that should be 'min-height' (screenshot invalid)

cheers!

Reproduce the listed Moon examples in the online compiler and separate parser/compiler expression cases from the editor styling request. Review the language's expression and assignment handling, then verify chosen cases against generated Lua; for the UI item, inspect prism-editor__container and confirm the textarea is clickable throughout. Agree on a narrower scope before implementation.