type-fail.hoon

++  showbadcode
  |=  [code=tape]
  =+  ^=  result
    (mule |.((slap !>(.) (ream (crip code)))))
  ?:  ?=(%.y -.result)
     =+  good=p.result  :: successful!
       ;code
           ;pre: {code}
           ;pre: product => {<good>}
           ;pre: result => {~(ram re (sell good))}
       ==
  =+  error=p.result     :: Oh noes it didn't work.
    ;code
      ;pre: {code}
      ;*  %+  turn
            error
          |=  a=tank
          ^-  manx
          ;pre: error: {~(ram re a)}
    ==
++  testbadcode
  (showbadcode "=+(a=1 a)")
:: Usage example below.
;pre: {<testbadcode>}  :: this works and outputs: [[%code ~] [[%pre ~] [[%~. [%~. "=+(a=1 a)"] ~] ~] ~] [[%pre ~] [[%~. [%~. "product => "] ~] ~] [[%~. [%~. "[p=#t/@ud q=1]"] ~] ~] ~] [[%pre ~] [[%~. [%~. "result => "] ~] ~] [[%~. [%~. "1"] ~] ~] ~] ~]
;-  testbadcode :: This causes a type-fail error
;-  %-  showbadcode  """  :: This also causes a type-fail error.
                     =+  a=1
                     b
                     """