Revision 49270c41-4403-45c2-bd43-e531e3fc8977 - Code Golf Stack Exchange

# [Haskell], line length 6, <s>400</s> 343 bytes

<!-- language-all: lang-hs -->

 {main=
 putStr
 $s++((
 ++
 ":\n")
 .show
 =<<s)
 ++
 "[]}";
 s='{':
 'm':
 'a':
 'i':
 'n':
 '=':
 '\n':
 'p':
 'u':
 't':
 'S':
 't':
 'r':
 '\n':
 '$':
 's':
 '+':
 '+':
 '(':
 '(':
 '\n':
 '+':
 '+':
 '\n':
 '"':
 ':':
 '\\':
 'n':
 '"':
 ')':
 '\n':
 '.':
 's':
 'h':
 'o':
 'w':
 '\n':
 '=':
 '<':
 '<':
 's':
 ')':
 '\n':
 '+':
 '+':
 '\n':
 '"':
 '[':
 ']':
 '}':
 '"':
 ';':
 '\n':
 's':
 '=':
 []}

[Try it online!][TIO-jduc9bp7] I'm not aware of a way around `putStr`, thus the line length of 6. The outer curly braces allow to get rid of the otherwerwise required indention after a newline within a single declaration.

[Haskell]: https://www.haskell.org/
[TIO-jduc9bp7]: https://tio.run/##bdBLCoQwDAbgfY5RBJWCB1B7CpfqoosBZXxhFBfi2ev8lUlhmM1HmqRJaWf5/RoG587R9pOhZd@qbaWItU4S0ppU3kwqpYy7@SBTlpz6bN1eqiA28RnnFI/Agh5MwIDGhwvYwQYqidbQEwEGWkiEpydUnrMCuT83stcn09CUyeAOzOAIZf/MUuCf239X1qAFl@SK0MPfuZ9Pcu4G "Haskell – Try It Online"