Avoid parse error occurred when the field name generated by TH matches any of Haskell keywords

[ccycle]

To avoid the problem that GHC fails compiling due to parse error when the field name generated by Template Haskell matches any of Haskell keywords, this PR fixes mkRecordName to suffix _ if the field name matches any of keywords.

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[parsonsmatt]

Thanks for writing this up! One minor performance quibble.

At a future point, it would be nice to customize this behavior.

Since anyone writing type as a field name currently will receive GHC error, I think we can safely call this a bugfix. Mind doing a patch version bump and adding a changelog notice?

[parsonsmatt]

Lots of list lookups like this is pretty inefficient - would prefer to see a Set lookup

Suggested change

	avoidKeyword name = if name `elem` keywords then name ++ "_" else name
	keywords :: [Text]
	keywords =
	["case","class","data","default","deriving","do","else"
	,"if","import","in","infix","infixl","infixr","instance","let","module"
	,"newtype","of","then","type","where","_"
	,"foreign"
	]
	avoidKeyword name = if name `Set.member` haskellKeywords then name ++ "_" else name
	haskellKeywords :: Set Text
	haskellKeywords = Set.fromList
	["case","class","data","default","deriving","do","else"
	,"if","import","in","infix","infixl","infixr","instance","let","module"
	,"newtype","of","then","type","where","_"
	,"foreign"
	]

Floating it to the top-level ensures we aren't constructing the Set for each call to mkRecordName, though I would guess GHC is capable of performing that optimization on it's own

[ccycle]

Thank you for your review, I changed the suggested part and added a notice to bump up a patch version in ChangeLog.

[parsonsmatt]

awesome, thanks! I'll release this today.