happy-go-lucky vs slaphappy

happy-go-lucky and slaphappy both are adjectives.

Word	Noun	Adjective	Verb	Adverb
happy-go-lucky	No	Yes	No	No
slaphappy	No	Yes	No	No

As adjectives, happy-go-lucky and slaphappy are synonyms defined as:

Other synonyms of happy-go-lucky include carefree, devil-may-care, freewheeling, harum-scarum.

happy-go-lucky (adjective)	slaphappy (adjective)
cheerfully irresponsible	dazed from or as if from repeated blows
	cheerfully irresponsible