While yam's rule of thumb (viz. that if you can add salt to it, it's savory, if you can add sugar to it, it's not) is appropriate for the western palate and cuisine, it flounders and drowns in many a non-western context, where food predilections are rather different.
Well I remember the first time I experienced this apparent category confusion: peanut butter, eaten as a child, bought by my mother from a market in Ghana. Burning mouth, wide shocked eyes. It contained quite a bit of hot chili. They use it, it turns out, for stew. Not toast.
Much later, fresh watermelon in Mexico. Sprinkled with salt and chili. That was a surprise.
And Thai food, a cuisine with which I am intimately acquainted, just blows those thumbs right out of the water. Not only a mixture of sugar, salt, and chili on your pineapple, canteloupe, watermelon. Also, salt in your orange juice. Sugar on your pad thai. Fish sauce on your green mango. Does it never end?
It's a topsy-turvy world indeed out there, fellow gourmands.