style tags compile even without a value in some cases

[evbo]

This compiles and probably shouldn't in case someone accidentally adds a style tag and forgets a value for it, causing runtime failure:

div()(
  div(style := /*what if this is a dangerous typo? compiler should catch it!*/
    h3(style := js.Dynamic.literal("marginBottom" -> 20))("no idea!"),
    "why this compile?!"
  )
)

Originally reported on gitter: https://gitter.im/shadaj/slinky?at=60c608fad855766185d5a4a2

[shadaj]

Ah, style is defined to take a js.Object (so that js.Dynamic.literal can be used), but ReactElement is also a js.Object, so it can be used there instead. The ideal solution would be to change style to take a js.Dictionary, but unfortunately then we lose the literal syntax.