Haskell build with unresolved type family

build.md

TortueLama12.hs:14:1: warning: [-Wmissing-signatures]
    Top-level binding with no type signature:
      v :: Foo (Bar Float Float)
   |
14 | v = (Foo @Float) `frob` (Foo @Float)

Bar Float Float does not exists, and yet it typecheck.

More, if I add Bar _ _ = TypeError (Text "nice message") in the type family, it fails as expected.

TortueLama12.hs

{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeApplications #-}

data Foo k = Foo

type family Bar a b where
  Bar Int Int = Int

frob :: Foo k -> Foo k' -> Foo (Bar k k')
frob Foo Foo = Foo

v = (Foo @Float) `frob` (Foo @Float)