For a motivational example I propose a piece of code using a library https://github.com/typeable/schematic, which defines a fancy record-like object and requires some type annotations:

jsonExample = withRepr @SchemaExample
   $  field @"foo" [12]
   :& field @"bar" (Just "bar")
   :& RNil

By using the same function as an infix operator, it may be possible to rewrite it to something along the lines of

(.=) = field

jsonExample = withRepr @SchemaExample
   $  @"foo" .= [12]
   :& @"bar" .= (Just "bar")
   :& RNil

To do that, we'll need to associate a type application with the function to the right of it. I imagine it'll introduce ambiguity to the parser, but it can be dealt with by allowing a different syntactical construct for a right type application. Haven't checked with a grammar, but it can be something like this:

jsonExample = withRepr @SchemaExample
   $  "foo"@ .= [12]
   :& "bar"@ .= (Just "bar")
   :& RNil