Deduce types when a function is applied to a record selector

[julianhyde]

Deduce types when a function is applied to a record selector. For example, map #x [{x=1, y=2}, {x=2, y=3}] applies the map function to the record selector #x.

The record selector has a function type {x: something, ...} -> something. When the type resolver has deduced the argument type, in this case {x: int, y: int}, we can deduce what something is.

So we can deduce that #x has type {x: int, y: int} -> int, and the expression map #x [{x=1, y=2}, {x=2, y=3}] has type int list.

[julianhyde]

Fixed in 73992cd.