Inconsistent field serialization

[liveh2o]

I'm seeing some inconsistencies in how we handle field serialization for different field types, which seems wrong.

Given the following definition:

message Account {
  optional double balance = 1
  optional int64 balance_updated_at = 2  
  optional int64 transactions_count = 3
}

Protobuf gladly accepts a string for double fields, presumably because strings respond to to_f:

2.2.0 > a = Account.new
=> #<Account balance=0.0 transactions_count=0 balance_updated_at=0
2.2.0 > a.balance = "123"
=> 123.0 

However, it does not accept a string for integer fields, even though strings respond to to_i:

2.2.0 > a = Account.new
=> #<Account balance=0.0 transactions_count=0 balance_updated_at=0
2.2.0 > a.transactions_count = "1"
TypeError: Unacceptable value 1 for field transactions_count of type Protobuf::Field::Int64Field

Curiously, it will accept a time for integer fields, but does not convert it to an integer, even though it does so with strings on double fields:

2.2.0 > a = Account.new
=> #<Account balance=0.0 transactions_count=0 balance_updated_at=0
2.2.0 > a.balance_updated_at = Time.current
=> Tue, 24 Feb 2015 20:09:08 UTC +00:00

This, of course, becomes a problem once it attempts to encode the message:

2.2.0 > a = Account.new(:balance_updated_at => Time.current)
=> #<Account balance=0.0 transactions_count=0 balance_updated_at=Tue, 24 Feb 2015 20:09:08 UTC +00:00
2.2.0 > a.encode
NoMethodError: undefined method `&' for Tue, 24 Feb 2015 21:17:58 UTC +00:00:Time
  ...

There may actually be two issues here, but I wanted to document the inconsistent behavior so we can start discussion a possible solution. If we need to split this into two, I'm happy to do so.

[localshred]

Wow, that is shocking. Definitely should get some test cases in place for these.