JDK 16 RFR of JDK-8071961: Add javac lint warning when a default constructor is created

[Joe Darcy]

On 7/30/2020 6:33 PM, Joe Darcy wrote:
> On 7/30/2020 11:17 AM, Alex Buckley wrote:
>> On 7/30/2020 10:15 AM, Joe Darcy wrote:
>>> On 7/30/2020 12:51 AM, Alex Buckley wrote:
>>>> On 7/29/2020 9:32 PM, Joe Darcy wrote:

[snip]


>>
> Like most javac lint warnings, this one being proposed to be triggered 
> by inclusion of a default constructor is localized in nature. From my 
> perspective, the situation being noted  is a not a separate 
> (re)compilation hazard or even indirectly an issue for the clients. 
> (From earlier in the thread, since the MANDATED information is not 
> persisted into the class file, the compiler cannot reliably warn 
> callers of a default constructor such a constructor is being called, 
> if that is a concern.) Rather, the message is to the author/maintainer 
> of class Foo being compiled -- "BTW, since you left one out, clients 
> of your class Foo will see a constructor not present in your source 
> code. Make sure your are okay with that and all it implies."
>
PS In the next iteration of the webrev,

     http://cr.openjdk.java.net/~darcy/8071961.6

the messages have been updated to

  185 javac.opt.Xlint.desc.missing-declared-ctor=\
  186     Warn about missing declared constructors in public classes in 
exported packages.

1763 # 0: symbol, 1: symbol, 2: symbol
1764 compiler.warn.missing-declared-ctor=\
1765     class {0} in exported package {1} of module {2} does not 
declare any explicit constructors, exposing a default constructor to clients

Cheers,

-Joe