New Issue: Generated '--help' could print the default value of config vars

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19003, "aconsroe-hpe", "Generated '--help' could print the default value of config vars", "2022-01-14T15:28:48Z"

Using examples/hello6 as an example, using the generated --help flag gives something like:

→ chpl examples/hello6-taskpar-dist.chpl
→ ./hello6-taskpar-dist -h
...
hello6-taskpar-dist config vars:
            printLocaleName: bool
             tasksPerLocale: int(64)

As a user, it would be handy to see the default value of those config vars. Something like:

...
hello6-taskpar-dist config vars:
            printLocaleName: bool    = true
             tasksPerLocale: int(64) = 1

In this case, hello6 initializes these with a simple constant and printing them out would be straightforward.

config const printLocaleName = true;
config const tasksPerLocale = 1;

Some more complicated cases would need a different strategy. That would be things like:

config const flag = true;
config const x = if flag then 10 else 20;
config const fileOut = "myprefix" + x:string;
config const numIterations = computeGoodNumberOfIterations(x);
config const split:int;
split = x * 2;

In these cases, we would have to choose what to print. Some ideas would be:

  1. Nothing -- only print easy cases where the RHS of the init is a literal
  2. Source location -- print the filename and source line of the expression that declares the config
  3. Expression -- stringify the expression on the RHS of the init so the user could see x: int(64) = if flag then 10 else 20