User Defined Attributes

[Adam D. Ruppe]

On Tuesday, 6 November 2012 at 07:55:51 UTC, Walter Bright wrote:
> User Defined Attributes (UDA) are compile time expressions that 
> can be attached to a declaration.

Hmmm, it didn't work on the most important place for my use case, 
function parameters:

void a(["test"] int foo) {
     pragma(msg, __traits(getAttributes, foo));
}

test.d(1): Error: basic type expected, not [
test.d(1): Error: found 'int' when expecting ')'
test.d(1): Error: semicolon expected following function 
declaration
test.d(1): Error: no identifier for declarator foo
test.d(1): Error: semicolon expected, not ')'
test.d(1): Error: Declaration expected, not ')'



The reason why this is important to me is I have a nice automatic 
form builder given a function signature. I'd like to add things 
like hints about the params that my existing code can take a look 
at.


(a problem that might remain is being able to reference the 
parameters outside... I use a ParameterTypeTuple and .stringof 
right now but that probably won't work for getAttributes. But we 
can always solve that later.)