https://issues.dlang.org/show_bug.cgi?id=20543
Issue ID: 20543
Summary: Need a way to get the default initializers in an
aggregation
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P1
Component: dmd
Assignee: [email protected]
Reporter: [email protected]
Currently there are no traits to extract default initializers out of an
aggregate type.
For example:
-----
struct S
{
int x = 1;
int y = 0;
int z;
}
-----
There is a workaround: Use S.init to retrieve default values.
However, it is not reliable. Because S.init == S(1, 0, 0), but in fact 'z' does
not have a *user-provided* initializer, it only has an initializer due to
T.init.
This distinction is important for things like Configuration structures.
I propose a simple API: __traits(hasInitializer, ...). Then, it can be composed
with fairly simply:
static if (__traits(hasInitializer, S.x))
doSomething(S.init.x);
static if (!__traits(hasInitializer, S.z))
doSomethingElse();
--
