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// REQUIRED_ARGS: -o-
/*
TEST_OUTPUT:
---
---
*/
mixin template Helpers()
{
static if (is(Flags!Move))
{
Flags!Move flags;
}
else
{
pragma(msg, "X: ", __traits(derivedMembers, Flags!Move));
}
}
template Flags(T)
{
mixin({
int defs = 1;
foreach (name; __traits(derivedMembers, Move))
{
defs++;
}
if (defs)
{
return "struct Flags { bool x; }";
}
else
{
return "";
}
}());
}
struct Move
{
int a;
mixin Helpers!();
}
enum a7815 = Move.init.flags;
/+
This originally was an invalid case:
When the Move struct member is analyzed:
1. mixin Helpers!() is instantiated.
2. In Helpers!(), static if and its condition is(Flags!Move)) evaluated.
3. In Flags!Move, string mixin evaluates and CTFE lambda.
4. __traits(derivedMembers, Move) tries to see the member of Move.
4a. mixin Helpers!() member is analyzed.
4b. `static if (is(Flags!Move))` in Helpers!() is evaluated
4c. The Flags!Move instantiation is already in progress, so it cannot be resolved.
4d. `static if` fails because Flags!Move cannot be determined as a type.
5. __traits(derivedMembers, Move) returns a 1-length tuple("a").
6. The lambda in Flags!Move returns a string "struct Flags {...}", then
Flags!Move is instantiated to a new struct Flags.
7. Finally Move struct does not have flags member, then the `enum a7815`
definition will fail in its initializer.
Now, static if will behave like a string mixin: it is invisible during its own expansion.
+/
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