On Thursday, 25 September 2014 at 22:11:20 UTC, Mathias LANG
wrote:
I'm a bit puzzled with the following behavior:
----
import std.typetuple, std.traits;
struct UDAStruct {
string identifier;
}
class MyClass {
@(UDAStruct("p1"), UDAStruct("p2"), UDAStruct("P3")) // P3
is a typo
void func(int p1, string p2, float p3) {}
}
unittest {
alias Func = MyClass.func;
enum ParamNames = ParameterIdentifierTuple!Func;
enum ParamAttr = __traits(getAttributes, Func);
foreach (attr; ParamAttr) {
template CmpName(string PName) {
pragma(msg, "Instantiated for: "~PName);
enum CmpName = (PName == attr.identifier);
}
pragma(msg, "Current attr is: "~attr.identifier);
static assert(anySatisfy!(CmpName, ParamNames));
}
// Foreach does introduce a scope, as this produce no
compile time error.
template CmpName(string test) { enum CmpName = test; }
static assert(CmpName!"?" == "?");
}
void main() {}
----
The output is (FE 2.066 & 2.065 tested):
148 geod24@barsoom2 ~ % dmd -unittest -run test.d
Current attr is: p1
Instantiated for: p1
Instantiated for: p2
Instantiated for: p3
Current attr is: p2
Current attr is: P3
Obviously one call tell it's not what I expected. It looks like
DMD is reusing the instantiations of the template of the first
loop for p2 and P3.
The 2 lines at the end check that foreach does introduce a
scope, but it behaves differently than what we're use to.
Is there a way around this ?
I tried to move CmpName outside the loop, then declare `alias
Cmp(string x) = CmpName(attr, x);` in the loop, but it doesn't
help (I guess the same thing happens?).
a way around this is not to use anySatisfy nor the template, for
example this works as expected:
import std.typetuple, std.traits;
struct UDAStruct {
string identifier;
}
class MyClass {
@(UDAStruct("p1"), UDAStruct("p2"), UDAStruct("P3")) // P3
isa typo
void func(int p1, string p2, float p3) {}
}
------
void main(string[] args){
alias Func = MyClass.func;
enum ParamNames = ParameterIdentifierTuple!Func;
enum ParamAttr = __traits(getAttributes, Func);
foreach(i,attr; ParamAttr) {
static assert(attr.identifier == ParamNames[i],
attr.identifier);
}
}
------
which is less abstruse. However I don't know if it has hurted
your eyes too but the output lines order shows there is a problem
too:
Current attr is: p1
Instantiated for: p1
Instantiated for: p2
Instantiated for: p3
Current attr is: p2
Current attr is: P3
instead of
Current attr is: p1
Instantiated for: p1
Current attr is: p2
Instantiated for: p2
Current attr is: P3
Instantiated for: p3
o!o
