Comment #0 by verylonglogin.reg — 2012-11-10T23:28:55Z
Function parameter types tuple retrieved with `IsExpression` contains parameter storage classes unless indexed (slicing remains storage classes).
It is not documented that typetuple can contain parameter storage classes so it may lead to unexpected behavior and looks inconsistent because `is(typetuple1 == typetuple2)` is `true` for tuples with different storage classes.
---
template TypeTuple(T...)
{ alias T TypeTuple; }
template t(alias func)
{
static if (is(typeof(func) Args == function))
{
static assert(is(Args == TypeTuple!(int, int, int, int))); // passes
pragma(msg, "Args: ", Args); // (int, ref int, out int, auto int)
pragma(msg, "Args[1..2]: ", Args[1..2]); // (ref int)
pragma(msg, "Args[1]: ", Args[1]); // int
void g1(Args[0 .. 3]) { } // void(int, ref int, out int)
pragma(msg, "typeof(g1): ", typeof(g1));
void g2(Args[3]) { } // void(int)
pragma(msg, "typeof(g2): ", typeof(g2));
void g3(Args[3 .. 4]) { } // void(auto ref int), error, line 20
}
else
static assert(0);
}
void f(T)(int, ref int, out int, auto ref T)
{
alias t!f tf;
}
void main()
{
int i;
f(0, i, i, 0);
}
---
Compiler output:
---
Args: (int, ref int, out int, auto int)
Args[1..2]: (ref int)
Args[1]: int
typeof(g1): void(int, ref int, out int)
typeof(g2): void(int)
main.d(20): Error: auto can only be used for template function parameters
main.d(29): Error: template instance main.t!(f) error instantiating
main.d(36): instantiated from here: f!(int)
main.d(36): Error: template instance main.f!(int) error instantiating
---
Comment #1 by verylonglogin.reg — 2012-11-10T23:34:15Z
Workaround to remove storage classes:
---
import std.typetuple;
template DeStorage(T) { alias T DeStorage; }
alias staticMap!(DeStorage, ArgsWithStorageClasses) Args;
---
Note, it it's not documented, that `staticMap` will use indexing (`A[x]`) instead of slicing (`A[x .. x+1]`) and in latter case this workaround will not work so you have to copy/paste `staticMap` with current behavior to you code.
Comment #2 by robert.schadek — 2024-12-13T18:02:45Z