On Wednesday, 20 August 2014 at 20:46:20 UTC, Paul D Anderson
wrote:
Re-compiling existing code with version 2.066 generates a lot
of errors complaining about implicit conversion to const.
Typical is this call (inside a struct with properties 1 & 2):
z.sign = x.sign ^ y.sign;
Error: None of the overloads of 'sign' are callable using
argument types bool (const), candidates are:
1) @property
@safe
bool sign() const
{
return signed;
}
2) @property
@safe
bool sign(in bool value)
{
signed = value;
return signed;
}
What changed? It ran okay with early beta versions, but not
with the release.
Paul
The problem (not obvious from the above) is that a templated type
is bringing its qualifiers into the template.
Here is a small example:
T add(T)(in T x, in T y)
{
T z;
z = x + y;
return z;
}
void main()
{
const double a = 1.0;
const double b = 2.0;
double c;
c = add(a,b);
}
Error: Cannot modify immutable expression z
---
Since a and b are const double the deduced template type is also
const double. Then when z is declared as type T it is also const.
This compiled and ran in beta 5 but not in beta 6.
If I modify the above so that declaration and assignment are
performed at the same time:
T z = x + y;
This compiles and assigns the (const double) value 3.0 to z.
After the function call c contains the double value 3.0, but it
is no longer const.
The error can be avoided by declaring z to be of type Unqual!T in
most cases.
I don't know if this is expected behavior that just wasn't
enforced before, or if this is something new. Either way I don't
like it. And I'm a little surprised I'm the only one affected by
this. I'll keep digging.
Paul
