Re: Checking the Return Type of a Template Alias Parameter in assertCTFEable
2014/02/28 23:06 Nordlöw :
>
> I have a solution to Issue 388 at
>
> https://github.com/nordlow/dmd/commits/master
>
> that works nicely for my projects.
>
> This patch however generates a handful of warnings in Phobos unittests.
>
> All of these are IMO fixable except for one which I don't know how to fix
namely the definition of assertCTFEable in exception.d
>
> I need to change this to explicitly capture the return value of the
template alias argument dg when this is non-void. My try so far was to
change
>
> version(unittest) package
> @property void assertCTFEable(alias dg)()
> {
> static assert({ dg(); return true; }());
> dg();
> }
>
> to
>
> version(unittest) package
> @property void assertCTFEable(alias dg)()
> {
> static assert
> ({
> static if (is(typeof(db()) == void)) {
> dg();
> } else {
> auto x = dg();
> }
> return true;
> }());
> static if (is(typeof(db()) == void)) {
> dg();
> } else {
> auto x = dg();
> }
> }
>
> gives the following error when in Phobos make unittest:
>
> std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
> {
> S[] r = array(repeat((S __ctmp1582 = 0;
> , __ctmp1582).this(1), 2LU));
> assert(equal(r, [(S __ctmp1591 = 0;
> , __ctmp1591).this(1), (S __ctmp1592 = 0;
> , __ctmp1592).this(1)]));
> }
> ).assertCTFEable.__lambda1.x type void is inferred from initializer
(*function ()
> {
> S[] r = array(repeat((S __ctmp1582 = 0;
> , __ctmp1582).this(1), 2LU));
> assert(equal(r, [(S __ctmp1591 = 0;
> , __ctmp1591).this(1), (S __ctmp1592 = 0;
> , __ctmp1592).this(1)]));
> }
> )(), and variables cannot be of type void
> std/exception.d(1392): Error: expression (*function ()
> {
> S[] r = array(repeat((S __ctmp1582 = 0;
> , __ctmp1582).this(1), 2LU));
> assert(equal(r, [(S __ctmp1591 = 0;
> , __ctmp1591).this(1), (S __ctmp1592 = 0;
> , __ctmp1592).this(1)]));
> }
> )() is void and has no value
>
> How can I in a general way check if dg evaluates to void or not?
Maybe:
cast(void)dg();
Kenji Hara
Re: Checking the Return Type of a Template Alias Parameter in assertCTFEable
Wonderful! Now can I request a pull for DMD and Phobos for Issue 3882. :)
Re: Checking the Return Type of a Template Alias Parameter in assertCTFEable
On Friday, 28 February 2014 at 16:13:19 UTC, Nordlöw wrote:
On Friday, 28 February 2014 at 15:03:29 UTC, John Colvin wrote:
On Friday, 28 February 2014 at 14:02:35 UTC, Nordlöw wrote:
I have a solution to Issue 388 at
https://github.com/nordlow/dmd/commits/master
that works nicely for my projects.
This patch however generates a handful of warnings in Phobos
unittests.
All of these are IMO fixable except for one which I don't
know how to fix namely the definition of assertCTFEable in
exception.d
I need to change this to explicitly capture the return value
of the template alias argument dg when this is non-void. My
try so far was to change
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert({ dg(); return true; }());
dg();
}
to
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
}
gives the following error when in Phobos make unittest:
std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
).assertCTFEable.__lambda1.x type void is inferred from
initializer (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)(), and variables cannot be of type void
std/exception.d(1392): Error: expression (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)() is void and has no value
How can I in a general way check if dg evaluates to void or
not?
Either use std.traits.ReturnType, or see from it's
implementation.
I tried
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(ReturnType!(db()) == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(ReturnType!(db()) == void)) {
dg();
} else {
auto x = dg();
}
}
but this instead fails as
std/exception.d(1392): Error: variable
std.conv.__unittestL932_18.assertCTFEable!(dg).assertCTFEable.__lambda1.x
type void is inferred from initializer dg(), and variables
cannot be of type void
std/exception.d(1392): Error: expression dg() is void and has
no value
std/exception.d(1402): Error: variable
std.conv.__unittestL932_18.assertCTFEable!(dg).assertCTFEable.x
type void is inferred from initializer dg(), and variables
cannot be of type void
std/exception.d(1402): Error: expression dg() is void and has
no value
std/conv.d(974): Error: template instance
std.conv.__unittestL932_18.assertCTFEable!(dg) error
instantiating
std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
{
assert(to(4611686018427387904LU) == "4611686018427387904");
assert(to(4294967296L) == "4294967296");
assert(to(-138L) == "-138");
}
).assertCTFEable.__lambda1.x type void is inferred from
initializer (*function ()
{
assert(to(4611686018427387904LU) == "4611686018427387904");
assert(to(4294967296L) == "4294967296");
assert(to(-138L) == "-138");
}
)(), and variables cannot be of type void
Should be
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(ReturnType!dg == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(ReturnType!dg == void)) {
dg();
} else {
auto x = dg();
}
}
Re: Checking the Return Type of a Template Alias Parameter in assertCTFEable
On Friday, 28 February 2014 at 15:03:29 UTC, John Colvin wrote:
On Friday, 28 February 2014 at 14:02:35 UTC, Nordlöw wrote:
I have a solution to Issue 388 at
https://github.com/nordlow/dmd/commits/master
that works nicely for my projects.
This patch however generates a handful of warnings in Phobos
unittests.
All of these are IMO fixable except for one which I don't know
how to fix namely the definition of assertCTFEable in
exception.d
I need to change this to explicitly capture the return value
of the template alias argument dg when this is non-void. My
try so far was to change
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert({ dg(); return true; }());
dg();
}
to
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
}
gives the following error when in Phobos make unittest:
std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
).assertCTFEable.__lambda1.x type void is inferred from
initializer (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)(), and variables cannot be of type void
std/exception.d(1392): Error: expression (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)() is void and has no value
How can I in a general way check if dg evaluates to void or
not?
Either use std.traits.ReturnType, or see from it's
implementation.
I tried
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(ReturnType!(db()) == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(ReturnType!(db()) == void)) {
dg();
} else {
auto x = dg();
}
}
but this instead fails as
std/exception.d(1392): Error: variable
std.conv.__unittestL932_18.assertCTFEable!(dg).assertCTFEable.__lambda1.x
type void is inferred from initializer dg(), and variables cannot
be of type void
std/exception.d(1392): Error: expression dg() is void and has no
value
std/exception.d(1402): Error: variable
std.conv.__unittestL932_18.assertCTFEable!(dg).assertCTFEable.x
type void is inferred from initializer dg(), and variables cannot
be of type void
std/exception.d(1402): Error: expression dg() is void and has no
value
std/conv.d(974): Error: template instance
std.conv.__unittestL932_18.assertCTFEable!(dg) error instantiating
std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
{
assert(to(4611686018427387904LU) == "4611686018427387904");
assert(to(4294967296L) == "4294967296");
assert(to(-138L) == "-138");
}
).assertCTFEable.__lambda1.x type void is inferred from
initializer (*function ()
{
assert(to(4611686018427387904LU) == "4611686018427387904");
assert(to(4294967296L) == "4294967296");
assert(to(-138L) == "-138");
}
)(), and variables cannot be of type void
Re: Checking the Return Type of a Template Alias Parameter in assertCTFEable
On Friday, 28 February 2014 at 14:02:35 UTC, Nordlöw wrote:
I have a solution to Issue 388 at
https://github.com/nordlow/dmd/commits/master
that works nicely for my projects.
This patch however generates a handful of warnings in Phobos
unittests.
All of these are IMO fixable except for one which I don't know
how to fix namely the definition of assertCTFEable in
exception.d
I need to change this to explicitly capture the return value of
the template alias argument dg when this is non-void. My try so
far was to change
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert({ dg(); return true; }());
dg();
}
to
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
}
gives the following error when in Phobos make unittest:
std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
).assertCTFEable.__lambda1.x type void is inferred from
initializer (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)(), and variables cannot be of type void
std/exception.d(1392): Error: expression (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)() is void and has no value
How can I in a general way check if dg evaluates to void or not?
Either use std.traits.ReturnType, or see from it's implementation.
Checking the Return Type of a Template Alias Parameter in assertCTFEable
I have a solution to Issue 388 at
https://github.com/nordlow/dmd/commits/master
that works nicely for my projects.
This patch however generates a handful of warnings in Phobos
unittests.
All of these are IMO fixable except for one which I don't know
how to fix namely the definition of assertCTFEable in exception.d
I need to change this to explicitly capture the return value of
the template alias argument dg when this is non-void. My try so
far was to change
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert({ dg(); return true; }());
dg();
}
to
version(unittest) package
@property void assertCTFEable(alias dg)()
{
static assert
({
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
return true;
}());
static if (is(typeof(db()) == void)) {
dg();
} else {
auto x = dg();
}
}
gives the following error when in Phobos make unittest:
std/exception.d(1392): Error: variable
std.exception.assertCTFEable!(function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
).assertCTFEable.__lambda1.x type void is inferred from
initializer (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)(), and variables cannot be of type void
std/exception.d(1392): Error: expression (*function ()
{
S[] r = array(repeat((S __ctmp1582 = 0;
, __ctmp1582).this(1), 2LU));
assert(equal(r, [(S __ctmp1591 = 0;
, __ctmp1591).this(1), (S __ctmp1592 = 0;
, __ctmp1592).this(1)]));
}
)() is void and has no value
How can I in a general way check if dg evaluates to void or not?
Re: template alias = parameter
On Tuesday, 17 September 2013 at 12:10:11 UTC, Dicebot wrote:
Any two different alias parameter values mean different
template instances. Static introspection demands it:
```
auto foo(alias T)()
{
static if (is(typeof(T) : int) && (T == 42))
return true;
else
return false;
}
```
Yes, that's what I was saying (or trying? thanks anyway). The
problem is that I can't get that and implicit instantiation at
the same time.
I mean, if void foo(T)(T x) makes T=int when called with foo(42),
I was hoping that maybe void foo(alias V)(int V) would make V=42.
But no. Well, it was a long shot, but it was worth the try.
Re: template alias = parameter
On Tuesday, 17 September 2013 at 11:50:56 UTC, Luís Marques wrote:
On Tuesday, 17 September 2013 at 11:46:07 UTC, Dicebot wrote:
It should not be possible as template instances with same
template parameter list share same body in code gen.
Well, my long shot idea was to use an alias template parameter,
that way different values would mean different template
parameters. But it seems I can't make the alias template
parameter implicitly match in any way.
Any two different alias parameter values mean different template
instances. Static introspection demands it:
```
auto foo(alias T)()
{
static if (is(typeof(T) : int) && (T == 42))
return true;
else
return false;
}
```
Re: template alias = parameter
On Tuesday, 17 September 2013 at 11:46:07 UTC, Dicebot wrote: It should not be possible as template instances with same template parameter list share same body in code gen. Well, my long shot idea was to use an alias template parameter, that way different values would mean different template parameters. But it seems I can't make the alias template parameter implicitly match in any way.
Re: template alias = parameter
On Tuesday, 17 September 2013 at 11:43:24 UTC, Luís Marques wrote: These examples came from a set of experiments where I was trying to do something which I expected would probably not be possible: make a template function generate different code 1) without varying the function types, 2) without explicitly instantiating the template using "!". (this was for compatibility purposes). It should not be possible as template instances with same template parameter list share same body in code gen.
Re: template alias = parameter
Thanks. I think what is weird is that the template parameters are allowed to have the same name as the normal parameters, which confused my mental model and made me wonder what was even the expected behavior. These examples came from a set of experiments where I was trying to do something which I expected would probably not be possible: make a template function generate different code 1) without varying the function types, 2) without explicitly instantiating the template using "!". (this was for compatibility purposes).
Re: template alias = parameter
On Tuesday, 17 September 2013 at 11:24:10 UTC, Luís Marques wrote:
Could you please comment on the following behaviors? Are all of
them intended? Are they internally coherent, with respect to
each
other?
Looks fine to me.
1)
void foo(alias f)(int f)
{
writeln(f);
}
foo(42);
Error: does not match template
`alias` is never inferred so error is expected. You did not
provide any template parameters to foo. `void foo(T)(T f)` would
have worked because `T` can be inferred.
2)
...
foo!(42)(42);
> 42
Explicit template parameter + normal parameter. Name of normal
parameter shadows alias name (would have expected a warning/error
here tbh).
3)
...
foo!(7)(42);
> 42
Same as (2).
4)
void foo(alias f)(int g=f)
{
writeln(g);
}
foo(42);
Error: does not match template
Again, you do not provide template parameter, it can't match.
`foo!(42)()` should have worked here.
5)
void foo(alias f=42)(int g=f)
{
writeln(g);
}
foo();
> 42
Default parameters can be used everywhere so no need to provide
any parameter explicitly.
template alias = parameter
Could you please comment on the following behaviors? Are all of
them intended? Are they internally coherent, with respect to each
other?
1)
void foo(alias f)(int f)
{
writeln(f);
}
foo(42);
Error: does not match template
2)
...
foo!(42)(42);
> 42
3)
...
foo!(7)(42);
> 42
4)
void foo(alias f)(int g=f)
{
writeln(g);
}
foo(42);
Error: does not match template
5)
void foo(alias f=42)(int g=f)
{
writeln(g);
}
foo();
> 42
Template alias parameter does not accept primitives?
template Foo(alias A) {
alias A Foo;
}
Foo!(int) x;
This piece of code will not compile in both D1 and D2 because 'int'
cannot be matched with 'alias A'. Is this expected? Why is that?
Refs:
1. http://codepad.org/GQFBdC0T
2. http://ideone.com/yke0h
