digitalmars.D.bugs - [Issue 8339] New: is(typeof(...)) is reporting true when it's false due to nested function error
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http://d.puremagic.com/issues/show_bug.cgi?id=8339
Summary: is(typeof(...)) is reporting true when it's false due
to nested function error
Product: D
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: blocker
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: jmdavisProg gmx.com
--- Comment #0 from Jonathan M Davis <jmdavisProg gmx.com> 2012-07-02 22:43:22
PDT ---
This code fails to compile:
import std.algorithm;
private bool testEmptyInit(R)()
{
static if(is(typeof({R range;})))
{
R range;
return range.empty;
}
else
return false;
}
void main()
{
testEmptyInit!(typeof(filter!"true"([0, 1, 2, 3])));
}
giving this error
h.d(7): Error: function std.algorithm.filter!("true").filter!(int[]).filter is
a nested function and cannot be accessed from
h.testEmptyInit!(FilteredRange).testEmptyInit
So, the compiler thinks that is(typeof({R range;})) is true for the type of
filter's result and then it gives an error saying that it's invalid to use it,
meaning that it's _not_ valid and therefore is(typeof({R range;})) should be
false.
If bug# 5941 were fixed, this wouldn't be as big an issue (though the fact that
you can get an error for using a construct when the test for using it passes is
definitely a bug regardless), but as long as bug# 5941 exists, this is a major
blocker for being able to create a template to check for whether the init value
of a range type is empty or not.
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Jul 02 2012
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=8339
Don <clugdbug yahoo.com.au> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |clugdbug yahoo.com.au
--- Comment #1 from Don <clugdbug yahoo.com.au> 2012-07-12 06:11:44 PDT ---
So, the compiler thinks that is(typeof({R range;})) is true for the type of
filter's result and then it gives an error saying that it's invalid to use it,
meaning that it's _not_ valid and therefore is(typeof({R range;})) should be
false.
That doesn't follow.
is(typeof(X)) only checks for a valid type. It does *not* check that the code
compiles. Checking that typeof(X) compiles is weaker than checking that X
compiles. There are several cases where you can obtain a type from something
you cannot possibly use. For example you can use typeof(this) in a static
member function.
OTOH
__traits(compiles, {R range; }) almost certainly behaves the same way, but it
isn't supposed to.
The issue is that the 'nested function' error is happening in the glue layer.
It should be happening in the front end.
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Jul 12 2012
http://d.puremagic.com/issues/show_bug.cgi?id=8339
--- Comment #2 from Jonathan M Davis <jmdavisProg gmx.com> 2012-07-15 22:48:35
PDT ---
We use is(typeof(exp)) to check for compilability all over the place. Are you
saying that we should be using __traits(compiles, exp) instead?
Using __traits(compiles, {R range;}) still fails here. But should it work as
I'm trying to do here if the glue layer issues is fixed?
If not, how am I supposed to test that I can actually _use_ R.init in addition
to it existing? Or is it the case that I should _always_ be able to use R.init
if it exists?
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Jul 15 2012
http://d.puremagic.com/issues/show_bug.cgi?id=8339 --- Comment #3 from Don <clugdbug yahoo.com.au> 2012-07-16 07:13:18 PDT --- (In reply to comment #2)We use is(typeof(exp)) to check for compilability all over the place. Are you saying that we should be using __traits(compiles, exp) instead?Probably. Mostly is(typeof()) does what you want, but just be aware that it's a trick. It's just checking for existence of a type, not for compilability. It's widespread because it works for D1, which doesn't have __traits. It's also rather better tested than __traits...Using __traits(compiles, {R range;}) still fails here. But should it work as I'm trying to do here if the glue layer issues is fixed?Yes, it should work. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jul 16 2012
http://d.puremagic.com/issues/show_bug.cgi?id=8339
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |pull
--- Comment #4 from Kenji Hara <k.hara.pg gmail.com> 2012-08-18 02:48:43 PDT ---
https://github.com/D-Programming-Language/dmd/pull/1087
https://github.com/D-Programming-Language/phobos/pull/751
Front-end layer should check the frame access is really correct or not.
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Aug 18 2012
http://d.puremagic.com/issues/show_bug.cgi?id=8339 --- Comment #5 from github-bugzilla puremagic.com 2012-08-18 08:24:06 PDT --- Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/4a0546480078d51a0ad4dbf141c71bf818e034ec fix Issue 8339 - is(typeof(...)) is reporting true when it's false due to nested function error Avoid frame access check and disabled default construction in predicate templates. https://github.com/D-Programming-Language/phobos/commit/6d42d0286010fce62afe52ad3307cbf38102fe0b Merge pull request #751 from 9rnsr/fix8339 Supplemental change for dmd/pull/1087 (fix Issue 8339) -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 18 2012
http://d.puremagic.com/issues/show_bug.cgi?id=8339 --- Comment #6 from github-bugzilla puremagic.com 2012-08-21 12:53:13 PDT --- Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/a8be86a36d7071092eb6a4a1efddd9552af2581d fix Issue 8339 - is(typeof(...)) is reporting true when it's false due to nested function error https://github.com/D-Programming-Language/dmd/commit/578ba6634f9dbb0eb1e132d46dd14c89542497d6 Merge pull request #1087 from 9rnsr/fix8339 Issue 8339 - is(typeof(...)) is reporting true when it's false due to nested function error -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 21 2012
http://d.puremagic.com/issues/show_bug.cgi?id=8339
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |bugzilla digitalmars.com
Resolution| |FIXED
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