Rename and improve "traceable" templates.

Rename and improve "traceable" templates.

The NeedsTracing<T>::value expression would previously return true
if T had a trace() method or T == Member<U>. It would not be
true if T == WeakMember<U>; something that was convenient when
using NeedsTracing<> in connection with hash table backing stores,
needing to determine whether to trace the elements of the table, but
not if they were weak references & delegate that to weak processing.

As NeedsTracing<T> has grown an increasing number of uses besides
the handling of backing store tracing, where exempting WeakMember<>
makes no great sense, it is time to alter its meaning to accommodate
those uses better. And at the same time rename it to follow the various
other predicate templates we provide over types. So,

 NeedsTracing<T> => IsTraceable<T> (includes weak)
 NeedsTracingLazily<T> => IsTraceableInCollection<T> (excludes weak)
 NeedsTracingTrait<Trait> => IsTraceableInCollectionTrait<T>

Along with these changes, tidy up the static_assert() error messages in
a few places.

R=
BUG=

Committed: https://crrev.com/87a7aa55418719988c0267efcb83a6d83233ea2a
Cr-Commit-Position: refs/heads/master@{#399389}

[sof, 2016-06-11 20:38:12]

Description was changed from

==========
Rename and improve "traceable" templates.

R=
BUG=
==========

to

==========
Rename and improve "traceable" templates.

The NeedsTracing<T>::value expression would previously return true
if T had a trace() method or T == Member<U>. It would not be
true if T == WeakMember<U>; something that was convenient when
using NeedsTracing<> in connection with hash table backing stores,
needing to determine whether to trace the elements of the table, but
not if they were weak references & delegate that to weak processing.

As NeedsTracing<T> has grown an increasing number of uses besides
the handling of backing store tracing, where exempting WeakMember<>
makes no great sense, it is time to alter its meaning to accommodate
those uses better. And at the same time rename it to follow the various
other predicate templates we provide over types. So,

 NeedsTracing<T> => IsTraceable<T> (includes weak)
 NeedsTracingLazily<T> => IsTraceableInCollection<T> (excludes weak)
 NeedsTracingTrait<Trait> => IsTraceableInCollectionTrait<T>

Along with these changes, tidy up the static_assert() error messages in
a few places.

R=
BUG=
==========

[sof, 2016-06-11 20:39:02]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2016-06-11 20:39:04]

please take a look.

[haraken, 2016-06-12 07:11:30]

haraken@chromium.org changed reviewers:
+ haraken@chromium.org

[haraken, 2016-06-12 07:11:31]

LGTM

https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
File third_party/WebKit/Source/wtf/HashTraits.h (left):

https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
third_party/WebKit/Source/wtf/HashTraits.h:65: struct NeedsTracingLazily {

Nit: I'm okay with keeping the word "lazily" to make it clearer that the trait
needs to be instantiated lazily.

BTW, do we have any verification that the trait is instantiated lazily (i.e., at
a proper timing)?

[sof, 2016-06-12 07:29:44]

https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
File third_party/WebKit/Source/wtf/HashTraits.h (left):

https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
third_party/WebKit/Source/wtf/HashTraits.h:65: struct NeedsTracingLazily {
On 2016/06/12 07:11:31, haraken wrote:
> 
> Nit: I'm okay with keeping the word "lazily" to make it clearer that the trait
> needs to be instantiated lazily.
> 
> BTW, do we have any verification that the trait is instantiated lazily (i.e.,
at
> a proper timing)?

None other than it would fail to compile, i think. Exposing that (instantiation)
implementation detail in the name of this nested template, doesn't gain us much
imho.

[haraken, 2016-06-12 08:59:23]

On 2016/06/12 07:29:44, sof wrote:
>
https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
> File third_party/WebKit/Source/wtf/HashTraits.h (left):
> 
>
https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
> third_party/WebKit/Source/wtf/HashTraits.h:65: struct NeedsTracingLazily {
> On 2016/06/12 07:11:31, haraken wrote:
> > 
> > Nit: I'm okay with keeping the word "lazily" to make it clearer that the
trait
> > needs to be instantiated lazily.
> > 
> > BTW, do we have any verification that the trait is instantiated lazily
(i.e.,
> at
> > a proper timing)?
> 
> None other than it would fail to compile, i think. Exposing that
(instantiation)
> implementation detail in the name of this nested template, doesn't gain us
much
> imho.

As long as it fails to compile, I'm fine :)

[sof, 2016-06-12 14:30:51]

On 2016/06/12 08:59:23, haraken wrote:
> On 2016/06/12 07:29:44, sof wrote:
> >
>
https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
> > File third_party/WebKit/Source/wtf/HashTraits.h (left):
> > 
> >
>
https://codereview.chromium.org/2065443002/diff/60001/third_party/WebKit/Sour...
> > third_party/WebKit/Source/wtf/HashTraits.h:65: struct NeedsTracingLazily {
> > On 2016/06/12 07:11:31, haraken wrote:
> > > 
> > > Nit: I'm okay with keeping the word "lazily" to make it clearer that the
> trait
> > > needs to be instantiated lazily.
> > > 
> > > BTW, do we have any verification that the trait is instantiated lazily
> (i.e.,
> > at
> > > a proper timing)?
> > 
> > None other than it would fail to compile, i think. Exposing that
> (instantiation)
> > implementation detail in the name of this nested template, doesn't gain us
> much
> > imho.
> 
> As long as it fails to compile, I'm fine :)

That kind of static error is hard to miss :)

I'll look into reducing the use of IsTraceableInCollectionTrait<> in a followup;
I think that's possible now that we don't have transition types.

[sof, 2016-06-12 15:11:43]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-06-12 15:11:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2065443002/60001

[commit-bot: I haz the power, 2016-06-12 15:15:54]

Description was changed from

==========
Rename and improve "traceable" templates.

The NeedsTracing<T>::value expression would previously return true
if T had a trace() method or T == Member<U>. It would not be
true if T == WeakMember<U>; something that was convenient when
using NeedsTracing<> in connection with hash table backing stores,
needing to determine whether to trace the elements of the table, but
not if they were weak references & delegate that to weak processing.

As NeedsTracing<T> has grown an increasing number of uses besides
the handling of backing store tracing, where exempting WeakMember<>
makes no great sense, it is time to alter its meaning to accommodate
those uses better. And at the same time rename it to follow the various
other predicate templates we provide over types. So,

 NeedsTracing<T> => IsTraceable<T> (includes weak)
 NeedsTracingLazily<T> => IsTraceableInCollection<T> (excludes weak)
 NeedsTracingTrait<Trait> => IsTraceableInCollectionTrait<T>

Along with these changes, tidy up the static_assert() error messages in
a few places.

R=
BUG=
==========

to

==========
Rename and improve "traceable" templates.

The NeedsTracing<T>::value expression would previously return true
if T had a trace() method or T == Member<U>. It would not be
true if T == WeakMember<U>; something that was convenient when
using NeedsTracing<> in connection with hash table backing stores,
needing to determine whether to trace the elements of the table, but
not if they were weak references & delegate that to weak processing.

As NeedsTracing<T> has grown an increasing number of uses besides
the handling of backing store tracing, where exempting WeakMember<>
makes no great sense, it is time to alter its meaning to accommodate
those uses better. And at the same time rename it to follow the various
other predicate templates we provide over types. So,

 NeedsTracing<T> => IsTraceable<T> (includes weak)
 NeedsTracingLazily<T> => IsTraceableInCollection<T> (excludes weak)
 NeedsTracingTrait<Trait> => IsTraceableInCollectionTrait<T>

Along with these changes, tidy up the static_assert() error messages in
a few places.

R=
BUG=
==========

[commit-bot: I haz the power, 2016-06-12 15:15:55]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-06-12 15:17:51]

Description was changed from

==========
Rename and improve "traceable" templates.

The NeedsTracing<T>::value expression would previously return true
if T had a trace() method or T == Member<U>. It would not be
true if T == WeakMember<U>; something that was convenient when
using NeedsTracing<> in connection with hash table backing stores,
needing to determine whether to trace the elements of the table, but
not if they were weak references & delegate that to weak processing.

As NeedsTracing<T> has grown an increasing number of uses besides
the handling of backing store tracing, where exempting WeakMember<>
makes no great sense, it is time to alter its meaning to accommodate
those uses better. And at the same time rename it to follow the various
other predicate templates we provide over types. So,

 NeedsTracing<T> => IsTraceable<T> (includes weak)
 NeedsTracingLazily<T> => IsTraceableInCollection<T> (excludes weak)
 NeedsTracingTrait<Trait> => IsTraceableInCollectionTrait<T>

Along with these changes, tidy up the static_assert() error messages in
a few places.

R=
BUG=
==========

to

==========
Rename and improve "traceable" templates.

The NeedsTracing<T>::value expression would previously return true
if T had a trace() method or T == Member<U>. It would not be
true if T == WeakMember<U>; something that was convenient when
using NeedsTracing<> in connection with hash table backing stores,
needing to determine whether to trace the elements of the table, but
not if they were weak references & delegate that to weak processing.

As NeedsTracing<T> has grown an increasing number of uses besides
the handling of backing store tracing, where exempting WeakMember<>
makes no great sense, it is time to alter its meaning to accommodate
those uses better. And at the same time rename it to follow the various
other predicate templates we provide over types. So,

 NeedsTracing<T> => IsTraceable<T> (includes weak)
 NeedsTracingLazily<T> => IsTraceableInCollection<T> (excludes weak)
 NeedsTracingTrait<Trait> => IsTraceableInCollectionTrait<T>

Along with these changes, tidy up the static_assert() error messages in
a few places.

R=
BUG=

Committed: https://crrev.com/87a7aa55418719988c0267efcb83a6d83233ea2a
Cr-Commit-Position: refs/heads/master@{#399389}
==========

[commit-bot: I haz the power, 2016-06-12 15:17:52]

Patchset 4 (id:??) landed as
https://crrev.com/87a7aa55418719988c0267efcb83a6d83233ea2a
Cr-Commit-Position: refs/heads/master@{#399389}