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concat_idents! is not very useful #13294

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alexcrichton opened this Issue Apr 3, 2014 · 5 comments

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@alexcrichton @huonw @pnkfelix @kmcallister @cmr @steveklabnik
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alexcrichton commented Apr 3, 2014

It cannot access local variables due to hygiene, it can't be used to create names of a function (not where a macro can appear), and it can basically only be used to access non-hygienic things.

I believe the utility of this macro has been greatly reduced over time, and it may be time to just remove it (or feature gate it)

Nominating (it's a core built-in macro)

@alexcrichton alexcrichton added the I-nominated label Apr 3, 2014

@alexcrichton alexcrichton referenced this issue Apr 3, 2014

Merged

std: Document builtin syntax extensions #13255

huonw added a commit to huonw/rust that referenced this issue Apr 3, 2014

@huonw
rustc: feature-gate `concat_idents!`. 
concat_idents! is not as useful as it could be, due to macros only being
allowed in limited places, and hygiene, so lets feature gate it until we
make a decision about it.

cc rust-lang#13294
b2e0cb3

@huonw huonw referenced this issue Apr 3, 2014

Merged

rustc: feature-gate `concat_idents!`. #13295

huonw added a commit to huonw/rust that referenced this issue Apr 4, 2014

@huonw
rustc: feature-gate `concat_idents!`. 
concat_idents! is not as useful as it could be, due to macros only being
allowed in limited places, and hygiene, so lets feature gate it until we
make a decision about it.

cc rust-lang#13294
be80ddc

huonw added a commit to huonw/rust that referenced this issue Apr 4, 2014

@huonw
rustc: feature-gate `concat_idents!`. 
concat_idents! is not as useful as it could be, due to macros only being
allowed in limited places, and hygiene, so lets feature gate it until we
make a decision about it.

cc rust-lang#13294
6c5e1d0

bors added a commit that referenced this issue Apr 4, 2014

@bors
auto merge of #13295 : huonw/rust/gate-concat-idents, r=alexcrichton 
rustc: feature-gate `concat_idents!`.

concat_idents! is not as useful as it could be, due to macros only being
allowed in limited places, and hygiene, so lets feature gate it until we
make a decision about it.

cc #13294
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huonw commented Apr 4, 2014

(Feature gated in #13295.)
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pnkfelix commented Apr 10, 2014

not accepted for 1.0 milestone as this is now feature gated.

Assigning P-low (rather than closing) so that we can determine what else, if anything, to do here.

@pnkfelix pnkfelix added P-low and removed I-nominated labels Apr 10, 2014

@huonw huonw referenced this issue Apr 11, 2014

Closed

Can't define a function name using concat_idents!() #12249

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kmcallister commented Apr 11, 2014

I think a good concat_idents! is important, although not urgent. Otherwise it's a big regression from C.

aturon added a commit to aturon/rust that referenced this issue Apr 23, 2014

@aturon
fix std::f32 and std::f64 constants 
Some of the constant values in std::f32 were incorrectly copied from
std::f64.  More broadly, both modules defined their constants redundantly
in two places, which is what led to the bug.  Moreover, the specs for
some of the constants were incorrent, even when the values were correct.

Closes rust-lang#13294.  Closes rust-lang#11537
ab225b1

@aturon aturon referenced this issue Apr 23, 2014

Merged

fix std::f32 and std::f64 constants #13710

@Manishearth Manishearth referenced this issue Aug 28, 2014

Closed

RFC for allowing macros in all ident positions #215

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cmr commented Mar 16, 2015

I agree with @kmcallister, it's a quite useful feature in some cases.

@kylewlacy kylewlacy referenced this issue Sep 1, 2015

Open

macro_rules! should support gensym for creating items #1266

@Toby-S Toby-S referenced this issue Nov 5, 2015

Open

Tracking issue for `concat_idents` #29599

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steveklabnik commented May 24, 2016

Closing in favor of #29599

@steveklabnik steveklabnik closed this May 24, 2016

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