Use local_inner_macros to resolve all helper macros within $crate #165
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This fixes the following error when using Rust 2018 style macro imports.
use bitflags::bitflags;
error: cannot find macro `__bitflags!` in this scope
--> src/main.rs:5:1
|
5 | / bitflags! {
6 | | struct Flags: u32 {
7 | | const A = 0b00000001;
8 | | const B = 0b00000010;
... |
11 | | }
12 | | }
| |_^ help: you could try the macro: `bitflags`
|
The `local_inner_macros` modifier resolves all macro invocations made
from within that macro as helpers in the same crate. So if `bitflags!`
expands to an invocation of `__bitflags!` then this would be resolved as
`$crate::__bitflags!` rather than requiring the caller to have
`__bitflags` in scope.
The attribute is ignored by pre-2018 compilers so bitflags will continue
to work as normal with #[macro_use].
In the future when dropping compatibility with pre-2018 compilers we can
remove the `local_inner_macros` modifier and use our own explicit
`$crate::` prefixes on invocations of helper macros.
Dylan-DPC-zz
approved these changes
Jul 26, 2018
KodrAus
approved these changes
Jul 26, 2018
| // local_inner_macros so can only directly call macros from this crate. | ||
| #[macro_export] | ||
| #[doc(hidden)] | ||
| macro_rules! __bitflags_stringify { |
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Ah interesting... Is this a workaround to an inherent feature of local_inner_macros or just an implementation detail that might not be necessary in the future?
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This is what local_inner_macros means -- macro calls in the expansion are resolved as local helper macros. So a local_inner_macros macro cannot directly call a macro from a different crate, such as stringify from std.
|
bors: r+ |
bors bot
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Jul 27, 2018
165: Use local_inner_macros to resolve all helper macros within $crate r=Dylan-DPC a=dtolnay
This fixes the following error when using Rust 2018 style macro imports.
```rust
use bitflags::bitflags;
```
```console
error: cannot find macro `__bitflags!` in this scope
--> src/main.rs:5:1
|
5 | / bitflags! {
6 | | struct Flags: u32 {
7 | | const A = 0b00000001;
8 | | const B = 0b00000010;
... |
11 | | }
12 | | }
| |_^ help: you could try the macro: `bitflags`
|
```
The `local_inner_macros` modifier resolves all macro invocations made from within that macro as helpers in the same crate. So if `bitflags!` expands to an invocation of `__bitflags!` then this would be resolved as `$crate::__bitflags!` rather than requiring the caller to have `__bitflags` in scope.
The attribute is ignored by pre-2018 compilers so bitflags will continue to work as normal with #[macro_use].
In the future when dropping compatibility with pre-2018 compilers we can remove the `local_inner_macros` modifier and use our own explicit `$crate::` prefixes on invocations of helper macros.
Co-authored-by: David Tolnay <dtolnay@gmail.com>
Build succeeded |
nickolay
added a commit
to nickolay/git-absorb
that referenced
this pull request
Jul 15, 2019
I thought I needed it for Commit::parent_count(); turns out that I didn't, but since I've tested the update anyway I thought I'd include it. I had to delete Cargo.lock and let cargo regenerate it, since otherwise I got an error that I think was fixed in a newer bitflags version: bitflags/bitflags#165
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This fixes the following error when using Rust 2018 style macro imports.
The
local_inner_macrosmodifier resolves all macro invocations made from within that macro as helpers in the same crate. So ifbitflags!expands to an invocation of__bitflags!then this would be resolved as$crate::__bitflags!rather than requiring the caller to have__bitflagsin scope.The attribute is ignored by pre-2018 compilers so bitflags will continue to work as normal with #[macro_use].
In the future when dropping compatibility with pre-2018 compilers we can remove the
local_inner_macrosmodifier and use our own explicit$crate::prefixes on invocations of helper macros.