commit | b1374b73fd70915af4f15a0edcc6e4b160c401a9 | [log] [tgz] |
---|---|---|
author | David LeGare <legare@google.com> | Fri Mar 04 02:40:49 2022 +0000 |
committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Fri Mar 04 02:40:49 2022 +0000 |
tree | 48d606b99293af6a54b62974e1fce1b142efe4a2 | |
parent | d621923283ed31ed0be834e23e654ae9c910d7c5 [diff] | |
parent | 1d3368d466e4cd2dd370a47a1b9abda44b716dbf [diff] |
Update paste to 1.0.6 am: 91d4cbedf7 am: 97d152c79f am: 8300a97826 am: 1d3368d466 Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/paste/+/2006010 Change-Id: I2875af543c9743a67b558dedae5a76955c69590a
The nightly-only concat_idents!
macro in the Rust standard library is notoriously underpowered in that its concatenated identifiers can only refer to existing items, they can never be used to define something new.
This crate provides a flexible way to paste together identifiers in a macro, including using pasted identifiers to define new items.
[dependencies] paste = "1.0"
This approach works with any Rust compiler 1.31+.
Within the paste!
macro, identifiers inside [<
...>]
are pasted together to form a single identifier.
use paste::paste; paste! { // Defines a const called `QRST`. const [<Q R S T>]: &str = "success!"; } fn main() { assert_eq!( paste! { [<Q R S T>].len() }, 8, ); }
The next example shows a macro that generates accessor methods for some struct fields. It demonstrates how you might find it useful to bundle a paste invocation inside of a macro_rules macro.
use paste::paste; macro_rules! make_a_struct_and_getters { ($name:ident { $($field:ident),* }) => { // Define a struct. This expands to: // // pub struct S { // a: String, // b: String, // c: String, // } pub struct $name { $( $field: String, )* } // Build an impl block with getters. This expands to: // // impl S { // pub fn get_a(&self) -> &str { &self.a } // pub fn get_b(&self) -> &str { &self.b } // pub fn get_c(&self) -> &str { &self.c } // } paste! { impl $name { $( pub fn [<get_ $field>](&self) -> &str { &self.$field } )* } } } } make_a_struct_and_getters!(S { a, b, c }); fn call_some_getters(s: &S) -> bool { s.get_a() == s.get_b() && s.get_c().is_empty() }
Use $var:lower
or $var:upper
in the segment list to convert an interpolated segment to lower- or uppercase as part of the paste. For example, [<ld_ $reg:lower _expr>]
would paste to ld_bc_expr
if invoked with $reg=Bc
.
Use $var:snake
to convert CamelCase input to snake_case. Use $var:camel
to convert snake_case to CamelCase. These compose, so for example $var:snake:upper
would give you SCREAMING_CASE.
The precise Unicode conversions are as defined by str::to_lowercase
and str::to_uppercase
.
Within the paste!
macro, arguments to a #[doc ...] attribute are implicitly concatenated together to form a coherent documentation string.
use paste::paste; macro_rules! method_new { ($ret:ident) => { paste! { #[doc = "Create a new `" $ret "` object."] pub fn new() -> $ret { todo!() } } }; } pub struct Paste {} method_new!(Paste); // expands to #[doc = "Create a new `Paste` object"]