Re: [PATCH] rust: macros: update 'paste!' macro to accept string literals

Boqun Feng
2023-10-24T16:52:04Z

On Sun, Oct 08, 2023 at 05:48:18AM -0400, Trevor Gross wrote:
> Enable combining identifiers with string literals in the 'paste!' macro.
> This allows combining user-specified strings with affixes to create
> namespaced identifiers.
>
> This sample code:
>
> macro_rules! m {
> ($name:lit) => {
> paste!(struct [<_some_ $name _struct_>];)
> }
> }
>
> m!("foo_bar");
>
> Would previously cause a compilation error. It will now generate:
>
> struct _some_foo_bar_struct_;
>
> Reported-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
> Signed-off-by: Trevor Gross <tmgross@umich.edu>

This looks good to me, but could you (in a follow-up patch mabye) add an
example demonstrating the usage, which could also serve as a test if we
can run doctest for macro doc. Thanks!

Regards,
Boqun

> ---
>
> Original mention of this problem in [1]
>
> [1]: https://lore.kernel.org/rust-for-linux/20231008.164906.1151622782836568538.fujita.tomonori@gmail.com/
>
> rust/macros/paste.rs | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/rust/macros/paste.rs b/rust/macros/paste.rs
> index 385a78434224..f40d42b35b58 100644
> --- a/rust/macros/paste.rs
> +++ b/rust/macros/paste.rs
> @@ -9,7 +9,15 @@ fn concat(tokens: &[TokenTree], group_span: Span) -> TokenTree {
> loop {
> match tokens.next() {
> None => break,
> - Some(TokenTree::Literal(lit)) => segments.push((lit.to_string(), lit.span())),
> + Some(TokenTree::Literal(lit)) => {
> + // Allow us to concat string literals by stripping quotes
> + let mut value = lit.to_string();
> + if value.starts_with('"') && value.ends_with('"') {
> + value.remove(0);
> + value.pop();
> + }
> + segments.push((value, lit.span()));
> + }
> Some(TokenTree::Ident(ident)) => {
> let mut value = ident.to_string();
> if value.starts_with("r#") {
> --
> 2.34.1
>
>