[gcc/devel/rust/master] libproc_macro: Add is_available interface

[gcc/devel/rust/master] libproc_macro: Add is_available interface

[Thomas Schwinge]

https://gcc.gnu.org/g:f9ff02ad6ff0343743ebbfa492a512000445ed52

commit f9ff02ad6ff0343743ebbfa492a512000445ed52
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Mon Feb 13 16:33:47 2023 +0100

    libproc_macro: Add is_available interface
    
    Add the rust interface for the is_available function in libproc_macro.
    
    ChangeLog:
    
            * librust/proc_macro/rust/lib.rs: Add is_available.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 librust/proc_macro/rust/lib.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/librust/proc_macro/rust/lib.rs b/librust/proc_macro/rust/lib.rs
index 4b6272dc11b..65cf8eb2bce 100644
--- a/librust/proc_macro/rust/lib.rs
+++ b/librust/proc_macro/rust/lib.rs
@@ -12,6 +12,17 @@ mod literal;
 mod punct;
 mod span;
 
+/// Determines whether proc_macro has been made accessible to the currently
+/// running program.
+///
+/// # Note
+///
+/// This function provide a non panicking way to detect whether the API is
+/// invoked from inside of a procedural macro.
+pub fn is_available() -> bool {
+    todo!("Implement this function")
+}
+
 /// A single token or a delimited sequence of token trees.
 #[derive(Clone)]
 pub enum TokenTree {