aya-log-ebpf: allow macros in expr position

This is load-bearing in aya-template.

aya-log-ebpf-macros/src/expand.rs

@@ -152,6 +152,7 @@ pub(crate) fn log(args: LogArgs, level_expr: Option<TokenStream>) -> Result<Toke
     let len = Ident::new("len", Span::mixed_site());
     let record = Ident::new("record", Span::mixed_site());
     Ok(quote! {
+        {
             let #level = #level_expr;
             if ::aya_log_ebpf::macro_support::level_enabled(#level) {
                 match ::aya_log_ebpf::macro_support::AYA_LOG_BUF.get_ptr_mut(0).and_then(|ptr| unsafe { ptr.as_mut() }) {
@@ -183,6 +184,7 @@ pub(crate) fn log(args: LogArgs, level_expr: Option<TokenStream>) -> Result<Toke
                     }
                 }
             }
+        }
     })
 }
 

test/integration-ebpf/src/log.rs

@@ -83,7 +83,8 @@ pub fn test_log(ctx: ProbeContext) {
 
         let no_copy = NoCopy {};
 
-        debug!(&ctx, "{:x}", no_copy.consume());
+        // Check usage in expression position.
+        let () = debug!(&ctx, "{:x}", no_copy.consume());
     }
 }