Rollup merge of #81472 - Aaron1011:fix/revert-cursor-clone, r=petrochenkov

Clone entire `TokenCursor` when collecting tokens

Reverts PR #80830
Fixes taiki-e/pin-project#312

We can have an arbitrary number of `None`-delimited group frames pushed
on the stack due to proc-macro invocations, which can legally be exited.
Attempting to account for this would add a lot of complexity for a tiny
performance gain, so let's just use the original strategy.

2 files changed, 40 insertions, 0 deletions

diff --git a/src/test/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs b/src/test/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs
new file mode 100644
index 00000000000..a6903283aa1
--- /dev/null
+++ b/src/test/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs
@@ -0,0 +1,23 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+#![feature(proc_macro_quote)]
+
+extern crate proc_macro;
+use proc_macro::{TokenStream, quote};
+
+#[proc_macro_attribute]
+pub fn first_attr(_: TokenStream, input: TokenStream) -> TokenStream {
+    let recollected: TokenStream = input.into_iter().collect();
+    quote! {
+        #[second_attr]
+        $recollected
+    }
+}
+
+#[proc_macro_attribute]
+pub fn second_attr(_: TokenStream, input: TokenStream) -> TokenStream {
+    let _recollected: TokenStream = input.into_iter().collect();
+    TokenStream::new()
+}
diff --git a/src/test/ui/proc-macro/nonterminal-recollect-attr.rs b/src/test/ui/proc-macro/nonterminal-recollect-attr.rs
new file mode 100644
index 00000000000..5d4649b78c2
--- /dev/null
+++ b/src/test/ui/proc-macro/nonterminal-recollect-attr.rs
@@ -0,0 +1,17 @@
+// check-pass
+// aux-build:nonterminal-recollect-attr.rs
+
+extern crate nonterminal_recollect_attr;
+use nonterminal_recollect_attr::*;
+
+macro_rules! my_macro {
+    ($v:ident) => {
+        #[first_attr]
+        $v struct Foo {
+            field: u8
+        }
+    }
+}
+
+my_macro!(pub);
+fn main() {}