chore: checkpoint before Python removal

vendor/proc-macro2/src/num.rs

@@ -0,0 +1,17 @@
+// TODO: use NonZero<char> in Rust 1.89+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct NonZeroChar(char);
+
+impl NonZeroChar {
+    pub fn new(ch: char) -> Option<Self> {
+        if ch == '\0' {
+            None
+        } else {
+            Some(NonZeroChar(ch))
+        }
+    }
+
+    pub fn get(self) -> char {
+        self.0
+    }
+}