No more syntex for serde_derive

serde_codegen_internals/src/ctxt.rs

@@ -0,0 +1,29 @@
+use std::fmt::Display;
+use std::cell::Cell;
+
+#[derive(Default)]
+pub struct Ctxt {
+    err_count: Cell<usize>,
+}
+
+impl Ctxt {
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    pub fn error<T: Display>(&self, msg: T) {
+        println!("{}", msg);
+        self.err_count.set(self.err_count.get() + 1);
+    }
+}
+
+impl Drop for Ctxt {
+    fn drop(&mut self) {
+        let err_count = self.err_count.get();
+        if err_count == 1 {
+            panic!("1 error");
+        } else if err_count > 1 {
+            panic!("{} errors", err_count);
+        }
+    }
+}