Add test for Item::Verbatim splitting a None group

(see issue #1235)

tests/regression/issue1235.rs

@@ -0,0 +1,32 @@
+use proc_macro2::{Delimiter, Group};
+use quote::quote;
+
+#[test]
+fn main() {
+    // Okay. Rustc allows top-level `static` with no value syntactically, but
+    // not semantically. Syn parses as Item::Verbatim.
+    let tokens = quote!(
+        pub static FOO: usize;
+        pub static BAR: usize;
+    );
+    let file = syn::parse2::<syn::File>(tokens).unwrap();
+    println!("{:#?}", file);
+
+    // Okay.
+    let inner = Group::new(
+        Delimiter::None,
+        quote!(static FOO: usize = 0; pub static BAR: usize = 0),
+    );
+    let tokens = quote!(pub #inner;);
+    let file = syn::parse2::<syn::File>(tokens).unwrap();
+    println!("{:#?}", file);
+
+    // Parser crash.
+    let inner = Group::new(
+        Delimiter::None,
+        quote!(static FOO: usize; pub static BAR: usize),
+    );
+    let tokens = quote!(pub #inner;);
+    let file = syn::parse2::<syn::File>(tokens).unwrap();
+    println!("{:#?}", file);
+}