Added regression test for issue rust-lang#67062

Author: ForrestOfBarnes

tests/ui/proc-macro/auxiliary/delimiter-none-issue-67062.rs

@@ -0,0 +1,12 @@
+extern crate proc_macro;
+
+use proc_macro::{Literal, Punct, Spacing, TokenStream, TokenTree};
+
+#[proc_macro]
+pub fn add_mul(input: TokenStream) -> TokenStream {
+    let mul_2 = vec![
+        TokenTree::from(Punct::new('*', Spacing::Alone)),
+        TokenTree::from(Literal::u8_unsuffixed(2)),
+    ];
+    input.into_iter().chain(mul_2.into_iter()).collect()
+}

tests/ui/proc-macro/delimiter-none-issue-67062.rs

@@ -0,0 +1,18 @@
+//@ run-pass
+//@ proc-macro: delimiter-none-issue-67062.rs
+
+// Regression test for #67062.
+
+#[macro_use]
+extern crate delimiter_none_issue_67062;
+
+macro_rules! mbe {
+    ($e: expr) => ( add_mul!($e) )
+}
+
+fn main() {
+    // Order of operations check. This should evalue to (2 + 2) * 2, but using
+    // Delimiter::None instead of parentheses.
+    let x = mbe!(2 + 2);
+    assert_eq!(x, 8);
+}