Add test of NtTy in a qpath

Currently fails:

    error: expected identifier, found `ToOwned`
      --> src/test/ui/macros/macro-interpolation.rs:23:19
       |
    LL |         <$type as $trait>::$name
       |                   ^^^^^^ expected identifier
    ...
    LL |     let _: qpath!(ty, <str as ToOwned>::Owned);
       |            -----------------------------------
       |            |
       |            this macro call doesn't expand to a type
       |            in this macro invocation

Author: dtolnay

src/test/ui/macros/macro-interpolation.rs

@@ -15,13 +15,18 @@ macro_rules! overly_complicated {
 }
 
 macro_rules! qpath {
-    (<$type:ty as $trait:path>::$name:ident) => {
+    (path, <$type:ty as $trait:path>::$name:ident) => {
+        <$type as $trait>::$name
+    };
+
+    (ty, <$type:ty as $trait:ty>::$name:ident) => {
         <$type as $trait>::$name
     };
 }
 
 pub fn main() {
-    let _: qpath!(<str as ToOwned>::Owned);
+    let _: qpath!(path, <str as ToOwned>::Owned);
+    let _: qpath!(ty, <str as ToOwned>::Owned);
 
     assert!(overly_complicated!(f, x, Option<usize>, { return Some(x); },
                                Some(8), Some(y), y) == 8)