fix pretty print for qpath

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2328,13 +2328,14 @@ impl<'a> State<'a> {
             self.print_path(path, false, depth);
         }
         self.s.word(">");
+        for item_segment in &path.segments[qself.position..] {
             self.s.word("::");
-        let item_segment = path.segments.last().unwrap();
             self.print_ident(item_segment.ident);
             if let Some(ref args) = item_segment.args {
                 self.print_generic_args(args, colons_before_params)
             }
         }
+    }
 
     crate fn print_pat(&mut self, pat: &ast::Pat) {
         self.maybe_print_comment(pat.span.lo());

src/test/pretty/qpath-associated-type-bound.rs

@@ -0,0 +1,16 @@
+// pp-exact
+
+
+mod m {
+    pub trait Tr {
+        type Ts: super::Tu;
+    }
+}
+
+trait Tu {
+    fn dummy() { }
+}
+
+fn foo<T: m::Tr>() { <T as m::Tr>::Ts::dummy(); }
+
+fn main() { }