Update trans/save's span hacks for fully qualified UFCS paths.

Author: eddyb

src/librustc_trans/save/span_utils.rs

@@ -238,6 +238,7 @@ impl<'a> SpanUtils<'a> {
         let mut toks = self.retokenise_span(span);
         // We keep track of how many brackets we're nested in
         let mut bracket_count = 0;
+        let mut found_ufcs_sep = false;
         loop {
             let ts = toks.real_token();
             if ts.tok == token::Eof {
@@ -254,13 +255,20 @@ impl<'a> SpanUtils<'a> {
             }
             bracket_count += match ts.tok {
                 token::Lt => 1,
-                token::Gt => -1,
+                token::Gt => {
+                    // Ignore the `>::` in `<Type as Trait>::AssocTy`.
+                    if !found_ufcs_sep && bracket_count == 0 {
+                        found_ufcs_sep = true;
+                        0
+                    } else {
+                        -1
+                    }
+                }
                 token::BinOp(token::Shl) => 2,
                 token::BinOp(token::Shr) => -2,
                 _ => 0
             };
-            if ts.tok.is_ident() &&
-               bracket_count == nesting {
+            if ts.tok.is_ident() && bracket_count == nesting {
                 result.push(self.make_sub_span(span, Some(ts.sp)).unwrap());
             }
         }