Fix ICE when compiling fn f<T: ?for<'a> Sized>() {}

src/librustc_typeck/collect.rs

@@ -1665,7 +1665,6 @@ fn is_unsized<'gcx: 'tcx, 'tcx>(astconv: &AstConv<'gcx, 'tcx>,
     for ab in ast_bounds {
         if let &hir::TraitTyParamBound(ref ptr, hir::TraitBoundModifier::Maybe) = ab  {
             if unbound.is_none() {
-                assert!(ptr.bound_lifetimes.is_empty());
                 unbound = Some(ptr.trait_ref.clone());
             } else {
                 span_err!(tcx.sess, span, E0203,

src/test/run-pass/issue-39089.rs

@@ -0,0 +1,13 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn f<T: ?for<'a> Sized>() {}
+
+fn main() {}