auto merge of #17762 : bkoropoff/rust/issue-17734, r=alexcrichton

Closes issue #17734

r? @nick29581

Author: bors

src/librustc/middle/trans/glue.rs

@@ -429,7 +429,7 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: ty::t)
                     tvec::make_drop_glue_unboxed(bcx, v0, ty, true)
                 }
                 ty::ty_str => {
-                    let unit_ty = ty::sequence_element_type(bcx.tcx(), t);
+                    let unit_ty = ty::sequence_element_type(bcx.tcx(), content_ty);
                     tvec::make_drop_glue_unboxed(bcx, v0, unit_ty, true)
                 }
                 ty::ty_trait(..) => {

src/test/run-pass/issue-17734.rs

@@ -0,0 +1,23 @@
+// Copyright 2014 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.
+
+// Test that generating drop glue for Box<str> doesn't ICE
+
+fn f(s: Box<str>) -> Box<str> {
+    s
+}
+
+fn main() {
+    // There is currently no safe way to construct a `Box<str>`, so improvise
+    let box_arr: Box<[u8]> = box ['h' as u8, 'e' as u8, 'l' as u8, 'l' as u8, 'o' as u8];
+    let box_str: Box<str> = unsafe { std::mem::transmute(box_arr) };
+    assert_eq!(box_str.as_slice(), "hello");
+    f(box_str);
+}