Run cleanup for base struct in functional struct update expressions

Fixes #17302.

Author: Jakub Wieczorek

src/librustc/middle/trans/expr.rs

@@ -1380,7 +1380,11 @@ pub fn trans_adt<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
         assert_eq!(discr, 0);
 
         match ty::expr_kind(bcx.tcx(), &*base.expr) {
-            ty::LvalueExpr => {
+            ty::RvalueDpsExpr | ty::RvalueDatumExpr if !ty::type_needs_drop(bcx.tcx(), ty) => {
+                bcx = trans_into(bcx, &*base.expr, SaveIn(addr));
+            },
+            ty::RvalueStmtExpr => bcx.tcx().sess.bug("unexpected expr kind for struct base expr"),
+            _ => {
                 let base_datum = unpack_datum!(bcx, trans_to_lvalue(bcx, &*base.expr, "base"));
                 for &(i, t) in base.fields.iter() {
                     let datum = base_datum.get_element(
@@ -1389,11 +1393,7 @@ pub fn trans_adt<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
                     let dest = adt::trans_field_ptr(bcx, &*repr, addr, discr, i);
                     bcx = datum.store_to(bcx, dest);
                 }
-            },
-            ty::RvalueDpsExpr | ty::RvalueDatumExpr => {
-                bcx = trans_into(bcx, &*base.expr, SaveIn(addr));
-            },
-            ty::RvalueStmtExpr => bcx.tcx().sess.bug("unexpected expr kind for struct base expr")
+            }
         }
     }
 

src/test/run-pass/issue-17302.rs

@@ -0,0 +1,34 @@
+// 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.
+
+static mut DROPPED: [bool, ..2] = [false, false];
+
+struct A(uint);
+struct Foo { _a: A, _b: int }
+
+impl Drop for A {
+    fn drop(&mut self) {
+        let A(i) = *self;
+        unsafe { DROPPED[i] = true; }
+    }
+}
+
+fn main() {
+    {
+        Foo {
+            _a: A(0),
+            ..Foo { _a: A(1), _b: 2 }
+        };
+    }
+    unsafe {
+        assert!(DROPPED[0]);
+        assert!(DROPPED[1]);
+    }
+}