trans: don't ICE when trying to create ADT trans-items

ADTs are translated in-place from rustc_trans::callee, so no trans-items
are needed.

This fix will be superseded by the shimmir branch, but I prefer not to
backport that to beta.

Fixes #39823.

Author: arielb1

src/librustc_trans/collector.rs

@@ -615,19 +615,13 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                                               def_id: DefId)
                                               -> bool {
             match tcx.item_type(def_id).sty {
-                ty::TyFnDef(def_id, _, f) => {
+                ty::TyFnDef(def_id, _, _) => {
                     // Some constructors also have type TyFnDef but they are
                     // always instantiated inline and don't result in a
                     // translation item. Same for FFI functions.
                     if let Some(hir_map::NodeForeignItem(_)) = tcx.hir.get_if_local(def_id) {
                         return false;
                     }
-
-                    if let Some(adt_def) = f.sig.output().skip_binder().ty_adt_def() {
-                        if adt_def.variants.iter().any(|v| def_id == v.did) {
-                            return false;
-                        }
-                    }
                 }
                 ty::TyClosure(..) => {}
                 _ => return false
@@ -689,6 +683,16 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
 fn should_trans_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                   def_id: DefId)
                                   -> bool {
+    if let ty::TyFnDef(_, _, f) = tcx.item_type(def_id).sty {
+        if let Some(adt_def) = f.sig.output().skip_binder().ty_adt_def() {
+            if adt_def.variants.iter().any(|v| def_id == v.did) {
+                // HACK: ADT constructors are translated in-place and
+                // do not have a trans-item.
+                return false;
+            }
+        }
+    }
+
     if def_id.is_local() {
         true
     } else {

src/test/run-pass/auxiliary/issue_39823.rs

@@ -0,0 +1,17 @@
+// Copyright 2017 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.
+
+#![crate_type="rlib"]
+
+#[derive(Debug, PartialEq)]
+pub struct RemoteC(pub u32);
+
+#[derive(Debug, PartialEq)]
+pub struct RemoteG<T>(pub T);

src/test/run-pass/issue-39823.rs

@@ -0,0 +1,34 @@
+// Copyright 2016 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.
+
+// aux-build:issue_39823.rs
+
+extern crate issue_39823;
+use issue_39823::{RemoteC, RemoteG};
+
+#[derive(Debug, PartialEq)]
+struct LocalC(u32);
+
+#[derive(Debug, PartialEq)]
+struct LocalG<T>(T);
+
+fn main() {
+    let virtual_localc : &Fn(_) -> LocalC = &LocalC;
+    assert_eq!(virtual_localc(1), LocalC(1));
+
+    let virtual_localg : &Fn(_) -> LocalG<u32> = &LocalG;
+    assert_eq!(virtual_localg(1), LocalG(1));
+
+    let virtual_remotec : &Fn(_) -> RemoteC = &RemoteC;
+    assert_eq!(virtual_remotec(1), RemoteC(1));
+
+    let virtual_remoteg : &Fn(_) -> RemoteG<u32> = &RemoteG;
+    assert_eq!(virtual_remoteg(1), RemoteG(1));
+}