Fix mozjs crater failure

Author: oli-obk

src/librustc_mir/interpret/eval_context.rs

@@ -246,7 +246,10 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
     }
 
     pub(super) fn resolve(&self, def_id: DefId, substs: &'tcx Substs<'tcx>) -> EvalResult<'tcx, ty::Instance<'tcx>> {
-        let substs = self.tcx.trans_apply_param_substs(self.substs(), &substs);
+        trace!("resolve: {:?}, {:#?}", def_id, substs);
+        trace!("substs: {:#?}", self.substs());
+        trace!("param_env: {:#?}", self.param_env);
+        let substs = self.tcx.trans_apply_param_substs_env(self.substs(), self.param_env, &substs);
         ty::Instance::resolve(
             *self.tcx,
             self.param_env,
@@ -690,8 +693,13 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
                                     bug!("reifying a fn ptr that requires \
                                           const arguments");
                                 }
-                                let instance = self.resolve(def_id, substs)?;
-                                let fn_ptr = self.memory.create_fn_alloc(instance);
+                                let instance: EvalResult<'tcx, _> = ty::Instance::resolve(
+                                    *self.tcx,
+                                    self.param_env,
+                                    def_id,
+                                    substs,
+                                ).ok_or(EvalErrorKind::TypeckError.into());
+                                let fn_ptr = self.memory.create_fn_alloc(instance?);
                                 let valty = ValTy {
                                     value: Value::ByVal(PrimVal::Ptr(fn_ptr)),
                                     ty: dest_ty,

src/test/run-pass/ctfe/mozjs-error.rs

@@ -0,0 +1,37 @@
+// Copyright 2018 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.
+
+struct CustomAutoRooterVFTable {
+    trace: unsafe extern "C" fn(this: *mut i32, trc: *mut u32),
+}
+
+unsafe trait CustomAutoTraceable: Sized {
+    const vftable: CustomAutoRooterVFTable = CustomAutoRooterVFTable {
+        trace: Self::trace,
+    };
+
+    unsafe extern "C" fn trace(this: *mut i32, trc: *mut u32) {
+        let this = this as *const Self;
+        let this = this.as_ref().unwrap();
+        Self::do_trace(this, trc);
+    }
+
+    fn do_trace(&self, trc: *mut u32);
+}
+
+unsafe impl CustomAutoTraceable for () {
+    fn do_trace(&self, _: *mut u32) {
+        // nop
+    }
+}
+
+fn main() {
+    let _ = <()>::vftable;
+}