Don't resolve impl Trait in function def constants to the concrete type

Author: oli-obk

src/librustc/mir/mod.rs

@@ -2105,7 +2105,7 @@ impl<'tcx> Operand<'tcx> {
             span,
             ty,
             user_ty: None,
-            literal: ty::Const::zero_sized(tcx, tcx.param_env(def_id).and(ty)),
+            literal: ty::Const::fn_def(tcx, ty),
         })
     }
 

src/librustc/ty/sty.rs

@@ -2000,12 +2000,10 @@ impl<'tcx> Const<'tcx> {
     }
 
     #[inline]
-    pub fn zero_sized(tcx: TyCtxt<'_, '_, 'tcx>, ty: ParamEnvAnd<'tcx, Ty<'tcx>>,) -> &'tcx Self {
-        let ty = tcx.lift_to_global(&ty).unwrap();
-        let layout = tcx.layout_of(ty).unwrap_or_else(|e| {
-            panic!("could not compute layout for {:?}: {:?}", ty, e)
-        });
-        Self::from_bytes(tcx, &[], layout)
+    pub fn fn_def(tcx: TyCtxt<'_, '_, 'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
+        let alloc = Allocation::from_bytes(&[], ty::layout::Align::from_bytes(1, 1).unwrap());
+        let const_val = ConstValue::from_allocation(tcx, alloc);
+        Self::from_const_value(tcx, const_val, ty)
     }
 
     #[inline]

src/librustc_mir/hair/cx/expr.rs

@@ -851,7 +851,7 @@ fn method_callee<'a, 'gcx, 'tcx>(
         ty,
         span,
         kind: ExprKind::Literal {
-            literal: ty::Const::zero_sized(cx.tcx(), cx.param_env.and(ty)),
+            literal: ty::Const::fn_def(cx.tcx(), ty),
             user_ty,
         },
     }
@@ -910,9 +910,9 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         Def::SelfCtor(..) => {
             let user_ty = user_substs_applied_to_def(cx, expr.hir_id, &def);
             ExprKind::Literal {
-                literal: ty::Const::zero_sized(
+                literal: ty::Const::fn_def(
                     cx.tcx,
-                    cx.param_env.and(cx.tables().node_id_to_type(expr.hir_id)),
+                    cx.tables().node_id_to_type(expr.hir_id),
                 ),
                 user_ty,
             }

src/librustc_mir/hair/cx/mod.rs

@@ -221,7 +221,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
             if item.kind == ty::AssociatedKind::Method && item.ident.name == method_name {
                 let method_ty = self.tcx.type_of(item.def_id);
                 let method_ty = method_ty.subst(self.tcx, substs);
-                return (method_ty, ty::Const::zero_sized(self.tcx, self.param_env.and(method_ty)));
+                return (method_ty, ty::Const::fn_def(self.tcx, method_ty));
             }
         }
 

src/librustc_mir/shim.rs

@@ -445,7 +445,7 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
             span: self.span,
             ty: func_ty,
             user_ty: None,
-            literal: ty::Const::zero_sized(self.tcx, self.tcx.param_env(self.def_id).and(func_ty)),
+            literal: ty::Const::fn_def(self.tcx, func_ty),
         });
 
         let ref_loc = self.make_place(
@@ -688,7 +688,6 @@ fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let sig = tcx.fn_sig(def_id);
     let sig = tcx.erase_late_bound_regions(&sig);
     let span = tcx.def_span(def_id);
-    let param_env = tcx.param_env(def_id);
 
     debug!("build_call_shim: sig={:?}", sig);
 
@@ -734,7 +733,7 @@ fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 span,
                 ty,
                 user_ty: None,
-                literal: ty::Const::zero_sized(tcx, param_env.and(ty)),
+                literal: ty::Const::fn_def(tcx, ty),
              }),
              vec![rcvr])
         }