Add a stub for ast_const_to_const

Author: varkor

src/librustc_typeck/astconv.rs

@@ -25,6 +25,7 @@ use rustc::traits;
 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
 use rustc::ty::{GenericParamDef, GenericParamDefKind};
 use rustc::ty::wf::object_region_bounds;
+use rustc::mir::interpret::ConstValue;
 use rustc_target::spec::abi;
 use std::slice;
 use require_c_abi_if_variadic;
@@ -1559,8 +1560,30 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         result_ty
     }
 
-    pub fn ast_const_to_const(&self, _ct: &hir::ConstArg, _ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
-        unimplemented!() // TODO(const_generics)
+    pub fn ast_const_to_const(&self, ast_const: &hir::ConstArg, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
+        debug!("ast_const_to_const(id={:?}, ast_ty={:?})", ast_const.value.id, ast_const);
+        let tcx = self.tcx();
+        let def_id = tcx.hir.local_def_id(ast_const.value.id);
+
+        let const_val = ConstValue::Unevaluated(def_id, Substs::identity_for_item(tcx, def_id));
+        // TODO(const_generics)
+        /*if let hir::Expr_::ExprPath(hir::QPath::Resolved(None, ref path)) = ast_const.node {
+            if let Def::ConstParam(def_id) = path.def {
+                self.prohibit_type_params(&path.segments);
+
+                let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
+                let item_id = tcx.hir.get_parent_node(node_id);
+                let item_def_id = tcx.hir.local_def_id(item_id);
+                let generics = tcx.generics_of(item_def_id);
+                let index = generics.const_param_to_index[&tcx.hir.local_def_id(node_id)];
+                const_val = ConstValue::Param(ParamConst::new(index, tcx.hir.name(node_id)));
+            }
+        }*/
+
+        tcx.mk_const(ty::Const {
+            val: const_val,
+            ty,
+        })
     }
 
     pub fn impl_trait_ty_to_ty(