Add TyKind::TyAlias support in rustc_const_eval

Author: GuillaumeGomez

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -152,6 +152,8 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
         // FIXME(oli-obk): we can probably encode closures just like structs
         | ty::Closure(..)
         | ty::Generator(..)
+        // FIXME: we could look behind type aliases.
+        | ty::TyAlias(..)
         | ty::GeneratorWitness(..) => Err(ValTreeCreationError::NonSupportedType),
     }
 }
@@ -320,7 +322,8 @@ pub fn valtree_to_const_value<'tcx>(
         | ty::RawPtr(_)
         | ty::Str
         | ty::Slice(_)
-        | ty::Dynamic(..) => bug!("no ValTree should have been created for type {:?}", ty.kind()),
+        | ty::Dynamic(..)
+        | ty::TyAlias(..) => bug!("no ValTree should have been created for type {:?}", ty.kind()),
     }
 }
 

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -10,10 +10,9 @@ use rustc_middle::mir::{
     interpret::{ConstValue, GlobalId, InterpResult, PointerArithmetic, Scalar},
     BinOp, NonDivergingIntrinsic,
 };
-use rustc_middle::ty;
 use rustc_middle::ty::layout::LayoutOf as _;
 use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::{Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_target::abi::{Abi, Align, Primitive, Size};
 
@@ -102,6 +101,7 @@ pub(crate) fn eval_nullary_intrinsic<'tcx>(
             | ty::Never
             | ty::Tuple(_)
             | ty::Error(_) => ConstValue::from_machine_usize(0u64, &tcx),
+            ty::TyAlias(..) => bug!("unexpected TyAlias in eval_nullary_intrinsic"),
         },
         other => bug!("`{}` is not a zero arg intrinsic", other),
     })

compiler/rustc_const_eval/src/interpret/intrinsics/type_name.rs

@@ -64,6 +64,11 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
             | ty::Closure(def_id, substs)
             | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),
             ty::Foreign(def_id) => self.print_def_path(def_id, &[]),
+            ty::TyAlias(def_id, substs) => {
+                let binder_ty = self.tcx.bound_type_of(def_id);
+                let ty = binder_ty.subst(self.tcx, substs);
+                self.print_type(ty)
+            }
 
             ty::GeneratorWitness(_) => bug!("type_name: unexpected `GeneratorWitness`"),
         }

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -603,7 +603,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
             | ty::Param(..)
             | ty::Opaque(..)
             | ty::Projection(..)
-            | ty::GeneratorWitness(..) => bug!("Encountered invalid type {:?}", ty),
+            | ty::GeneratorWitness(..)
+            | ty::TyAlias(..) => bug!("Encountered invalid type {:?}", ty),
         }
     }