Handle const generic pattern types

Author: spastorino

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2223,6 +2223,24 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                         Err(LitToConstError::TypeError) => todo!(),
                                     }
                                 }
+
+                                hir::ExprKind::Path(hir::QPath::Resolved(
+                                    _,
+                                    &hir::Path {
+                                        res: Res::Def(DefKind::ConstParam, def_id), ..
+                                    },
+                                )) => {
+                                    let ty = tcx
+                                        .type_of(def_id)
+                                        .no_bound_vars()
+                                        .expect("const parameter types cannot be generic");
+                                    let item_def_id = tcx.parent(def_id);
+                                    let generics = tcx.generics_of(item_def_id);
+                                    let index = generics.param_def_id_to_index[&def_id];
+                                    let name = tcx.item_name(def_id);
+                                    ty::Const::new_param(tcx, ty::ParamConst::new(index, name), ty)
+                                }
+
                                 _ => {
                                     let err = tcx
                                         .dcx()

compiler/rustc_ty_utils/src/layout.rs

@@ -133,10 +133,14 @@ fn layout_of_uncached<'tcx>(
                 ty::PatternKind::Range { start, end, include_end } => {
                     if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &mut layout.abi {
                         if let Some(start) = start {
-                            scalar.valid_range_mut().start = start.eval_bits(tcx, param_env);
+                            scalar.valid_range_mut().start = start
+                                .try_eval_bits(tcx, param_env)
+                                .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
                         }
                         if let Some(end) = end {
-                            let mut end = end.eval_bits(tcx, param_env);
+                            let mut end = end
+                                .try_eval_bits(tcx, param_env)
+                                .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
                             if !include_end {
                                 end = end.wrapping_sub(1);
                             }

tests/ui/type/pattern_types/const_generics.rs

@@ -1,3 +1,5 @@
+//@ check-pass
+
 #![feature(pattern_types)]
 #![feature(core_pattern_types)]
 #![feature(core_pattern_type)]
@@ -7,7 +9,5 @@ use std::pat::pattern_type;
 trait Foo {}
 
 impl<const START: u32, const END: u32> Foo for pattern_type!(u32 is START..=END) {}
-//~^ ERROR: range patterns must have constant range start and end
-//~| ERROR: range patterns must have constant range start and end
 
 fn main() {}