include lifetime in ParamKind and in Generics::provenance_split

10 files changed, 116 insertions, 50 deletions

diff --git a/crates/hir-ty/src/builder.rs b/crates/hir-ty/src/builder.rs
index c485c9b2e80..e311338a2d6 100644
--- a/crates/hir-ty/src/builder.rs
+++ b/crates/hir-ty/src/builder.rs
@@ -15,15 +15,16 @@ use hir_def::{
 use smallvec::SmallVec;
 
 use crate::{
-    consteval::unknown_const_as_generic, db::HirDatabase, infer::unify::InferenceTable, primitive,
-    to_assoc_type_id, to_chalk_trait_id, utils::generics, Binders, BoundVar, CallableSig,
-    GenericArg, GenericArgData, Interner, ProjectionTy, Substitution, TraitRef, Ty, TyDefId, TyExt,
-    TyKind,
+    consteval::unknown_const_as_generic, db::HirDatabase, error_lifetime,
+    infer::unify::InferenceTable, primitive, static_lifetime, to_assoc_type_id, to_chalk_trait_id,
+    utils::generics, Binders, BoundVar, CallableSig, GenericArg, GenericArgData, Interner,
+    ProjectionTy, Substitution, TraitRef, Ty, TyDefId, TyExt, TyKind,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ParamKind {
     Type,
+    Lifetime,
     Const(Ty),
 }
 
@@ -107,6 +108,9 @@ impl<D> TyBuilder<D> {
             ParamKind::Const(ty) => {
                 BoundVar::new(debruijn, idx).to_const(Interner, ty.clone()).cast(Interner)
             }
+            ParamKind::Lifetime => {
+                BoundVar::new(debruijn, idx).to_lifetime(Interner).cast(Interner)
+            }
         });
         this.vec.extend(filler.take(this.remaining()).casted(Interner));
         assert_eq!(this.remaining(), 0);
@@ -119,6 +123,7 @@ impl<D> TyBuilder<D> {
         let filler = this.param_kinds[this.vec.len()..].iter().map(|x| match x {
             ParamKind::Type => TyKind::Error.intern(Interner).cast(Interner),
             ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+            ParamKind::Lifetime => error_lifetime().cast(Interner),
         });
         this.vec.extend(filler.casted(Interner));
         assert_eq!(this.remaining(), 0);
@@ -130,6 +135,8 @@ impl<D> TyBuilder<D> {
         self.fill(|x| match x {
             ParamKind::Type => table.new_type_var().cast(Interner),
             ParamKind::Const(ty) => table.new_const_var(ty.clone()).cast(Interner),
+            // FIXME: create new_lifetime_var in table
+            ParamKind::Lifetime => static_lifetime().cast(Interner),
         })
     }
 
@@ -142,7 +149,8 @@ impl<D> TyBuilder<D> {
     fn assert_match_kind(&self, a: &chalk_ir::GenericArg<Interner>, e: &ParamKind) {
         match (a.data(Interner), e) {
             (GenericArgData::Ty(_), ParamKind::Type)
-            | (GenericArgData::Const(_), ParamKind::Const(_)) => (),
+            | (GenericArgData::Const(_), ParamKind::Const(_))
+            | (GenericArgData::Lifetime(_), ParamKind::Lifetime) => (),
             _ => panic!("Mismatched kinds: {a:?}, {:?}, {:?}", self.vec, self.param_kinds),
         }
     }
@@ -217,6 +225,7 @@ impl TyBuilder<()> {
     ) -> TyBuilder<()> {
         let generics = generics(db.upcast(), def.into());
         assert!(generics.parent_generics().is_some() == parent_subst.is_some());
+        let lt_iter = generics.iter_lt_self().map(|_| ParamKind::Lifetime);
         let params = generics
             .iter_self()
             .map(|(id, data)| match data {
@@ -225,6 +234,7 @@ impl TyBuilder<()> {
                     ParamKind::Const(db.const_param_ty(ConstParamId::from_unchecked(id)))
                 }
             })
+            .chain(lt_iter)
             .collect();
         TyBuilder::new((), params, parent_subst)
     }
diff --git a/crates/hir-ty/src/display.rs b/crates/hir-ty/src/display.rs
index 269db57bc34..32be0f248bf 100644
--- a/crates/hir-ty/src/display.rs
+++ b/crates/hir-ty/src/display.rs
@@ -938,15 +938,23 @@ impl HirDisplay for Ty {
                 f.end_location_link();
                 if parameters.len(Interner) > 0 {
                     let generics = generics(db.upcast(), def.into());
-                    let (parent_params, self_param, type_params, const_params, _impl_trait_params) =
-                        generics.provenance_split();
-                    let total_len = parent_params + self_param + type_params + const_params;
+                    let (
+                        parent_params,
+                        self_param,
+                        type_params,
+                        const_params,
+                        _impl_trait_params,
+                        lifetime_params,
+                    ) = generics.provenance_split();
+                    let total_len =
+                        parent_params + self_param + type_params + const_params + lifetime_params;
                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
                     if total_len > 0 {
                         // `parameters` are in the order of fn's params (including impl traits),
                         // parent's params (those from enclosing impl or trait, if any).
                         let parameters = parameters.as_slice(Interner);
-                        let fn_params_len = self_param + type_params + const_params;
+                        let fn_params_len =
+                            self_param + type_params + const_params + lifetime_params;
                         let fn_params = parameters.get(..fn_params_len);
                         let parent_params = parameters.get(parameters.len() - parent_params..);
                         let params = parent_params.into_iter().chain(fn_params).flatten();
diff --git a/crates/hir-ty/src/infer/expr.rs b/crates/hir-ty/src/infer/expr.rs
index a3dab1fd9d5..edfc8a81654 100644
--- a/crates/hir-ty/src/infer/expr.rs
+++ b/crates/hir-ty/src/infer/expr.rs
@@ -13,7 +13,7 @@ use hir_def::{
         ArithOp, Array, BinaryOp, ClosureKind, Expr, ExprId, LabelId, Literal, Statement, UnaryOp,
     },
     lang_item::{LangItem, LangItemTarget},
-    path::{GenericArg, GenericArgs, Path},
+    path::{GenericArgs, Path},
     BlockId, ConstParamId, FieldId, ItemContainerId, Lookup, TupleFieldId, TupleId,
 };
 use hir_expand::name::{name, Name};
@@ -1816,10 +1816,17 @@ impl InferenceContext<'_> {
         def_generics: Generics,
         generic_args: Option<&GenericArgs>,
     ) -> Substitution {
-        let (parent_params, self_params, type_params, const_params, impl_trait_params) =
-            def_generics.provenance_split();
+        let (
+            parent_params,
+            self_params,
+            type_params,
+            const_params,
+            impl_trait_params,
+            lifetime_params,
+        ) = def_generics.provenance_split();
         assert_eq!(self_params, 0); // method shouldn't have another Self param
-        let total_len = parent_params + type_params + const_params + impl_trait_params;
+        let total_len =
+            parent_params + type_params + const_params + impl_trait_params + lifetime_params;
         let mut substs = Vec::with_capacity(total_len);
 
         // handle provided arguments
@@ -1828,9 +1835,8 @@ impl InferenceContext<'_> {
             for (arg, kind_id) in generic_args
                 .args
                 .iter()
-                .filter(|arg| !matches!(arg, GenericArg::Lifetime(_)))
-                .take(type_params + const_params)
-                .zip(def_generics.iter_id())
+                .take(type_params + const_params + lifetime_params)
+                .zip(def_generics.iter_id_with_lt())
             {
                 if let Some(g) = generic_arg_to_chalk(
                     self.db,
@@ -1850,6 +1856,8 @@ impl InferenceContext<'_> {
                             DebruijnIndex::INNERMOST,
                         )
                     },
+                    // FIXME: create make_lifetimes and infer lifetimes
+                    |_, _| static_lifetime(),
                 ) {
                     substs.push(g);
                 }
diff --git a/crates/hir-ty/src/infer/path.rs b/crates/hir-ty/src/infer/path.rs
index 44b35b2ebbc..9a1835b625b 100644
--- a/crates/hir-ty/src/infer/path.rs
+++ b/crates/hir-ty/src/infer/path.rs
@@ -11,7 +11,7 @@ use stdx::never;
 
 use crate::{
     builder::ParamKind,
-    consteval,
+    consteval, error_lifetime,
     method_resolution::{self, VisibleFromModule},
     to_chalk_trait_id,
     utils::generics,
@@ -111,6 +111,7 @@ impl InferenceContext<'_> {
                 it.next().unwrap_or_else(|| match x {
                     ParamKind::Type => self.result.standard_types.unknown.clone().cast(Interner),
                     ParamKind::Const(ty) => consteval::unknown_const_as_generic(ty.clone()),
+                    ParamKind::Lifetime => error_lifetime().cast(Interner),
                 })
             })
             .build();
diff --git a/crates/hir-ty/src/infer/unify.rs b/crates/hir-ty/src/infer/unify.rs
index 93fd54455b9..a6c5666911a 100644
--- a/crates/hir-ty/src/infer/unify.rs
+++ b/crates/hir-ty/src/infer/unify.rs
@@ -807,6 +807,7 @@ impl<'a> InferenceTable<'a> {
             .fill(|it| {
                 let arg = match it {
                     ParamKind::Type => self.new_type_var(),
+                    ParamKind::Lifetime => unreachable!("Tuple with lifetime parameter"),
                     ParamKind::Const(_) => unreachable!("Tuple with const parameter"),
                 };
                 arg_tys.push(arg.clone());
diff --git a/crates/hir-ty/src/lib.rs b/crates/hir-ty/src/lib.rs
index 97a8f8660a4..f5410ca6a14 100644
--- a/crates/hir-ty/src/lib.rs
+++ b/crates/hir-ty/src/lib.rs
@@ -92,8 +92,8 @@ pub use lower::{
 };
 pub use mapping::{
     from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id, from_placeholder_idx,
-    lt_from_placeholder_idx, to_assoc_type_id, to_chalk_trait_id, to_foreign_def_id,
-    to_placeholder_idx,
+    lt_from_placeholder_idx, lt_to_placeholder_idx, to_assoc_type_id, to_chalk_trait_id,
+    to_foreign_def_id, to_placeholder_idx,
 };
 pub use method_resolution::check_orphan_rules;
 pub use traits::TraitEnvironment;
diff --git a/crates/hir-ty/src/lower.rs b/crates/hir-ty/src/lower.rs
index 3327d284799..453ac2fca78 100644
--- a/crates/hir-ty/src/lower.rs
+++ b/crates/hir-ty/src/lower.rs
@@ -34,9 +34,9 @@ use hir_def::{
         ConstRef, LifetimeRef, TraitBoundModifier, TraitRef as HirTraitRef, TypeBound, TypeRef,
     },
     AdtId, AssocItemId, ConstId, ConstParamId, DefWithBodyId, EnumId, EnumVariantId, FunctionId,
-    GenericDefId, HasModule, ImplId, InTypeConstLoc, ItemContainerId, LocalFieldId, Lookup,
-    ModuleDefId, StaticId, StructId, TraitId, TypeAliasId, TypeOrConstParamId, TypeOwnerId,
-    TypeParamId, UnionId, VariantId,
+    GenericDefId, GenericParamId, HasModule, ImplId, InTypeConstLoc, ItemContainerId, LocalFieldId,
+    Lookup, ModuleDefId, StaticId, StructId, TraitId, TypeAliasId, TypeOrConstParamId, TypeOwnerId,
+    UnionId, VariantId,
 };
 use hir_expand::{name::Name, ExpandResult};
 use intern::Interned;
@@ -377,15 +377,20 @@ impl<'a> TyLoweringContext<'a> {
                             list_params,
                             const_params,
                             _impl_trait_params,
+                            lifetime_params,
                         ) = if let Some(def) = self.resolver.generic_def() {
                             let generics = generics(self.db.upcast(), def);
                             generics.provenance_split()
                         } else {
-                            (0, 0, 0, 0, 0)
+                            (0, 0, 0, 0, 0, 0)
                         };
                         TyKind::BoundVar(BoundVar::new(
                             self.in_binders,
-                            idx as usize + self_params + list_params + const_params,
+                            idx as usize
+                                + self_params
+                                + list_params
+                                + const_params
+                                + lifetime_params,
                         ))
                         .intern(Interner)
                     }
@@ -818,14 +823,21 @@ impl<'a> TyLoweringContext<'a> {
             return Substitution::empty(Interner);
         };
         let def_generics = generics(self.db.upcast(), def);
-        let (parent_params, self_params, type_params, const_params, impl_trait_params) =
-            def_generics.provenance_split();
-        let item_len = self_params + type_params + const_params + impl_trait_params;
+        let (
+            parent_params,
+            self_params,
+            type_params,
+            const_params,
+            impl_trait_params,
+            lifetime_params,
+        ) = def_generics.provenance_split();
+        let item_len =
+            self_params + type_params + const_params + impl_trait_params + lifetime_params;
         let total_len = parent_params + item_len;
 
         let ty_error = TyKind::Error.intern(Interner).cast(Interner);
 
-        let mut def_generic_iter = def_generics.iter_id();
+        let mut def_generic_iter = def_generics.iter_id_with_lt();
 
         let fill_self_params = || {
             for x in explicit_self_ty
@@ -835,7 +847,10 @@ impl<'a> TyLoweringContext<'a> {
                 .take(self_params)
             {
                 if let Some(id) = def_generic_iter.next() {
-                    assert!(id.is_left());
+                    assert!(matches!(
+                        id,
+                        GenericParamId::TypeParamId(_) | GenericParamId::LifetimeParamId(_)
+                    ));
                     substs.push(x);
                 }
             }
@@ -847,19 +862,13 @@ impl<'a> TyLoweringContext<'a> {
                 fill_self_params();
             }
             let expected_num = if generic_args.has_self_type {
-                self_params + type_params + const_params
+                self_params + type_params + const_params + lifetime_params
             } else {
                 type_params + const_params
             };
             let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
             // if args are provided, it should be all of them, but we can't rely on that
-            for arg in generic_args
-                .args
-                .iter()
-                .filter(|arg| !matches!(arg, GenericArg::Lifetime(_)))
-                .skip(skip)
-                .take(expected_num)
-            {
+            for arg in generic_args.args.iter().skip(skip).take(expected_num) {
                 if let Some(id) = def_generic_iter.next() {
                     if let Some(x) = generic_arg_to_chalk(
                         self.db,
@@ -868,6 +877,7 @@ impl<'a> TyLoweringContext<'a> {
                         &mut (),
                         |_, type_ref| self.lower_ty(type_ref),
                         |_, const_ref, ty| self.lower_const(const_ref, ty),
+                        |_, lifetime_ref| self.lower_lifetime(lifetime_ref),
                     ) {
                         had_explicit_args = true;
                         substs.push(x);
@@ -883,9 +893,12 @@ impl<'a> TyLoweringContext<'a> {
 
         // These params include those of parent.
         let remaining_params: SmallVec<[_; 2]> = def_generic_iter
-            .map(|eid| match eid {
-                Either::Left(_) => ty_error.clone(),
-                Either::Right(x) => unknown_const_as_generic(self.db.const_param_ty(x)),
+            .map(|id| match id {
+                GenericParamId::ConstParamId(x) => {
+                    unknown_const_as_generic(self.db.const_param_ty(x))
+                }
+                GenericParamId::TypeParamId(_) => ty_error.clone(),
+                GenericParamId::LifetimeParamId(_) => error_lifetime().cast(Interner),
             })
             .collect();
         assert_eq!(remaining_params.len() + substs.len(), total_len);
@@ -1719,7 +1732,7 @@ pub(crate) fn generic_defaults_query(
     let generic_params = generics(db.upcast(), def);
     let parent_start_idx = generic_params.len_self();
 
-    let defaults = Arc::from_iter(generic_params.iter().enumerate().map(|(idx, (id, p))| {
+    let toc_iter = generic_params.iter().enumerate().map(|(idx, (id, p))| {
         match p {
             TypeOrConstParamData::TypeParamData(p) => {
                 let mut ty =
@@ -1747,7 +1760,14 @@ pub(crate) fn generic_defaults_query(
                 make_binders(db, &generic_params, val)
             }
         }
-    }));
+    });
+
+    let lt_iter = generic_params
+        .iter_lt()
+        .enumerate()
+        .map(|_| make_binders(db, &generic_params, static_lifetime().cast(Interner)));
+
+    let defaults = Arc::from_iter(toc_iter.chain(lt_iter));
 
     defaults
 }
@@ -2127,23 +2147,29 @@ pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mut
 /// Returns `Some` of the lowered generic arg. `None` if the provided arg is a lifetime.
 pub(crate) fn generic_arg_to_chalk<'a, T>(
     db: &dyn HirDatabase,
-    kind_id: Either<TypeParamId, ConstParamId>,
+    kind_id: GenericParamId,
     arg: &'a GenericArg,
     this: &mut T,
     for_type: impl FnOnce(&mut T, &TypeRef) -> Ty + 'a,
     for_const: impl FnOnce(&mut T, &ConstRef, Ty) -> Const + 'a,
+    for_lifetime: impl FnOnce(&mut T, &LifetimeRef) -> Lifetime + 'a,
 ) -> Option<crate::GenericArg> {
     let kind = match kind_id {
-        Either::Left(_) => ParamKind::Type,
-        Either::Right(id) => {
+        GenericParamId::TypeParamId(_) => ParamKind::Type,
+        GenericParamId::ConstParamId(id) => {
             let ty = db.const_param_ty(id);
             ParamKind::Const(ty)
         }
+        GenericParamId::LifetimeParamId(_) => ParamKind::Lifetime,
     };
     Some(match (arg, kind) {
         (GenericArg::Type(type_ref), ParamKind::Type) => for_type(this, type_ref).cast(Interner),
         (GenericArg::Const(c), ParamKind::Const(c_ty)) => for_const(this, c, c_ty).cast(Interner),
+        (GenericArg::Lifetime(lifetime_ref), ParamKind::Lifetime) => {
+            for_lifetime(this, lifetime_ref).cast(Interner)
+        }
         (GenericArg::Const(_), ParamKind::Type) => TyKind::Error.intern(Interner).cast(Interner),
+        (GenericArg::Lifetime(_), ParamKind::Type) => TyKind::Error.intern(Interner).cast(Interner),
         (GenericArg::Type(t), ParamKind::Const(c_ty)) => {
             // We want to recover simple idents, which parser detects them
             // as types. Maybe here is not the best place to do it, but
@@ -2159,7 +2185,9 @@ pub(crate) fn generic_arg_to_chalk<'a, T>(
             }
             unknown_const_as_generic(c_ty)
         }
-        (GenericArg::Lifetime(_), _) => return None,
+        (GenericArg::Lifetime(_), ParamKind::Const(c_ty)) => unknown_const_as_generic(c_ty),
+        (GenericArg::Type(_), ParamKind::Lifetime) => error_lifetime().cast(Interner),
+        (GenericArg::Const(_), ParamKind::Lifetime) => error_lifetime().cast(Interner),
     })
 }
 
diff --git a/crates/hir-ty/src/mapping.rs b/crates/hir-ty/src/mapping.rs
index 14746260396..c61d8277142 100644
--- a/crates/hir-ty/src/mapping.rs
+++ b/crates/hir-ty/src/mapping.rs
@@ -151,7 +151,7 @@ pub fn lt_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> L
     db.lookup_intern_lifetime_param_id(interned_id)
 }
 
-pub(crate) fn lt_to_placeholder_idx(db: &dyn HirDatabase, id: LifetimeParamId) -> PlaceholderIndex {
+pub fn lt_to_placeholder_idx(db: &dyn HirDatabase, id: LifetimeParamId) -> PlaceholderIndex {
     let interned_id = db.intern_lifetime_param_id(id);
     PlaceholderIndex {
         ui: chalk_ir::UniverseIndex::ROOT,
diff --git a/crates/hir-ty/src/utils.rs b/crates/hir-ty/src/utils.rs
index 5e084ffb08b..39e7bdd9623 100644
--- a/crates/hir-ty/src/utils.rs
+++ b/crates/hir-ty/src/utils.rs
@@ -367,11 +367,12 @@ impl Generics {
     }
 
     /// (parent total, self param, type param list, const param list, impl trait)
-    pub(crate) fn provenance_split(&self) -> (usize, usize, usize, usize, usize) {
+    pub(crate) fn provenance_split(&self) -> (usize, usize, usize, usize, usize, usize) {
         let mut self_params = 0;
         let mut type_params = 0;
         let mut impl_trait_params = 0;
         let mut const_params = 0;
+        let mut lifetime_params = 0;
         self.params.iter().for_each(|(_, data)| match data {
             TypeOrConstParamData::TypeParamData(p) => match p.provenance {
                 TypeParamProvenance::TypeParamList => type_params += 1,
@@ -381,8 +382,10 @@ impl Generics {
             TypeOrConstParamData::ConstParamData(_) => const_params += 1,
         });
 
+        self.params.iter_lt().for_each(|(_, _)| lifetime_params += 1);
+
         let parent_len = self.parent_generics().map_or(0, Generics::len);
-        (parent_len, self_params, type_params, const_params, impl_trait_params)
+        (parent_len, self_params, type_params, const_params, impl_trait_params, lifetime_params)
     }
 
     pub(crate) fn param_idx(&self, param: TypeOrConstParamId) -> Option<usize> {
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 4f9697f7fe4..f3065fab826 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -65,7 +65,7 @@ use hir_ty::{
     consteval::{try_const_usize, unknown_const_as_generic, ConstExt},
     db::InternedClosure,
     diagnostics::BodyValidationDiagnostic,
-    known_const_to_ast,
+    error_lifetime, known_const_to_ast,
     layout::{Layout as TyLayout, RustcEnumVariantIdx, RustcFieldIdx, TagEncoding},
     method_resolution::{self, TyFingerprint},
     mir::{interpret_mir, MutBorrowKind},
@@ -1106,6 +1106,7 @@ impl Field {
                     generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
                 }
                 ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+                ParamKind::Lifetime => error_lifetime().cast(Interner),
             })
             .build();
         let ty = db.field_types(var_id)[self.id].clone().substitute(Interner, &substs);
@@ -1447,6 +1448,7 @@ impl Adt {
                 match x {
                     ParamKind::Type => r.cast(Interner),
                     ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+                    ParamKind::Lifetime => error_lifetime().cast(Interner),
                 }
             })
             .build();
@@ -1865,6 +1867,7 @@ impl Function {
                 generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
             }
             ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+            ParamKind::Lifetime => error_lifetime().cast(Interner),
         };
 
         let parent_substs =
@@ -1963,6 +1966,7 @@ impl Function {
                         .unwrap_or_else(|| TyKind::Error.intern(Interner))
                         .cast(Interner),
                     ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+                    ParamKind::Lifetime => error_lifetime().cast(Interner),
                 })
                 .build()
         });
@@ -2221,6 +2225,7 @@ impl SelfParam {
                 generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
             }
             ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+            ParamKind::Lifetime => error_lifetime().cast(Interner),
         };
 
         let parent_substs = TyBuilder::subst_for_def(db, parent_id, None).fill(&mut filler).build();
@@ -4114,6 +4119,7 @@ impl Type {
                         // FIXME: this code is not covered in tests.
                         unknown_const_as_generic(ty.clone())
                     }
+                    ParamKind::Lifetime => error_lifetime().cast(Interner),
                 }
             })
             .build();
@@ -4144,6 +4150,7 @@ impl Type {
                 match it {
                     ParamKind::Type => args.next().unwrap().ty.clone().cast(Interner),
                     ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+                    ParamKind::Lifetime => error_lifetime().cast(Interner),
                 }
             })
             .build();