Merge #6818

6818: Add Lifetimes to the HIR r=matklad a=Veykril

This doesn't handle resolve yet as I don't know yet how that will be used. I'll get to that once I start moving the lifetime reference PR to the hir.

This also adds a new `hir` name type for lifetimes and labels, `hir::LifetimeName`.

Co-authored-by: Lukas Wirth <[email protected]>

16 files changed, 249 insertions, 96 deletions

diff --git a/crates/assists/src/ast_transform.rs b/crates/assists/src/ast_transform.rs
index 66e4634b1..da94e9987 100644
--- a/crates/assists/src/ast_transform.rs
+++ b/crates/assists/src/ast_transform.rs
@@ -89,7 +89,7 @@ impl<'a> SubstituteTypeParams<'a> {
         let substs = get_syntactic_substs(impl_def).unwrap_or_default();
         let generic_def: hir::GenericDef = trait_.into();
         let substs_by_param: FxHashMap<_, _> = generic_def
-            .params(source_scope.db)
+            .type_params(source_scope.db)
             .into_iter()
             // this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
             .skip(1)
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index 9a1e9ba49..fcc42c6bb 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -19,8 +19,9 @@ use hir_def::{
     src::HasSource as _,
     type_ref::{Mutability, TypeRef},
     AdtId, AssocContainerId, AssocItemId, AssocItemLoc, AttrDefId, ConstId, DefWithBodyId, EnumId,
-    FunctionId, GenericDefId, HasModule, ImplId, LocalEnumVariantId, LocalFieldId, LocalModuleId,
-    Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId, TypeParamId, UnionId,
+    FunctionId, GenericDefId, HasModule, ImplId, LifetimeParamId, LocalEnumVariantId, LocalFieldId,
+    LocalModuleId, Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId, TypeParamId,
+    UnionId,
 };
 use hir_def::{find_path::PrefixKind, item_scope::ItemInNs, visibility::Visibility};
 use hir_expand::{
@@ -831,7 +832,7 @@ impl SelfParam {
             .params
             .first()
             .map(|param| match *param {
-                TypeRef::Reference(_, mutability) => mutability.into(),
+                TypeRef::Reference(.., mutability) => mutability.into(),
                 _ => Access::Owned,
             })
             .unwrap_or(Access::Owned)
@@ -1098,8 +1099,25 @@ impl_from!(
 );
 
 impl GenericDef {
-    pub fn params(self, db: &dyn HirDatabase) -> Vec<TypeParam> {
-        let generics: Arc<hir_def::generics::GenericParams> = db.generic_params(self.into());
+    pub fn params(self, db: &dyn HirDatabase) -> Vec<GenericParam> {
+        let generics = db.generic_params(self.into());
+        let ty_params = generics
+            .types
+            .iter()
+            .map(|(local_id, _)| TypeParam { id: TypeParamId { parent: self.into(), local_id } })
+            .map(GenericParam::TypeParam);
+        let lt_params = generics
+            .lifetimes
+            .iter()
+            .map(|(local_id, _)| LifetimeParam {
+                id: LifetimeParamId { parent: self.into(), local_id },
+            })
+            .map(GenericParam::LifetimeParam);
+        ty_params.chain(lt_params).collect()
+    }
+
+    pub fn type_params(self, db: &dyn HirDatabase) -> Vec<TypeParam> {
+        let generics = db.generic_params(self.into());
         generics
             .types
             .iter()
@@ -1176,6 +1194,13 @@ impl Local {
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum GenericParam {
+    TypeParam(TypeParam),
+    LifetimeParam(LifetimeParam),
+}
+impl_from!(TypeParam, LifetimeParam for GenericParam);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct TypeParam {
     pub(crate) id: TypeParamId,
 }
@@ -1215,6 +1240,18 @@ impl TypeParam {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct LifetimeParam {
+    pub(crate) id: LifetimeParamId,
+}
+
+impl LifetimeParam {
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        let params = db.generic_params(self.id.parent);
+        params.lifetimes[self.id.local_id].name.clone()
+    }
+}
+
 // FIXME: rename from `ImplDef` to `Impl`
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ImplDef {
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 302a52491..0f399a2c6 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -35,8 +35,8 @@ pub use crate::{
     code_model::{
         Access, Adt, AsAssocItem, AssocItem, AssocItemContainer, Callable, CallableKind, Const,
         Crate, CrateDependency, DefWithBody, Enum, EnumVariant, Field, FieldSource, Function,
-        GenericDef, HasVisibility, ImplDef, Local, MacroDef, Module, ModuleDef, ScopeDef, Static,
-        Struct, Trait, Type, TypeAlias, TypeParam, Union, VariantDef,
+        GenericDef, HasVisibility, ImplDef, LifetimeParam, Local, MacroDef, Module, ModuleDef,
+        ScopeDef, Static, Struct, Trait, Type, TypeAlias, TypeParam, Union, VariantDef,
     },
     has_source::HasSource,
     semantics::{PathResolution, Semantics, SemanticsScope},
@@ -56,8 +56,9 @@ pub use hir_def::{
     visibility::Visibility,
 };
 pub use hir_expand::{
-    name::known, name::AsName, name::Name, ExpandResult, HirFileId, InFile, MacroCallId,
-    MacroCallLoc, /* FIXME */ MacroDefId, MacroFile, Origin,
+    name::{known, AsName, Name},
+    ExpandResult, HirFileId, InFile, MacroCallId, MacroCallLoc, /* FIXME */ MacroDefId,
+    MacroFile, Origin,
 };
 pub use hir_ty::display::HirDisplay;
 
diff --git a/crates/hir_def/src/generics.rs b/crates/hir_def/src/generics.rs
index 835fe3fbd..5189c7e9f 100644
--- a/crates/hir_def/src/generics.rs
+++ b/crates/hir_def/src/generics.rs
@@ -21,7 +21,7 @@ use crate::{
     keys,
     src::HasChildSource,
     src::HasSource,
-    type_ref::{TypeBound, TypeRef},
+    type_ref::{LifetimeRef, TypeBound, TypeRef},
     AdtId, GenericDefId, LocalTypeParamId, Lookup, TypeParamId,
 };
 
@@ -33,6 +33,12 @@ pub struct TypeParamData {
     pub provenance: TypeParamProvenance,
 }
 
+/// Data about a generic parameter (to a function, struct, impl, ...).
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct LifetimeParamData {
+    pub name: Name,
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum TypeParamProvenance {
     TypeParamList,
@@ -44,7 +50,7 @@ pub enum TypeParamProvenance {
 #[derive(Clone, PartialEq, Eq, Debug, Default)]
 pub struct GenericParams {
     pub types: Arena<TypeParamData>,
-    // lifetimes: Arena<LocalLifetimeParamId, LifetimeParamData>,
+    pub lifetimes: Arena<LifetimeParamData>,
     pub where_predicates: Vec<WherePredicate>,
 }
 
@@ -53,16 +59,17 @@ pub struct GenericParams {
 /// It might still result in multiple actual predicates though, because of
 /// associated type bindings like `Iterator<Item = u32>`.
 #[derive(Clone, PartialEq, Eq, Debug)]
-pub struct WherePredicate {
-    pub target: WherePredicateTarget,
-    pub bound: TypeBound,
+pub enum WherePredicate {
+    TypeBound { target: WherePredicateTypeTarget, bound: TypeBound },
+    Lifetime { target: LifetimeRef, bound: LifetimeRef },
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
-pub enum WherePredicateTarget {
+pub enum WherePredicateTypeTarget {
     TypeRef(TypeRef),
     /// For desugared where predicates that can directly refer to a type param.
     TypeParam(LocalTypeParamId),
+    // FIXME: ForLifetime(Vec<LifetimeParamId>, TypeRef)
 }
 
 type SourceMap = ArenaMap<LocalTypeParamId, Either<ast::Trait, ast::TypeParam>>;
@@ -123,7 +130,7 @@ impl GenericParams {
     }
 
     fn new(db: &dyn DefDatabase, def: GenericDefId) -> (GenericParams, InFile<SourceMap>) {
-        let mut generics = GenericParams { types: Arena::default(), where_predicates: Vec::new() };
+        let mut generics = GenericParams::default();
         let mut sm = ArenaMap::default();
 
         // FIXME: add `: Sized` bound for everything except for `Self` in traits
@@ -171,7 +178,7 @@ impl GenericParams {
                 // add super traits as bounds on Self
                 // i.e., trait Foo: Bar is equivalent to trait Foo where Self: Bar
                 let self_param = TypeRef::Path(name![Self].into());
-                generics.fill_bounds(&lower_ctx, &src.value, self_param);
+                generics.fill_bounds(&lower_ctx, &src.value, Either::Left(self_param));
 
                 generics.fill(&lower_ctx, &mut sm, &src.value);
                 src.file_id
@@ -218,12 +225,12 @@ impl GenericParams {
         &mut self,
         lower_ctx: &LowerCtx,
         node: &dyn ast::TypeBoundsOwner,
-        type_ref: TypeRef,
+        target: Either<TypeRef, LifetimeRef>,
     ) {
         for bound in
             node.type_bound_list().iter().flat_map(|type_bound_list| type_bound_list.bounds())
         {
-            self.add_where_predicate_from_bound(lower_ctx, bound, type_ref.clone());
+            self.add_where_predicate_from_bound(lower_ctx, bound, target.clone());
         }
     }
 
@@ -246,19 +253,30 @@ impl GenericParams {
             sm.insert(param_id, Either::Right(type_param.clone()));
 
             let type_ref = TypeRef::Path(name.into());
-            self.fill_bounds(&lower_ctx, &type_param, type_ref);
+            self.fill_bounds(&lower_ctx, &type_param, Either::Left(type_ref));
+        }
+        for lifetime_param in params.lifetime_params() {
+            let name = lifetime_param
+                .lifetime_token()
+                .map_or_else(Name::missing, |tok| Name::new_lifetime(&tok));
+            let param = LifetimeParamData { name: name.clone() };
+            let _param_id = self.lifetimes.alloc(param);
+            let lifetime_ref = LifetimeRef::new_name(name);
+            self.fill_bounds(&lower_ctx, &lifetime_param, Either::Right(lifetime_ref));
         }
     }
 
     fn fill_where_predicates(&mut self, lower_ctx: &LowerCtx, where_clause: ast::WhereClause) {
         for pred in where_clause.predicates() {
-            let type_ref = match pred.ty() {
-                Some(type_ref) => type_ref,
-                None => continue,
+            let target = if let Some(type_ref) = pred.ty() {
+                Either::Left(TypeRef::from_ast(lower_ctx, type_ref))
+            } else if let Some(lifetime_tok) = pred.lifetime_token() {
+                Either::Right(LifetimeRef::from_token(lifetime_tok))
+            } else {
+                continue;
             };
-            let type_ref = TypeRef::from_ast(lower_ctx, type_ref);
             for bound in pred.type_bound_list().iter().flat_map(|l| l.bounds()) {
-                self.add_where_predicate_from_bound(lower_ctx, bound, type_ref.clone());
+                self.add_where_predicate_from_bound(lower_ctx, bound, target.clone());
             }
         }
     }
@@ -267,15 +285,24 @@ impl GenericParams {
         &mut self,
         lower_ctx: &LowerCtx,
         bound: ast::TypeBound,
-        type_ref: TypeRef,
+        target: Either<TypeRef, LifetimeRef>,
     ) {
         if bound.question_mark_token().is_some() {
             // FIXME: remove this bound
             return;
         }
         let bound = TypeBound::from_ast(lower_ctx, bound);
-        self.where_predicates
-            .push(WherePredicate { target: WherePredicateTarget::TypeRef(type_ref), bound });
+        let predicate = match (target, bound) {
+            (Either::Left(type_ref), bound) => WherePredicate::TypeBound {
+                target: WherePredicateTypeTarget::TypeRef(type_ref),
+                bound,
+            },
+            (Either::Right(lifetime), TypeBound::Lifetime(bound)) => {
+                WherePredicate::Lifetime { target: lifetime, bound }
+            }
+            _ => return,
+        };
+        self.where_predicates.push(predicate);
     }
 
     pub(crate) fn fill_implicit_impl_trait_args(&mut self, type_ref: &TypeRef) {
@@ -288,8 +315,8 @@ impl GenericParams {
                 };
                 let param_id = self.types.alloc(param);
                 for bound in bounds {
-                    self.where_predicates.push(WherePredicate {
-                        target: WherePredicateTarget::TypeParam(param_id),
+                    self.where_predicates.push(WherePredicate::TypeBound {
+                        target: WherePredicateTypeTarget::TypeParam(param_id),
                         bound: bound.clone(),
                     });
                 }
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index c017b352d..c6ada271e 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -255,7 +255,7 @@ impl GenericParamsStorage {
 }
 
 static EMPTY_GENERICS: GenericParams =
-    GenericParams { types: Arena::new(), where_predicates: Vec::new() };
+    GenericParams { types: Arena::new(), lifetimes: Arena::new(), where_predicates: Vec::new() };
 
 #[derive(Default, Debug, Eq, PartialEq)]
 struct ItemTreeData {
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 63b2826f8..f7ce2e26d 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -13,6 +13,7 @@ use syntax::{
 use crate::{
     attr::Attrs,
     generics::{GenericParams, TypeParamData, TypeParamProvenance},
+    type_ref::LifetimeRef,
 };
 
 use super::*;
@@ -292,12 +293,16 @@ impl Ctx {
                         let self_type = TypeRef::Path(name![Self].into());
                         match self_param.kind() {
                             ast::SelfParamKind::Owned => self_type,
-                            ast::SelfParamKind::Ref => {
-                                TypeRef::Reference(Box::new(self_type), Mutability::Shared)
-                            }
-                            ast::SelfParamKind::MutRef => {
-                                TypeRef::Reference(Box::new(self_type), Mutability::Mut)
-                            }
+                            ast::SelfParamKind::Ref => TypeRef::Reference(
+                                Box::new(self_type),
+                                self_param.lifetime_token().map(LifetimeRef::from_token),
+                                Mutability::Shared,
+                            ),
+                            ast::SelfParamKind::MutRef => TypeRef::Reference(
+                                Box::new(self_type),
+                                self_param.lifetime_token().map(LifetimeRef::from_token),
+                                Mutability::Mut,
+                            ),
                         }
                     }
                 };
@@ -629,8 +634,7 @@ impl Ctx {
                 // add super traits as bounds on Self
                 // i.e., trait Foo: Bar is equivalent to trait Foo where Self: Bar
                 let self_param = TypeRef::Path(name![Self].into());
-                generics.fill_bounds(&self.body_ctx, trait_def, self_param);
-
+                generics.fill_bounds(&self.body_ctx, trait_def, Either::Left(self_param));
                 generics.fill(&self.body_ctx, &mut sm, node);
             }
             GenericsOwner::Impl => {
diff --git a/crates/hir_def/src/lib.rs b/crates/hir_def/src/lib.rs
index a75d4d302..7e2199a9c 100644
--- a/crates/hir_def/src/lib.rs
+++ b/crates/hir_def/src/lib.rs
@@ -225,6 +225,13 @@ pub struct TypeParamId {
 pub type LocalTypeParamId = Idx<generics::TypeParamData>;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct LifetimeParamId {
+    pub parent: GenericDefId,
+    pub local_id: LocalLifetimeParamId,
+}
+pub type LocalLifetimeParamId = Idx<generics::LifetimeParamData>;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum ContainerId {
     ModuleId(ModuleId),
     DefWithBodyId(DefWithBodyId),
diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
index 5b8c1e449..00a69a8a6 100644
--- a/crates/hir_def/src/path.rs
+++ b/crates/hir_def/src/path.rs
@@ -7,7 +7,7 @@ use std::{
     sync::Arc,
 };
 
-use crate::body::LowerCtx;
+use crate::{body::LowerCtx, type_ref::LifetimeRef};
 use base_db::CrateId;
 use hir_expand::{
     hygiene::Hygiene,
@@ -145,7 +145,7 @@ pub struct AssociatedTypeBinding {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum GenericArg {
     Type(TypeRef),
-    // or lifetime...
+    Lifetime(LifetimeRef),
 }
 
 impl Path {
diff --git a/crates/hir_def/src/path/lower.rs b/crates/hir_def/src/path/lower.rs
index 07b9723ce..60fa7646b 100644
--- a/crates/hir_def/src/path/lower.rs
+++ b/crates/hir_def/src/path/lower.rs
@@ -15,7 +15,7 @@ use super::AssociatedTypeBinding;
 use crate::{
     body::LowerCtx,
     path::{GenericArg, GenericArgs, ModPath, Path, PathKind},
-    type_ref::{TypeBound, TypeRef},
+    type_ref::{LifetimeRef, TypeBound, TypeRef},
 };
 
 pub(super) use lower_use::lower_use_tree;
@@ -170,8 +170,14 @@ pub(super) fn lower_generic_args(
                     bindings.push(AssociatedTypeBinding { name, type_ref, bounds });
                 }
             }
-            // Lifetimes and constants are ignored for now.
-            ast::GenericArg::LifetimeArg(_) | ast::GenericArg::ConstArg(_) => (),
+            ast::GenericArg::LifetimeArg(lifetime_arg) => {
+                if let Some(lifetime) = lifetime_arg.lifetime_token() {
+                    let lifetime_ref = LifetimeRef::from_token(lifetime);
+                    args.push(GenericArg::Lifetime(lifetime_ref))
+                }
+            }
+            // constants are ignored for now.
+            ast::GenericArg::ConstArg(_) => (),
         }
     }
 
diff --git a/crates/hir_def/src/type_ref.rs b/crates/hir_def/src/type_ref.rs
index 1a78c1444..347ceabb9 100644
--- a/crates/hir_def/src/type_ref.rs
+++ b/crates/hir_def/src/type_ref.rs
@@ -1,6 +1,7 @@
 //! HIR for references to types. Paths in these are not yet resolved. They can
 //! be directly created from an ast::TypeRef, without further queries.
-use syntax::ast::{self};
+use hir_expand::name::Name;
+use syntax::{ast, SyntaxToken};
 
 use crate::{body::LowerCtx, path::Path};
 
@@ -58,7 +59,7 @@ pub enum TypeRef {
     Tuple(Vec<TypeRef>),
     Path(Path),
     RawPtr(Box<TypeRef>, Mutability),
-    Reference(Box<TypeRef>, Mutability),
+    Reference(Box<TypeRef>, Option<LifetimeRef>, Mutability),
     Array(Box<TypeRef> /*, Expr*/),
     Slice(Box<TypeRef>),
     /// A fn pointer. Last element of the vector is the return type.
@@ -70,10 +71,29 @@ pub enum TypeRef {
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct LifetimeRef {
+    pub name: Name,
+}
+
+impl LifetimeRef {
+    pub(crate) fn new_name(name: Name) -> Self {
+        LifetimeRef { name }
+    }
+
+    pub(crate) fn from_token(token: SyntaxToken) -> Self {
+        LifetimeRef { name: Name::new_lifetime(&token) }
+    }
+
+    pub fn missing() -> LifetimeRef {
+        LifetimeRef { name: Name::missing() }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub enum TypeBound {
     Path(Path),
-    // also for<> bounds
-    // also Lifetimes
+    // ForLifetime(Vec<LifetimeRef>, Path), FIXME ForLifetime
+    Lifetime(LifetimeRef),
     Error,
 }
 
@@ -107,8 +127,9 @@ impl TypeRef {
             }
             ast::Type::RefType(inner) => {
                 let inner_ty = TypeRef::from_ast_opt(&ctx, inner.ty());
+                let lifetime = inner.lifetime_token().map(|t| LifetimeRef::from_token(t));
                 let mutability = Mutability::from_mutable(inner.mut_token().is_some());
-                TypeRef::Reference(Box::new(inner_ty), mutability)
+                TypeRef::Reference(Box::new(inner_ty), lifetime, mutability)
             }
             ast::Type::InferType(_inner) => TypeRef::Placeholder,
             ast::Type::FnPtrType(inner) => {
@@ -163,14 +184,14 @@ impl TypeRef {
                     types.iter().for_each(|t| go(t, f))
                 }
                 TypeRef::RawPtr(type_ref, _)
-                | TypeRef::Reference(type_ref, _)
+                | TypeRef::Reference(type_ref, ..)
                 | TypeRef::Array(type_ref)
                 | TypeRef::Slice(type_ref) => go(&type_ref, f),
                 TypeRef::ImplTrait(bounds) | TypeRef::DynTrait(bounds) => {
                     for bound in bounds {
                         match bound {
                             TypeBound::Path(path) => go_path(path, f),
-                            TypeBound::Error => (),
+                            TypeBound::Lifetime(_) | TypeBound::Error => (),
                         }
                     }
                 }
@@ -186,8 +207,12 @@ impl TypeRef {
             for segment in path.segments().iter() {
                 if let Some(args_and_bindings) = segment.args_and_bindings {
                     for arg in &args_and_bindings.args {
-                        let crate::path::GenericArg::Type(type_ref) = arg;
-                        go(type_ref, f);
+                        match arg {
+                            crate::path::GenericArg::Type(type_ref) => {
+                                go(type_ref, f);
+                            }
+                            crate::path::GenericArg::Lifetime(_) => {}
+                        }
                     }
                     for binding in &args_and_bindings.bindings {
                         if let Some(type_ref) = &binding.type_ref {
@@ -196,7 +221,7 @@ impl TypeRef {
                         for bound in &binding.bounds {
                             match bound {
                                 TypeBound::Path(path) => go_path(path, f),
-                                TypeBound::Error => (),
+                                TypeBound::Lifetime(_) | TypeBound::Error => (),
                             }
                         }
                     }
@@ -232,7 +257,10 @@ impl TypeBound {
                 };
                 TypeBound::Path(path)
             }
-            ast::TypeBoundKind::ForType(_) | ast::TypeBoundKind::Lifetime(_) => TypeBound::Error,
+            ast::TypeBoundKind::ForType(_) => TypeBound::Error, // FIXME ForType
+            ast::TypeBoundKind::Lifetime(lifetime) => {
+                TypeBound::Lifetime(LifetimeRef::from_token(lifetime))
+            }
         }
     }
 
diff --git a/crates/hir_expand/src/name.rs b/crates/hir_expand/src/name.rs
index b26ffa1ef..583ed6142 100644
--- a/crates/hir_expand/src/name.rs
+++ b/crates/hir_expand/src/name.rs
@@ -38,7 +38,7 @@ impl Name {
     }
 
     pub fn new_lifetime(lt: &syntax::SyntaxToken) -> Name {
-        assert!(lt.kind() == syntax::SyntaxKind::LIFETIME);
+        assert_eq!(lt.kind(), syntax::SyntaxKind::LIFETIME);
         Name(Repr::Text(lt.text().clone()))
     }
 
@@ -250,6 +250,8 @@ pub mod known {
     pub const SELF_PARAM: super::Name = super::Name::new_inline("self");
     pub const SELF_TYPE: super::Name = super::Name::new_inline("Self");
 
+    pub const STATIC_LIFETIME: super::Name = super::Name::new_inline("'static");
+
     #[macro_export]
     macro_rules! name {
         (self) => {
@@ -258,6 +260,9 @@ pub mod known {
         (Self) => {
             $crate::name::known::SELF_TYPE
         };
+        ('static) => {
+            $crate::name::known::STATIC_LIFETIME
+        };
         ($ident:ident) => {
             $crate::name::known::$ident
         };
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index e77481906..0d968cc68 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -4,7 +4,7 @@ use std::fmt;
 
 use crate::{
     db::HirDatabase, utils::generics, ApplicationTy, CallableDefId, FnSig, GenericPredicate,
-    Obligation, OpaqueTyId, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
+    Lifetime, Obligation, OpaqueTyId, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
 };
 use hir_def::{
     find_path, generics::TypeParamProvenance, item_scope::ItemInNs, AdtId, AssocContainerId,
@@ -710,6 +710,19 @@ impl HirDisplay for GenericPredicate {
     }
 }
 
+impl HirDisplay for Lifetime {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        match self {
+            Lifetime::Parameter(id) => {
+                let generics = generics(f.db.upcast(), id.parent);
+                let param_data = &generics.params.lifetimes[id.local_id];
+                write!(f, "{}", &param_data.name)
+            }
+            Lifetime::Static => write!(f, "'static"),
+        }
+    }
+}
+
 impl HirDisplay for Obligation {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         match self {
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index d7ad198b3..ca005bc99 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -862,6 +862,7 @@ impl<'a> InferenceContext<'a> {
                         let ty = self.make_ty(type_ref);
                         substs.push(ty);
                     }
+                    GenericArg::Lifetime(_) => {}
                 }
             }
         };
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 5a8c97198..357bd92f9 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -29,8 +29,8 @@ use base_db::{salsa, CrateId};
 use hir_def::{
     expr::ExprId,
     type_ref::{Mutability, Rawness},
-    AdtId, AssocContainerId, DefWithBodyId, GenericDefId, HasModule, Lookup, TraitId, TypeAliasId,
-    TypeParamId,
+    AdtId, AssocContainerId, DefWithBodyId, GenericDefId, HasModule, LifetimeParamId, Lookup,
+    TraitId, TypeAliasId, TypeParamId,
 };
 use itertools::Itertools;
 
@@ -52,6 +52,12 @@ pub use traits::{InEnvironment, Obligation, ProjectionPredicate, TraitEnvironmen
 
 pub use chalk_ir::{BoundVar, DebruijnIndex};
 
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub enum Lifetime {
+    Parameter(LifetimeParamId),
+    Static,
+}
+
 /// A type constructor or type name: this might be something like the primitive
 /// type `bool`, a struct like `Vec`, or things like function pointers or
 /// tuples.
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 708e2af0f..92f779360 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -12,7 +12,7 @@ use base_db::CrateId;
 use hir_def::{
     adt::StructKind,
     builtin_type::BuiltinType,
-    generics::{TypeParamProvenance, WherePredicate, WherePredicateTarget},
+    generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
     path::{GenericArg, Path, PathSegment, PathSegments},
     resolver::{HasResolver, Resolver, TypeNs},
     type_ref::{TypeBound, TypeRef},
@@ -171,7 +171,7 @@ impl Ty {
                 let inner_ty = Ty::from_hir(ctx, inner);
                 Ty::apply_one(TypeCtor::Slice, inner_ty)
             }
-            TypeRef::Reference(inner, mutability) => {
+            TypeRef::Reference(inner, _, mutability) => {
                 let inner_ty = Ty::from_hir(ctx, inner);
                 Ty::apply_one(TypeCtor::Ref(*mutability), inner_ty)
             }
@@ -555,7 +555,7 @@ fn substs_from_path_segment(
 
     substs.extend(iter::repeat(Ty::Unknown).take(parent_params));
 
-    let mut had_explicit_args = false;
+    let mut had_explicit_type_args = false;
 
     if let Some(generic_args) = &segment.args_and_bindings {
         if !generic_args.has_self_type {
@@ -568,10 +568,11 @@ fn substs_from_path_segment(
         for arg in generic_args.args.iter().skip(skip).take(expected_num) {
             match arg {
                 GenericArg::Type(type_ref) => {
-                    had_explicit_args = true;
+                    had_explicit_type_args = true;
                     let ty = Ty::from_hir(ctx, type_ref);
                     substs.push(ty);
                 }
+                GenericArg::Lifetime(_) => {}
             }
         }
     }
@@ -579,7 +580,7 @@ fn substs_from_path_segment(
     // handle defaults. In expression or pattern path segments without
     // explicitly specified type arguments, missing type arguments are inferred
     // (i.e. defaults aren't used).
-    if !infer_args || had_explicit_args {
+    if !infer_args || had_explicit_type_args {
         if let Some(def_generic) = def_generic {
             let defaults = ctx.db.generic_defaults(def_generic);
             assert_eq!(total_len, defaults.len());
@@ -657,7 +658,7 @@ impl TraitRef {
     ) -> Option<TraitRef> {
         match bound {
             TypeBound::Path(path) => TraitRef::from_path(ctx, path, Some(self_ty)),
-            TypeBound::Error => None,
+            TypeBound::Lifetime(_) | TypeBound::Error => None,
         }
     }
 }
@@ -667,22 +668,30 @@ impl GenericPredicate {
         ctx: &'a TyLoweringContext<'a>,
         where_predicate: &'a WherePredicate,
     ) -> impl Iterator<Item = GenericPredicate> + 'a {
-        let self_ty = match &where_predicate.target {
-            WherePredicateTarget::TypeRef(type_ref) => Ty::from_hir(ctx, type_ref),
-            WherePredicateTarget::TypeParam(param_id) => {
-                let generic_def = ctx.resolver.generic_def().expect("generics in scope");
-                let generics = generics(ctx.db.upcast(), generic_def);
-                let param_id = hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
-                match ctx.type_param_mode {
-                    TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
-                    TypeParamLoweringMode::Variable => {
-                        let idx = generics.param_idx(param_id).expect("matching generics");
-                        Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, idx))
+        match where_predicate {
+            WherePredicate::TypeBound { target, bound } => {
+                let self_ty = match target {
+                    WherePredicateTypeTarget::TypeRef(type_ref) => Ty::from_hir(ctx, type_ref),
+                    WherePredicateTypeTarget::TypeParam(param_id) => {
+                        let generic_def = ctx.resolver.generic_def().expect("generics in scope");
+                        let generics = generics(ctx.db.upcast(), generic_def);
+                        let param_id =
+                            hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
+                        match ctx.type_param_mode {
+                            TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
+                            TypeParamLoweringMode::Variable => {
+                                let idx = generics.param_idx(param_id).expect("matching generics");
+                                Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, idx))
+                            }
+                        }
                     }
-                }
+                };
+                GenericPredicate::from_type_bound(ctx, bound, self_ty)
+                    .collect::<Vec<_>>()
+                    .into_iter()
             }
-        };
-        GenericPredicate::from_type_bound(ctx, &where_predicate.bound, self_ty)
+            WherePredicate::Lifetime { .. } => vec![].into_iter(),
+        }
     }
 
     pub(crate) fn from_type_bound<'a>(
@@ -707,7 +716,7 @@ fn assoc_type_bindings_from_type_bound<'a>(
 ) -> impl Iterator<Item = GenericPredicate> + 'a {
     let last_segment = match bound {
         TypeBound::Path(path) => path.segments().last(),
-        TypeBound::Error => None,
+        TypeBound::Error | TypeBound::Lifetime(_) => None,
     };
     last_segment
         .into_iter()
@@ -872,11 +881,16 @@ pub(crate) fn generic_predicates_for_param_query(
     resolver
         .where_predicates_in_scope()
         // we have to filter out all other predicates *first*, before attempting to lower them
-        .filter(|pred| match &pred.target {
-            WherePredicateTarget::TypeRef(type_ref) => {
-                Ty::from_hir_only_param(&ctx, type_ref) == Some(param_id)
-            }
-            WherePredicateTarget::TypeParam(local_id) => *local_id == param_id.local_id,
+        .filter(|pred| match pred {
+            WherePredicate::TypeBound {
+                target: WherePredicateTypeTarget::TypeRef(type_ref),
+                ..
+            } => Ty::from_hir_only_param(&ctx, type_ref) == Some(param_id),
+            WherePredicate::TypeBound {
+                target: WherePredicateTypeTarget::TypeParam(local_id),
+                ..
+            } => *local_id == param_id.local_id,
+            WherePredicate::Lifetime { .. } => false,
         })
         .flat_map(|pred| {
             GenericPredicate::from_where_predicate(&ctx, pred)
diff --git a/crates/hir_ty/src/utils.rs b/crates/hir_ty/src/utils.rs
index e3e244268..af880c065 100644
--- a/crates/hir_ty/src/utils.rs
+++ b/crates/hir_ty/src/utils.rs
@@ -2,11 +2,10 @@
 //! query, but can't be computed directly from `*Data` (ie, which need a `db`).
 use std::sync::Arc;
 
-use hir_def::generics::WherePredicateTarget;
 use hir_def::{
     adt::VariantData,
     db::DefDatabase,
-    generics::{GenericParams, TypeParamData, TypeParamProvenance},
+    generics::{GenericParams, TypeParamData, TypeParamProvenance, WherePredicateTypeTarget},
     path::Path,
     resolver::{HasResolver, TypeNs},
     type_ref::TypeRef,
@@ -27,14 +26,19 @@ fn direct_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     generic_params
         .where_predicates
         .iter()
-        .filter_map(|pred| match &pred.target {
-            WherePredicateTarget::TypeRef(TypeRef::Path(p)) if p == &Path::from(name![Self]) => {
-                pred.bound.as_path()
-            }
-            WherePredicateTarget::TypeParam(local_id) if Some(*local_id) == trait_self => {
-                pred.bound.as_path()
-            }
-            _ => None,
+        .filter_map(|pred| match pred {
+            hir_def::generics::WherePredicate::TypeBound { target, bound } => match target {
+                WherePredicateTypeTarget::TypeRef(TypeRef::Path(p))
+                    if p == &Path::from(name![Self]) =>
+                {
+                    bound.as_path()
+                }
+                WherePredicateTypeTarget::TypeParam(local_id) if Some(*local_id) == trait_self => {
+                    bound.as_path()
+                }
+                _ => None,
+            },
+            hir_def::generics::WherePredicate::Lifetime { .. } => None,
         })
         .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path.mod_path()) {
             Some(TypeNs::TraitId(t)) => Some(t),