7 files changed, 70 insertions, 18 deletions

diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index b7ded3478..97b7a8b5f 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -18,10 +18,10 @@ use hir_def::{
     resolver::{HasResolver, Resolver},
     src::HasSource as _,
     type_ref::{Mutability, TypeRef},
-    AdtId, AssocContainerId, AssocItemId, AssocItemLoc, AttrDefId, ConstId, DefWithBodyId, EnumId,
-    FunctionId, GenericDefId, HasModule, ImplId, LifetimeParamId, LocalEnumVariantId, LocalFieldId,
-    LocalModuleId, Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId, TypeParamId,
-    UnionId,
+    AdtId, AssocContainerId, AssocItemId, AssocItemLoc, AttrDefId, ConstId, ConstParamId,
+    DefWithBodyId, EnumId, 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::{
@@ -1125,7 +1125,12 @@ impl GenericDef {
                 id: LifetimeParamId { parent: self.into(), local_id },
             })
             .map(GenericParam::LifetimeParam);
-        ty_params.chain(lt_params).collect()
+        let const_params = generics
+            .consts
+            .iter()
+            .map(|(local_id, _)| ConstParam { id: ConstParamId { parent: self.into(), local_id } })
+            .map(GenericParam::ConstParam);
+        ty_params.chain(lt_params).chain(const_params).collect()
     }
 
     pub fn type_params(self, db: &dyn HirDatabase) -> Vec<TypeParam> {
@@ -1237,8 +1242,9 @@ impl Label {
 pub enum GenericParam {
     TypeParam(TypeParam),
     LifetimeParam(LifetimeParam),
+    ConstParam(ConstParam),
 }
-impl_from!(TypeParam, LifetimeParam for GenericParam);
+impl_from!(TypeParam, LifetimeParam, ConstParam for GenericParam);
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct TypeParam {
@@ -1300,6 +1306,26 @@ impl LifetimeParam {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct ConstParam {
+    pub(crate) id: ConstParamId,
+}
+
+impl ConstParam {
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        let params = db.generic_params(self.id.parent);
+        params.consts[self.id.local_id].name.clone()
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.id.parent.module(db.upcast()).into()
+    }
+
+    pub fn parent(self, _db: &dyn HirDatabase) -> GenericDef {
+        self.id.parent.into()
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct Impl {
     pub(crate) id: ImplId,
diff --git a/crates/hir/src/from_id.rs b/crates/hir/src/from_id.rs
index a0792b9a6..2422887e3 100644
--- a/crates/hir/src/from_id.rs
+++ b/crates/hir/src/from_id.rs
@@ -44,6 +44,7 @@ from_id![
     (hir_def::ImplId, crate::Impl),
     (hir_def::TypeParamId, crate::TypeParam),
     (hir_def::LifetimeParamId, crate::LifetimeParam),
+    (hir_def::ConstParamId, crate::ConstParam),
     (hir_expand::MacroDefId, crate::MacroDef)
 ];
 
diff --git a/crates/hir/src/has_source.rs b/crates/hir/src/has_source.rs
index 0dc07c33e..dd7c0c570 100644
--- a/crates/hir/src/has_source.rs
+++ b/crates/hir/src/has_source.rs
@@ -10,8 +10,8 @@ use hir_expand::InFile;
 use syntax::ast;
 
 use crate::{
-    db::HirDatabase, Const, Enum, Field, FieldSource, Function, Impl, LifetimeParam, MacroDef,
-    Module, Static, Struct, Trait, TypeAlias, TypeParam, Union, Variant,
+    db::HirDatabase, Const, ConstParam, Enum, Field, FieldSource, Function, Impl, LifetimeParam,
+    MacroDef, Module, Static, Struct, Trait, TypeAlias, TypeParam, Union, Variant,
 };
 
 pub trait HasSource {
@@ -140,3 +140,11 @@ impl HasSource for LifetimeParam {
         child_source.map(|it| it[self.id.local_id].clone())
     }
 }
+
+impl HasSource for ConstParam {
+    type Ast = ast::ConstParam;
+    fn source(self, db: &dyn HirDatabase) -> InFile<Self::Ast> {
+        let child_source = self.id.parent.child_source(db.upcast());
+        child_source.map(|it| it[self.id.local_id].clone())
+    }
+}
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 7ac9fd507..8ac27e2dd 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -34,9 +34,9 @@ pub use crate::{
     attrs::{HasAttrs, Namespace},
     code_model::{
         Access, Adt, AsAssocItem, AssocItem, AssocItemContainer, Callable, CallableKind, Const,
-        Crate, CrateDependency, DefWithBody, Enum, Field, FieldSource, Function, GenericDef,
-        HasVisibility, Impl, Label, LifetimeParam, Local, MacroDef, Module, ModuleDef, ScopeDef,
-        Static, Struct, Trait, Type, TypeAlias, TypeParam, Union, Variant, VariantDef,
+        ConstParam, Crate, CrateDependency, DefWithBody, Enum, Field, FieldSource, Function,
+        GenericDef, HasVisibility, Impl, Label, LifetimeParam, Local, MacroDef, Module, ModuleDef,
+        ScopeDef, Static, Struct, Trait, Type, TypeAlias, TypeParam, Union, Variant, VariantDef,
     },
     has_source::HasSource,
     semantics::{PathResolution, Semantics, SemanticsScope},
diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index 67cd16e31..cd689c869 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -25,9 +25,9 @@ use crate::{
     diagnostics::Diagnostic,
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
     source_analyzer::{resolve_hir_path, SourceAnalyzer},
-    AssocItem, Callable, Crate, Field, Function, HirFileId, Impl, InFile, Label, LifetimeParam,
-    Local, MacroDef, Module, ModuleDef, Name, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam,
-    VariantDef,
+    AssocItem, Callable, ConstParam, Crate, Field, Function, HirFileId, Impl, InFile, Label,
+    LifetimeParam, Local, MacroDef, Module, ModuleDef, Name, Path, ScopeDef, Trait, Type,
+    TypeAlias, TypeParam, VariantDef,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -38,6 +38,7 @@ pub enum PathResolution {
     Local(Local),
     /// A generic parameter
     TypeParam(TypeParam),
+    ConstParam(ConstParam),
     SelfType(Impl),
     Macro(MacroDef),
     AssocItem(AssocItem),
@@ -59,7 +60,9 @@ impl PathResolution {
             PathResolution::Def(ModuleDef::TypeAlias(alias)) => {
                 Some(TypeNs::TypeAliasId((*alias).into()))
             }
-            PathResolution::Local(_) | PathResolution::Macro(_) => None,
+            PathResolution::Local(_) | PathResolution::Macro(_) | PathResolution::ConstParam(_) => {
+                None
+            }
             PathResolution::TypeParam(param) => Some(TypeNs::GenericParam((*param).into())),
             PathResolution::SelfType(impl_def) => Some(TypeNs::SelfType((*impl_def).into())),
             PathResolution::AssocItem(AssocItem::Const(_))
@@ -744,6 +747,7 @@ to_def_impls![
     (crate::Variant, ast::Variant, enum_variant_to_def),
     (crate::TypeParam, ast::TypeParam, type_param_to_def),
     (crate::LifetimeParam, ast::LifetimeParam, lifetime_param_to_def),
+    (crate::ConstParam, ast::ConstParam, const_param_to_def),
     (crate::MacroDef, ast::MacroRules, macro_rules_to_def),
     (crate::Local, ast::IdentPat, bind_pat_to_def),
     (crate::Label, ast::Label, label_to_def),
diff --git a/crates/hir/src/semantics/source_to_def.rs b/crates/hir/src/semantics/source_to_def.rs
index 424e6e8a9..4b9ebff72 100644
--- a/crates/hir/src/semantics/source_to_def.rs
+++ b/crates/hir/src/semantics/source_to_def.rs
@@ -6,9 +6,9 @@ use hir_def::{
     dyn_map::DynMap,
     expr::{LabelId, PatId},
     keys::{self, Key},
-    ConstId, DefWithBodyId, EnumId, EnumVariantId, FieldId, FunctionId, GenericDefId, ImplId,
-    LifetimeParamId, ModuleId, StaticId, StructId, TraitId, TypeAliasId, TypeParamId, UnionId,
-    VariantId,
+    ConstId, ConstParamId, DefWithBodyId, EnumId, EnumVariantId, FieldId, FunctionId, GenericDefId,
+    ImplId, LifetimeParamId, ModuleId, StaticId, StructId, TraitId, TypeAliasId, TypeParamId,
+    UnionId, VariantId,
 };
 use hir_expand::{name::AsName, AstId, MacroDefKind};
 use rustc_hash::FxHashMap;
@@ -157,6 +157,18 @@ impl SourceToDefCtx<'_, '_> {
         dyn_map[keys::LIFETIME_PARAM].get(&src).copied()
     }
 
+    pub(super) fn const_param_to_def(
+        &mut self,
+        src: InFile<ast::ConstParam>,
+    ) -> Option<ConstParamId> {
+        let container: ChildContainer =
+            self.find_generic_param_container(src.as_ref().map(|it| it.syntax()))?.into();
+        let db = self.db;
+        let dyn_map =
+            &*self.cache.entry(container).or_insert_with(|| container.child_by_source(db));
+        dyn_map[keys::CONST_PARAM].get(&src).copied()
+    }
+
     // FIXME: use DynMap as well?
     pub(super) fn macro_rules_to_def(
         &mut self,
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index bddc49c05..30a8e513d 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -479,6 +479,7 @@ pub(crate) fn resolve_hir_path(
                 ValueNs::StructId(it) => PathResolution::Def(Struct::from(it).into()),
                 ValueNs::EnumVariantId(it) => PathResolution::Def(Variant::from(it).into()),
                 ValueNs::ImplSelf(impl_id) => PathResolution::SelfType(impl_id.into()),
+                ValueNs::GenericParam(it) => PathResolution::ConstParam(it.into()),
             };
             Some(res)
         });