6 files changed, 637 insertions, 2 deletions

diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index a5bb60e85..77f091288 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -12,6 +12,7 @@ use ra_syntax::{
     },
     AstNode, AstPtr,
 };
+use test_utils::tested_by;
 
 use crate::{
     body::{Body, BodySourceMap, Expander, PatPtr},
@@ -153,6 +154,7 @@ where
                         None => self.collect_expr_opt(condition.expr()),
                         // if let -- desugar to match
                         Some(pat) => {
+                            tested_by!(infer_resolve_while_let);
                             let pat = self.collect_pat(pat);
                             let match_expr = self.collect_expr_opt(condition.expr());
                             let placeholder_pat = self.missing_pat();
diff --git a/crates/ra_hir_def/src/body/scope.rs b/crates/ra_hir_def/src/body/scope.rs
index aeb71ff22..5d7d17231 100644
--- a/crates/ra_hir_def/src/body/scope.rs
+++ b/crates/ra_hir_def/src/body/scope.rs
@@ -174,7 +174,7 @@ mod tests {
     use hir_expand::{name::AsName, Source};
     use ra_db::{fixture::WithFixture, FileId, SourceDatabase};
     use ra_syntax::{algo::find_node_at_offset, ast, AstNode};
-    use test_utils::{assert_eq_text, extract_offset};
+    use test_utils::{assert_eq_text, covers, extract_offset};
 
     use crate::{db::DefDatabase2, test_db::TestDB, FunctionId, ModuleDefId};
 
@@ -382,4 +382,20 @@ mod tests {
             53,
         );
     }
+
+    #[test]
+    fn infer_resolve_while_let() {
+        covers!(infer_resolve_while_let);
+        do_check_local_name(
+            r#"
+fn test() {
+    let foo: Option<f32> = None;
+    while let Option::Some(spam) = foo {
+        spam<|>
+    }
+}
+"#,
+            75,
+        );
+    }
 }
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
index 0af41de87..d579f5c7e 100644
--- a/crates/ra_hir_def/src/lib.rs
+++ b/crates/ra_hir_def/src/lib.rs
@@ -19,6 +19,7 @@ pub mod expr;
 pub mod body;
 pub mod generics;
 pub mod traits;
+pub mod resolver;
 
 #[cfg(test)]
 mod test_db;
diff --git a/crates/ra_hir_def/src/marks.rs b/crates/ra_hir_def/src/marks.rs
index 0b99eac71..65239ca0a 100644
--- a/crates/ra_hir_def/src/marks.rs
+++ b/crates/ra_hir_def/src/marks.rs
@@ -11,4 +11,5 @@ test_utils::marks!(
     prelude_is_macro_use
     macro_dollar_crate_self
     macro_dollar_crate_other
+    infer_resolve_while_let
 );
diff --git a/crates/ra_hir_def/src/resolver.rs b/crates/ra_hir_def/src/resolver.rs
new file mode 100644
index 000000000..840785baa
--- /dev/null
+++ b/crates/ra_hir_def/src/resolver.rs
@@ -0,0 +1,608 @@
+//! Name resolution façade.
+use std::sync::Arc;
+
+use hir_expand::{
+    name::{self, Name},
+    MacroDefId,
+};
+use ra_db::CrateId;
+use rustc_hash::FxHashSet;
+
+use crate::{
+    body::scope::{ExprScopes, ScopeId},
+    builtin_type::BuiltinType,
+    db::DefDatabase2,
+    expr::{ExprId, PatId},
+    generics::GenericParams,
+    nameres::{per_ns::PerNs, CrateDefMap},
+    path::{Path, PathKind},
+    AdtId, AstItemDef, ConstId, ContainerId, CrateModuleId, DefWithBodyId, EnumId, EnumVariantId,
+    FunctionId, GenericDefId, ImplId, Lookup, ModuleDefId, ModuleId, StaticId, StructId, TraitId,
+    TypeAliasId, UnionId,
+};
+
+#[derive(Debug, Clone, Default)]
+pub struct Resolver {
+    scopes: Vec<Scope>,
+}
+
+// FIXME how to store these best
+#[derive(Debug, Clone)]
+pub(crate) struct ModuleItemMap {
+    crate_def_map: Arc<CrateDefMap>,
+    module_id: CrateModuleId,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct ExprScope {
+    owner: DefWithBodyId,
+    expr_scopes: Arc<ExprScopes>,
+    scope_id: ScopeId,
+}
+
+#[derive(Debug, Clone)]
+pub(crate) enum Scope {
+    /// All the items and imported names of a module
+    ModuleScope(ModuleItemMap),
+    /// Brings the generic parameters of an item into scope
+    GenericParams { def: GenericDefId, params: Arc<GenericParams> },
+    /// Brings `Self` in `impl` block into scope
+    ImplBlockScope(ImplId),
+    /// Brings `Self` in enum, struct and union definitions into scope
+    AdtScope(AdtId),
+    /// Local bindings
+    ExprScope(ExprScope),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum TypeNs {
+    SelfType(ImplId),
+    GenericParam(u32),
+    AdtId(AdtId),
+    AdtSelfType(AdtId),
+    EnumVariantId(EnumVariantId),
+    TypeAliasId(TypeAliasId),
+    BuiltinType(BuiltinType),
+    TraitId(TraitId),
+    // Module belong to type ns, but the resolver is used when all module paths
+    // are fully resolved.
+    // ModuleId(ModuleId)
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum ResolveValueResult {
+    ValueNs(ValueNs),
+    Partial(TypeNs, usize),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum ValueNs {
+    LocalBinding(PatId),
+    FunctionId(FunctionId),
+    ConstId(ConstId),
+    StaticId(StaticId),
+    StructId(StructId),
+    EnumVariantId(EnumVariantId),
+}
+
+impl Resolver {
+    /// Resolve known trait from std, like `std::futures::Future`
+    pub fn resolve_known_trait(&self, db: &impl DefDatabase2, path: &Path) -> Option<TraitId> {
+        let res = self.resolve_module_path(db, path).take_types()?;
+        match res {
+            ModuleDefId::TraitId(it) => Some(it),
+            _ => None,
+        }
+    }
+
+    /// Resolve known struct from std, like `std::boxed::Box`
+    pub fn resolve_known_struct(&self, db: &impl DefDatabase2, path: &Path) -> Option<StructId> {
+        let res = self.resolve_module_path(db, path).take_types()?;
+        match res {
+            ModuleDefId::AdtId(AdtId::StructId(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    /// Resolve known enum from std, like `std::result::Result`
+    pub fn resolve_known_enum(&self, db: &impl DefDatabase2, path: &Path) -> Option<EnumId> {
+        let res = self.resolve_module_path(db, path).take_types()?;
+        match res {
+            ModuleDefId::AdtId(AdtId::EnumId(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    /// pub only for source-binder
+    pub fn resolve_module_path(&self, db: &impl DefDatabase2, path: &Path) -> PerNs {
+        let (item_map, module) = match self.module() {
+            Some(it) => it,
+            None => return PerNs::none(),
+        };
+        let (module_res, segment_index) = item_map.resolve_path(db, module, path);
+        if segment_index.is_some() {
+            return PerNs::none();
+        }
+        module_res
+    }
+
+    pub fn resolve_path_in_type_ns(
+        &self,
+        db: &impl DefDatabase2,
+        path: &Path,
+    ) -> Option<(TypeNs, Option<usize>)> {
+        if path.is_type_relative() {
+            return None;
+        }
+        let first_name = &path.segments.first()?.name;
+        let skip_to_mod = path.kind != PathKind::Plain;
+        for scope in self.scopes.iter().rev() {
+            match scope {
+                Scope::ExprScope(_) => continue,
+                Scope::GenericParams { .. } | Scope::ImplBlockScope(_) if skip_to_mod => continue,
+
+                Scope::GenericParams { params, .. } => {
+                    if let Some(param) = params.find_by_name(first_name) {
+                        let idx = if path.segments.len() == 1 { None } else { Some(1) };
+                        return Some((TypeNs::GenericParam(param.idx), idx));
+                    }
+                }
+                Scope::ImplBlockScope(impl_) => {
+                    if first_name == &name::SELF_TYPE {
+                        let idx = if path.segments.len() == 1 { None } else { Some(1) };
+                        return Some((TypeNs::SelfType(*impl_), idx));
+                    }
+                }
+                Scope::AdtScope(adt) => {
+                    if first_name == &name::SELF_TYPE {
+                        let idx = if path.segments.len() == 1 { None } else { Some(1) };
+                        return Some((TypeNs::AdtSelfType(*adt), idx));
+                    }
+                }
+                Scope::ModuleScope(m) => {
+                    let (module_def, idx) = m.crate_def_map.resolve_path(db, m.module_id, path);
+                    let res = match module_def.take_types()? {
+                        ModuleDefId::AdtId(it) => TypeNs::AdtId(it),
+                        ModuleDefId::EnumVariantId(it) => TypeNs::EnumVariantId(it),
+
+                        ModuleDefId::TypeAliasId(it) => TypeNs::TypeAliasId(it),
+                        ModuleDefId::BuiltinType(it) => TypeNs::BuiltinType(it),
+
+                        ModuleDefId::TraitId(it) => TypeNs::TraitId(it),
+
+                        ModuleDefId::FunctionId(_)
+                        | ModuleDefId::ConstId(_)
+                        | ModuleDefId::StaticId(_)
+                        | ModuleDefId::ModuleId(_) => return None,
+                    };
+                    return Some((res, idx));
+                }
+            }
+        }
+        None
+    }
+
+    pub fn resolve_path_in_type_ns_fully(
+        &self,
+        db: &impl DefDatabase2,
+        path: &Path,
+    ) -> Option<TypeNs> {
+        let (res, unresolved) = self.resolve_path_in_type_ns(db, path)?;
+        if unresolved.is_some() {
+            return None;
+        }
+        Some(res)
+    }
+
+    pub fn resolve_path_in_value_ns<'p>(
+        &self,
+        db: &impl DefDatabase2,
+        path: &'p Path,
+    ) -> Option<ResolveValueResult> {
+        if path.is_type_relative() {
+            return None;
+        }
+        let n_segments = path.segments.len();
+        let tmp = name::SELF_PARAM;
+        let first_name = if path.is_self() { &tmp } else { &path.segments.first()?.name };
+        let skip_to_mod = path.kind != PathKind::Plain && !path.is_self();
+        for scope in self.scopes.iter().rev() {
+            match scope {
+                Scope::AdtScope(_)
+                | Scope::ExprScope(_)
+                | Scope::GenericParams { .. }
+                | Scope::ImplBlockScope(_)
+                    if skip_to_mod =>
+                {
+                    continue
+                }
+
+                Scope::ExprScope(scope) if n_segments <= 1 => {
+                    let entry = scope
+                        .expr_scopes
+                        .entries(scope.scope_id)
+                        .iter()
+                        .find(|entry| entry.name() == first_name);
+
+                    if let Some(e) = entry {
+                        return Some(ResolveValueResult::ValueNs(ValueNs::LocalBinding(e.pat())));
+                    }
+                }
+                Scope::ExprScope(_) => continue,
+
+                Scope::GenericParams { params, .. } if n_segments > 1 => {
+                    if let Some(param) = params.find_by_name(first_name) {
+                        let ty = TypeNs::GenericParam(param.idx);
+                        return Some(ResolveValueResult::Partial(ty, 1));
+                    }
+                }
+                Scope::GenericParams { .. } => continue,
+
+                Scope::ImplBlockScope(impl_) if n_segments > 1 => {
+                    if first_name == &name::SELF_TYPE {
+                        let ty = TypeNs::SelfType(*impl_);
+                        return Some(ResolveValueResult::Partial(ty, 1));
+                    }
+                }
+                Scope::AdtScope(adt) if n_segments > 1 => {
+                    if first_name == &name::SELF_TYPE {
+                        let ty = TypeNs::AdtSelfType(*adt);
+                        return Some(ResolveValueResult::Partial(ty, 1));
+                    }
+                }
+                Scope::ImplBlockScope(_) | Scope::AdtScope(_) => continue,
+
+                Scope::ModuleScope(m) => {
+                    let (module_def, idx) = m.crate_def_map.resolve_path(db, m.module_id, path);
+                    return match idx {
+                        None => {
+                            let value = match module_def.take_values()? {
+                                ModuleDefId::FunctionId(it) => ValueNs::FunctionId(it),
+                                ModuleDefId::AdtId(AdtId::StructId(it)) => ValueNs::StructId(it),
+                                ModuleDefId::EnumVariantId(it) => ValueNs::EnumVariantId(it),
+                                ModuleDefId::ConstId(it) => ValueNs::ConstId(it),
+                                ModuleDefId::StaticId(it) => ValueNs::StaticId(it),
+
+                                ModuleDefId::AdtId(AdtId::EnumId(_))
+                                | ModuleDefId::AdtId(AdtId::UnionId(_))
+                                | ModuleDefId::TraitId(_)
+                                | ModuleDefId::TypeAliasId(_)
+                                | ModuleDefId::BuiltinType(_)
+                                | ModuleDefId::ModuleId(_) => return None,
+                            };
+                            Some(ResolveValueResult::ValueNs(value))
+                        }
+                        Some(idx) => {
+                            let ty = match module_def.take_types()? {
+                                ModuleDefId::AdtId(it) => TypeNs::AdtId(it),
+                                ModuleDefId::TraitId(it) => TypeNs::TraitId(it),
+                                ModuleDefId::TypeAliasId(it) => TypeNs::TypeAliasId(it),
+                                ModuleDefId::BuiltinType(it) => TypeNs::BuiltinType(it),
+
+                                ModuleDefId::ModuleId(_)
+                                | ModuleDefId::FunctionId(_)
+                                | ModuleDefId::EnumVariantId(_)
+                                | ModuleDefId::ConstId(_)
+                                | ModuleDefId::StaticId(_) => return None,
+                            };
+                            Some(ResolveValueResult::Partial(ty, idx))
+                        }
+                    };
+                }
+            }
+        }
+        None
+    }
+
+    pub fn resolve_path_in_value_ns_fully(
+        &self,
+        db: &impl DefDatabase2,
+        path: &Path,
+    ) -> Option<ValueNs> {
+        match self.resolve_path_in_value_ns(db, path)? {
+            ResolveValueResult::ValueNs(it) => Some(it),
+            ResolveValueResult::Partial(..) => None,
+        }
+    }
+
+    pub fn resolve_path_as_macro(&self, db: &impl DefDatabase2, path: &Path) -> Option<MacroDefId> {
+        let (item_map, module) = self.module()?;
+        item_map.resolve_path(db, module, path).0.get_macros()
+    }
+
+    pub fn process_all_names(&self, db: &impl DefDatabase2, f: &mut dyn FnMut(Name, ScopeDef)) {
+        for scope in self.scopes.iter().rev() {
+            scope.process_names(db, f);
+        }
+    }
+
+    pub fn traits_in_scope(&self, db: &impl DefDatabase2) -> FxHashSet<TraitId> {
+        let mut traits = FxHashSet::default();
+        for scope in &self.scopes {
+            if let Scope::ModuleScope(m) = scope {
+                if let Some(prelude) = m.crate_def_map.prelude() {
+                    let prelude_def_map = db.crate_def_map(prelude.krate);
+                    traits.extend(prelude_def_map[prelude.module_id].scope.traits());
+                }
+                traits.extend(m.crate_def_map[m.module_id].scope.traits());
+            }
+        }
+        traits
+    }
+
+    fn module(&self) -> Option<(&CrateDefMap, CrateModuleId)> {
+        self.scopes.iter().rev().find_map(|scope| match scope {
+            Scope::ModuleScope(m) => Some((&*m.crate_def_map, m.module_id)),
+
+            _ => None,
+        })
+    }
+
+    pub fn krate(&self) -> Option<CrateId> {
+        self.module().map(|t| t.0.krate())
+    }
+
+    pub fn where_predicates_in_scope<'a>(
+        &'a self,
+    ) -> impl Iterator<Item = &'a crate::generics::WherePredicate> + 'a {
+        self.scopes
+            .iter()
+            .filter_map(|scope| match scope {
+                Scope::GenericParams { params, .. } => Some(params),
+                _ => None,
+            })
+            .flat_map(|params| params.where_predicates.iter())
+    }
+
+    pub fn generic_def(&self) -> Option<GenericDefId> {
+        self.scopes.iter().find_map(|scope| match scope {
+            Scope::GenericParams { def, .. } => Some(*def),
+            _ => None,
+        })
+    }
+
+    pub fn body_owner(&self) -> Option<DefWithBodyId> {
+        self.scopes.iter().find_map(|scope| match scope {
+            Scope::ExprScope(it) => Some(it.owner),
+            _ => None,
+        })
+    }
+}
+
+impl Resolver {
+    pub(crate) fn push_scope(mut self, scope: Scope) -> Resolver {
+        self.scopes.push(scope);
+        self
+    }
+
+    pub(crate) fn push_generic_params_scope(
+        self,
+        db: &impl DefDatabase2,
+        def: GenericDefId,
+    ) -> Resolver {
+        let params = db.generic_params(def);
+        if params.params.is_empty() {
+            self
+        } else {
+            self.push_scope(Scope::GenericParams { def, params })
+        }
+    }
+
+    pub(crate) fn push_impl_block_scope(self, impl_block: ImplId) -> Resolver {
+        self.push_scope(Scope::ImplBlockScope(impl_block))
+    }
+
+    pub(crate) fn push_module_scope(
+        self,
+        crate_def_map: Arc<CrateDefMap>,
+        module_id: CrateModuleId,
+    ) -> Resolver {
+        self.push_scope(Scope::ModuleScope(ModuleItemMap { crate_def_map, module_id }))
+    }
+
+    pub(crate) fn push_expr_scope(
+        self,
+        owner: DefWithBodyId,
+        expr_scopes: Arc<ExprScopes>,
+        scope_id: ScopeId,
+    ) -> Resolver {
+        self.push_scope(Scope::ExprScope(ExprScope { owner, expr_scopes, scope_id }))
+    }
+}
+
+pub enum ScopeDef {
+    PerNs(PerNs),
+    ImplSelfType(ImplId),
+    AdtSelfType(AdtId),
+    GenericParam(u32),
+    Local(PatId),
+}
+
+impl Scope {
+    fn process_names(&self, db: &impl DefDatabase2, f: &mut dyn FnMut(Name, ScopeDef)) {
+        match self {
+            Scope::ModuleScope(m) => {
+                // FIXME: should we provide `self` here?
+                // f(
+                //     Name::self_param(),
+                //     PerNs::types(Resolution::Def {
+                //         def: m.module.into(),
+                //     }),
+                // );
+                m.crate_def_map[m.module_id].scope.entries().for_each(|(name, res)| {
+                    f(name.clone(), ScopeDef::PerNs(res.def));
+                });
+                m.crate_def_map[m.module_id].scope.legacy_macros().for_each(|(name, macro_)| {
+                    f(name.clone(), ScopeDef::PerNs(PerNs::macros(macro_)));
+                });
+                m.crate_def_map.extern_prelude().iter().for_each(|(name, &def)| {
+                    f(name.clone(), ScopeDef::PerNs(PerNs::types(def.into())));
+                });
+                if let Some(prelude) = m.crate_def_map.prelude() {
+                    let prelude_def_map = db.crate_def_map(prelude.krate);
+                    prelude_def_map[prelude.module_id].scope.entries().for_each(|(name, res)| {
+                        f(name.clone(), ScopeDef::PerNs(res.def));
+                    });
+                }
+            }
+            Scope::GenericParams { params, .. } => {
+                for param in params.params.iter() {
+                    f(param.name.clone(), ScopeDef::GenericParam(param.idx))
+                }
+            }
+            Scope::ImplBlockScope(i) => {
+                f(name::SELF_TYPE, ScopeDef::ImplSelfType((*i).into()));
+            }
+            Scope::AdtScope(i) => {
+                f(name::SELF_TYPE, ScopeDef::AdtSelfType((*i).into()));
+            }
+            Scope::ExprScope(scope) => {
+                scope.expr_scopes.entries(scope.scope_id).iter().for_each(|e| {
+                    f(e.name().clone(), ScopeDef::Local(e.pat()));
+                });
+            }
+        }
+    }
+}
+
+// needs arbitrary_self_types to be a method... or maybe move to the def?
+pub fn resolver_for_expr(
+    db: &impl DefDatabase2,
+    owner: DefWithBodyId,
+    expr_id: ExprId,
+) -> Resolver {
+    let scopes = db.expr_scopes(owner);
+    resolver_for_scope(db, owner, scopes.scope_for(expr_id))
+}
+
+pub fn resolver_for_scope(
+    db: &impl DefDatabase2,
+    owner: DefWithBodyId,
+    scope_id: Option<ScopeId>,
+) -> Resolver {
+    let mut r = owner.resolver(db);
+    let scopes = db.expr_scopes(owner);
+    let scope_chain = scopes.scope_chain(scope_id).collect::<Vec<_>>();
+    for scope in scope_chain.into_iter().rev() {
+        r = r.push_expr_scope(owner, Arc::clone(&scopes), scope);
+    }
+    r
+}
+
+pub trait HasResolver {
+    /// Builds a resolver for type references inside this def.
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver;
+}
+
+impl HasResolver for ModuleId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        let def_map = db.crate_def_map(self.krate);
+        Resolver::default().push_module_scope(def_map, self.module_id)
+    }
+}
+
+impl HasResolver for TraitId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.module(db).resolver(db).push_generic_params_scope(db, self.into())
+    }
+}
+
+impl HasResolver for AdtId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        let module = match self {
+            AdtId::StructId(it) => it.0.module(db),
+            AdtId::UnionId(it) => it.0.module(db),
+            AdtId::EnumId(it) => it.module(db),
+        };
+
+        module
+            .resolver(db)
+            .push_generic_params_scope(db, self.into())
+            .push_scope(Scope::AdtScope(self.into()))
+    }
+}
+
+impl HasResolver for StructId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        AdtId::from(self).resolver(db)
+    }
+}
+
+impl HasResolver for UnionId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        AdtId::from(self).resolver(db)
+    }
+}
+
+impl HasResolver for EnumId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        AdtId::from(self).resolver(db)
+    }
+}
+
+impl HasResolver for FunctionId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.lookup(db).container.resolver(db).push_generic_params_scope(db, self.into())
+    }
+}
+
+impl HasResolver for DefWithBodyId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        match self {
+            DefWithBodyId::ConstId(c) => c.resolver(db),
+            DefWithBodyId::FunctionId(f) => f.resolver(db),
+            DefWithBodyId::StaticId(s) => s.resolver(db),
+        }
+    }
+}
+
+impl HasResolver for ConstId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.lookup(db).container.resolver(db)
+    }
+}
+
+impl HasResolver for StaticId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.module(db).resolver(db)
+    }
+}
+
+impl HasResolver for TypeAliasId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.lookup(db).container.resolver(db).push_generic_params_scope(db, self.into())
+    }
+}
+
+impl HasResolver for ContainerId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        match self {
+            ContainerId::TraitId(it) => it.resolver(db),
+            ContainerId::ImplId(it) => it.resolver(db),
+            ContainerId::ModuleId(it) => it.resolver(db),
+        }
+    }
+}
+
+impl HasResolver for GenericDefId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        match self {
+            GenericDefId::FunctionId(inner) => inner.resolver(db),
+            GenericDefId::AdtId(adt) => adt.resolver(db),
+            GenericDefId::TraitId(inner) => inner.resolver(db),
+            GenericDefId::TypeAliasId(inner) => inner.resolver(db),
+            GenericDefId::ImplId(inner) => inner.resolver(db),
+            GenericDefId::EnumVariantId(inner) => inner.parent.resolver(db),
+            GenericDefId::ConstId(inner) => inner.resolver(db),
+        }
+    }
+}
+
+impl HasResolver for ImplId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.module(db)
+            .resolver(db)
+            .push_generic_params_scope(db, self.into())
+            .push_impl_block_scope(self)
+    }
+}
diff --git a/crates/ra_hir_def/src/traits.rs b/crates/ra_hir_def/src/traits.rs
index 877d73d66..6c2d5b2a9 100644
--- a/crates/ra_hir_def/src/traits.rs
+++ b/crates/ra_hir_def/src/traits.rs
@@ -11,7 +11,7 @@ use ra_syntax::ast::{self, NameOwner};
 
 use crate::{
     db::DefDatabase2, AssocItemId, AstItemDef, ConstLoc, ContainerId, FunctionLoc, Intern, TraitId,
-    TypeAliasLoc,
+    TypeAliasId, TypeAliasLoc,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -56,4 +56,11 @@ impl TraitData {
         };
         Arc::new(TraitData { name, items, auto })
     }
+
+    pub fn associated_types(&self) -> impl Iterator<Item = TypeAliasId> + '_ {
+        self.items.iter().filter_map(|item| match item {
+            AssocItemId::TypeAliasId(t) => Some(*t),
+            _ => None,
+        })
+    }
 }