13 files changed, 297 insertions, 201 deletions

diff --git a/crates/ra_hir/src/code_model_api.rs b/crates/ra_hir/src/code_model_api.rs
index f59a60c07..905615127 100644
--- a/crates/ra_hir/src/code_model_api.rs
+++ b/crates/ra_hir/src/code_model_api.rs
@@ -16,6 +16,7 @@ use crate::{
     code_model_impl::def_id_to_ast,
     docs::{Documentation, Docs, docs_from_ast},
     module_tree::ModuleId,
+    ids::FunctionId,
 };
 
 /// hir::Crate describes a single crate. It's the main interface with which
@@ -49,7 +50,6 @@ pub enum Def {
     Struct(Struct),
     Enum(Enum),
     EnumVariant(EnumVariant),
-    Function(Function),
     Const(Const),
     Static(Static),
     Trait(Trait),
@@ -67,6 +67,7 @@ pub struct Module {
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum ModuleDef {
     Module(Module),
+    Function(Function),
     Def(DefId),
 }
 
@@ -76,6 +77,12 @@ impl Into<ModuleDef> for Module {
     }
 }
 
+impl Into<ModuleDef> for Function {
+    fn into(self) -> ModuleDef {
+        ModuleDef::Function(self)
+    }
+}
+
 impl Into<ModuleDef> for DefId {
     fn into(self) -> ModuleDef {
         ModuleDef::Def(self)
@@ -225,7 +232,7 @@ impl Struct {
     }
 
     pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
-        db.generic_params(self.def_id)
+        db.generic_params(self.def_id.into())
     }
 }
 
@@ -262,7 +269,7 @@ impl Enum {
     }
 
     pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
-        db.generic_params(self.def_id)
+        db.generic_params(self.def_id.into())
     }
 }
 
@@ -320,9 +327,9 @@ impl Docs for EnumVariant {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct Function {
-    pub(crate) def_id: DefId,
+    pub(crate) id: FunctionId,
 }
 
 pub use crate::code_model_impl::function::ScopeEntryWithSyntax;
@@ -359,21 +366,17 @@ impl FnSignature {
 }
 
 impl Function {
-    pub fn def_id(&self) -> DefId {
-        self.def_id
-    }
-
     pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::FnDef>) {
-        def_id_to_ast(db, self.def_id)
+        self.id.loc(db).source(db)
     }
 
     pub fn body_syntax_mapping(&self, db: &impl HirDatabase) -> Arc<BodySyntaxMapping> {
-        db.body_syntax_mapping(self.def_id)
+        db.body_syntax_mapping(*self)
     }
 
     pub fn scopes(&self, db: &impl HirDatabase) -> ScopesWithSyntaxMapping {
-        let scopes = db.fn_scopes(self.def_id);
-        let syntax_mapping = db.body_syntax_mapping(self.def_id);
+        let scopes = db.fn_scopes(*self);
+        let syntax_mapping = db.body_syntax_mapping(*self);
         ScopesWithSyntaxMapping {
             scopes,
             syntax_mapping,
@@ -381,15 +384,15 @@ impl Function {
     }
 
     pub fn signature(&self, db: &impl HirDatabase) -> Arc<FnSignature> {
-        db.fn_signature(self.def_id)
+        db.fn_signature(*self)
     }
 
     pub fn infer(&self, db: &impl HirDatabase) -> Arc<InferenceResult> {
-        db.infer(self.def_id)
+        db.infer(*self)
     }
 
     pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
-        db.generic_params(self.def_id)
+        db.generic_params((*self).into())
     }
 }
 
@@ -456,7 +459,7 @@ impl Trait {
     }
 
     pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
-        db.generic_params(self.def_id)
+        db.generic_params(self.def_id.into())
     }
 }
 
@@ -481,7 +484,7 @@ impl Type {
     }
 
     pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
-        db.generic_params(self.def_id)
+        db.generic_params(self.def_id.into())
     }
 }
 
diff --git a/crates/ra_hir/src/code_model_impl/function.rs b/crates/ra_hir/src/code_model_impl/function.rs
index c68c6bfbf..d8dafb10e 100644
--- a/crates/ra_hir/src/code_model_impl/function.rs
+++ b/crates/ra_hir/src/code_model_impl/function.rs
@@ -2,41 +2,48 @@ mod scope;
 
 use std::sync::Arc;
 
-use ra_syntax::{TreeArc, ast::{self, NameOwner}};
+use ra_syntax::ast::{self, NameOwner};
 
 use crate::{
-    DefId, HirDatabase, Name, AsName, Function, FnSignature, Module,
+    HirDatabase, Name, AsName, Function, FnSignature, Module, HirFileId,
     type_ref::{TypeRef, Mutability},
     expr::Body,
     impl_block::ImplBlock,
-    code_model_impl::def_id_to_ast,
+    ids::FunctionLoc,
 };
 
 pub use self::scope::{FnScopes, ScopesWithSyntaxMapping, ScopeEntryWithSyntax};
 
 impl Function {
-    pub(crate) fn new(def_id: DefId) -> Function {
-        Function { def_id }
+    pub(crate) fn from_ast(
+        db: &impl HirDatabase,
+        module: Module,
+        file_id: HirFileId,
+        ast: &ast::FnDef,
+    ) -> Function {
+        let loc: FunctionLoc = FunctionLoc::from_ast(db, module, file_id, ast);
+        let id = loc.id(db);
+        Function { id }
     }
 
     pub(crate) fn body(&self, db: &impl HirDatabase) -> Arc<Body> {
-        db.body_hir(self.def_id)
+        db.body_hir(*self)
     }
 
     pub(crate) fn module(&self, db: &impl HirDatabase) -> Module {
-        self.def_id.module(db)
+        self.id.loc(db).module
     }
 
     /// The containing impl block, if this is a method.
     pub(crate) fn impl_block(&self, db: &impl HirDatabase) -> Option<ImplBlock> {
-        self.def_id.impl_block(db)
+        let module_impls = db.impls_in_module(self.module(db));
+        ImplBlock::containing(module_impls, (*self).into())
     }
 }
 
 impl FnSignature {
-    pub(crate) fn fn_signature_query(db: &impl HirDatabase, def_id: DefId) -> Arc<FnSignature> {
-        // FIXME: we're using def_id_to_ast here to avoid returning Cancelable... this is a bit hacky
-        let node: TreeArc<ast::FnDef> = def_id_to_ast(db, def_id).1;
+    pub(crate) fn fn_signature_query(db: &impl HirDatabase, func: Function) -> Arc<FnSignature> {
+        let (_, node) = func.source(db);
         let name = node
             .name()
             .map(|n| n.as_name())
diff --git a/crates/ra_hir/src/code_model_impl/module.rs b/crates/ra_hir/src/code_model_impl/module.rs
index 5d00e905b..b2828c7be 100644
--- a/crates/ra_hir/src/code_model_impl/module.rs
+++ b/crates/ra_hir/src/code_model_impl/module.rs
@@ -135,6 +135,7 @@ impl Module {
                         None => PerNs::none(),
                     }
                 }
+                ModuleDef::Function(_) => PerNs::none(),
                 ModuleDef::Def(def) => {
                     match def.resolve(db) {
                         Def::Enum(e) => {
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index 0898daa3c..97de7da31 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -7,14 +7,14 @@ use crate::{
     DefId, MacroCallId, Name, HirFileId,
     SourceFileItems, SourceItemId, Crate, Module, HirInterner,
     query_definitions,
-    FnSignature, FnScopes,
+    Function, FnSignature, FnScopes,
     macros::MacroExpansion,
     module_tree::ModuleTree,
     nameres::{ItemMap, lower::{LoweredModule, ImportSourceMap}},
-    ty::{InferenceResult, Ty, method_resolution::CrateImplBlocks},
+    ty::{InferenceResult, Ty, method_resolution::CrateImplBlocks, TypableDef},
     adt::{StructData, EnumData, EnumVariantData},
     impl_block::ModuleImplBlocks,
-    generics::GenericParams,
+    generics::{GenericParams, GenericDef},
 };
 
 #[salsa::query_group]
@@ -26,7 +26,7 @@ pub trait HirDatabase: SyntaxDatabase + AsRef<HirInterner> {
     fn expand_macro_invocation(&self, invoc: MacroCallId) -> Option<Arc<MacroExpansion>>;
 
     #[salsa::invoke(query_definitions::fn_scopes)]
-    fn fn_scopes(&self, def_id: DefId) -> Arc<FnScopes>;
+    fn fn_scopes(&self, func: Function) -> Arc<FnScopes>;
 
     #[salsa::invoke(crate::adt::StructData::struct_data_query)]
     fn struct_data(&self, def_id: DefId) -> Arc<StructData>;
@@ -38,10 +38,10 @@ pub trait HirDatabase: SyntaxDatabase + AsRef<HirInterner> {
     fn enum_variant_data(&self, def_id: DefId) -> Arc<EnumVariantData>;
 
     #[salsa::invoke(crate::ty::infer)]
-    fn infer(&self, def_id: DefId) -> Arc<InferenceResult>;
+    fn infer(&self, func: Function) -> Arc<InferenceResult>;
 
     #[salsa::invoke(crate::ty::type_for_def)]
-    fn type_for_def(&self, def_id: DefId) -> Ty;
+    fn type_for_def(&self, def: TypableDef) -> Ty;
 
     #[salsa::invoke(crate::ty::type_for_field)]
     fn type_for_field(&self, def_id: DefId, field: Name) -> Option<Ty>;
@@ -77,14 +77,14 @@ pub trait HirDatabase: SyntaxDatabase + AsRef<HirInterner> {
     fn impls_in_crate(&self, krate: Crate) -> Arc<CrateImplBlocks>;
 
     #[salsa::invoke(crate::expr::body_hir)]
-    fn body_hir(&self, def_id: DefId) -> Arc<crate::expr::Body>;
+    fn body_hir(&self, func: Function) -> Arc<crate::expr::Body>;
 
     #[salsa::invoke(crate::expr::body_syntax_mapping)]
-    fn body_syntax_mapping(&self, def_id: DefId) -> Arc<crate::expr::BodySyntaxMapping>;
+    fn body_syntax_mapping(&self, func: Function) -> Arc<crate::expr::BodySyntaxMapping>;
 
     #[salsa::invoke(crate::generics::GenericParams::generic_params_query)]
-    fn generic_params(&self, def_id: DefId) -> Arc<GenericParams>;
+    fn generic_params(&self, def: GenericDef) -> Arc<GenericParams>;
 
     #[salsa::invoke(crate::FnSignature::fn_signature_query)]
-    fn fn_signature(&self, def_id: DefId) -> Arc<FnSignature>;
+    fn fn_signature(&self, func: Function) -> Arc<FnSignature>;
 }
diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index 1a3821692..29469af2c 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -9,7 +9,11 @@ use ra_syntax::{
     ast::{self, LoopBodyOwner, ArgListOwner, NameOwner, LiteralFlavor}
 };
 
-use crate::{Path, type_ref::{Mutability, TypeRef}, Name, HirDatabase, DefId, Def, name::AsName};
+use crate::{
+    Path, Name, HirDatabase, Function,
+    name::AsName,
+    type_ref::{Mutability, TypeRef},
+};
 use crate::ty::primitive::{UintTy, UncertainIntTy, UncertainFloatTy};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -435,8 +439,8 @@ impl Pat {
 
 // Queries
 
-pub(crate) fn body_hir(db: &impl HirDatabase, def_id: DefId) -> Arc<Body> {
-    Arc::clone(&body_syntax_mapping(db, def_id).body)
+pub(crate) fn body_hir(db: &impl HirDatabase, func: Function) -> Arc<Body> {
+    Arc::clone(&body_syntax_mapping(db, func).body)
 }
 
 struct ExprCollector {
@@ -955,14 +959,8 @@ pub(crate) fn collect_fn_body_syntax(node: &ast::FnDef) -> BodySyntaxMapping {
     collector.into_body_syntax_mapping(params, body)
 }
 
-pub(crate) fn body_syntax_mapping(db: &impl HirDatabase, def_id: DefId) -> Arc<BodySyntaxMapping> {
-    let def = def_id.resolve(db);
-
-    let body_syntax_mapping = match def {
-        Def::Function(f) => collect_fn_body_syntax(&f.source(db).1),
-        // TODO: consts, etc.
-        _ => panic!("Trying to get body for item type without body"),
-    };
-
+pub(crate) fn body_syntax_mapping(db: &impl HirDatabase, func: Function) -> Arc<BodySyntaxMapping> {
+    let (_, fn_def) = func.source(db);
+    let body_syntax_mapping = collect_fn_body_syntax(&fn_def);
     Arc::new(body_syntax_mapping)
 }
diff --git a/crates/ra_hir/src/generics.rs b/crates/ra_hir/src/generics.rs
index d8248ad49..88c53705f 100644
--- a/crates/ra_hir/src/generics.rs
+++ b/crates/ra_hir/src/generics.rs
@@ -5,9 +5,9 @@
 
 use std::sync::Arc;
 
-use ra_syntax::ast::{TypeParamList, AstNode, NameOwner};
+use ra_syntax::ast::{self, AstNode, NameOwner, TypeParamsOwner};
 
-use crate::{db::HirDatabase, DefId, Name, AsName};
+use crate::{db::HirDatabase, DefId, Name, AsName, Function};
 
 /// Data about a generic parameter (to a function, struct, impl, ...).
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -22,26 +22,62 @@ pub struct GenericParams {
     pub(crate) params: Vec<GenericParam>,
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+pub enum GenericDef {
+    Function(Function),
+    Def(DefId),
+}
+
+impl From<Function> for GenericDef {
+    fn from(func: Function) -> GenericDef {
+        GenericDef::Function(func)
+    }
+}
+
+impl From<DefId> for GenericDef {
+    fn from(def_id: DefId) -> GenericDef {
+        GenericDef::Def(def_id)
+    }
+}
+
 impl GenericParams {
-    pub(crate) fn generic_params_query(db: &impl HirDatabase, def_id: DefId) -> Arc<GenericParams> {
-        let (_file_id, node) = def_id.source(db);
+    pub(crate) fn generic_params_query(
+        db: &impl HirDatabase,
+        def: GenericDef,
+    ) -> Arc<GenericParams> {
         let mut generics = GenericParams::default();
-        if let Some(type_param_list) = node.children().find_map(TypeParamList::cast) {
-            for (idx, type_param) in type_param_list.type_params().enumerate() {
-                let name = type_param
-                    .name()
-                    .map(AsName::as_name)
-                    .unwrap_or_else(Name::missing);
-                let param = GenericParam {
-                    idx: idx as u32,
-                    name,
-                };
-                generics.params.push(param);
+        match def {
+            GenericDef::Function(func) => {
+                let (_, fn_def) = func.source(db);
+                if let Some(type_param_list) = fn_def.type_param_list() {
+                    generics.fill(type_param_list)
+                }
+            }
+            GenericDef::Def(def_id) => {
+                let (_file_id, node) = def_id.source(db);
+                if let Some(type_param_list) = node.children().find_map(ast::TypeParamList::cast) {
+                    generics.fill(type_param_list)
+                }
             }
         }
+
         Arc::new(generics)
     }
 
+    fn fill(&mut self, params: &ast::TypeParamList) {
+        for (idx, type_param) in params.type_params().enumerate() {
+            let name = type_param
+                .name()
+                .map(AsName::as_name)
+                .unwrap_or_else(Name::missing);
+            let param = GenericParam {
+                idx: idx as u32,
+                name,
+            };
+            self.params.push(param);
+        }
+    }
+
     pub(crate) fn find_by_name(&self, name: &Name) -> Option<&GenericParam> {
         self.params.iter().find(|p| &p.name == name)
     }
diff --git a/crates/ra_hir/src/ids.rs b/crates/ra_hir/src/ids.rs
index 73f1379f1..913341bd5 100644
--- a/crates/ra_hir/src/ids.rs
+++ b/crates/ra_hir/src/ids.rs
@@ -1,9 +1,11 @@
+use std::marker::PhantomData;
+
 use ra_db::{LocationIntener, FileId};
 use ra_syntax::{TreeArc, SyntaxNode, SourceFile, AstNode, ast};
 use ra_arena::{Arena, RawId, impl_arena_id};
 
 use crate::{
-    HirDatabase, Def, Function, Struct, Enum, EnumVariant, ImplBlock, Crate,
+    HirDatabase, Def, Struct, Enum, EnumVariant, Crate,
     Module, Trait, Type, Static, Const,
 };
 
@@ -129,15 +131,56 @@ impl MacroCallLoc {
     }
 }
 
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct ItemLoc<N: AstNode> {
+    pub(crate) module: Module,
+    raw: SourceItemId,
+    _ty: PhantomData<N>,
+}
+
+impl<N: AstNode> ItemLoc<N> {
+    pub(crate) fn from_ast(
+        db: &impl HirDatabase,
+        module: Module,
+        file_id: HirFileId,
+        ast: &N,
+    ) -> ItemLoc<N> {
+        let items = db.file_items(file_id);
+        let raw = SourceItemId {
+            file_id,
+            item_id: Some(items.id_of(file_id, ast.syntax())),
+        };
+        ItemLoc {
+            module,
+            raw,
+            _ty: PhantomData,
+        }
+    }
+
+    pub(crate) fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<N>) {
+        let syntax = db.file_item(self.raw);
+        let ast = N::cast(&syntax)
+            .unwrap_or_else(|| panic!("invalid ItemLoc: {:?}", self.raw))
+            .to_owned();
+        (self.raw.file_id, ast)
+    }
+}
+
+impl<N: AstNode> Clone for ItemLoc<N> {
+    fn clone(&self) -> ItemLoc<N> {
+        ItemLoc {
+            module: self.module,
+            raw: self.raw,
+            _ty: PhantomData,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct FunctionId(RawId);
 impl_arena_id!(FunctionId);
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub struct FunctionLoc {
-    pub(crate) module: Module,
-    pub(crate) source_item_id: SourceItemId,
-}
+pub(crate) type FunctionLoc = ItemLoc<ast::FnDef>;
 
 impl FunctionId {
     pub(crate) fn loc(self, db: &impl AsRef<HirInterner>) -> FunctionLoc {
@@ -196,10 +239,7 @@ impl DefId {
     pub fn resolve(self, db: &impl HirDatabase) -> Def {
         let loc = self.loc(db);
         match loc.kind {
-            DefKind::Function => {
-                let function = Function::new(self);
-                Def::Function(function)
-            }
+            DefKind::Function => unreachable!(),
             DefKind::Struct => {
                 let struct_def = Struct::new(self);
                 Def::Struct(struct_def)
@@ -243,12 +283,6 @@ impl DefId {
     pub fn krate(&self, db: &impl HirDatabase) -> Option<Crate> {
         self.module(db).krate(db)
     }
-
-    /// Returns the containing impl block, if this is an impl item.
-    pub fn impl_block(self, db: &impl HirDatabase) -> Option<ImplBlock> {
-        let module_impls = db.impls_in_module(self.loc(db).module);
-        ImplBlock::containing(module_impls, self)
-    }
 }
 
 impl DefLoc {
diff --git a/crates/ra_hir/src/impl_block.rs b/crates/ra_hir/src/impl_block.rs
index ba8b84da2..29becd317 100644
--- a/crates/ra_hir/src/impl_block.rs
+++ b/crates/ra_hir/src/impl_block.rs
@@ -6,7 +6,7 @@ use ra_syntax::ast::{self, AstNode};
 
 use crate::{
     DefId, DefLoc, DefKind, SourceItemId, SourceFileItems,
-    Function, HirFileId, HirInterner,
+    Function, HirFileId,
     db::HirDatabase,
     type_ref::TypeRef,
 };
@@ -22,9 +22,9 @@ pub struct ImplBlock {
 impl ImplBlock {
     pub(crate) fn containing(
         module_impl_blocks: Arc<ModuleImplBlocks>,
-        def_id: DefId,
+        item: ImplItem,
     ) -> Option<ImplBlock> {
-        let impl_id = *module_impl_blocks.impls_by_def.get(&def_id)?;
+        let impl_id = *module_impl_blocks.impls_by_def.get(&item)?;
         Some(ImplBlock {
             module_impl_blocks,
             impl_id,
@@ -64,7 +64,7 @@ pub struct ImplData {
 
 impl ImplData {
     pub(crate) fn from_ast(
-        db: &impl AsRef<HirInterner>,
+        db: &impl HirDatabase,
         file_id: HirFileId,
         file_items: &SourceFileItems,
         module: Module,
@@ -93,7 +93,9 @@ impl ImplData {
                     };
                     let def_id = def_loc.id(db);
                     match item_node.kind() {
-                        ast::ImplItemKind::FnDef(..) => ImplItem::Method(Function::new(def_id)),
+                        ast::ImplItemKind::FnDef(it) => {
+                            ImplItem::Method(Function::from_ast(db, module, file_id, it))
+                        }
                         ast::ImplItemKind::ConstDef(..) => ImplItem::Const(def_id),
                         ast::ImplItemKind::TypeDef(..) => ImplItem::Type(def_id),
                     }
@@ -122,7 +124,8 @@ impl ImplData {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+//TODO: rename to ImplDef?
 pub enum ImplItem {
     Method(Function),
     // these don't have their own types yet
@@ -131,13 +134,9 @@ pub enum ImplItem {
     // Existential
 }
 
-impl ImplItem {
-    pub fn def_id(&self) -> DefId {
-        match self {
-            ImplItem::Method(f) => f.def_id(),
-            ImplItem::Const(def_id) => *def_id,
-            ImplItem::Type(def_id) => *def_id,
-        }
+impl From<Function> for ImplItem {
+    fn from(func: Function) -> ImplItem {
+        ImplItem::Method(func)
     }
 }
 
@@ -153,7 +152,7 @@ impl_arena_id!(ImplId);
 #[derive(Debug, PartialEq, Eq)]
 pub struct ModuleImplBlocks {
     pub(crate) impls: Arena<ImplId, ImplData>,
-    impls_by_def: FxHashMap<DefId, ImplId>,
+    impls_by_def: FxHashMap<ImplItem, ImplId>,
 }
 
 impl ModuleImplBlocks {
@@ -181,8 +180,8 @@ impl ModuleImplBlocks {
             let impl_block =
                 ImplData::from_ast(db, file_id, &source_file_items, module, impl_block_ast);
             let id = self.impls.alloc(impl_block);
-            for impl_item in &self.impls[id].items {
-                self.impls_by_def.insert(impl_item.def_id(), id);
+            for &impl_item in &self.impls[id].items {
+                self.impls_by_def.insert(impl_item, id);
             }
         }
     }
diff --git a/crates/ra_hir/src/nameres/lower.rs b/crates/ra_hir/src/nameres/lower.rs
index 6f003bd66..1f8adc7eb 100644
--- a/crates/ra_hir/src/nameres/lower.rs
+++ b/crates/ra_hir/src/nameres/lower.rs
@@ -9,7 +9,7 @@ use rustc_hash::FxHashMap;
 
 use crate::{
     SourceItemId, Path, ModuleSource, HirDatabase, Name, SourceFileItems,
-    HirFileId, MacroCallLoc, AsName, PerNs, DefKind, DefLoc,
+    HirFileId, MacroCallLoc, AsName, PerNs, DefKind, DefLoc, Function,
     ModuleDef, Module,
 };
 
@@ -149,7 +149,14 @@ impl LoweredModule {
         let name = match item.kind() {
             ast::ModuleItemKind::StructDef(it) => it.name(),
             ast::ModuleItemKind::EnumDef(it) => it.name(),
-            ast::ModuleItemKind::FnDef(it) => it.name(),
+            ast::ModuleItemKind::FnDef(it) => {
+                if let Some(name) = it.name() {
+                    let func = Function::from_ast(db, module, file_id, it);
+                    self.declarations
+                        .insert(name.as_name(), PerNs::values(func.into()));
+                }
+                return;
+            }
             ast::ModuleItemKind::TraitDef(it) => it.name(),
             ast::ModuleItemKind::TypeDef(it) => it.name(),
             ast::ModuleItemKind::ImplBlock(_) => {
@@ -218,7 +225,7 @@ fn assign_def_id(
 impl DefKind {
     fn for_syntax_kind(kind: SyntaxKind) -> PerNs<DefKind> {
         match kind {
-            SyntaxKind::FN_DEF => PerNs::values(DefKind::Function),
+            SyntaxKind::FN_DEF => unreachable!(),
             SyntaxKind::STRUCT_DEF => PerNs::both(DefKind::Struct, DefKind::StructCtor),
             SyntaxKind::ENUM_DEF => PerNs::types(DefKind::Enum),
             SyntaxKind::TRAIT_DEF => PerNs::types(DefKind::Trait),
diff --git a/crates/ra_hir/src/query_definitions.rs b/crates/ra_hir/src/query_definitions.rs
index a8ed887b3..cf8c7e435 100644
--- a/crates/ra_hir/src/query_definitions.rs
+++ b/crates/ra_hir/src/query_definitions.rs
@@ -10,14 +10,14 @@ use ra_syntax::{
 use ra_db::{CrateId};
 
 use crate::{
-    SourceFileItems, SourceItemId, DefId, HirFileId,
-    FnScopes, Module,
+    SourceFileItems, SourceItemId, HirFileId,
+    Function, FnScopes, Module,
     db::HirDatabase,
     nameres::{ItemMap, Resolver},
 };
 
-pub(super) fn fn_scopes(db: &impl HirDatabase, def_id: DefId) -> Arc<FnScopes> {
-    let body = db.body_hir(def_id);
+pub(super) fn fn_scopes(db: &impl HirDatabase, func: Function) -> Arc<FnScopes> {
+    let body = db.body_hir(func);
     let res = FnScopes::new(body);
     Arc::new(res)
 }
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index c3bd31d6b..d1bf163d1 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -14,7 +14,7 @@ use ra_syntax::{
 
 use crate::{
     HirDatabase, Function, SourceItemId, ModuleDef,
-    DefKind, DefLoc, AsName, Module,
+    AsName, Module,
 };
 
 /// Locates the module by `FileId`. Picks topmost module in the file.
@@ -105,29 +105,18 @@ pub fn function_from_source(
     fn_def: &ast::FnDef,
 ) -> Option<Function> {
     let module = module_from_child_node(db, file_id, fn_def.syntax())?;
-    let res = function_from_module(db, &module, fn_def);
+    let res = function_from_module(db, module, fn_def);
     Some(res)
 }
 
 pub fn function_from_module(
     db: &impl HirDatabase,
-    module: &Module,
+    module: Module,
     fn_def: &ast::FnDef,
 ) -> Function {
     let (file_id, _) = module.definition_source(db);
     let file_id = file_id.into();
-    let file_items = db.file_items(file_id);
-    let item_id = file_items.id_of(file_id, fn_def.syntax());
-    let source_item_id = SourceItemId {
-        file_id,
-        item_id: Some(item_id),
-    };
-    let def_loc = DefLoc {
-        module: module.clone(),
-        kind: DefKind::Function,
-        source_item_id,
-    };
-    Function::new(def_loc.id(db))
+    Function::from_ast(db, module, file_id, fn_def)
 }
 
 pub fn function_from_child_node(
diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 4c96579ee..f9cdbcab3 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -382,7 +382,8 @@ impl Ty {
 
         // Resolve in module (in type namespace)
         let resolved = match module.resolve_path(db, path).take_types() {
-            Some(ModuleDef::Def(r)) => r,
+            Some(ModuleDef::Def(r)) => r.into(),
+            Some(ModuleDef::Function(f)) => f.into(),
             None | Some(ModuleDef::Module(_)) => return Ty::Unknown,
         };
         let ty = db.type_for_def(resolved);
@@ -399,36 +400,38 @@ impl Ty {
         impl_block: Option<&ImplBlock>,
         outer_generics: &GenericParams,
         path: &Path,
-        resolved: DefId,
+        resolved: TypableDef,
     ) -> Substs {
         let mut substs = Vec::new();
-        let def = resolved.resolve(db);
         let last = path
             .segments
             .last()
             .expect("path should have at least one segment");
-        let (def_generics, segment) = match def {
-            Def::Struct(s) => (s.generic_params(db), last),
-            Def::Enum(e) => (e.generic_params(db), last),
-            Def::Function(f) => (f.generic_params(db), last),
-            Def::Trait(t) => (t.generic_params(db), last),
-            Def::EnumVariant(ev) => {
-                // the generic args for an enum variant may be either specified
-                // on the segment referring to the enum, or on the segment
-                // referring to the variant. So `Option::<T>::None` and
-                // `Option::None::<T>` are both allowed (though the former is
-                // preferred). See also `def_ids_for_path_segments` in rustc.
-                let len = path.segments.len();
-                let segment = if len >= 2 && path.segments[len - 2].args_and_bindings.is_some() {
-                    // Option::<T>::None
-                    &path.segments[len - 2]
-                } else {
-                    // Option::None::<T>
-                    last
-                };
-                (ev.parent_enum(db).generic_params(db), segment)
-            }
-            _ => return Substs::empty(),
+        let (def_generics, segment) = match resolved {
+            TypableDef::Function(func) => (func.generic_params(db), last),
+            TypableDef::Def(def_id) => match def_id.resolve(db) {
+                Def::Struct(s) => (s.generic_params(db), last),
+                Def::Enum(e) => (e.generic_params(db), last),
+                Def::Trait(t) => (t.generic_params(db), last),
+                Def::EnumVariant(ev) => {
+                    // the generic args for an enum variant may be either specified
+                    // on the segment referring to the enum, or on the segment
+                    // referring to the variant. So `Option::<T>::None` and
+                    // `Option::None::<T>` are both allowed (though the former is
+                    // preferred). See also `def_ids_for_path_segments` in rustc.
+                    let len = path.segments.len();
+                    let segment = if len >= 2 && path.segments[len - 2].args_and_bindings.is_some()
+                    {
+                        // Option::<T>::None
+                        &path.segments[len - 2]
+                    } else {
+                        // Option::None::<T>
+                        last
+                    };
+                    (ev.parent_enum(db).generic_params(db), segment)
+                }
+                _ => return Substs::empty(),
+            },
         };
         // substs_from_path
         if let Some(generic_args) = &segment.args_and_bindings {
@@ -660,21 +663,40 @@ pub(crate) fn type_for_enum_variant(db: &impl HirDatabase, ev: EnumVariant) -> T
     type_for_enum(db, enum_parent)
 }
 
-pub(super) fn type_for_def(db: &impl HirDatabase, def_id: DefId) -> Ty {
-    let def = def_id.resolve(db);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum TypableDef {
+    Function(Function),
+    Def(DefId),
+}
+
+impl From<Function> for TypableDef {
+    fn from(func: Function) -> TypableDef {
+        TypableDef::Function(func)
+    }
+}
+
+impl From<DefId> for TypableDef {
+    fn from(func: DefId) -> TypableDef {
+        TypableDef::Def(func)
+    }
+}
+
+pub(super) fn type_for_def(db: &impl HirDatabase, def: TypableDef) -> Ty {
     match def {
-        Def::Function(f) => type_for_fn(db, f),
-        Def::Struct(s) => type_for_struct(db, s),
-        Def::Enum(e) => type_for_enum(db, e),
-        Def::EnumVariant(ev) => type_for_enum_variant(db, ev),
-        _ => {
-            log::debug!(
-                "trying to get type for item of unknown type {:?} {:?}",
-                def_id,
-                def
-            );
-            Ty::Unknown
-        }
+        TypableDef::Function(f) => type_for_fn(db, f),
+        TypableDef::Def(def_id) => match def_id.resolve(db) {
+            Def::Struct(s) => type_for_struct(db, s),
+            Def::Enum(e) => type_for_enum(db, e),
+            Def::EnumVariant(ev) => type_for_enum_variant(db, ev),
+            _ => {
+                log::debug!(
+                    "trying to get type for item of unknown type {:?} {:?}",
+                    def_id,
+                    def
+                );
+                Ty::Unknown
+            }
+        },
     }
 }
 
@@ -694,28 +716,23 @@ pub(super) fn type_for_field(db: &impl HirDatabase, def_id: DefId, field: Name)
         ),
     };
     let module = def_id.module(db);
-    let impl_block = def_id.impl_block(db);
+    // We can't have an impl block ere, right?
+    // let impl_block = def_id.impl_block(db);
     let type_ref = variant_data.get_field_type_ref(&field)?;
-    Some(Ty::from_hir(
-        db,
-        &module,
-        impl_block.as_ref(),
-        &generics,
-        &type_ref,
-    ))
+    Some(Ty::from_hir(db, &module, None, &generics, &type_ref))
 }
 
 /// The result of type inference: A mapping from expressions and patterns to types.
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct InferenceResult {
     /// For each method call expr, record the function it resolved to.
-    method_resolutions: FxHashMap<ExprId, DefId>,
+    method_resolutions: FxHashMap<ExprId, Function>,
     type_of_expr: ArenaMap<ExprId, Ty>,
     type_of_pat: ArenaMap<PatId, Ty>,
 }
 
 impl InferenceResult {
-    pub fn method_resolution(&self, expr: ExprId) -> Option<DefId> {
+    pub fn method_resolution(&self, expr: ExprId) -> Option<Function> {
         self.method_resolutions.get(&expr).map(|it| *it)
     }
 }
@@ -745,7 +762,7 @@ struct InferenceContext<'a, D: HirDatabase> {
     module: Module,
     impl_block: Option<ImplBlock>,
     var_unification_table: InPlaceUnificationTable<TypeVarId>,
-    method_resolutions: FxHashMap<ExprId, DefId>,
+    method_resolutions: FxHashMap<ExprId, Function>,
     type_of_expr: ArenaMap<ExprId, Ty>,
     type_of_pat: ArenaMap<PatId, Ty>,
     /// The return type of the function being inferred.
@@ -871,8 +888,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.type_of_expr.insert(expr, ty);
     }
 
-    fn write_method_resolution(&mut self, expr: ExprId, def_id: DefId) {
-        self.method_resolutions.insert(expr, def_id);
+    fn write_method_resolution(&mut self, expr: ExprId, func: Function) {
+        self.method_resolutions.insert(expr, func);
     }
 
     fn write_pat_ty(&mut self, pat: PatId, ty: Ty) {
@@ -1060,7 +1077,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         // resolve in module
         let resolved = match self.module.resolve_path(self.db, &path).take_values()? {
-            ModuleDef::Def(it) => it,
+            ModuleDef::Def(it) => it.into(),
+            ModuleDef::Function(func) => func.into(),
             ModuleDef::Module(_) => return None,
         };
         let ty = self.db.type_for_def(resolved);
@@ -1073,8 +1091,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Some(path) => path,
             None => return (Ty::Unknown, None),
         };
-        let def_id = match self.module.resolve_path(self.db, &path).take_types() {
-            Some(ModuleDef::Def(def_id)) => def_id,
+        let def = match self.module.resolve_path(self.db, &path).take_types() {
+            Some(ModuleDef::Def(def_id)) => def_id.into(),
+            Some(ModuleDef::Function(func)) => func.into(),
             _ => return (Ty::Unknown, None),
         };
         // TODO remove the duplication between here and `Ty::from_path`?
@@ -1086,20 +1105,23 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             self.impl_block.as_ref(),
             &generics,
             path,
-            def_id,
+            def,
         );
-        match def_id.resolve(self.db) {
-            Def::Struct(s) => {
-                let ty = type_for_struct(self.db, s);
-                let ty = self.insert_type_vars(ty.apply_substs(substs));
-                (ty, Some(def_id))
-            }
-            Def::EnumVariant(ev) => {
-                let ty = type_for_enum_variant(self.db, ev);
-                let ty = self.insert_type_vars(ty.apply_substs(substs));
-                (ty, Some(def_id))
-            }
-            _ => (Ty::Unknown, None),
+        match def {
+            TypableDef::Def(def_id) => match def_id.resolve(self.db) {
+                Def::Struct(s) => {
+                    let ty = type_for_struct(self.db, s);
+                    let ty = self.insert_type_vars(ty.apply_substs(substs));
+                    (ty, Some(def_id))
+                }
+                Def::EnumVariant(ev) => {
+                    let ty = type_for_enum_variant(self.db, ev);
+                    let ty = self.insert_type_vars(ty.apply_substs(substs));
+                    (ty, Some(def_id))
+                }
+                _ => (Ty::Unknown, None),
+            },
+            TypableDef::Function(_) => (Ty::Unknown, None),
         }
     }
 
@@ -1216,7 +1238,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 .resolve_path(self.db, &path)
                 .take_values()
                 .and_then(|module_def| match module_def {
-                    ModuleDef::Def(it) => Some(it),
+                    ModuleDef::Def(it) => Some(it.into()),
+                    ModuleDef::Function(func) => Some(func.into()),
                     ModuleDef::Module(_) => None,
                 })
                 .map_or(Ty::Unknown, |resolved| self.db.type_for_def(resolved)),
@@ -1339,9 +1362,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let receiver_ty = self.infer_expr(*receiver, &Expectation::none());
                 let resolved = receiver_ty.clone().lookup_method(self.db, method_name);
                 let method_ty = match resolved {
-                    Some(def_id) => {
-                        self.write_method_resolution(expr, def_id);
-                        self.db.type_for_def(def_id)
+                    Some(func) => {
+                        self.write_method_resolution(expr, func);
+                        self.db.type_for_def(func.into())
                     }
                     None => Ty::Unknown,
                 };
@@ -1610,16 +1633,15 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     }
 }
 
-pub fn infer(db: &impl HirDatabase, def_id: DefId) -> Arc<InferenceResult> {
+pub fn infer(db: &impl HirDatabase, func: Function) -> Arc<InferenceResult> {
     db.check_canceled();
-    let function = Function::new(def_id); // TODO: consts also need inference
-    let body = function.body(db);
-    let scopes = db.fn_scopes(def_id);
-    let module = function.module(db);
-    let impl_block = function.impl_block(db);
+    let body = func.body(db);
+    let scopes = db.fn_scopes(func);
+    let module = func.module(db);
+    let impl_block = func.impl_block(db);
     let mut ctx = InferenceContext::new(db, body, scopes, module, impl_block);
 
-    let signature = function.signature(db);
+    let signature = func.signature(db);
     ctx.collect_fn_signature(&signature);
 
     ctx.infer_body();
diff --git a/crates/ra_hir/src/ty/method_resolution.rs b/crates/ra_hir/src/ty/method_resolution.rs
index a5567a78f..0084b24dc 100644
--- a/crates/ra_hir/src/ty/method_resolution.rs
+++ b/crates/ra_hir/src/ty/method_resolution.rs
@@ -118,11 +118,11 @@ impl Ty {
     // TODO: cache this as a query?
     // - if so, what signature? (TyFingerprint, Name)?
     // - or maybe cache all names and def_ids of methods per fingerprint?
-    pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Option<DefId> {
+    pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Option<Function> {
         self.iterate_methods(db, |f| {
             let sig = f.signature(db);
             if sig.name() == name && sig.has_self_param() {
-                Some(f.def_id())
+                Some(f)
             } else {
                 None
             }