4 files changed, 109 insertions, 21 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 9891b0785..eb6a14eda 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -1,5 +1,5 @@
 //! FIXME: write short doc here
-use std::sync::Arc;
+use std::{iter, sync::Arc};
 
 use arrayvec::ArrayVec;
 use either::Either;
@@ -12,6 +12,7 @@ use hir_def::{
     import_map,
     per_ns::PerNs,
     resolver::{HasResolver, Resolver},
+    src::HasSource as _,
     type_ref::{Mutability, TypeRef},
     AdtId, AssocContainerId, ConstId, DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule,
     ImplId, LocalEnumVariantId, LocalFieldId, LocalModuleId, Lookup, ModuleId, StaticId, StructId,
@@ -25,8 +26,8 @@ use hir_expand::{
 use hir_ty::{
     autoderef,
     display::{HirDisplayError, HirFormatter},
-    method_resolution, ApplicationTy, Canonical, GenericPredicate, InEnvironment, Substs,
-    TraitEnvironment, Ty, TyDefId, TypeCtor,
+    method_resolution, ApplicationTy, CallableDefId, Canonical, FnSig, GenericPredicate,
+    InEnvironment, Substs, TraitEnvironment, Ty, TyDefId, TypeCtor,
 };
 use ra_db::{CrateId, Edition, FileId};
 use ra_prof::profile;
@@ -40,7 +41,7 @@ use stdx::impl_from;
 use crate::{
     db::{DefDatabase, HirDatabase},
     has_source::HasSource,
-    CallableDefId, HirDisplay, InFile, Name,
+    HirDisplay, InFile, Name,
 };
 
 /// hir::Crate describes a single crate. It's the main interface with which
@@ -1168,6 +1169,12 @@ impl Type {
         Type::new(db, krate, def, ty)
     }
 
+    pub fn is_unit(&self) -> bool {
+        matches!(
+            self.ty.value,
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Tuple { cardinality: 0 }, .. })
+        )
+    }
     pub fn is_bool(&self) -> bool {
         matches!(self.ty.value, Ty::Apply(ApplicationTy { ctor: TypeCtor::Bool, .. }))
     }
@@ -1225,9 +1232,10 @@ impl Type {
         db.trait_solve(self.krate, goal).is_some()
     }
 
-    // FIXME: this method is broken, as it doesn't take closures into account.
-    pub fn as_callable(&self) -> Option<CallableDefId> {
-        Some(self.ty.value.as_callable()?.0)
+    pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
+        let (id, substs) = self.ty.value.as_callable()?;
+        let sig = db.callable_item_signature(id).subst(substs);
+        Some(Callable { ty: self.clone(), sig, id, is_bound_method: false })
     }
 
     pub fn is_closure(&self) -> bool {
@@ -1512,6 +1520,70 @@ impl HirDisplay for Type {
     }
 }
 
+// FIXME: closures
+#[derive(Debug)]
+pub struct Callable {
+    ty: Type,
+    sig: FnSig,
+    id: CallableDefId,
+    pub(crate) is_bound_method: bool,
+}
+
+pub enum CallableKind {
+    Function(Function),
+    TupleStruct(Struct),
+    TupleEnumVariant(EnumVariant),
+}
+
+impl Callable {
+    pub fn kind(&self) -> CallableKind {
+        match self.id {
+            CallableDefId::FunctionId(it) => CallableKind::Function(it.into()),
+            CallableDefId::StructId(it) => CallableKind::TupleStruct(it.into()),
+            CallableDefId::EnumVariantId(it) => CallableKind::TupleEnumVariant(it.into()),
+        }
+    }
+    pub fn receiver_param(&self, db: &dyn HirDatabase) -> Option<ast::SelfParam> {
+        let func = match self.id {
+            CallableDefId::FunctionId(it) if self.is_bound_method => it,
+            _ => return None,
+        };
+        let src = func.lookup(db.upcast()).source(db.upcast());
+        let param_list = src.value.param_list()?;
+        param_list.self_param()
+    }
+    pub fn params(
+        &self,
+        db: &dyn HirDatabase,
+    ) -> Vec<(Option<Either<ast::SelfParam, ast::Pat>>, Type)> {
+        let types = self
+            .sig
+            .params()
+            .iter()
+            .skip(if self.is_bound_method { 1 } else { 0 })
+            .map(|ty| self.ty.derived(ty.clone()));
+        let patterns = match self.id {
+            CallableDefId::FunctionId(func) => {
+                let src = func.lookup(db.upcast()).source(db.upcast());
+                src.value.param_list().map(|param_list| {
+                    param_list
+                        .self_param()
+                        .map(|it| Some(Either::Left(it)))
+                        .filter(|_| !self.is_bound_method)
+                        .into_iter()
+                        .chain(param_list.params().map(|it| it.pat().map(Either::Right)))
+                })
+            }
+            CallableDefId::StructId(_) => None,
+            CallableDefId::EnumVariantId(_) => None,
+        };
+        patterns.into_iter().flatten().chain(iter::repeat(None)).zip(types).collect()
+    }
+    pub fn return_type(&self) -> Type {
+        self.ty.derived(self.sig.ret().clone())
+    }
+}
+
 /// For IDE only
 #[derive(Debug)]
 pub enum ScopeDef {
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index cf7134923..31f3241c9 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -32,10 +32,10 @@ mod has_source;
 
 pub use crate::{
     code_model::{
-        Adt, AsAssocItem, AssocItem, AssocItemContainer, AttrDef, Const, Crate, CrateDependency,
-        DefWithBody, Docs, Enum, EnumVariant, Field, FieldSource, Function, GenericDef, HasAttrs,
-        HasVisibility, ImplDef, Local, MacroDef, Module, ModuleDef, ScopeDef, Static, Struct,
-        Trait, Type, TypeAlias, TypeParam, Union, VariantDef, Visibility,
+        Adt, AsAssocItem, AssocItem, AssocItemContainer, AttrDef, Callable, CallableKind, Const,
+        Crate, CrateDependency, DefWithBody, Docs, Enum, EnumVariant, Field, FieldSource, Function,
+        GenericDef, HasAttrs, HasVisibility, ImplDef, Local, MacroDef, Module, ModuleDef, ScopeDef,
+        Static, Struct, Trait, Type, TypeAlias, TypeParam, Union, VariantDef, Visibility,
     },
     has_source::HasSource,
     semantics::{original_range, PathResolution, Semantics, SemanticsScope},
@@ -52,7 +52,8 @@ pub use hir_def::{
     type_ref::Mutability,
 };
 pub use hir_expand::{
-    hygiene::Hygiene, name::Name, HirFileId, InFile, MacroCallId, MacroCallLoc, MacroDefId,
+    hygiene::Hygiene, name::Name, HirFileId, InFile, MacroCallId, MacroCallLoc,
+    MacroDefId, /* FIXME */
     MacroFile, Origin,
 };
-pub use hir_ty::{display::HirDisplay, CallableDefId};
+pub use hir_ty::display::HirDisplay;
diff --git a/crates/ra_hir/src/semantics.rs b/crates/ra_hir/src/semantics.rs
index 155b666d7..f5283ab22 100644
--- a/crates/ra_hir/src/semantics.rs
+++ b/crates/ra_hir/src/semantics.rs
@@ -6,7 +6,7 @@ use std::{cell::RefCell, fmt, iter::successors};
 
 use hir_def::{
     resolver::{self, HasResolver, Resolver},
-    AsMacroCall, TraitId, VariantId,
+    AsMacroCall, FunctionId, TraitId, VariantId,
 };
 use hir_expand::{diagnostics::AstDiagnostic, hygiene::Hygiene, ExpansionInfo};
 use hir_ty::associated_type_shorthand_candidates;
@@ -24,8 +24,8 @@ use crate::{
     diagnostics::Diagnostic,
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
     source_analyzer::{resolve_hir_path, resolve_hir_path_qualifier, SourceAnalyzer},
-    AssocItem, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef, Module, ModuleDef,
-    Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, VariantDef,
+    AssocItem, Callable, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef, Module,
+    ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, VariantDef,
 };
 use resolver::TypeNs;
 
@@ -197,7 +197,11 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
     }
 
     pub fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
-        self.imp.resolve_method_call(call)
+        self.imp.resolve_method_call(call).map(Function::from)
+    }
+
+    pub fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
+        self.imp.resolve_method_call_as_callable(call)
     }
 
     pub fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {
@@ -385,10 +389,21 @@ impl<'db> SemanticsImpl<'db> {
         self.analyze(param.syntax()).type_of_self(self.db, &param)
     }
 
-    fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
+    fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<FunctionId> {
         self.analyze(call.syntax()).resolve_method_call(self.db, call)
     }
 
+    fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
+        // FIXME: this erases Substs
+        let func = self.resolve_method_call(call)?;
+        let ty = self.db.value_ty(func.into());
+        let resolver = self.analyze(call.syntax()).resolver;
+        let ty = Type::new_with_resolver(self.db, &resolver, ty.value)?;
+        let mut res = ty.as_callable(self.db)?;
+        res.is_bound_method = true;
+        Some(res)
+    }
+
     fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {
         self.analyze(field.syntax()).resolve_field(self.db, field)
     }
diff --git a/crates/ra_hir/src/source_analyzer.rs b/crates/ra_hir/src/source_analyzer.rs
index ecb54f653..86a47a9e5 100644
--- a/crates/ra_hir/src/source_analyzer.rs
+++ b/crates/ra_hir/src/source_analyzer.rs
@@ -14,7 +14,7 @@ use hir_def::{
     },
     expr::{ExprId, Pat, PatId},
     resolver::{resolver_for_scope, Resolver, TypeNs, ValueNs},
-    AsMacroCall, DefWithBodyId, FieldId, LocalFieldId, VariantId,
+    AsMacroCall, DefWithBodyId, FieldId, FunctionId, LocalFieldId, VariantId,
 };
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
 use hir_ty::{
@@ -142,9 +142,9 @@ impl SourceAnalyzer {
         &self,
         db: &dyn HirDatabase,
         call: &ast::MethodCallExpr,
-    ) -> Option<Function> {
+    ) -> Option<FunctionId> {
         let expr_id = self.expr_id(db, &call.clone().into())?;
-        self.infer.as_ref()?.method_resolution(expr_id).map(Function::from)
+        self.infer.as_ref()?.method_resolution(expr_id)
     }
 
     pub(crate) fn resolve_field(