From 082ef52bcb15d779c6aff78d9860d328bf7df9b2 Mon Sep 17 00:00:00 2001
From: Florian Diebold <flodiebold@gmail.com>
Date: Mon, 7 Jan 2019 13:44:54 +0100
Subject: Implement basic inherent method resolution

---
 crates/ra_hir/src/ty.rs | 39 ++++++++++++++++++++++++++++++++-------
 1 file changed, 32 insertions(+), 7 deletions(-)

(limited to 'crates/ra_hir/src/ty.rs')

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 2d533eb6a..2dcba5283 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -17,6 +17,7 @@ mod autoderef;
 mod primitive;
 #[cfg(test)]
 mod tests;
+pub(crate) mod method_resolution;
 
 use std::borrow::Cow;
 use std::ops::Index;
@@ -891,14 +892,38 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
                 ret_ty
             }
-            Expr::MethodCall { receiver, args, .. } => {
-                let _receiver_ty = self.infer_expr(*receiver, &Expectation::none())?;
-                // TODO resolve method...
-                for (_i, arg) in args.iter().enumerate() {
-                    // TODO unify / expect argument type
-                    self.infer_expr(*arg, &Expectation::none())?;
+            Expr::MethodCall {
+                receiver,
+                args,
+                method_name,
+            } => {
+                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.db.type_for_def(def_id)?,
+                    None => Ty::Unknown,
+                };
+                let method_ty = self.insert_type_vars(method_ty);
+                let (expected_receiver_ty, arg_tys, ret_ty) = match &method_ty {
+                    Ty::FnPtr(sig) => {
+                        if sig.input.len() > 0 {
+                            (&sig.input[0], &sig.input[1..], sig.output.clone())
+                        } else {
+                            (&Ty::Unknown, &[][..], sig.output.clone())
+                        }
+                    }
+                    _ => (&Ty::Unknown, &[][..], Ty::Unknown),
+                };
+                // TODO we would have to apply the autoderef/autoref steps here
+                // to get the correct receiver type to unify...
+                self.unify(expected_receiver_ty, &receiver_ty);
+                for (i, arg) in args.iter().enumerate() {
+                    self.infer_expr(
+                        *arg,
+                        &Expectation::has_type(arg_tys.get(i).cloned().unwrap_or(Ty::Unknown)),
+                    )?;
                 }
-                Ty::Unknown
+                ret_ty
             }
             Expr::Match { expr, arms } => {
                 let _ty = self.infer_expr(*expr, &Expectation::none())?;
-- 
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