From 7a8e7b4db8cbbfc03af5fd08994a979bb1e08512 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Fri, 8 Nov 2019 07:43:44 +0300
Subject: [PATCH] fix interface methods that return a value

---
 vlib/compiler/cgen.v                 |  1 +
 vlib/compiler/fn.v                   |  2 +-
 vlib/compiler/tests/interface_test.v | 10 ++++++----
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/vlib/compiler/cgen.v b/vlib/compiler/cgen.v
index 239eb0222b..ba220acc44 100644
--- a/vlib/compiler/cgen.v
+++ b/vlib/compiler/cgen.v
@@ -389,6 +389,7 @@ fn sort_structs(types []Type) []Type {
 	return types_sorted
 }
 
+// Generates interface table and interface indexes
 fn (v &V) interface_table() string {
        mut sb := strings.new_builder(100)
        for _, t in v.table.typesmap {
diff --git a/vlib/compiler/fn.v b/vlib/compiler/fn.v
index dfdf6308fb..a79951023c 100644
--- a/vlib/compiler/fn.v
+++ b/vlib/compiler/fn.v
@@ -735,7 +735,7 @@ fn (p mut Parser) fn_call(f mut Fn, method_ph int, receiver_var, receiver_type s
 				p.cgen.resetln('')
 				var := p.expr_var.name
 				iname := f.args[0].typ // Speaker
-				p.gen('((void (*)())(${iname}_name_table[${var}._interface_idx][$idx]))(${var}._object)')
+				p.gen('(($f.typ (*)())(${iname}_name_table[${var}._interface_idx][$idx]))(${var}._object)')
 			}
 		}
 		//println('r=$receiver.typ RT=$receiver_type')
diff --git a/vlib/compiler/tests/interface_test.v b/vlib/compiler/tests/interface_test.v
index f37db18eeb..18364a108b 100644
--- a/vlib/compiler/tests/interface_test.v
+++ b/vlib/compiler/tests/interface_test.v
@@ -27,16 +27,18 @@ struct Foo {
 	speaker Speaker
 }	
 
-fn perform_speak(s Speaker) bool {
+fn perform_speak(s Speaker) {
 	s.speak()
-	return true
+	assert true
+	name := s.name()
+	assert name == 'Dog' || name == 'Cat'
 }
 
 fn test_perform_speak() {
 	d := Dog{}
-	assert perform_speak(d)
+	perform_speak(d)
 	cat := Cat{}
-	assert perform_speak(cat)
+	perform_speak(cat)
 	f := Foo {
 		//speaker: d
 	}