From 40b8d9ca3dbddf04ea9b9d73bd75d3aa149201ba Mon Sep 17 00:00:00 2001
From: Ned Palacios <npdoesmc@gmail.com>
Date: Sat, 2 Jan 2021 00:33:23 +0800
Subject: [PATCH] checker: fix infer_fn_type for generic methods (#7767)

---
 vlib/v/checker/check_types.v        |  2 +-
 vlib/v/tests/generics_method_test.v | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index bab606b2ac..3bca0fb59a 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -419,7 +419,7 @@ pub fn (mut c Checker) infer_fn_types(f table.Fn, mut call_expr ast.CallExpr) {
 	gt_name := 'T'
 	mut typ := table.void_type
 	for i, param in f.params {
-		arg := call_expr.args[i]
+		arg := if i != 0 && call_expr.is_method { call_expr.args[i - 1] } else { call_expr.args[i] }
 		if param.typ.has_flag(.generic) {
 			typ = arg.typ
 			break
diff --git a/vlib/v/tests/generics_method_test.v b/vlib/v/tests/generics_method_test.v
index ef54376d20..d5b2f58293 100644
--- a/vlib/v/tests/generics_method_test.v
+++ b/vlib/v/tests/generics_method_test.v
@@ -19,3 +19,19 @@ fn test_generic_method() {
 		y: 6
 	}
 }
+
+struct Person {
+mut:
+	name string
+}
+
+fn (mut p Person) show<T>(name string, data T) string {
+	p.name = name
+	return 'name: $p.name, data: $data'
+}
+
+fn test_generic_method_with_fixed_arg_type() {
+	mut person := Person{}
+	res := person.show('bob', 10)
+	assert res == 'name: bob, data: 10'
+}