checker: fixed type inference over a generic function

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

vlib/v/checker/check_types.v

@@ -535,7 +535,7 @@ pub fn (mut c Checker) infer_fn_generic_types(func ast.Fn, mut node ast.CallExpr
 		for i, param in func.params {
 			mut to_set := ast.void_type
 			// resolve generic struct receiver
-			if i == 0 && node.is_method && param.typ.has_flag(.generic) {
+			if node.is_method && param.typ.has_flag(.generic) {
 				sym := c.table.sym(node.receiver_type)
 				match sym.info {
 					ast.Struct, ast.Interface, ast.SumType {

vlib/v/checker/tests/generic_type_inference.vv

@@ -1,7 +1,6 @@
 import datatypes
 
 struct KeyVal<T> {
-mut:
 	key string
 	val T
 }