markused: fix fn marked as used when variable and fn uses same name (fix #25649) (#25650)

Author: felipensp

vlib/v/markused/walker.v

@@ -728,7 +728,11 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 					} else if node.name in w.all_globals {
 						w.mark_global_as_used(node.name)
 					} else {
-						w.fn_by_name(node.name)
+						if (node.kind == .variable && node.obj is ast.Var && node.obj.is_used
+							&& node.obj.typ != 0 && w.table.type_kind(node.obj.typ) == .function)
+							|| (node.kind == .unresolved && node.name.contains('.')) {
+							w.fn_by_name(node.name)
+						}
 					}
 					if !w.uses_atomic && node.info is ast.IdentVar {
 						w.uses_atomic = node.info.typ.has_flag(.atomic_f)

vlib/v/tests/skip_unused/for_linked_list.run.out

@@ -0,0 +1,40 @@
+struct Node {
+mut:
+	value int
+	prev  ?&Node
+	next  ?&Node
+}
+
+struct LinkedList {
+mut:
+	length int
+	head   ?&Node
+}
+
+pub fn (mut l LinkedList) push(value int) {
+	mut new_node := &Node{
+		value: value
+	}
+
+	if mut head := l.head {
+		for head.next != none {
+			if mut head_next := head.next {
+				head = head_next
+			}
+		}
+		head.next = new_node
+		new_node.prev = head
+	} else {
+		l.head = new_node
+	}
+}
+
+fn main() {
+	mut list := LinkedList{
+		length: 0
+		head:   none
+	}
+	list.push(1)
+	list.push(2)
+	list.push(3)
+}