cgen: fix codegen for interface method closure get (fix #24810) (#24818)

vlib/v/gen/c/cgen.v

@@ -4473,7 +4473,7 @@ fn (mut g Gen) gen_closure_fn(expr_styp string, m ast.Fn, name string) {
 			method_name = g.generic_fn_name(rec_sym.info.concrete_types, m.name)
 		}
 	}
-	if rec_sym.info is ast.Interface {
+	if rec_sym.info is ast.Interface && rec_sym.info.get_methods().contains(method_name) {
 		left_cc_type := g.cc_type(g.table.unaliased_type(receiver.typ), false)
 		left_type_name := util.no_dots(left_cc_type)
 		sb.write_string('${c_name(left_type_name)}_name_table[a0->_typ]._method_${method_name}(')

vlib/v/tests/interfaces/interface_method_closure_test.v

@@ -0,0 +1,23 @@
+interface Doer {
+	job string
+}
+
+fn (d Doer) do() string {
+	return '${d.job}'
+}
+
+struct Expector {
+	do_fn fn () string @[required]
+}
+
+struct Actioner {
+	job string
+}
+
+fn test_main() {
+	a := &Actioner{'dier'}
+	e := Expector{
+		do_fn: Doer(a).do
+	}
+	assert e.do_fn() == 'dier'
+}