cgen: fix iterator on alias to fn ptr (fix #25911) (#25978)

Author: felipensp

vlib/v/gen/c/for.v

@@ -548,19 +548,25 @@ fn (mut g Gen) for_in_stmt(node_ ast.ForInStmt) {
 		g.writeln('\tif (${t_var}.state != 0) break;')
 		val := if node.val_var in ['', '_'] { g.new_tmp_var() } else { node.val_var }
 		val_styp := g.styp(ret_typ.clear_option_and_result())
+		ret_sym := g.table.final_sym(ret_typ)
 		if node.val_is_mut {
 			if ret_typ.is_any_kind_of_pointer() {
 				g.writeln('\t${val_styp} ${val} = *(${val_styp}*)${t_var}.data;')
 			} else {
 				g.writeln('\t${val_styp}* ${val} = (${val_styp}*)${t_var}.data;')
 			}
 		} else {
-			ret_is_fixed_array := g.table.sym(ret_typ).is_array_fixed()
+			ret_is_fixed_array := ret_sym.is_array_fixed()
 			if ret_is_fixed_array {
 				g.writeln('\t${val_styp} ${val} = {0};')
 				g.write('\tmemcpy(${val}, ${t_var}.data, sizeof(${val_styp}));')
 			} else {
-				g.writeln('\t${val_styp} ${val} = *(${val_styp}*)${t_var}.data;')
+				if ret_sym.info is ast.FnType {
+					g.write_fntype_decl(val, ret_sym.info)
+					g.writeln(' = **(${val_styp}**)&${t_var}.data;')
+				} else {
+					g.writeln('\t${val_styp} ${val} = *(${val_styp}*)${t_var}.data;')
+				}
 			}
 		}
 	} else if node.kind == .aggregate {

vlib/v/tests/fns/iter_alias_fn_test.v

@@ -0,0 +1,25 @@
+type MyFn = fn ()
+
+struct Iter {
+	f MyFn = fn () {}
+mut:
+	done bool
+}
+
+fn (mut it Iter) next() ?&MyFn {
+	if it.done {
+		return none
+	}
+	it.done = true
+	return &it.f
+}
+
+fn test_main() {
+	mut c := 0
+	for p in Iter{} {
+		println(p)
+		p()
+		c += 1
+	}
+	assert c == 1
+}