From febd54b77cf977bc121133b19344ba9baed31319 Mon Sep 17 00:00:00 2001
From: shove <shove@163.com>
Date: Sat, 25 Nov 2023 02:26:02 +0800
Subject: [PATCH] checker: disallow directly indexing sumtype and interface,
 when using as parameters(fix #19811) (#19982)

---
 vlib/v/checker/checker.v                            |  3 ++-
 .../tests/index_sumtype_or_interface_params_err.out | 13 +++++++++++++
 .../tests/index_sumtype_or_interface_params_err.vv  |  8 ++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/checker/tests/index_sumtype_or_interface_params_err.out
 create mode 100644 vlib/v/checker/tests/index_sumtype_or_interface_params_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 73fce3405849be..7cdf77cee19ec0 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -4319,7 +4319,8 @@ fn (mut c Checker) index_expr(mut node ast.IndexExpr) ast.Type {
 	}
 	is_aggregate_arr := typ_sym.kind == .aggregate
 		&& (typ_sym.info as ast.Aggregate).types.filter(c.table.type_kind(it) !in [.array, .array_fixed, .string, .map]).len == 0
-	if typ_sym.kind !in [.array, .array_fixed, .string, .map] && !typ.is_ptr()
+	if typ_sym.kind !in [.array, .array_fixed, .string, .map]
+		&& (!typ.is_ptr() || typ_sym.kind in [.sum_type, .interface_])
 		&& typ !in [ast.byteptr_type, ast.charptr_type] && !typ.has_flag(.variadic)
 		&& !is_aggregate_arr {
 		c.error('type `${typ_sym.name}` does not support indexing', node.pos)
diff --git a/vlib/v/checker/tests/index_sumtype_or_interface_params_err.out b/vlib/v/checker/tests/index_sumtype_or_interface_params_err.out
new file mode 100644
index 00000000000000..714ffc811bcd06
--- /dev/null
+++ b/vlib/v/checker/tests/index_sumtype_or_interface_params_err.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/index_sumtype_or_interface_params_err.vv:6:9: error: type `Foo` does not support indexing
+    4 | 
+    5 | fn sum_type_or_interface_as_parameters(mut foo Foo, mut bar Bar) {
+    6 |     _ = foo[0]
+      |            ~~~
+    7 |     _ = bar[0]
+    8 | }
+vlib/v/checker/tests/index_sumtype_or_interface_params_err.vv:7:9: error: type `Bar` does not support indexing
+    5 | fn sum_type_or_interface_as_parameters(mut foo Foo, mut bar Bar) {
+    6 |     _ = foo[0]
+    7 |     _ = bar[0]
+      |            ~~~
+    8 | }
diff --git a/vlib/v/checker/tests/index_sumtype_or_interface_params_err.vv b/vlib/v/checker/tests/index_sumtype_or_interface_params_err.vv
new file mode 100644
index 00000000000000..c686b777bfcbc7
--- /dev/null
+++ b/vlib/v/checker/tests/index_sumtype_or_interface_params_err.vv
@@ -0,0 +1,8 @@
+type Foo = int | map[int]int
+
+interface Bar {}
+
+fn sum_type_or_interface_as_parameters(mut foo Foo, mut bar Bar) {
+	_ = foo[0]
+	_ = bar[0]
+}