From 9f532f1ba9b967f9b8c526736ee99853a98732cf Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Tue, 13 Feb 2024 22:48:34 +0530
Subject: [PATCH]  checker: disallow sum type holding alias ptrs (#20786)

---
 vlib/v/checker/checker.v                                | 9 +++++++--
 vlib/v/checker/tests/sum_type_holding_alias_ptr_err.out | 9 +++++++++
 vlib/v/checker/tests/sum_type_holding_alias_ptr_err.vv  | 6 ++++++
 3 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/checker/tests/sum_type_holding_alias_ptr_err.out
 create mode 100644 vlib/v/checker/tests/sum_type_holding_alias_ptr_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 2d4ef02d0..1230b6141 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -627,10 +627,15 @@ fn (mut c Checker) sum_type_decl(node ast.SumTypeDecl) {
 	for variant in node.variants {
 		c.ensure_type_exists(variant.typ, variant.pos)
 		sym := c.table.sym(variant.typ)
-		if variant.typ.is_ptr() {
+		if variant.typ.is_ptr() || (sym.info is ast.Alias && sym.info.parent_type.is_ptr()) {
 			variant_name := sym.name.all_after_last('.')
 			lb, rb := if sym.kind == .struct_ { '{', '}' } else { '(', ')' }
-			c.add_error_detail('declare the sum type with non-reference types: `${node.name} = ${variant_name} | ...`
+			msg := if sym.info is ast.Alias && sym.info.parent_type.is_ptr() {
+				'alias as non-reference type'
+			} else {
+				'the sum type with non-reference types'
+			}
+			c.add_error_detail('declare ${msg}: `${node.name} = ${variant_name} | ...`
 and use a reference to the sum type instead: `var := &${node.name}(${variant_name}${lb}val${rb})`')
 			c.error('sum type cannot hold a reference type', variant.pos)
 		}
diff --git a/vlib/v/checker/tests/sum_type_holding_alias_ptr_err.out b/vlib/v/checker/tests/sum_type_holding_alias_ptr_err.out
new file mode 100644
index 000000000..dce526dd6
--- /dev/null
+++ b/vlib/v/checker/tests/sum_type_holding_alias_ptr_err.out
@@ -0,0 +1,9 @@
+vlib/v/checker/tests/sum_type_holding_alias_ptr_err.vv:3:12: error: sum type cannot hold a reference type
+    1 | type Alias1 = &int
+    2 | type Alias2 = &string
+    3 | type Qwe = Alias1 | Alias2
+      |            ~~~~~~
+    4 | 
+    5 | fn main() {
+Details: declare alias as non-reference type: `Qwe = Alias1 | ...`
+and use a reference to the sum type instead: `var := &Qwe(Alias1(val))`
diff --git a/vlib/v/checker/tests/sum_type_holding_alias_ptr_err.vv b/vlib/v/checker/tests/sum_type_holding_alias_ptr_err.vv
new file mode 100644
index 000000000..c37d19859
--- /dev/null
+++ b/vlib/v/checker/tests/sum_type_holding_alias_ptr_err.vv
@@ -0,0 +1,6 @@
+type Alias1 = &int
+type Alias2 = &string
+type Qwe = Alias1 | Alias2
+
+fn main() {
+}
-- 
2.39.5