From 4018a784b316621c1510d71e9c5243793aab5106 Mon Sep 17 00:00:00 2001
From: Hitalo Souza <63821277+enghitalo@users.noreply.github.com>
Date: Wed, 13 Dec 2023 16:24:16 -0400
Subject: [PATCH] checker: cast sumtype to its variant generic type (#20166)

---
 vlib/v/checker/checker.v                        |  5 +++--
 .../tests/cast_sumtype_as_generic_err.out       | 13 +++++++++++++
 .../tests/cast_sumtype_as_generic_err.vv        | 16 ++++++++++++++++
 vlib/v/tests/cast_sumtype_as_generic_test.v     | 17 +++++++++++++++++
 4 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/checker/tests/cast_sumtype_as_generic_err.out
 create mode 100644 vlib/v/checker/tests/cast_sumtype_as_generic_err.vv
 create mode 100644 vlib/v/tests/cast_sumtype_as_generic_test.v

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index a488b69d0..1cce6dd20 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2628,10 +2628,11 @@ pub fn (mut c Checker) expr(mut node ast.Expr) ast.Type {
 		ast.AsCast {
 			node.expr_type = c.expr(mut node.expr)
 			expr_type_sym := c.table.sym(node.expr_type)
-			type_sym := c.table.sym(node.typ)
+			type_sym := c.table.sym(c.unwrap_generic(node.typ))
 			if expr_type_sym.kind == .sum_type {
 				c.ensure_type_exists(node.typ, node.pos)
-				if !c.table.sumtype_has_variant(node.expr_type, node.typ, true) {
+				if !c.table.sumtype_has_variant(c.unwrap_generic(node.expr_type), c.unwrap_generic(node.typ),
+					true) {
 					addr := '&'.repeat(node.typ.nr_muls())
 					c.error('cannot cast `${expr_type_sym.name}` to `${addr}${type_sym.name}`',
 						node.pos)
diff --git a/vlib/v/checker/tests/cast_sumtype_as_generic_err.out b/vlib/v/checker/tests/cast_sumtype_as_generic_err.out
new file mode 100644
index 000000000..3cb132890
--- /dev/null
+++ b/vlib/v/checker/tests/cast_sumtype_as_generic_err.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/cast_sumtype_as_generic_err.vv:15:10: error: cannot cast `bool` to `SumType`
+   13 | fn main() {
+   14 |     println(SumType('la').cast_to[string]())
+   15 |     println(SumType(true).cast_to[bool]())
+      |             ~~~~~~~~~~~~~
+   16 | }
+vlib/v/checker/tests/cast_sumtype_as_generic_err.vv:10:11: error: cannot cast `SumType` to `bool`
+    8 |
+    9 | fn (a SumType) cast_to[T]() T {
+   10 |     return a as T
+      |              ~~
+   11 | }
+   12 |
\ No newline at end of file
diff --git a/vlib/v/checker/tests/cast_sumtype_as_generic_err.vv b/vlib/v/checker/tests/cast_sumtype_as_generic_err.vv
new file mode 100644
index 000000000..986d7e5bd
--- /dev/null
+++ b/vlib/v/checker/tests/cast_sumtype_as_generic_err.vv
@@ -0,0 +1,16 @@
+module main
+
+struct Chacabum {
+	a int
+}
+
+type SumType = Chacabum | int | string
+
+fn (a SumType) cast_to[T]() T {
+	return a as T
+}
+
+fn main() {
+	println(SumType('la').cast_to[string]())
+	println(SumType(true).cast_to[bool]())
+}
diff --git a/vlib/v/tests/cast_sumtype_as_generic_test.v b/vlib/v/tests/cast_sumtype_as_generic_test.v
new file mode 100644
index 000000000..77a8beaef
--- /dev/null
+++ b/vlib/v/tests/cast_sumtype_as_generic_test.v
@@ -0,0 +1,17 @@
+module main
+
+struct Chacabum {
+	a int
+}
+
+type SumType = Chacabum | int | string
+
+fn (a SumType) cast_to[T]() T {
+	return a as T
+}
+
+fn test_cast_to_generics() {
+	assert SumType(1).cast_to[int]() == 1
+	assert SumType('la').cast_to[string]() == 'la'
+	assert SumType(Chacabum{}).cast_to[Chacabum]() == Chacabum{}
+}
-- 
2.39.5