From 74f9ce6b86acdaf20d4ed05f1365337eef72d3e8 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Mon, 30 Sep 2024 13:32:36 -0300
Subject: [PATCH 1/2] fix

---
 vlib/v/gen/c/str_intp.v                       |  4 +++-
 .../comptime/comptime_variant_interp_test.v   | 23 +++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/comptime/comptime_variant_interp_test.v

diff --git a/vlib/v/gen/c/str_intp.v b/vlib/v/gen/c/str_intp.v
index 4f1e894cde33de..1c9285fdeb4f43 100644
--- a/vlib/v/gen/c/str_intp.v
+++ b/vlib/v/gen/c/str_intp.v
@@ -191,7 +191,9 @@ fn (mut g Gen) str_val(node ast.StringInterLiteral, i int, fmts []u8) {
 	} else if fmt == `s` || typ.has_flag(.variadic) {
 		mut exp_typ := typ
 		if expr is ast.Ident {
-			if expr.obj is ast.Var {
+			if g.comptime.is_comptime_var(expr) {
+				exp_typ = g.comptime.get_comptime_var_type(expr)
+			} else if expr.obj is ast.Var {
 				if expr.obj.smartcasts.len > 0 {
 					exp_typ = g.unwrap_generic(expr.obj.smartcasts.last())
 					cast_sym := g.table.sym(exp_typ)
diff --git a/vlib/v/tests/comptime/comptime_variant_interp_test.v b/vlib/v/tests/comptime/comptime_variant_interp_test.v
new file mode 100644
index 00000000000000..c2f32ab7130daa
--- /dev/null
+++ b/vlib/v/tests/comptime/comptime_variant_interp_test.v
@@ -0,0 +1,23 @@
+module main
+
+struct Foo {
+	a int
+}
+
+type SumType = Foo | int | string
+
+fn (v SumType) cast[T](val T) string {
+	mut res := ''
+	$for variant_value in v.variants {
+		if v is variant_value {
+			println('v: ${v}')
+			res = 'v: ${v}'
+			println(res)
+		}
+	}
+	return res
+}
+
+fn test_main() {
+	assert SumType(1).cast[int](1) == 'v: 1'
+}

From 1701cc375d87be6411adad9757389808df50cd90 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Mon, 30 Sep 2024 14:18:37 -0300
Subject: [PATCH 2/2] fix

---
 vlib/v/gen/c/str_intp.v | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/vlib/v/gen/c/str_intp.v b/vlib/v/gen/c/str_intp.v
index 1c9285fdeb4f43..94503ef2ff5d06 100644
--- a/vlib/v/gen/c/str_intp.v
+++ b/vlib/v/gen/c/str_intp.v
@@ -191,7 +191,7 @@ fn (mut g Gen) str_val(node ast.StringInterLiteral, i int, fmts []u8) {
 	} else if fmt == `s` || typ.has_flag(.variadic) {
 		mut exp_typ := typ
 		if expr is ast.Ident {
-			if g.comptime.is_comptime_var(expr) {
+			if g.comptime.get_ct_type_var(expr) == .smartcast {
 				exp_typ = g.comptime.get_comptime_var_type(expr)
 			} else if expr.obj is ast.Var {
 				if expr.obj.smartcasts.len > 0 {