From 25894417a54e5ad527cb98f00bf3f67b4e0c53ca Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 11 Mar 2026 13:52:04 +0300
Subject: [PATCH] cgen: error that occures when using gcc, clang or msvc but
 not tcc (fixes #25711)

---
 vlib/v/gen/c/cgen.v                           | 11 ++++++-
 .../sumtypes/sumtype_as_cast_fn_call_test.v   | 32 +++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/sumtypes/sumtype_as_cast_fn_call_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index c29c957d0..e21a02f86 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -8548,8 +8548,14 @@ fn (mut g Gen) as_cast(node ast.AsCast) {
 		}
 	} else {
 		mut is_optional_ident_var := false
+		mut wrap_in_addr := false
 		if g.inside_smartcast {
-			g.write('&')
+			if node.expr.is_lvalue() {
+				g.write('&')
+			} else {
+				wrap_in_addr = true
+				g.write('ADDR(${styp}, ')
+			}
 		}
 		if node.expr is ast.Ident {
 			if node.expr.info is ast.IdentVar && node.expr.info.is_option
@@ -8574,6 +8580,9 @@ fn (mut g Gen) as_cast(node ast.AsCast) {
 		if !is_optional_ident_var {
 			g.expr(node.expr)
 		}
+		if wrap_in_addr {
+			g.write(')')
+		}
 	}
 }
 
diff --git a/vlib/v/tests/sumtypes/sumtype_as_cast_fn_call_test.v b/vlib/v/tests/sumtypes/sumtype_as_cast_fn_call_test.v
new file mode 100644
index 000000000..9a4c0215f
--- /dev/null
+++ b/vlib/v/tests/sumtypes/sumtype_as_cast_fn_call_test.v
@@ -0,0 +1,32 @@
+module main
+
+type AstNode = BoolCondition | Expression
+
+struct Expression {
+	value int
+}
+
+struct BoolCondition {
+mut:
+	con_simple AstNode
+	is_simple  bool
+}
+
+fn parse_expression() Expression {
+	return Expression{
+		value: 1
+	}
+}
+
+fn parse_simple_boolean_expr() BoolCondition {
+	mut final_expr := BoolCondition{}
+	final_expr.is_simple = true
+	final_expr.con_simple = parse_expression() as Expression
+	return final_expr
+}
+
+fn test_sumtype_as_cast_of_fn_call() {
+	result := parse_simple_boolean_expr()
+	assert result.is_simple
+	assert (result.con_simple as Expression).value == 1
+}
-- 
2.39.5