From 24ec3966dcc0246f92c8ade4638bbfa1f70fb07e Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Mon, 11 May 2026 02:04:10 +0300
Subject: [PATCH] parser: set TypeSymbol.language for C aliases, so redefining
 a C type alias (e.g. type C.WCHAR = u16) works

---
 vlib/v/parser/parser.v                              |  1 +
 vlib/v/tests/aliases/c_alias_redeclaration_test.c.v | 11 +++++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 vlib/v/tests/aliases/c_alias_redeclaration_test.c.v

diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index c1a6c23bf..41bd55a8d 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -3278,6 +3278,7 @@ fn (mut p Parser) type_decl() ast.TypeDecl {
 		cname:      util.no_dots(prepend_mod_name)
 		mod:        p.mod
 		parent_idx: pidx
+		language:   language
 		info:       ast.Alias{
 			parent_type: parent_type
 			language:    parent_language
diff --git a/vlib/v/tests/aliases/c_alias_redeclaration_test.c.v b/vlib/v/tests/aliases/c_alias_redeclaration_test.c.v
new file mode 100644
index 000000000..9105ecf30
--- /dev/null
+++ b/vlib/v/tests/aliases/c_alias_redeclaration_test.c.v
@@ -0,0 +1,11 @@
+// Redeclaring an existing C type alias should be accepted. Before the
+// parser was setting TypeSymbol.language=.c for C aliases, the table's
+// "Allow C type aliases to override existing C types" override never fired
+// and the second declaration failed with `cannot register alias`.
+
+type C.RedeclareU16Alias = u16
+type C.RedeclareU16Alias = u16
+
+fn test_c_alias_redeclaration_compiles() {
+	assert true
+}
-- 
2.39.5