From bad436c9f1367ce5239c209c5f363526b85a4f07 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Tue, 6 Feb 2024 13:27:04 -0300
Subject: [PATCH] parser: fn type declaration does not check already registered
 name (#20732)

---
 vlib/v/parser/parse_type.v                       |  5 +++++
 vlib/v/parser/tests/already_existing_sym_err.out |  5 +++++
 vlib/v/parser/tests/already_existing_sym_err.vv  | 16 ++++++++++++++++
 3 files changed, 26 insertions(+)
 create mode 100644 vlib/v/parser/tests/already_existing_sym_err.out
 create mode 100644 vlib/v/parser/tests/already_existing_sym_err.vv

diff --git a/vlib/v/parser/parse_type.v b/vlib/v/parser/parse_type.v
index 4d094b3c4..d9ed8b282 100644
--- a/vlib/v/parser/parse_type.v
+++ b/vlib/v/parser/parse_type.v
@@ -321,7 +321,12 @@ fn (mut p Parser) parse_fn_type(name string, generic_types []ast.Type) ast.Type
 	// MapFooFn typedefs are manually added in cheaders.v
 	// because typedefs get generated after the map struct is generated
 	has_decl := p.builtin_mod && name.starts_with('Map') && name.ends_with('Fn')
+	already_exists := p.table.find_type_idx(name) != 0
 	idx := p.table.find_or_register_fn_type(func, false, has_decl)
+	if already_exists && p.table.sym_by_idx(idx).kind != .function {
+		p.error_with_pos('cannot register fn `${name}`, another type with this name exists',
+			fn_type_pos)
+	}
 	if has_generic {
 		return ast.new_type(idx).set_flag(.generic)
 	}
diff --git a/vlib/v/parser/tests/already_existing_sym_err.out b/vlib/v/parser/tests/already_existing_sym_err.out
new file mode 100644
index 000000000..999832510
--- /dev/null
+++ b/vlib/v/parser/tests/already_existing_sym_err.out
@@ -0,0 +1,5 @@
+vlib/v/parser/tests/already_existing_sym_err.vv:16:6: error: cannot register fn `vnkxcb.Nk_plugin_alloc`, another type with this name exists
+   14 | }
+   15 | 
+   16 | type Nk_plugin_alloc = fn (Nk_handle, voidptr, Nk_size) voidptr
+      |      ~~~~~~~~~~~~~~~
diff --git a/vlib/v/parser/tests/already_existing_sym_err.vv b/vlib/v/parser/tests/already_existing_sym_err.vv
new file mode 100644
index 000000000..0f1899373
--- /dev/null
+++ b/vlib/v/parser/tests/already_existing_sym_err.vv
@@ -0,0 +1,16 @@
+@[translated]
+module vnkxcb
+
+type Nk_size = u32
+
+union Nk_handle {
+	ptr voidptr
+	id int
+}
+
+enum Nk_plugin_alloc {
+	nk_tree_node
+	nk_tree_tab
+}
+
+type Nk_plugin_alloc = fn (Nk_handle, voidptr, Nk_size) voidptr
\ No newline at end of file
-- 
2.39.5