From 4acddd37b04e7b378b11b7a100ba5c51b844a8f5 Mon Sep 17 00:00:00 2001
From: Jengro <avey777@outlook.com>
Date: Sat, 27 Jun 2026 05:53:33 +0800
Subject: [PATCH] markused: fix generic fn instantiation dedup key collision
 for identical module names (#27399)

---
 vlib/v/markused/walker.v                      |  2 +-
 ...eric_fn_dedup_collision_issue_27398_test.v | 70 +++++++++++++++++++
 2 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/generic_fn_dedup_collision_issue_27398_test.v

diff --git a/vlib/v/markused/walker.v b/vlib/v/markused/walker.v
index 2b9fce094..76db5e7fc 100644
--- a/vlib/v/markused/walker.v
+++ b/vlib/v/markused/walker.v
@@ -510,7 +510,7 @@ fn (mut w Walker) record_used_fn_generic_types(fkey string, concrete_types []ast
 fn (w &Walker) fn_generic_types_key(fkey string, concrete_types []ast.Type) string {
 	mut parts := []string{cap: concrete_types.len}
 	for typ in concrete_types {
-		parts << w.table.type_to_str(typ)
+		parts << u32(typ).str()
 	}
 	return '${fkey}:${parts.join('|')}'
 }
diff --git a/vlib/v/tests/generic_fn_dedup_collision_issue_27398_test.v b/vlib/v/tests/generic_fn_dedup_collision_issue_27398_test.v
new file mode 100644
index 000000000..46fbaf13f
--- /dev/null
+++ b/vlib/v/tests/generic_fn_dedup_collision_issue_27398_test.v
@@ -0,0 +1,70 @@
+import os
+
+fn write_file(path string, content string) {
+	os.write_file(path, content) or { panic(err) }
+}
+
+fn test_generic_fn_dedup_collision_issue_27398() {
+	n_pairs := 24
+	tmp := os.join_path(os.vtmp_dir(), 'v_issue_27398_${os.getpid()}')
+	os.rmdir_all(tmp) or {}
+	defer {
+		os.rmdir_all(tmp) or {}
+	}
+
+	os.mkdir_all(os.join_path(tmp, 'api')) or { panic(err) }
+	write_file(os.join_path(tmp, 'api', 'common.v'), 'module api
+
+pub struct MyStruct[T] {
+pub:
+	value T
+}
+
+pub fn make_struct[T](val T) MyStruct[T] {
+	return MyStruct[T]{value: val}
+}
+')
+
+	common_mod := 'module common
+
+import api
+
+pub struct Type_a { pub: name string }
+pub struct Type_b { pub: age int }
+
+pub fn call_api() {
+	a := Type_a{name: "hello"}
+	b := Type_b{age: 42}
+	_ = api.make_struct(a)
+	_ = api.make_struct(b)
+}
+'
+
+	mut main_mod := 'module main\n\n'
+	for i in 0 .. n_pairs {
+		for _, s in ['a', 'b'] {
+			dir := os.join_path(tmp, 'm${i}${s}', 'common')
+			os.mkdir_all(dir) or { panic(err) }
+			write_file(os.join_path(dir, 'types.v'), common_mod)
+			main_mod += 'import m${i}${s}.common as m${i}${s}\n'
+		}
+	}
+	main_mod += '\nfn main() {\n'
+	for i in 0 .. n_pairs {
+		for _, s in ['a', 'b'] {
+			main_mod += '\tm${i}${s}.call_api()\n'
+		}
+	}
+	main_mod += '\tprintln("ok")\n}\n'
+	write_file(os.join_path(tmp, 'main.v'), main_mod)
+
+	old_wd := os.getwd()
+	os.chdir(tmp) or { panic(err) }
+	defer {
+		os.chdir(old_wd) or { panic(err) }
+	}
+	res := os.execute('${os.quoted_path(@VEXE)} -skip-unused run .')
+
+	assert res.exit_code == 0, 'compilation failed:\n${res.output}'
+	assert res.output.trim_space() == 'ok'
+}
-- 
2.39.5