From bb1bd90d4fd87586bb44360148766a9bebc2dca8 Mon Sep 17 00:00:00 2001
From: Hongbo Zhang <bobzhang1988@gmail.com>
Date: Thu, 16 Oct 2025 11:10:54 +0800
Subject: [PATCH 1/2] some weird interactions here

---
 quickcheck/arbitrary_test.mbt | 23 +++++++++++++++++++++++
 quickcheck/utils.mbt          | 18 ++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/quickcheck/arbitrary_test.mbt b/quickcheck/arbitrary_test.mbt
index 000c9e81d..fa5ac7032 100644
--- a/quickcheck/arbitrary_test.mbt
+++ b/quickcheck/arbitrary_test.mbt
@@ -103,3 +103,26 @@ test "arbitrary gen bytes" {
     ),
   )
 }
+
+
+///|
+priv trait Test0 {
+  sum(Self, x? : Int, y? : Int, z? : Int) -> Int
+}
+
+///|
+impl Test0 for Int with sum(self, x~ : Int = 3, y? = 2, z?) {
+  // weird both x~ and y? work here??
+  // y? should warn
+  self + x + y + (if z is Some(x) { x } else { 0 })
+}
+
+///|
+test "default argument in trait method" {
+  inspect((10).sum(), content="15") 
+  // weird warnings appear here
+  // Calling local `impl` with `.` or `Type::meth(..)` is deprecated, use `Trait::meth(..)` instead.
+  // this seems to be inconsistent with the fact that `Type::meth` will call `Trait::meth`
+  inspect((10).sum(x=1), content="13")
+  inspect((10).sum(x=1, y=1), content="12")
+}
diff --git a/quickcheck/utils.mbt b/quickcheck/utils.mbt
index 4123e0ec3..855195d93 100644
--- a/quickcheck/utils.mbt
+++ b/quickcheck/utils.mbt
@@ -21,3 +21,21 @@ pub fn[X : Arbitrary] samples(x : Int) -> Array[X] {
   }
   array
 }
+
+
+///|
+priv trait Test0 {
+  sum(Self, x? : Int, y? : Int) -> Int
+}
+
+///|
+impl Test0 for Int with sum(self, x? : Int = 3, y? = 2) {
+  self + x + y
+}
+
+///|
+test "default argument in trait method" {
+  inspect((10).sum(), content="15")
+  inspect((10).sum(x=1), content="13")
+  inspect((10).sum(x=1, y=1), content="12")
+}

From c57ad3232b17fd7de24deb9821100f23ac11b400 Mon Sep 17 00:00:00 2001
From: Hongbo Zhang <bobzhang1988@gmail.com>
Date: Thu, 16 Oct 2025 11:15:19 +0800
Subject: [PATCH 2/2] tweak

---
 quickcheck/arbitrary_test.mbt | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/quickcheck/arbitrary_test.mbt b/quickcheck/arbitrary_test.mbt
index fa5ac7032..5d1ed5c88 100644
--- a/quickcheck/arbitrary_test.mbt
+++ b/quickcheck/arbitrary_test.mbt
@@ -106,12 +106,12 @@ test "arbitrary gen bytes" {
 
 
 ///|
-priv trait Test0 {
+trait Test0 {
   sum(Self, x? : Int, y? : Int, z? : Int) -> Int
 }
 
 ///|
-impl Test0 for Int with sum(self, x~ : Int = 3, y? = 2, z?) {
+pub impl Test0 for Int with sum(self, x~ : Int = 3, y? = 2, z?) {
   // weird both x~ and y? work here??
   // y? should warn
   self + x + y + (if z is Some(x) { x } else { 0 })
@@ -124,5 +124,6 @@ test "default argument in trait method" {
   // Calling local `impl` with `.` or `Type::meth(..)` is deprecated, use `Trait::meth(..)` instead.
   // this seems to be inconsistent with the fact that `Type::meth` will call `Trait::meth`
   inspect((10).sum(x=1), content="13")
+  inspect(Int::sum((10), x=1, y=1), content="12")
   inspect((10).sum(x=1, y=1), content="12")
 }