Add 2 more test cases from 151284 and 151479

tests/ui/privacy/auxiliary/missing-mir-priv-bounds-extern-2.rs

@@ -0,0 +1,46 @@
+// Doesn't involve `impl Trait` unlike missing-mir-priv-bounds-extern.rs
+
+pub trait ToPriv {
+    type AssocPriv;
+}
+
+pub trait PubTr {
+    #[expect(private_bounds)]
+    type Assoc: ToPriv<AssocPriv = Priv>;
+}
+
+// Dummy and DummyToPriv are only used in call_handler
+struct Dummy;
+struct DummyToPriv;
+impl PubTr for Dummy {
+    type Assoc = DummyToPriv;
+}
+impl ToPriv for DummyToPriv {
+    type AssocPriv = Priv;
+}
+
+pub trait PubTrHandler {
+    fn handle<T: PubTr>();
+}
+pub fn call_handler<T: PubTrHandler>() {
+    T::handle::<Dummy>();
+}
+
+struct Priv;
+
+pub trait GetUnreachable {
+    type Assoc;
+}
+
+mod m {
+    pub struct Unreachable;
+
+    impl Unreachable {
+        #[expect(dead_code)]
+        pub fn generic<T>() {}
+    }
+
+    impl crate::GetUnreachable for crate::Priv {
+        type Assoc = Unreachable;
+    }
+}

tests/ui/privacy/auxiliary/missing-mir-priv-bounds-extern-3.rs

@@ -0,0 +1,35 @@
+struct Priv;
+
+pub trait Super {
+    type AssocSuper: GetUnreachable;
+}
+#[expect(private_bounds)]
+pub trait Sub: Super<AssocSuper = Priv> {}
+
+// This Dummy type is only used in call_handler
+struct Dummy;
+impl Super for Dummy {
+    type AssocSuper = Priv;
+}
+impl Sub for Dummy {}
+
+pub trait SubHandler {
+    fn handle<T: Sub>();
+}
+pub fn call_handler<T: SubHandler>() {
+    <T as SubHandler>::handle::<Dummy>();
+}
+
+pub trait GetUnreachable {
+    type Assoc;
+}
+mod m {
+    pub struct Unreachable;
+    impl Unreachable {
+        #[expect(dead_code)]
+        pub fn generic<T>() {}
+    }
+    impl crate::GetUnreachable for crate::Priv {
+        type Assoc = Unreachable;
+    }
+}

tests/ui/privacy/missing-mir-priv-bounds-2.rs

@@ -0,0 +1,29 @@
+// Test case from issue #151284.
+// A private associated type bound allows to leak another private type and result in missing MIR.
+
+//@ build-fail
+//@ aux-crate:dep=missing-mir-priv-bounds-extern-2.rs
+
+extern crate dep;
+use dep::{GetUnreachable, PubTr, PubTrHandler, ToPriv, call_handler};
+
+fn main() {
+    call_handler::<Handler>();
+}
+
+struct Handler;
+impl PubTrHandler for Handler {
+    fn handle<T: PubTr>() {
+        <T as Access>::AccessAssoc::generic::<i32>();
+    }
+}
+
+trait Access: PubTr {
+    type AccessAssoc;
+}
+
+impl<T: PubTr> Access for T {
+    type AccessAssoc = <<T::Assoc as ToPriv>::AssocPriv as GetUnreachable>::Assoc;
+}
+
+//~? ERROR missing optimized MIR

tests/ui/privacy/missing-mir-priv-bounds-2.stderr

@@ -0,0 +1,10 @@
+error: missing optimized MIR for `dep::m::Unreachable::generic::<i32>` in the crate `missing_mir_priv_bounds_extern_2`
+   |
+note: missing optimized MIR for this item (was the crate `missing_mir_priv_bounds_extern_2` compiled with `--emit=metadata`?)
+  --> $DIR/auxiliary/missing-mir-priv-bounds-extern-2.rs:40:9
+   |
+LL |         pub fn generic<T>() {}
+   |         ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/privacy/missing-mir-priv-bounds-3.rs

@@ -0,0 +1,30 @@
+// Test case from issue #151479.
+// A private associated type bound allows to leak another private type and result in missing MIR.
+
+//@ build-fail
+//@ aux-crate:dep=missing-mir-priv-bounds-extern-3.rs
+
+extern crate dep;
+use dep::{GetUnreachable, Sub, SubHandler, Super, call_handler};
+
+fn main() {
+    call_handler::<Handler>();
+}
+
+struct Handler;
+impl SubHandler for Handler {
+    fn handle<T: Sub>() {
+        <T as Access>::AccessAssoc::generic::<i32>();
+    }
+}
+
+// Without this indirection, Handler::handle notices that
+// it's mentioning dep::Priv.
+trait Access: Super {
+    type AccessAssoc;
+}
+impl<T: Super> Access for T {
+    type AccessAssoc = <<T as Super>::AssocSuper as GetUnreachable>::Assoc;
+}
+
+//~? ERROR missing optimized MIR

tests/ui/privacy/missing-mir-priv-bounds-3.stderr

@@ -0,0 +1,10 @@
+error: missing optimized MIR for `dep::m::Unreachable::generic::<i32>` in the crate `missing_mir_priv_bounds_extern_3`
+   |
+note: missing optimized MIR for this item (was the crate `missing_mir_priv_bounds_extern_3` compiled with `--emit=metadata`?)
+  --> $DIR/auxiliary/missing-mir-priv-bounds-extern-3.rs:30:9
+   |
+LL |         pub fn generic<T>() {}
+   |         ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+