From eb72e6764e30003fab1d46ecc22e4938b060aaed Mon Sep 17 00:00:00 2001
From: reddevilmidzy <midzy0228@gmail.com>
Date: Mon, 24 Nov 2025 16:06:15 +0900
Subject: [PATCH] Fix None handling for simplify_type in for_each_relevant_impl

---
 compiler/rustc_middle/src/ty/context.rs       |  8 ++++----
 .../traits/dispatch-from-dyn-blanket-impl.rs  | 10 ++++++++++
 .../dispatch-from-dyn-blanket-impl.stderr     | 19 +++++++++++++++++++
 3 files changed, 33 insertions(+), 4 deletions(-)
 create mode 100644 tests/ui/traits/dispatch-from-dyn-blanket-impl.rs
 create mode 100644 tests/ui/traits/dispatch-from-dyn-blanket-impl.stderr

diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 876297d3e407..3092c6e76c03 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -589,13 +589,13 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
             | ty::Never
             | ty::Tuple(_)
             | ty::UnsafeBinder(_) => {
-                let simp = ty::fast_reject::simplify_type(
+                if let Some(simp) = ty::fast_reject::simplify_type(
                     tcx,
                     self_ty,
                     ty::fast_reject::TreatParams::AsRigid,
-                )
-                .unwrap();
-                consider_impls_for_simplified_type(simp);
+                ) {
+                    consider_impls_for_simplified_type(simp);
+                }
             }
 
             // HACK: For integer and float variables we have to manually look at all impls
diff --git a/tests/ui/traits/dispatch-from-dyn-blanket-impl.rs b/tests/ui/traits/dispatch-from-dyn-blanket-impl.rs
new file mode 100644
index 000000000000..4e0e7ca9793f
--- /dev/null
+++ b/tests/ui/traits/dispatch-from-dyn-blanket-impl.rs
@@ -0,0 +1,10 @@
+// Test that blanket impl of DispatchFromDyn is rejected.
+// regression test for issue <https://github.com/rust-lang/rust/issues/148062>
+
+#![feature(dispatch_from_dyn)]
+
+impl<T> std::ops::DispatchFromDyn<T> for T {}
+//~^ ERROR type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+//~| ERROR the trait `DispatchFromDyn` may only be implemented for a coercion between structures
+
+fn main() {}
diff --git a/tests/ui/traits/dispatch-from-dyn-blanket-impl.stderr b/tests/ui/traits/dispatch-from-dyn-blanket-impl.stderr
new file mode 100644
index 000000000000..69f360817805
--- /dev/null
+++ b/tests/ui/traits/dispatch-from-dyn-blanket-impl.stderr
@@ -0,0 +1,19 @@
+error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+  --> $DIR/dispatch-from-dyn-blanket-impl.rs:6:6
+   |
+LL | impl<T> std::ops::DispatchFromDyn<T> for T {}
+   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |
+   = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
+   = note: only traits defined in the current crate can be implemented for a type parameter
+
+error[E0377]: the trait `DispatchFromDyn` may only be implemented for a coercion between structures
+  --> $DIR/dispatch-from-dyn-blanket-impl.rs:6:1
+   |
+LL | impl<T> std::ops::DispatchFromDyn<T> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0210, E0377.
+For more information about an error, try `rustc --explain E0210`.