From 328893e1a6d71c8017d6229960da13700076ca38 Mon Sep 17 00:00:00 2001
From: Shoyu Vanilla <modulo641@gmail.com>
Date: Mon, 19 Jan 2026 21:35:14 +0900
Subject: [PATCH] Fix an ICE on transmute goals with placeholders in
 `param_env`

---
 .../src/solve/trait_goals.rs                  |  2 +-
 .../transmute-with-type-params.rs             | 21 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/transmutability/transmute-with-type-params.rs

diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 651f073efb82..003841f3af3f 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -659,7 +659,7 @@ where
         }
 
         // `rustc_transmute` does not have support for type or const params
-        if goal.has_non_region_placeholders() {
+        if goal.predicate.has_non_region_placeholders() {
             return Err(NoSolution);
         }
 
diff --git a/tests/ui/transmutability/transmute-with-type-params.rs b/tests/ui/transmutability/transmute-with-type-params.rs
new file mode 100644
index 000000000000..f1630449a41b
--- /dev/null
+++ b/tests/ui/transmutability/transmute-with-type-params.rs
@@ -0,0 +1,21 @@
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@ [next] compile-flags: -Znext-solver
+//@ check-pass
+
+// A regression test for https://github.com/rust-lang/rust/issues/151300
+
+#![feature(transmutability)]
+use std::mem::TransmuteFrom;
+
+pub fn is_maybe_transmutable<Src, Dst>()
+where
+    Dst: TransmuteFrom<Src>,
+{
+}
+
+fn function_with_generic<T>() {
+    is_maybe_transmutable::<(), ()>();
+}
+
+fn main() {}