Unrolled build for #151373

rust-timer · web-flow · commit f1204cfbe5a5 · 2026-01-21T01:02:41.000+01:00
Rollup merge of #151373 - issue-151300, r=lcnr Fix an ICE on transmute goals with placeholders in `param_env` Fixes #151300 The next solver short-circuits `consider_builtin_transmute_candidate` when the goal contains non-region placeholders, since `rustc_transmute` does not support type parameters. However, this check should likely be refined to apply only to the predicate itself: excess bounds with type params in the param env can cause the goal to be rejected even when its predicate trivially holds. r? types
diff --git 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
@@ -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() {}

Original file line number	Diff line number	Diff line change
`@@ -659,7 +659,7 @@ where`
`659`	`659`	`}`
`660`	`660`
`661`	`661`	// `rustc_transmute` does not have support for type or const params
`662`		`- if goal.has_non_region_placeholders() {`
	`662`	`+ if goal.predicate.has_non_region_placeholders() {`
`663`	`663`	`return Err(NoSolution);`
`664`	`664`	`}`
`665`	`665`