From 9ec68e875800b4eed15d0093d0e023f3faac6de0 Mon Sep 17 00:00:00 2001
From: Tamir Duberstein <tamird@gmail.com>
Date: Sat, 22 Aug 2026 07:57:17 -0400
Subject: [PATCH] Fix large_futures ICE with the next solver

With the new trait solver enabled by default in nightly-2026-08-22 [1],
large_futures can ICE while inspecting an awaited future.

The lint switches to Codegen mode to obtain coroutine layouts but passes
a type whose opaque aliases are still marked rigid from type checking.
Because layout_of receives an already-Codegen environment, its
environment-change path does not clear those markers.

Clear alias rigidity and normalize the awaited type in that environment
before querying its layout. Codegen mode must remain: post-analysis
layout queries cannot compute coroutine sizes [2].

The regression covers direct and pinned futures under both solvers,
without other lint errors that could hide a delayed ICE.

Fixes rust-lang/rust#161495.

[1]: https://github.com/rust-lang/rust/pull/160619
[2]: https://github.com/rust-lang/rust/pull/145477
---
 clippy_lints/src/large_futures.rs     | 11 ++++++++---
 tests/ui/large_futures_next_solver.rs | 16 ++++++++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)
 create mode 100644 tests/ui/large_futures_next_solver.rs

diff --git a/clippy_lints/src/large_futures.rs b/clippy_lints/src/large_futures.rs
index 98516cfd4cb7..7f39f23b362a 100644
--- a/clippy_lints/src/large_futures.rs
+++ b/clippy_lints/src/large_futures.rs
@@ -7,6 +7,7 @@ use rustc_errors::Applicability;
 use rustc_hir::attrs::lang_items::LangItem;
 use rustc_hir::{Expr, ExprKind, MatchSource};
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
 use rustc_session::impl_lint_pass;
 
 declare_clippy_lint! {
@@ -65,9 +66,13 @@ impl<'tcx> LateLintPass<'tcx> for LargeFuture {
             && let ty = cx.typeck_results().expr_ty(arg)
             && let Some(future_trait_def_id) = cx.tcx.lang_items().future_trait()
             && implements_trait(cx, ty, future_trait_def_id, &[])
-            && let Ok(layout) = cx
-                .tcx
-                .layout_of(cx.typing_env().with_codegen_normalized(cx.tcx).as_query_input(ty))
+            && let typing_env = cx.typing_env().with_codegen_normalized(cx.tcx)
+            // Aliases that were rigid during type checking can be revealed in codegen mode.
+            && let Ok(ty) = cx.tcx.try_normalize_erasing_regions(
+                typing_env,
+                ty::set_aliases_to_non_rigid(cx.tcx, ty),
+            )
+            && let Ok(layout) = cx.tcx.layout_of(typing_env.as_query_input(ty))
             && let size = layout.layout.size()
             && size >= Size::from_bytes(self.future_size_threshold)
         {
diff --git a/tests/ui/large_futures_next_solver.rs b/tests/ui/large_futures_next_solver.rs
new file mode 100644
index 000000000000..86017484f5b4
--- /dev/null
+++ b/tests/ui/large_futures_next_solver.rs
@@ -0,0 +1,16 @@
+//@ check-pass
+//@ revisions: current next
+//@[next] compile-flags: -Znext-solver=globally
+
+// https://github.com/rust-lang/rust/issues/161495
+
+#![warn(clippy::large_futures)]
+
+async fn callee() {}
+
+async fn caller() {
+    callee().await;
+    std::pin::pin!(callee()).await;
+}
+
+fn main() {}