From dabbc7fddc7217dcffcf8612510561ceecb59cea Mon Sep 17 00:00:00 2001
From: Camille Gillot <gillot.camille@gmail.com>
Date: Sat, 16 Aug 2025 17:39:51 +0000
Subject: [PATCH] Reuse cached layout from PostAnalysis when possible.

---
 compiler/rustc_ty_utils/src/layout.rs          | 18 ++++++++++++++++++
 .../recursion/recursion_limit/zero-overflow.rs |  2 +-
 .../recursion_limit/zero-overflow.stderr       |  4 ++--
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 9cc15a374ff7..04fc732aa9d9 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -66,6 +66,24 @@ fn layout_of<'tcx>(
         return tcx.layout_of(typing_env.as_query_input(ty));
     }
 
+    match typing_env.typing_mode() {
+        ty::TypingMode::Codegen => {
+            let with_postanalysis =
+                ty::TypingEnv::new(typing_env.param_env, ty::TypingMode::PostAnalysis);
+            let res = tcx.layout_of(with_postanalysis.as_query_input(ty));
+            match res {
+                Err(LayoutError::TooGeneric(_)) => {}
+                _ => return res,
+            };
+        }
+        ty::TypingMode::Coherence
+        | ty::TypingMode::Analysis { .. }
+        | ty::TypingMode::Borrowck { .. }
+        | ty::TypingMode::PostBorrowckAnalysis { .. }
+        | ty::TypingMode::ErasedNotCoherence(_)
+        | ty::TypingMode::PostAnalysis => {}
+    }
+
     let cx = LayoutCx::new(tcx, typing_env);
 
     let layout = layout_of_uncached(&cx, ty)?;
diff --git a/tests/ui/recursion/recursion_limit/zero-overflow.rs b/tests/ui/recursion/recursion_limit/zero-overflow.rs
index 3887972a5162..718b8550c26c 100644
--- a/tests/ui/recursion/recursion_limit/zero-overflow.rs
+++ b/tests/ui/recursion/recursion_limit/zero-overflow.rs
@@ -1,4 +1,4 @@
-//~ ERROR overflow evaluating the requirement `&mut Self: DispatchFromDyn<&mut RustaceansAreAwesome>
+//~ ERROR queries overflow the depth limit!
 //~| HELP consider increasing the recursion limit
 //@ build-fail
 
diff --git a/tests/ui/recursion/recursion_limit/zero-overflow.stderr b/tests/ui/recursion/recursion_limit/zero-overflow.stderr
index fc03cc5b604b..ca100c7c81a0 100644
--- a/tests/ui/recursion/recursion_limit/zero-overflow.stderr
+++ b/tests/ui/recursion/recursion_limit/zero-overflow.stderr
@@ -1,7 +1,7 @@
-error[E0275]: overflow evaluating the requirement `&mut Self: DispatchFromDyn<&mut RustaceansAreAwesome>`
+error: queries overflow the depth limit!
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "2"]` attribute to your crate (`zero_overflow`)
+   = note: query depth increased by 2 when computing layout of `isize`
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0275`.