Fix ICE when ABI computation fails for unreachable/no-codegen instances

Replace delayed_bug with direct error emission in check_instance_abi,
since codegen may never process the instance (dead code or -Zno-codegen).

Author: rynewang

compiler/rustc_monomorphize/src/mono_checks/abi_check.rs

@@ -5,6 +5,7 @@ use rustc_hir::{CRATE_HIR_ID, HirId};
 use rustc_middle::mir::{self, Location, traversal};
 use rustc_middle::ty::{self, Instance, InstanceKind, Ty, TyCtxt};
 use rustc_span::def_id::DefId;
+use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 use rustc_target::callconv::{FnAbi, PassMode};
 
@@ -161,11 +162,10 @@ fn check_instance_abi<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) {
     {
         Ok(abi) => abi,
         Err(err) => {
-            // Emit the error directly rather than using `delayed_bug`, because codegen
-            // may never process this instance (e.g., unreachable code or `-Zno-codegen`),
-            // which would leave the error unreported and trigger an ICE.
-            let ty::layout::FnAbiError::Layout(layout_err) = err;
-            tcx.dcx().emit_err((*layout_err).into_diagnostic());
+            // Emit directly: codegen may never see this instance (dead code, `-Zno-codegen`).
+            let ty::layout::FnAbiError::Layout(layout_err) = *err;
+            let span = tcx.def_span(instance.def_id());
+            tcx.dcx().emit_err(Spanned { node: layout_err.into_diagnostic(), span });
             return;
         }
     };

tests/crashes/138008.rs

@@ -13,7 +13,7 @@ struct Wrapper<T: Trait> {
     _x: <T as Trait>::Assoc,
 }
 
-fn abi<T: Trait>(_: Option<Wrapper<T>>) {}
+fn abi<T: Trait>(_: Option<Wrapper<T>>) {} //~ ERROR a cycle occurred during layout computation
 
 fn indirect<T: Trait>() {
     abi::<T>(None);

tests/ui/layout/post-mono-layout-cycle.rs

@@ -5,12 +5,18 @@ error[E0391]: cycle detected when computing layout of `Wrapper<()>`
    = note: cycle used when computing layout of `core::option::Option<Wrapper<()>>`
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
+error: a cycle occurred during layout computation
+  --> $DIR/post-mono-layout-cycle.rs:16:1
+   |
+LL | fn abi<T: Trait>(_: Option<Wrapper<T>>) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 note: the above error was encountered while instantiating `fn abi::<()>`
   --> $DIR/post-mono-layout-cycle.rs:19:5
    |
 LL |     abi::<T>(None);
    |     ^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0391`.

tests/ui/layout/post-mono-layout-cycle.stderr

@@ -1,3 +1,5 @@
+error: values of the type `[&usize; usize::MAX]` are too big for the target architecture
+
 error[E0080]: values of the type `[&usize; usize::MAX]` are too big for the target architecture
   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
    |
@@ -14,6 +16,6 @@ note: the above error was encountered while instantiating `fn Box::<[&usize; usi
 LL |     let a: Box<_> = Box::new([&n; SIZE]);
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/limits/issue-17913.32bit.stderr

@@ -1,3 +1,6 @@
+error: values of the type `[&usize; usize::MAX]` are too big for the target architecture
+  --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
+
 error[E0080]: values of the type `[&usize; usize::MAX]` are too big for the target architecture
   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
    |
@@ -14,6 +17,6 @@ note: the above error was encountered while instantiating `fn Box::<[&usize; usi
 LL |     let a: Box<_> = Box::new([&n; SIZE]);
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/limits/issue-17913.64bit.stderr

@@ -19,3 +19,4 @@ fn main() {
 
 //~? ERROR are too big for the target architecture
 //~? ERROR are too big for the target architecture
+//~? ERROR are too big for the target architecture

tests/ui/limits/issue-17913.rs

@@ -0,0 +1,13 @@
+// Regression test for #149156.
+//@ build-fail
+//@ compile-flags: -Zno-codegen
+//@ only-x86_64
+
+#![crate_type = "lib"]
+#![allow(private_interfaces)]
+
+struct Struct([u8; 0xffff_ffff_ffff_ffff]);
+
+pub fn function(value: Struct) -> u8 { //~ ERROR are too big for the target architecture
+    value.0[0]
+}

tests/ui/simd/monomorphize-oversized-no-codegen.rs

@@ -0,0 +1,8 @@
+error: values of the type `[u8; usize::MAX]` are too big for the target architecture
+  --> $DIR/monomorphize-oversized-no-codegen.rs:11:1
+   |
+LL | pub fn function(value: Struct) -> u8 {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/simd/monomorphize-oversized-no-codegen.stderr

@@ -1,14 +1,13 @@
-// Regression test for #152204: ICE when oversized SIMD type appears in unreachable code
-//
-// Previously, `check_instance_abi` used `delayed_bug` for ABI computation
-// failures, assuming codegen would report the error. But unreachable code
-// is monomorphized without reaching codegen, leaving the error unreported.
+// Regression test for #152204.
+//@ build-fail
+//@ only-x86_64
 
 #![feature(portable_simd)]
 
 fn main() {
     if false {
         let _ = core::simd::Simd::<u8, 256>::splat(0);
-        //~^ ERROR the SIMD type `Simd<u8, 256>` has more elements than the limit 64
     }
 }
+
+//~? ERROR the SIMD type `Simd<u8, 256>` has more elements than the limit 64