Do not assert in op_to_const.

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -106,10 +106,16 @@ pub(crate) fn mk_eval_cx<'mir, 'tcx>(
 }
 
 /// This function converts an interpreter value into a MIR constant.
+///
+/// The `for_diagnostics` flag turns the usual rules for returning `ConstValue::Scalar` into a
+/// best-effort attempt. This is not okay for use in const-eval sine it breaks invariants rustc
+/// relies on, but it is okay for diagnostics which will just give up gracefully when they
+/// encounter an `Indirect` they cannot handle.
 #[instrument(skip(ecx), level = "debug")]
 pub(super) fn op_to_const<'tcx>(
     ecx: &CompileTimeEvalContext<'_, 'tcx>,
     op: &OpTy<'tcx>,
+    for_diagnostics: bool,
 ) -> ConstValue<'tcx> {
     // Handle ZST consistently and early.
     if op.layout.is_zst() {
@@ -133,7 +139,13 @@ pub(super) fn op_to_const<'tcx>(
         _ => false,
     };
     let immediate = if force_as_immediate {
-        Right(ecx.read_immediate(op).expect("normalization works on validated constants"))
+        match ecx.read_immediate(op) {
+            Ok(imm) => Right(imm),
+            Err(err) if !for_diagnostics => {
+                panic!("normalization works on validated constants: {err:?}")
+            }
+            _ => op.as_mplace_or_imm(),
+        }
     } else {
         op.as_mplace_or_imm()
     };
@@ -205,7 +217,7 @@ pub(crate) fn turn_into_const_value<'tcx>(
     );
 
     // Turn this into a proper constant.
-    op_to_const(&ecx, &mplace.into())
+    op_to_const(&ecx, &mplace.into(), /* for diagnostics */ false)
 }
 
 #[instrument(skip(tcx), level = "debug")]

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -72,7 +72,7 @@ pub(crate) fn eval_to_valtree<'tcx>(
 }
 
 #[instrument(skip(tcx), level = "debug")]
-pub(crate) fn try_destructure_mir_constant_for_diagnostics<'tcx>(
+pub(crate) fn try_destructure_mir_constant_for_user_output<'tcx>(
     tcx: TyCtxtAt<'tcx>,
     val: mir::ConstValue<'tcx>,
     ty: Ty<'tcx>,
@@ -99,7 +99,7 @@ pub(crate) fn try_destructure_mir_constant_for_diagnostics<'tcx>(
     let fields_iter = (0..field_count)
         .map(|i| {
             let field_op = ecx.project_field(&down, i).ok()?;
-            let val = op_to_const(&ecx, &field_op);
+            let val = op_to_const(&ecx, &field_op, /* for diagnostics */ true);
             Some((val, field_op.layout.ty))
         })
         .collect::<Option<Vec<_>>>()?;

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -232,7 +232,7 @@ pub fn valtree_to_const_value<'tcx>(
             let mut ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, CanAccessStatics::No);
             let imm = valtree_to_ref(&mut ecx, valtree, *inner_ty);
             let imm = ImmTy::from_immediate(imm, tcx.layout_of(param_env_ty).unwrap());
-            op_to_const(&ecx, &imm.into())
+            op_to_const(&ecx, &imm.into(), /* for diagnostics */ false)
         }
         ty::Tuple(_) | ty::Array(_, _) | ty::Adt(..) => {
             let layout = tcx.layout_of(param_env_ty).unwrap();
@@ -265,7 +265,7 @@ pub fn valtree_to_const_value<'tcx>(
             dump_place(&ecx, &place);
             intern_const_alloc_recursive(&mut ecx, InternKind::Constant, &place).unwrap();
 
-            op_to_const(&ecx, &place.into())
+            op_to_const(&ecx, &place.into(), /* for diagnostics */ false)
         }
         ty::Never
         | ty::Error(_)

compiler/rustc_const_eval/src/lib.rs

@@ -54,8 +54,8 @@ pub fn provide(providers: &mut Providers) {
         let (param_env, raw) = param_env_and_value.into_parts();
         const_eval::eval_to_valtree(tcx, param_env, raw)
     };
-    providers.hooks.try_destructure_mir_constant_for_diagnostics =
-        const_eval::try_destructure_mir_constant_for_diagnostics;
+    providers.hooks.try_destructure_mir_constant_for_user_output =
+        const_eval::try_destructure_mir_constant_for_user_output;
     providers.valtree_to_const_val = |tcx, (ty, valtree)| {
         const_eval::valtree_to_const_value(tcx, ty::ParamEnv::empty().and(ty), valtree)
     };

compiler/rustc_middle/src/hooks/mod.rs

@@ -66,7 +66,7 @@ macro_rules! declare_hooks {
 declare_hooks! {
     /// Tries to destructure an `mir::Const` ADT or array into its variant index
     /// and its field values. This should only be used for pretty printing.
-    hook try_destructure_mir_constant_for_diagnostics(val: mir::ConstValue<'tcx>, ty: Ty<'tcx>) -> Option<mir::DestructuredConstant<'tcx>>;
+    hook try_destructure_mir_constant_for_user_output(val: mir::ConstValue<'tcx>, ty: Ty<'tcx>) -> Option<mir::DestructuredConstant<'tcx>>;
 
     /// Getting a &core::panic::Location referring to a span.
     hook const_caller_location(file: rustc_span::Symbol, line: u32, col: u32) -> mir::ConstValue<'tcx>;

compiler/rustc_middle/src/mir/pretty.rs

@@ -1713,7 +1713,7 @@ fn pretty_print_const_value_tcx<'tcx>(
         (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_non_region_param() => {
             let ct = tcx.lift(ct).unwrap();
             let ty = tcx.lift(ty).unwrap();
-            if let Some(contents) = tcx.try_destructure_mir_constant_for_diagnostics(ct, ty) {
+            if let Some(contents) = tcx.try_destructure_mir_constant_for_user_output(ct, ty) {
                 let fields: Vec<(ConstValue<'_>, Ty<'_>)> = contents.fields.to_vec();
                 match *ty.kind() {
                     ty::Array(..) => {

src/tools/clippy/clippy_utils/src/consts.rs

@@ -710,7 +710,7 @@ fn field_of_struct<'tcx>(
     field: &Ident,
 ) -> Option<mir::Const<'tcx>> {
     if let mir::Const::Val(result, ty) = result
-        && let Some(dc) = lcx.tcx.try_destructure_mir_constant_for_diagnostics(result, ty)
+        && let Some(dc) = lcx.tcx.try_destructure_mir_constant_for_user_output(result, ty)
         && let Some(dc_variant) = dc.variant
         && let Some(variant) = adt_def.variants().get(dc_variant)
         && let Some(field_idx) = variant.fields.iter().position(|el| el.name == field.name)

tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff

@@ -0,0 +1,123 @@
+- // MIR for `main` before GVN
++ // MIR for `main` after GVN
+
+  fn main() -> () {
+      let mut _0: ();
+      let _1: std::alloc::Layout;
+      let mut _2: std::option::Option<std::alloc::Layout>;
+      let mut _3: *mut u8;
+      let mut _4: *mut [u8];
+      let mut _5: std::ptr::NonNull<[u8]>;
+      let mut _6: std::result::Result<std::ptr::NonNull<[u8]>, std::alloc::AllocError>;
+      let mut _7: &std::alloc::Global;
+      let mut _8: std::alloc::Layout;
+      scope 1 {
+          debug layout => _1;
+          let mut _9: &std::alloc::Global;
+          scope 2 {
+              debug ptr => _3;
+          }
+          scope 5 (inlined <std::alloc::Global as Allocator>::allocate) {
+              debug self => _9;
+              debug layout => _1;
+          }
+          scope 6 (inlined #[track_caller] Result::<NonNull<[u8]>, std::alloc::AllocError>::unwrap) {
+              debug self => _6;
+              let mut _12: isize;
+              let _13: std::alloc::AllocError;
+              let mut _14: !;
+              let _15: &str;
+              let mut _16: &dyn std::fmt::Debug;
+              let mut _17: &std::alloc::AllocError;
+              scope 7 {
+                  debug t => _5;
+              }
+              scope 8 {
+                  debug e => const std::alloc::AllocError;
+              }
+          }
+          scope 9 (inlined NonNull::<[u8]>::as_ptr) {
+              debug self => _5;
+              let mut _18: *const [u8];
+          }
+      }
+      scope 3 (inlined #[track_caller] Option::<Layout>::unwrap) {
+          debug self => _2;
+          let mut _10: isize;
+          let mut _11: !;
+          scope 4 {
+              debug val => _1;
+          }
+      }
+
+      bb0: {
+          StorageLive(_2);
+-         _2 = Option::<Layout>::None;
++         _2 = const Option::<Layout>::None;
+          StorageLive(_10);
+          _10 = const 0_isize;
+          switchInt(const 0_isize) -> [0: bb1, 1: bb3, otherwise: bb2];
+      }
+
+      bb1: {
+          _11 = core::panicking::panic(const "called `Option::unwrap()` on a `None` value") -> unwind unreachable;
+      }
+
+      bb2: {
+          unreachable;
+      }
+
+      bb3: {
+-         _1 = move ((_2 as Some).0: std::alloc::Layout);
++         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): ptr::alignment::AlignmentEnum32) }};
+          StorageDead(_10);
+          StorageDead(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          _9 = const _;
+-         _6 = std::alloc::Global::alloc_impl(_9, _1, const false) -> [return: bb4, unwind unreachable];
++         _6 = std::alloc::Global::alloc_impl(const {ALLOC1: &std::alloc::Global}, const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): ptr::alignment::AlignmentEnum32) }}, const false) -> [return: bb4, unwind unreachable];
+      }
+
+      bb4: {
+          StorageLive(_12);
+          StorageLive(_15);
+          _12 = discriminant(_6);
+          switchInt(move _12) -> [0: bb6, 1: bb5, otherwise: bb2];
+      }
+
+      bb5: {
+          _15 = const "called `Result::unwrap()` on an `Err` value";
+          StorageLive(_16);
+          StorageLive(_17);
+          _17 = &_13;
+          _16 = move _17 as &dyn std::fmt::Debug (PointerCoercion(Unsize));
+          StorageDead(_17);
+          _14 = result::unwrap_failed(move _15, move _16) -> unwind unreachable;
+      }
+
+      bb6: {
+          _5 = move ((_6 as Ok).0: std::ptr::NonNull<[u8]>);
+          StorageDead(_15);
+          StorageDead(_12);
+          StorageDead(_6);
+          StorageLive(_18);
+          _18 = (_5.0: *const [u8]);
+          _4 = move _18 as *mut [u8] (PtrToPtr);
+          StorageDead(_18);
+          StorageDead(_5);
+          _3 = move _4 as *mut u8 (PtrToPtr);
+          StorageDead(_4);
+          StorageDead(_3);
+          return;
+      }
+  }
++ 
++ ALLOC0 (size: 8, align: 4) {
++     00 00 00 00 __ __ __ __                         │ ....░░░░
++ }
++ 
++ ALLOC1 (size: 0, align: 1) {}
+

tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-unwind.diff

@@ -0,0 +1,92 @@
+- // MIR for `main` before GVN
++ // MIR for `main` after GVN
+
+  fn main() -> () {
+      let mut _0: ();
+      let _1: std::alloc::Layout;
+      let mut _2: std::option::Option<std::alloc::Layout>;
+      let mut _3: *mut u8;
+      let mut _4: *mut [u8];
+      let mut _5: std::ptr::NonNull<[u8]>;
+      let mut _6: std::result::Result<std::ptr::NonNull<[u8]>, std::alloc::AllocError>;
+      let mut _7: &std::alloc::Global;
+      let mut _8: std::alloc::Layout;
+      scope 1 {
+          debug layout => _1;
+          let mut _9: &std::alloc::Global;
+          scope 2 {
+              debug ptr => _3;
+          }
+          scope 5 (inlined <std::alloc::Global as Allocator>::allocate) {
+              debug self => _9;
+              debug layout => _1;
+          }
+          scope 6 (inlined NonNull::<[u8]>::as_ptr) {
+              debug self => _5;
+              let mut _12: *const [u8];
+          }
+      }
+      scope 3 (inlined #[track_caller] Option::<Layout>::unwrap) {
+          debug self => _2;
+          let mut _10: isize;
+          let mut _11: !;
+          scope 4 {
+              debug val => _1;
+          }
+      }
+
+      bb0: {
+          StorageLive(_2);
+-         _2 = Option::<Layout>::None;
++         _2 = const Option::<Layout>::None;
+          StorageLive(_10);
+          _10 = const 0_isize;
+          switchInt(const 0_isize) -> [0: bb2, 1: bb4, otherwise: bb3];
+      }
+
+      bb1: {
+          StorageDead(_6);
+          StorageLive(_12);
+          _12 = (_5.0: *const [u8]);
+          _4 = move _12 as *mut [u8] (PtrToPtr);
+          StorageDead(_12);
+          StorageDead(_5);
+          _3 = move _4 as *mut u8 (PtrToPtr);
+          StorageDead(_4);
+          StorageDead(_3);
+          return;
+      }
+
+      bb2: {
+          _11 = core::panicking::panic(const "called `Option::unwrap()` on a `None` value") -> unwind continue;
+      }
+
+      bb3: {
+          unreachable;
+      }
+
+      bb4: {
+-         _1 = move ((_2 as Some).0: std::alloc::Layout);
++         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): ptr::alignment::AlignmentEnum32) }};
+          StorageDead(_10);
+          StorageDead(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          _9 = const _;
+-         _6 = std::alloc::Global::alloc_impl(_9, _1, const false) -> [return: bb5, unwind continue];
++         _6 = std::alloc::Global::alloc_impl(const {ALLOC1: &std::alloc::Global}, const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): ptr::alignment::AlignmentEnum32) }}, const false) -> [return: bb5, unwind continue];
+      }
+
+      bb5: {
+          _5 = Result::<NonNull<[u8]>, std::alloc::AllocError>::unwrap(move _6) -> [return: bb1, unwind continue];
+      }
+  }
++ 
++ ALLOC0 (size: 8, align: 4) {
++     00 00 00 00 __ __ __ __                         │ ....░░░░
++ }
++ 
++ ALLOC1 (size: 0, align: 1) {}
+