Fix ICE in case of TypeId provenance being overridden with a non-type-id provenance

Author: oli-obk

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -6,7 +6,6 @@ use std::assert_matches::assert_matches;
 
 use rustc_abi::{FieldIdx, Size};
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
-use rustc_middle::mir::interpret::GlobalAlloc;
 use rustc_middle::mir::{self, BinOp, ConstValue, NonDivergingIntrinsic};
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{Ty, TyCtxt};
@@ -105,15 +104,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     .next(self)?
                     .expect("we know the layout of TypeId has at least 2 array elements");
                 let a = self.deref_pointer(&a)?;
-                let (a, offset_a, _) = self.ptr_get_alloc_id(a.ptr(), 0)?;
-                let GlobalAlloc::Type { ty: a } = self.tcx.global_alloc(a) else { bug!() };
+                let (a, offset_a) = self.get_ptr_type_id(a.ptr())?;
 
                 let (_idx, b) = b_fields
                     .next(self)?
                     .expect("we know the layout of TypeId has at least 2 array elements");
                 let b = self.deref_pointer(&b)?;
-                let (b, offset_b, _) = self.ptr_get_alloc_id(b.ptr(), 0)?;
-                let GlobalAlloc::Type { ty: b } = self.tcx.global_alloc(b) else { bug!() };
+                let (b, offset_b) = self.get_ptr_type_id(b.ptr())?;
 
                 let provenance_matches = a == b;
 

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -15,9 +15,9 @@ use std::{fmt, ptr};
 use rustc_abi::{Align, HasDataLayout, Size};
 use rustc_ast::Mutability;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
-use rustc_middle::bug;
 use rustc_middle::mir::display_allocation;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
+use rustc_middle::{bug, throw_ub_format};
 use tracing::{debug, instrument, trace};
 
 use super::{
@@ -946,6 +946,19 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         }
     }
 
+    /// Assume that the pointer points to the first chunk of a `TypeId` and return the type that its
+    /// provenance refers to, as well as the segment of the hash that this pointer covers.
+    pub fn get_ptr_type_id(
+        &self,
+        ptr: Pointer<Option<M::Provenance>>,
+    ) -> InterpResult<'tcx, (Ty<'tcx>, Size)> {
+        let (alloc_id, offset, _meta) = self.ptr_get_alloc_id(ptr, 0)?;
+        let GlobalAlloc::Type { ty } = self.tcx.global_alloc(alloc_id) else {
+            throw_ub_format!("type_id_eq: `TypeId` provenance is not a type id")
+        };
+        interp_ok((ty, offset))
+    }
+
     pub fn get_ptr_fn(
         &self,
         ptr: Pointer<Option<M::Provenance>>,

tests/ui/consts/const_transmute_type_id4.rs

@@ -0,0 +1,16 @@
+#![feature(const_type_id, const_trait_impl)]
+
+use std::any::TypeId;
+
+const _: () = {
+    let a = TypeId::of::<()>();
+    let mut b = TypeId::of::<()>();
+    unsafe {
+        let ptr = &mut b as *mut TypeId as *mut *const ();
+        std::ptr::write(ptr.offset(0), main as fn() as *const ());
+    }
+    assert!(a == b);
+    //~^ ERROR: type_id_eq: `TypeId` provenance is not a type id
+};
+
+fn main() {}

tests/ui/consts/const_transmute_type_id4.stderr

@@ -0,0 +1,14 @@
+error[E0080]: type_id_eq: `TypeId` provenance is not a type id
+  --> $DIR/const_transmute_type_id4.rs:12:13
+   |
+LL |     assert!(a == b);
+   |             ^^^^^^ evaluation of `_` failed inside this call
+   |
+note: inside `<TypeId as PartialEq>::eq`
+  --> $SRC_DIR/core/src/any.rs:LL:COL
+note: inside `<TypeId as PartialEq>::eq::ct`
+  --> $SRC_DIR/core/src/any.rs:LL:COL
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.