Auto merge of #71751 - oli-obk:const_ice, r=RalfJung

Move recursion check for zsts back to read site instead of access check site

Reverts https://github.com/rust-lang/rust/pull/71140#discussion_r413709446

Fix #71612
Fix #71709

r? @RalfJung

2 files changed, 8 insertions, 12 deletions

diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index d1881524172..39e428cee1d 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -400,18 +400,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
 
                 // We can still be zero-sized in this branch, in which case we have to
                 // return `None`.
-                if size.bytes() == 0 {
-                    // We may be reading from a static.
-                    // In order to ensure that `static FOO: Type = FOO;` causes a cycle error
-                    // instead of magically pulling *any* ZST value from the ether, we need to
-                    // actually access the referenced allocation. The caller is likely
-                    // to short-circuit on `None`, so we trigger the access here to
-                    // make sure it happens.
-                    self.get_raw(ptr.alloc_id)?;
-                    None
-                } else {
-                    Some(ptr)
-                }
+                if size.bytes() == 0 { None } else { Some(ptr) }
             }
         })
     }
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index e2fb9de486f..cc9fc170f6e 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -240,6 +240,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         {
             Some(ptr) => ptr,
             None => {
+                if let Scalar::Ptr(ptr) = mplace.ptr {
+                    // We may be reading from a static.
+                    // In order to ensure that `static FOO: Type = FOO;` causes a cycle error
+                    // instead of magically pulling *any* ZST value from the ether, we need to
+                    // actually access the referenced allocation.
+                    self.memory.get_raw(ptr.alloc_id)?;
+                }
                 return Ok(Some(ImmTy {
                     // zero-sized type
                     imm: Scalar::zst().into(),