Rollup merge of #69810 - thekuom:test/67523-dynamic-semantics-bindings-after-at,...

[rust.git] / src / librustc_mir / interpret / place.rs

diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index 8888e3fd4632a2a3e1549dea0f646c29e537257f..fff9c740f7e493ab944b1e607380b0dae6d933d5 100644 (file)
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -410,6 +410,14 @@ pub fn mplace_field(
                 stride * field
             }
             layout::FieldPlacement::Union(count) => {
+                // This is a narrow bug-fix for rust-lang/rust#69191: if we are
+                // trying to access absent field of uninhabited variant, then
+                // signal UB (but don't ICE the compiler).
+                // FIXME temporary hack to work around incoherence between
+                // layout computation and MIR building
+                if field >= count as u64 && base.layout.abi == layout::Abi::Uninhabited {
+                    throw_ub!(Unreachable);
+                }
                 assert!(
                     field < count as u64,
                     "Tried to access field {} of union {:#?} with {} fields",
@@ -432,12 +440,11 @@ pub fn mplace_field(
             // happens at run-time so that's okay.
             let align = match self.size_and_align_of(base.meta, field_layout)? {
                 Some((_, align)) => align,
-                None if offset == Size::ZERO =>
-                // An extern type at offset 0, we fall back to its static alignment.
-                // FIXME: Once we have made decisions for how to handle size and alignment
-                // of `extern type`, this should be adapted.  It is just a temporary hack
-                // to get some code to work that probably ought to work.
-                {
+                None if offset == Size::ZERO => {
+                    // An extern type at offset 0, we fall back to its static alignment.
+                    // FIXME: Once we have made decisions for how to handle size and alignment
+                    // of `extern type`, this should be adapted.  It is just a temporary hack
+                    // to get some code to work that probably ought to work.
                     field_layout.align.abi
                 }
                 None => bug!("Cannot compute offset for extern type field at non-0 offset"),
@@ -648,7 +655,7 @@ pub fn eval_place(
             }
             local => PlaceTy {
                 // This works even for dead/uninitialized locals; we check further when writing
-                place: Place::Local { frame: self.cur_frame(), local: local },
+                place: Place::Local { frame: self.cur_frame(), local },
                 layout: self.layout_of_local(self.frame(), local, None)?,
             },
         };