2 files changed, 4 insertions, 1 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index 7aa76fe1dae..d56323448ce 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -642,7 +642,7 @@ where
         // avoid force_allocation.
         let src = match self.read_immediate_raw(src)? {
             Ok(src_val) => {
-                assert!(!src.layout.is_unsized(), "cannot have unsized immediates");
+                assert!(!src.layout.is_unsized(), "cannot copy unsized immediates");
                 assert!(
                     !dest.layout.is_unsized(),
                     "the src is sized, so the dest must also be sized"
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
index 742339f2b0a..16ce5bc7175 100644
--- a/compiler/rustc_const_eval/src/interpret/projection.rs
+++ b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -100,6 +100,8 @@ where
         // This makes several assumptions about what layouts we will encounter; we match what
         // codegen does as good as we can (see `extract_field` in `rustc_codegen_ssa/src/mir/operand.rs`).
         let field_val: Immediate<_> = match (*base, base.layout.abi) {
+            // if the entire value is uninit, then so is the field (can happen in ConstProp)
+            (Immediate::Uninit, _) => Immediate::Uninit,
             // the field contains no information, can be left uninit
             _ if field_layout.is_zst() => Immediate::Uninit,
             // the field covers the entire type
@@ -124,6 +126,7 @@ where
                     b_val
                 })
             }
+            // everything else is a bug
             _ => span_bug!(
                 self.cur_span(),
                 "invalid field access on immediate {}, layout {:#?}",