Fix mir CString lowering not respecting the extra 0 byte for length calc

Author: Veykril

crates/hir-ty/src/mir/lower.rs

@@ -1121,11 +1121,13 @@ impl<'ctx> MirLowerCtx<'ctx> {
             }
             hir_def::hir::Literal::CString(b) => {
                 let b = b.as_bytes();
+                let bytes = b.iter().copied().chain(iter::once(0)).collect::<Vec<_>>();
+
                 let mut data = Vec::with_capacity(mem::size_of::<usize>() * 2);
                 data.extend(0usize.to_le_bytes());
-                data.extend(b.len().to_le_bytes());
+                data.extend(bytes.len().to_le_bytes());
                 let mut mm = MemoryMap::default();
-                mm.insert(0, b.iter().copied().chain(iter::once(0)).collect::<Vec<_>>());
+                mm.insert(0, bytes);
                 return Ok(Operand::from_concrete_const(data, mm, ty));
             }
             hir_def::hir::Literal::ByteString(b) => {