Fix MSVC warnings on enum class switches
diff --git a/src/backend/d3d12/InputStateD3D12.cpp b/src/backend/d3d12/InputStateD3D12.cpp
index 5a9e559..73b3acb 100644
--- a/src/backend/d3d12/InputStateD3D12.cpp
+++ b/src/backend/d3d12/InputStateD3D12.cpp
@@ -27,6 +27,8 @@
                 return DXGI_FORMAT_R32G32_FLOAT;
             case nxt::VertexFormat::FloatR32:
                 return DXGI_FORMAT_R32_FLOAT;
+            default:
+                UNREACHABLE();
         }
     }
 
@@ -36,6 +38,8 @@
                 return D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA;
             case nxt::InputStepMode::Instance:
                 return D3D12_INPUT_CLASSIFICATION_PER_INSTANCE_DATA;
+            default:
+                UNREACHABLE();
         }
     }