# Objective
Fix#18546 by adding a variant to `MergeMeshError`, for incompatible
primitive topologies.
## Solution
Made `MergeMeshError` into an enum with two variants;
`IncompatibleVertexAttributes` and `IncompatiblePrimitiveTopology`.
Added an if statement in `Mesh::merge` to check if the
`primitive_topology` field of `self` matches `other`.
Also renamed `MergeMeshError` to `MeshMergeError` to align with the two
other `MeshSomethingError`'s.
## Testing
Didn't do any.
