To reproduce:
1. Load the texarray-test project.
2. Load the main.unity scene.
3. Open Assets/TextureArraySplatLayered.shader in a text editor.
4. Change a line of code and save (to force a shader recompile).
5. Switch back to Unity and wait quite a long time for a the shader to compile (60 seconds?)

Actual result: See that the compile error is "Shader error in 'MegaSplat/MegaSplat_MacroLayered': Too many texture interpolators would be used for ForwardBase pass (11 out of max 10) at line 41"

7. Now uncomment this line, to fix it //djh o.Normal = half3(0, 1, 0);
8. Switch back to Unity and wait
9. See that there are no compile errors.

Expected: An error message which points the user in the right direction to solve the problem ( e.g. "You forgot to set the Normal shader output" )

Reproducible: 5.6.0a3, 5.5.0f1, 5.4.2p3, 5.3.7f1