Emit warning or error when using PartialType and IncludeInitializer for the same property

[Newex]

Imagine the situation:

// Input properties ...
[PartialType(typeof(int))]
[IncludeInitializer]
public string Hello { get; } = "World";

Will produce uncritically (without safeguards):

// Output property: Invalid csharp
public int Hello { get; } = "World";

We can see that the initializer is a string of "Hello World" which is trying to be assigned to an int property.

Why I think this is a good first issue?

I have marked in the PartialIncrementalSourceGenerator.cs file where a check for PartialType and IncludeInitializer has resulted in a true evaluation. The line is marked with a TODO comment. This might / could be a good place to start...