Motivation

For diagnostics emitted in attribute argument syntax nodes that are typeof expressions, the error lies on the types themselves, not the fact that a typeof expression was used. Therefore, semantically it would make more sense to only highlight the type that was used instead of the whole expression.

Another benefit is that it reduces clutter by having smaller chunks of code being highlighted with red squiggles.

Drawbacks

Smaller type names will be harder to distinguish an error on. The main problem would be those with too short names, of up to about 3 letters which seem to be common enough. In a dense document, along with the syntax that generic type arguments come with, users could have a harder time distinguishing where the error is at without resorting to having the IDE navigate them.

Example

Current:

[Attribute(__typeof(int*)__, __typeof(void)__)]

Proposed:

[Attribute(typeof(__int*__), typeof(__void__)]