unsafe keyword should be marked as redundant if the using unsafe directive doesn't require it

[jhinder]

Summary

If a "using unsafe" directive could also be a regular using directive, a new analyzer/fixer could identify and remove such redundant keywords.

Background and Motivation

It's legal, albeit pointless, to use a "using unsafe" or "using static unsafe" directive with types that would also be legal without the unsafe keyword. Examples:

using unsafe T = int;
using static unsafe System.Console;

Proposed Feature

Either a compiler diagnostic or an IDExxxx diagnostic (whichever is better suited for this scenario) that reports that the unsafe keyword is redundant. This could be complemented by a new code fixer that offers to remove that keyword.

Alternative Designs

n/a

[Youssef1313]

Looks like it falls into #48031 ?

[CyrusNajmabadi]

Agreed. Closing out as this is already tracked.