incremental: assertion failure when changing the kind of a container

[jacobly0]

#target=x86_64-linux-selfhosted
#update=initial version
#file=main.zig
const T = packed struct {};
pub fn main() void {
    @compileLog(T);
}
#expect_error=main.zig:3:5: error: found compile log statement
#expect_compile_log=@as(type, main.T)
#update=change packed struct to packed union
#file=main.zig
const T = packed union {};
pub fn main() void {
    @compileLog(T);
}
#expect_error=main.zig:3:5: error: found compile log statement
#expect_compile_log=@as(type, main.T)

Asserts with compiler safety, reports success even in the presence of other compiler errors without compiler safety.