const B = struct {
    pub fn func() void {
        @compileLog(@typeInfo(C).Struct.decls); // .{ .{ .name = "func" } }
        @compileLog(@hasDecl(C, "func")); // false
        _ = C.func; // ERROR: no member named func
    }
};

const C = struct {
    pub usingnamespace B;
};

pub fn main() !void {
    C.func();
}

export fn foo() void {
    foo();
}

const std = @import("std");

pub const Example = struct {
    usingnamespace struct {}; // works without this line

    pub fn foo() void {
        _ = Example.foo;  // error: struct 'main.Example' has no member named 'foo'
    }
};

pub fn main() !void {
    Example.foo();
}