https://issues.dlang.org/show_bug.cgi?id=20254

          Issue ID: 20254
           Summary: object.require doesn't work with Variant
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: druntime
          Assignee: nobody@puremagic.com
          Reporter: johnch_atms@hotmail.com

The following code produces as error:

  Variant[string] aa;
  auto value = aa.require("key", Variant("value"));

Output:

  `(*p).opAssign(value())` is not an lvalue and cannot be modified

Removing 'ref' from the function's definition allows it to compile but I'm assuming there's a reason for the ref return.

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