SOURCE_FILE@0..26
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      IDENT@3..4 "f"
    PARAM_LIST@4..22
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      SELF_PARAM@5..21
        ATTR@5..16
          POUND@5..6 "#"
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          PATH@7..15
            PATH_SEGMENT@7..15
              NAME_REF@7..15
                IDENT@7..15 "must_use"
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        NAME@17..21
          SELF_KW@17..21 "self"
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      L_CURLY@23..24 "{"
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