Composition, resist film, pattern forming method, and method for producing electronic device

A composition comprising:

• a compound A having a plurality of iodine atoms that are each an iodine atom bonded to a carbon atom;
• and
• a compound B having a plurality of specific functional groups that are each a specific functional group selected from the group consisting of a nitrogen-containing aromatic heterocyclic group, —NH2, an NH2 group protected with a removable protecting group, —NHRN1 an NHRN1 group protected with a removable protecting group, —NRN22, —C≡N, —OH, —ORO, —SH, —SRS, —PRP12, and —P(ORP2)2 and not having an iodine atom bonded to a carbon atom,
• the composition satisfying at least one of requirement 1 or requirement 2:
• Requirement 1:
• The compound A is a polymer having a repeating unit including the iodine atom bonded to a carbon atom,
• Requirement 2:
• The compound B is a polymer having a repeating unit including the specific functional group,
• wherein RN1, RN2, RO, RS, RP1, and RP2 each independently represent a monovalent hydrocarbon group optionally having a substituent, monovalent hydrocarbon groups represented by RN2 may be bonded to each other to form a ring, monovalent hydrocarbon groups represented by RP1 may be bonded to each other to form a ring, and monovalent hydrocarbon groups represented by RP2 may be bonded to each other to form a ring.