KOS_OP_MATCH_KEY

• Style: EXTRA (LABEL, CONST): label, key.

• Stack: [..., o] -> [..., o, v]; jump to a0 with nothing pushed on a miss.

• Semantics: Push the value under the constant key a1 in the mapping o read through Datum. An absent key is a miss. The mapping is probed without inserting: a dict is read directly and any other mapping through its get, so a defaultdict neither inserts nor invents the key.

• Compiler form: Emitted by the match compiler for a literal key of a mapping pattern.