Python projection semantic coverage

These families describe matrix obligations, not a closed Python grammar or a production dispatch enumeration. Monty owns expression admission, inference and execution. The matrix checks the declared witnesses through typed DAG validation and live execution against independent expected results, plus genuine rejection boundaries. Equivalent Python spellings need equivalent values and effects; they do not need identical generated compute source or identical IL nodes.

Rejection labels below identify typed compilation causes, not rendered prose. Checker diagnostics match exact semantic codes; host failures, unknown labels, and unrelated compiler causes do not satisfy a rejection obligation.

[
  {
    "operation": "field",
    "premise": "Current lambda row field; schema resolves its path",
    "transfer": "Preserve declared field value type",
    "law": "BC-03",
    "witnesses": [
      "render_parity_lang_with_mul"
    ],
    "invalid": [
      {
        "body": "return E.query().select(x=lambda self: self.score)",
        "error": "ReservedProjectionParameter"
      }
    ]
  },
  {
    "operation": "literal",
    "premise": "Literal operand with a closed materialized value contract",
    "transfer": "Retain its scalar or collection kind",
    "law": "BC-03",
    "witnesses": [
      "render_parity_lang_with_mul"
    ],
    "invalid": [
      {
        "body": "return E.query().select(x=lambda row: {1: 2})",
        "error": "DictionaryKeyNotString"
      }
    ]
  },
  {
    "operation": "arithmetic",
    "premise": "Typed operands with +, -, *, or /",
    "transfer": "Infer result type from admitted operand/operator combination",
    "law": "BC-03",
    "witnesses": [
      "render_parity_lang_with_mul",
      "render_parity_lang_with_div",
      "render_parity_lang_with_concat"
    ],
    "invalid": [
      {
        "body": "return E.query().select(x=lambda row: row.title - 2)",
        "error": "UnsupportedOperator"
      }
    ]
  },
  {
    "operation": "length",
    "premise": "len of a string, array or record",
    "transfer": "Produce typed length without arbitrary calls",
    "law": "BC-03",
    "witnesses": [
      "render_parity_lang_with_when_len"
    ],
    "invalid": [
      {
        "body": "return E.query().select(x=lambda row: len(7))",
        "error": "InvalidArgumentType"
      }
    ]
  },
  {
    "operation": "conditional",
    "premise": "Boolean condition and typed branches",
    "transfer": "Join complete branch contracts; declare both dependencies; evaluate selected branch",
    "law": "BC-03",
    "witnesses": [
      "render_parity_lang_with_when_len"
    ],
    "invalid": [
      {
        "body": "return E.query().select(x=lambda row: row.title if missing else row.owner)",
        "error": "UnresolvedReference"
      }
    ]
  }
]