Type Alias ReportType<T>

ReportType: T

Declares the parameter's type as ADVISORY: the engine delivers it when it can, and hands the body whatever actually arrived when it cannot, instead of answering #VALUE! on the body's behalf.

Type Parameters

Remarks

Excel has no marshalling contract. A function there is called with the operands as they are and calls library helpers for whatever it needs — LARGE asks for a range's values and gets every area of a union, ROWS never dereferences at all and answers #REF! when it sees two areas, SUMPRODUCT demands one rectangle and fails on the same argument. Three answers, no rule: the body's own access pattern is the whole of it.

A declared surface cannot express that, and modelling it would mean a marker per behavior. This is the boundary instead — ONE marker saying "the type is what the caller is told, not a guarantee to the body". The declared T still reaches the function help, the wizard and the linter, because that IS what the slot means to a user; it just stops being a gate.

argument	plain `IRange`	`ReportType<IRange>`
`A1:A5`	the range	the range
`(A1:A5,B1:B2)` — a union	`#VALUE!`, the call never runs	the areas, as `IRange[]`
a value, an error	`#VALUE!` / propagates	the value, the error

At the type level it is T — like AcceptError, and for the same reason: the marker is a RULE, not a type. A body that declares it and then assumes T will crash on the argument the marker exists to deliver, so narrow first. IFunctionArguments.getKindAt is total over what can arrive and IFunctionArguments.getAreaCountAt answers the union question the kind cannot — a plain reference is one area, a union is more.

Its use is meant to stay countable: a slot earns it with a rule Excel actually shows, never with a guess.

Example

export function ROWS(array: ReportType<IRange>): Scalar {
  if (FormulaContext.getArgs().getAreaCountAt(0) > 1) return FormulaError.BuiltIn.Ref!;
  return array.getRowCount();
}

Type Alias ReportType<T>

Type Parameters

Remarks

Example

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