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varError

varError = 10

Example​

function HasErrorCode(const Value: Variant): Boolean;
begin
  Result := (VarType(Value) and varTypeMask) = varError;
end;

Usage​

varError identifies a Variant that stores an HRESULT or SCODE value, including Automation's missing optional-parameter sentinel.

Additional Technical Info​

varError is the base TVarType code $000A for a stored 32-bit HRESULT/SCODE. The payload is data describing an operating-system or Automation status; merely holding it does not raise an exception.

Native Delphi uses a varError containing DISP_E_PARAMNOTFOUND ($80020004) for an omitted optional Automation argument. That is different from varEmpty, varNull, a returned failure HRESULT and a Delphi exception. The same tag can also contain other status codes.

Velox exposes the tag but not a safe general-purpose constructor for arbitrary HRESULT values. VarAsType is not a substitute for an API-specific error constructor, and numeric equality alone does not establish how a provider intends the code to be handled.

Handling guidance

  • Inspect the tag before interpreting the payload; normal numeric/string conversion can raise or lose HRESULT semantics.
  • Apply the owning API's contract and translate a known code into a governed Velox error/result only at the boundary.
  • Do not use this type to suppress exceptions or to signal ordinary business validation failures unless the receiving Automation API explicitly requires it.
  • By-reference forms inherit external lifetime and mutation risk.

VarType reads the tag without raising the stored error. Later conversion or dispatch may translate the HRESULT into a Variant/Automation exception.

The example is source-reviewed only; no HRESULT was constructed or handled.

External references

Created 2026-07-15