public override bool CheckInvocation(TexlBinding binding, TexlNode[] args, DType[] argTypes, IErrorContainer errors, out DType returnType, out Dictionary <TexlNode, DType> nodeToCoercedTypeMap)
{
Contracts.AssertValue(args);
Contracts.AssertValue(argTypes);
Contracts.Assert(args.Length == argTypes.Length);
Contracts.AssertValue(errors);
Contracts.Assert(MinArity <= args.Length && args.Length <= MaxArity);
bool fArgsValid = base.CheckInvocation(args, argTypes, errors, out returnType, out nodeToCoercedTypeMap);
Contracts.Assert(returnType.IsTable);
if (!argTypes[0].IsTable)
{
fArgsValid = false;
errors.EnsureError(DocumentErrorSeverity.Severe, args[0], TexlStrings.ErrNeedTable_Func, Name);
}
else
{
returnType = argTypes[0];
}
// The result type has N fewer columns, as specified by (args[1],args[2],args[3],...)
int count = args.Length;
for (var i = 1; i < count; i++)
{
TexlNode nameArg = args[i];
DType nameArgType = argTypes[i];
// Verify we have a string literal for the column name. Accd to spec, we don't support
// arbitrary expressions that evaluate to string values, because these values contribute to
// type analysis, so they need to be known upfront (before DropColumns executes).
StrLitNode nameNode;
if (nameArgType.Kind != DKind.String || (nameNode = nameArg.AsStrLit()) == null)
{
fArgsValid = false;
errors.EnsureError(DocumentErrorSeverity.Severe, nameArg, TexlStrings.ErrExpectedStringLiteralArg_Name, nameArg.ToString());
continue;
}
// Verify that the name is valid.
if (!DName.IsValidDName(nameNode.Value))
{
fArgsValid = false;
errors.EnsureError(DocumentErrorSeverity.Severe, nameArg, TexlStrings.ErrArgNotAValidIdentifier_Name, nameNode.Value);
continue;
}
DName columnName = new DName(nameNode.Value);
// Verify that the name exists.
DType columnType;
if (!returnType.TryGetType(columnName, out columnType))
{
fArgsValid = false;
returnType.ReportNonExistingName(FieldNameKind.Logical, errors, columnName, nameArg);
continue;
}
// Drop the specified column from the result type.
bool fError = false;
returnType = returnType.Drop(ref fError, DPath.Root, columnName);
Contracts.Assert(!fError);
}
return(fArgsValid);
}