public static ITypeSymbol ConvertToType(
this ISymbol symbol,
Compilation compilation,
bool extensionUsedAsInstance = false)
{
var type = symbol as ITypeSymbol;
if (type != null)
{
return(type);
}
var method = symbol as IMethodSymbol;
if (method != null && !method.Parameters.Any(p => p.RefKind != RefKind.None))
{
// Convert the symbol to Func<...> or Action<...>
if (method.ReturnsVoid)
{
var count = extensionUsedAsInstance ? method.Parameters.Length - 1 : method.Parameters.Length;
var skip = extensionUsedAsInstance ? 1 : 0;
count = Math.Max(0, count);
if (count == 0)
{
// Action
return(compilation.ActionType());
}
else
{
// Action<TArg1, ..., TArgN>
var actionName = "System.Action`" + count;
var actionType = compilation.GetTypeByMetadataName(actionName);
if (actionType != null)
{
var types = method.Parameters
.Skip(skip)
.Select(p =>
p.Type == null ?
compilation.GetSpecialType(SpecialType.System_Object) :
p.Type)
.ToArray();
return(actionType.Construct(types));
}
}
}
else
{
// Func<TArg1,...,TArgN,TReturn>
//
// +1 for the return type.
var count = extensionUsedAsInstance ? method.Parameters.Length - 1 : method.Parameters.Length;
var skip = extensionUsedAsInstance ? 1 : 0;
var functionName = "System.Func`" + (count + 1);
var functionType = compilation.GetTypeByMetadataName(functionName);
if (functionType != null)
{
var types = method.Parameters
.Skip(skip)
.Select(p => p.Type)
.Concat(method.ReturnType)
.Select(t => t ?? compilation.GetSpecialType(SpecialType.System_Object))
.ToArray();
return(functionType.Construct(types));
}
}
}
// Otherwise, just default to object.
return(compilation.ObjectType);
}