public static bool Apply(TypeParameterName typeParam, ResolvedType typeParamRes)
{
var walker = new CheckForConstriction(typeParam);
walker.OnType(typeParamRes);
return(walker.SharedState.IsConstrictive);
}
/// <summary>
/// Walks the given ResolvedType, typeParamRes, and returns true if there is a reference
/// to a different type parameter of the same callable as the given type parameter, typeParam,
/// or the same type parameter but in a nested type.
/// Otherwise returns false.
/// </summary>
public static bool IsConstrictiveResolution(TypeParameterName typeParam, ResolvedType typeParamRes)
{
if (typeParamRes.Resolution is ResolvedTypeKind.TypeParameter tp &&
tp.Item.Origin.Equals(typeParam.Item1))
{
// If given a type parameter whose origin matches the callable,
// the only valid resolution is a direct self-resolution
return(!tp.Item.TypeName.Equals(typeParam.Item2));
}
var walker = new CheckForConstriction(typeParam.Item1);
walker.OnType(typeParamRes);
return(walker.SharedState.IsConstrictive);
}
// Methods
/// <summary>
/// Updates the combinesOverParameterConstriction flag. If the flag is already set to true,
/// nothing will be done. If not, the given type parameter will be checked against the given
/// resolution for type parameter constriction, which is when one type parameter is dependent
/// on another type parameter of the same callable.
/// </summary>
private void UpdateConstrictionFlag(TypeParameterName typeParamName, ResolvedType typeParamResolution)
{
this.combinesOverParameterConstriction = this.combinesOverParameterConstriction ||
CheckForConstriction.IsConstrictiveResolution(typeParamName, typeParamResolution);
}