public override async ValueTask <ITypeSymbol> VisitTypeParameter(ITypeParameterSymbol symbol)
{
if (_availableTypeParameterNames.Contains(symbol.Name))
{
return(symbol);
}
switch (symbol.ConstraintTypes.Length)
{
case 0:
// If there are no constraint then there is no replacement required
// Just return the symbol
return(symbol);
case 1:
// If there is one constraint which is a INamedTypeSymbol then return the INamedTypeSymbol
// because the TypeParameter is expected to be of that type
// else return the original symbol
return(symbol.ConstraintTypes.ElementAt(0) as INamedTypeSymbol ?? (ITypeSymbol)symbol);
// More than one
default:
if (symbol.ConstraintTypes.All(t => t is INamedTypeSymbol))
{
var immutableProjects = _solution.Projects.ToImmutableHashSet();
var derivedImplementedTypesOfEachConstraintType = await Task.WhenAll(symbol.ConstraintTypes.Select(async ct =>
{
var derivedAndImplementedTypes = new List <INamedTypeSymbol>();
var derivedClasses = await SymbolFinder.FindDerivedClassesAsync((INamedTypeSymbol)ct, _solution, immutableProjects, _cancellationToken).ConfigureAwait(false);
var implementedTypes = await DependentTypeFinder.FindTransitivelyImplementingStructuresAndClassesAsync((INamedTypeSymbol)ct, _solution, immutableProjects, _cancellationToken).ConfigureAwait(false);
return(derivedClasses.Concat(implementedTypes.Select(s => s.Symbol)).ToList());
})).ConfigureAwait(false);
var intersectingTypes = derivedImplementedTypesOfEachConstraintType.Aggregate((x, y) => x.Intersect(y).ToList());
// If there was any intersecting derived type among the constraint types then pick the first of the lot.
if (intersectingTypes.Any())
{
var resultantIntersectingType = intersectingTypes.First();
// If the resultant intersecting type contains any Type arguments that could be replaced
// using the type constraints then recursively update the type until all constraints are appropriately handled
var typeConstraintConvertedType = await resultantIntersectingType.Accept(this).ConfigureAwait(false);
var knownSimilarTypesInCompilation = SymbolFinder.FindSimilarSymbols(typeConstraintConvertedType, _compilation, _cancellationToken);
if (knownSimilarTypesInCompilation.Any())
{
return(knownSimilarTypesInCompilation.First());
}
var resultantSimilarKnownTypes = SymbolFinder.FindSimilarSymbols(resultantIntersectingType, _compilation, _cancellationToken);
return(resultantSimilarKnownTypes.FirstOrDefault() ?? (ITypeSymbol)symbol);
}
}
return(symbol);
}
}
private async Task <ISet <INamedTypeSymbol> > GetDerivedAndImplementedTypesAsync(
INamedTypeSymbol constraintType, IImmutableSet <Project> projects)
{
var solution = _project.Solution;
var symbolAndProjectId = SymbolAndProjectId.Create(constraintType, _project.Id);
var derivedClasses = await SymbolFinder.FindDerivedClassesAsync(
symbolAndProjectId, solution, projects, _cancellationToken).ConfigureAwait(false);
var implementedTypes = await DependentTypeFinder.FindTransitivelyImplementingStructuresAndClassesAsync(
symbolAndProjectId, solution, projects, _cancellationToken).ConfigureAwait(false);
return(derivedClasses.Concat(implementedTypes).Select(t => t.Symbol).ToSet());
}