public static bool IsPotentialTypeName(this TypeSyntax typeSyntax, SemanticModel semanticModelOpt, CancellationToken cancellationToken)
{
if (typeSyntax == null)
{
return false;
}
if (typeSyntax is PredefinedTypeSyntax ||
typeSyntax is ArrayTypeSyntax ||
typeSyntax is GenericNameSyntax ||
typeSyntax is PointerTypeSyntax ||
typeSyntax is NullableTypeSyntax)
{
return true;
}
if (semanticModelOpt == null)
{
return false;
}
var nameSyntax = typeSyntax as NameSyntax;
if (nameSyntax == null)
{
return false;
}
var nameToken = nameSyntax.GetNameToken();
var symbols = semanticModelOpt.LookupName(nameToken, namespacesAndTypesOnly: true, cancellationToken: cancellationToken);
var firstSymbol = symbols.FirstOrDefault();
var typeSymbol = firstSymbol != null && firstSymbol.Kind == SymbolKind.Alias
? (firstSymbol as IAliasSymbol).Target
: firstSymbol as ITypeSymbol;
return typeSymbol != null
&& !typeSymbol.IsErrorType();
}
public static bool IsGenericTypeArgumentContext(
this SyntaxTree syntaxTree,
int position,
SyntaxToken tokenOnLeftOfPosition,
CancellationToken cancellationToken,
SemanticModel semanticModelOpt = null)
{
// cases:
// Foo<|
// Foo<Bar,|
// Foo<Bar<Baz<int[],|
var token = tokenOnLeftOfPosition;
token = token.GetPreviousTokenIfTouchingWord(position);
if (token.Kind() != SyntaxKind.LessThanToken && token.Kind() != SyntaxKind.CommaToken)
{
return false;
}
if (token.Parent is TypeArgumentListSyntax)
{
// Easy case, it was known to be a generic name, so this is a type argument context.
return true;
}
SyntaxToken nameToken;
if (!syntaxTree.IsInPartiallyWrittenGeneric(position, cancellationToken, out nameToken))
{
return false;
}
var name = nameToken.Parent as NameSyntax;
if (name == null)
{
return false;
}
// Looks viable! If they provided a binding, then check if it binds properly to
// an actual generic entity.
if (semanticModelOpt == null)
{
// No binding. Just make the decision based on the syntax tree.
return true;
}
// '?' is syntactically ambiguous in incomplete top-level statements:
//
// T ? foo<|
//
// Might be an incomplete conditional expression or an incomplete declaration of a method returning a nullable type.
// Bind T to see if it is a type. If it is we don't show signature help.
if (name.IsParentKind(SyntaxKind.LessThanExpression) &&
name.Parent.IsParentKind(SyntaxKind.ConditionalExpression) &&
name.Parent.Parent.IsParentKind(SyntaxKind.ExpressionStatement) &&
name.Parent.Parent.Parent.IsParentKind(SyntaxKind.GlobalStatement))
{
var conditionOrType = semanticModelOpt.GetSymbolInfo(
((ConditionalExpressionSyntax)name.Parent.Parent).Condition, cancellationToken);
if (conditionOrType.GetBestOrAllSymbols().FirstOrDefault() != null &&
conditionOrType.GetBestOrAllSymbols().FirstOrDefault().Kind == SymbolKind.NamedType)
{
return false;
}
}
var symbols = semanticModelOpt.LookupName(nameToken, namespacesAndTypesOnly: SyntaxFacts.IsInNamespaceOrTypeContext(name), cancellationToken: cancellationToken);
return symbols.Any(s =>
s.TypeSwitch(
(INamedTypeSymbol nt) => nt.Arity > 0,
(IMethodSymbol m) => m.Arity > 0));
}