/// <summary>
/// Tries to look up symbols inside a witness type parameter.
/// <para>
/// This lookup checks all of the concepts this witness implements
/// to see if any contain a viable method matching the symbol.
/// </para>
/// <para>
/// This lookup approach only works for methods and properties, and
/// returns members whose parents are type parameters. We rely on
/// later stages to detect this and resolve it back to a proper
/// statement.
/// </para>
/// </summary>
/// <param name="witness">
/// The type witness into which we are looking.
/// </param>
/// <param name="result">
/// The lookup result to populate.
/// </param>
/// <param name="name">
/// The name of the member being looked-up.
/// </param>
/// <param name="arity">
/// The arity of the member being looked up.
/// </param>
/// <param name="basesBeingResolved">
/// The set of bases being resolved.
/// </param>
/// <param name="options">
/// The lookup options in effect.
/// </param>
/// <param name="originalBinder">
/// The top-level binder.
/// </param>
/// <param name="diagnose">
/// Whether or not we are diagnosing.
/// </param>
/// <param name="useSiteDiagnostics">
/// Diagnostics set at the use-site.
/// </param>
internal void LookupSymbolsInWitness(
TypeParameterSymbol witness, LookupResult result, string name, int arity, ConsList <Symbol> basesBeingResolved, LookupOptions options, Binder originalBinder, bool diagnose, ref HashSet <DiagnosticInfo> useSiteDiagnostics)
{
Debug.Assert(witness.IsConceptWitness);
var concepts = witness.ProvidedConcepts;
if (concepts.IsDefaultOrEmpty)
{
return;
}
foreach (var c in concepts)
{
var members = GetCandidateMembers(c, name, options, originalBinder);
foreach (var member in members)
{
switch (member.Kind)
{
case SymbolKind.Method:
var method = (MethodSymbol)member;
// Suppose our witness is W : C<A>, and this finds C<A>.M(x).
// We need to return that we found W.M(x), but W is a type
// parameter! While we can handle this later on in binding,
// the main issue is changing C<A> to W, for which we use
// a synthesized method symbol.
var witnessMethod = new SynthesizedWitnessMethodSymbol(method, witness);
SingleLookupResult resultOfThisMethod = originalBinder.CheckViability(witnessMethod, arity, options, witness, diagnose, ref useSiteDiagnostics, basesBeingResolved);
result.MergeEqual(resultOfThisMethod);
break;
case SymbolKind.Property:
var prop = (PropertySymbol)member;
var witnessProp = new SynthesizedWitnessPropertySymbol(prop, witness);
SingleLookupResult resultOfThisProp = originalBinder.CheckViability(witnessProp, arity, options, witness, diagnose, ref useSiteDiagnostics, basesBeingResolved);
result.MergeEqual(resultOfThisProp);
break;
// We don't allow other types to be fields of a witness
}
}
}
}
/// <summary>
/// Tries to look up symbols inside a witness type parameter.
/// <para>
/// This lookup checks all of the concepts this witness implements
/// to see if any contain a viable method matching the symbol.
/// </para>
/// <para>
/// This lookup approach only works for methods, and returns a
/// method whose parent is a type parameter. We rely on later
/// binder stages to detect this and resolve it back to a proper
/// statement.
/// </para>
/// </summary>
/// <param name="witness">
/// The type witness into which we are looking.
/// </param>
/// <param name="result">
/// The lookup result to populate.
/// </param>
/// <param name="name">
/// The name of the member being looked-up.
/// </param>
/// <param name="arity">
/// The arity of the member being looked up.
/// </param>
/// <param name="basesBeingResolved">
/// The set of bases being resolved.
/// </param>
/// <param name="options">
/// The lookup options in effect.
/// </param>
/// <param name="originalBinder">
/// The top-level binder.
/// </param>
/// <param name="diagnose">
/// Whether or not we are diagnosing.
/// </param>
/// <param name="useSiteDiagnostics">
/// Diagnostics set at the use-site.
/// </param>
internal void LookupSymbolsInWitness(
TypeParameterSymbol witness, LookupResult result, string name, int arity, ConsList <Symbol> basesBeingResolved, LookupOptions options, Binder originalBinder, bool diagnose, ref HashSet <DiagnosticInfo> useSiteDiagnostics)
{
Debug.Assert(witness.IsConceptWitness);
// Concepts are just interfaces, so we look at every possible
// interface this witness has been constrained to implement.
foreach (var iface in witness.AllEffectiveInterfacesNoUseSiteDiagnostics)
{
if (!iface.IsConcept)
{
continue;
}
// We're assuming that the above handles inheritance for us.
// This may be a mistake.
var members = GetCandidateMembers(iface, name, options, originalBinder);
foreach (var member in members)
{
// Don't bother trying to resolve non-methods:
// concepts can't have them, and we only have shims for
// dealing with methods later on anyway.
if (member.Kind != SymbolKind.Method)
{
continue;
}
var method = member as MethodSymbol;
Debug.Assert(method != null);
// Suppose our witness is W : C<A>, and this finds C<A>.M(x).
// We need to return that we found W.M(x), but W is a type
// parameter! While we can handle this later on in binding,
// the main issue is changing C<A> to W, for which we use
// a synthesized method symbol.
var witnessMethod = new SynthesizedWitnessMethodSymbol(method, witness);
SingleLookupResult resultOfThisMember = originalBinder.CheckViability(witnessMethod, arity, options, witness, diagnose, ref useSiteDiagnostics, basesBeingResolved);
result.MergeEqual(resultOfThisMember);
}
}
}