public static ImmutableArray <TypeSymbol> GetReturnTypes(BoundBlock block, out int numberOfDistinctReturns)
{
var inferrer = new BlockReturns();
inferrer.Visit(block);
var result = inferrer.types.ToImmutableAndFree();
numberOfDistinctReturns = result.Length;
if (inferrer.hasReturnWithoutArgument)
{
numberOfDistinctReturns += 1;
}
return(result);
}
private TypeSymbol InferReturnType(ref HashSet <DiagnosticInfo> useSiteDiagnostics, out bool inferredFromSingeType)
{
int numberOfDistinctReturns;
var resultTypes = BlockReturns.GetReturnTypes(this.Body, out numberOfDistinctReturns);
inferredFromSingeType = numberOfDistinctReturns < 2;
TypeSymbol bestResultType;
if (resultTypes.IsDefaultOrEmpty)
{
bestResultType = null;
}
else if (resultTypes.Length == 1)
{
bestResultType = resultTypes[0];
}
else
{
bestResultType = BestTypeInferrer.InferBestType(resultTypes, this.Binder.Conversions, ref useSiteDiagnostics);
}
if (!Symbol.IsAsync)
{
return(bestResultType);
}
// Async:
if (resultTypes.IsEmpty)
{
// No return statements have expressions; inferred type Task:
return(this.Binder.Compilation.GetWellKnownType(WellKnownType.System_Threading_Tasks_Task));
}
if ((object)bestResultType == null || bestResultType.SpecialType == SpecialType.System_Void)
{
// If the best type was 'void', ERR_CantReturnVoid is reported while binding the "return void"
// statement(s).
return(null);
}
// Some non-void best type T was found; infer type Task<T>:
return(this.Binder.Compilation.GetWellKnownType(WellKnownType.System_Threading_Tasks_Task_T).Construct(bestResultType));
}
private static TypeSymbol InferReturnType(
BoundBlock block,
Binder binder,
TypeSymbol delegateType,
bool isAsync,
ref HashSet <DiagnosticInfo> useSiteDiagnostics,
out RefKind refKind,
out bool inferredFromSingleType)
{
int numberOfDistinctReturns;
var resultTypes = BlockReturns.GetReturnTypes(block, out refKind, out numberOfDistinctReturns);
inferredFromSingleType = numberOfDistinctReturns < 2;
TypeSymbol bestResultType;
if (resultTypes.IsDefaultOrEmpty)
{
bestResultType = null;
}
else if (resultTypes.Length == 1)
{
bestResultType = resultTypes[0];
}
else
{
bestResultType = BestTypeInferrer.InferBestType(resultTypes, binder.Conversions, ref useSiteDiagnostics);
}
if (!isAsync)
{
return(bestResultType);
}
// For async lambdas, the return type is the return type of the
// delegate Invoke method if Invoke has a Task-like return type.
// Otherwise the return type is Task or Task<T>.
NamedTypeSymbol taskType = null;
var delegateReturnType = delegateType?.GetDelegateType()?.DelegateInvokeMethod?.ReturnType as NamedTypeSymbol;
if ((object)delegateReturnType != null)
{
NamedTypeSymbol builderType;
MethodSymbol createBuilderMethod;
if (delegateReturnType.IsCustomTaskType(out builderType, out createBuilderMethod))
{
taskType = delegateReturnType;
}
}
if (resultTypes.IsEmpty)
{
// No return statements have expressions; use delegate InvokeMethod
// or infer type Task if delegate type not available.
return((object)taskType != null && taskType.Arity == 0 ?
taskType :
binder.Compilation.GetWellKnownType(WellKnownType.System_Threading_Tasks_Task));
}
if ((object)bestResultType == null || bestResultType.SpecialType == SpecialType.System_Void)
{
// If the best type was 'void', ERR_CantReturnVoid is reported while binding the "return void"
// statement(s).
return(null);
}
// Some non-void best type T was found; use delegate InvokeMethod
// or infer type Task<T> if delegate type not available.
var taskTypeT = (object)taskType != null && taskType.Arity == 1 ?
delegateReturnType.ConstructedFrom :
binder.Compilation.GetWellKnownType(WellKnownType.System_Threading_Tasks_Task_T);
return(taskTypeT.Construct(bestResultType));
}
public static ImmutableArray<TypeSymbol> GetReturnTypes(BoundBlock block, out int numberOfDistinctReturns)
{
var inferrer = new BlockReturns();
inferrer.Visit(block);
var result = inferrer._types.ToImmutableAndFree();
numberOfDistinctReturns = result.Length;
if (inferrer._hasReturnWithoutArgument)
{
numberOfDistinctReturns += 1;
}
return result;
}
