/// <summary>
/// Rewrites arguments of an invocation according to the receiving method or indexer.
/// It is assumed that each argument has already been lowered, but we may need
/// additional rewriting for the arguments, such as generating a params array, re-ordering
/// arguments based on <paramref name="argsToParamsOpt"/> map, inserting arguments for optional parameters, etc.
/// <paramref name="optionalParametersMethod"/> is the method used for values of any optional parameters.
/// For indexers, this method must be an accessor, and for methods it must be the method
/// itself. <paramref name="optionalParametersMethod"/> is needed for indexers since getter and setter
/// may have distinct optional parameter values.
/// </summary>
private ImmutableArray<BoundExpression> MakeArguments(
SyntaxNode syntax,
ImmutableArray<BoundExpression> rewrittenArguments,
Symbol methodOrIndexer,
MethodSymbol optionalParametersMethod,
bool expanded,
ImmutableArray<int> argsToParamsOpt,
ref ImmutableArray<RefKind> argumentRefKindsOpt,
out ImmutableArray<LocalSymbol> temps,
bool invokedAsExtensionMethod = false,
ThreeState enableCallerInfo = ThreeState.Unknown)
{
// Either the methodOrIndexer is a property, in which case the method used
// for optional parameters is an accessor of that property (or an overridden
// property), or the methodOrIndexer is used for optional parameters directly.
Debug.Assert(((methodOrIndexer.Kind == SymbolKind.Property) && optionalParametersMethod.IsAccessor()) ||
ReferenceEquals(methodOrIndexer, optionalParametersMethod));
// We need to do a fancy rewrite under the following circumstances:
// (1) a params array is being used; we need to generate the array.
// (2) there were named arguments that reordered the arguments; we might
// have to generate temporaries to ensure that the arguments are
// evaluated in source code order, not the actual call order.
// (3) there were optional parameters that had no corresponding arguments.
//
// If none of those are the case then we can just take an early out.
// An applicable "vararg" method could not possibly be applicable in its expanded
// form, and cannot possibly have named arguments or used optional parameters,
// because the __arglist() argument has to be positional and in the last position.
if (methodOrIndexer.GetIsVararg())
{
Debug.Assert(rewrittenArguments.Length == methodOrIndexer.GetParameterCount() + 1);
Debug.Assert(argsToParamsOpt.IsDefault);
Debug.Assert(!expanded);
temps = default(ImmutableArray<LocalSymbol>);
return rewrittenArguments;
}
var receiverNamedType = invokedAsExtensionMethod ?
((MethodSymbol)methodOrIndexer).Parameters[0].Type as NamedTypeSymbol :
methodOrIndexer.ContainingType;
bool isComReceiver = (object)receiverNamedType != null && receiverNamedType.IsComImport;
if (rewrittenArguments.Length == methodOrIndexer.GetParameterCount() &&
argsToParamsOpt.IsDefault &&
!expanded &&
!isComReceiver)
{
temps = default(ImmutableArray<LocalSymbol>);
return rewrittenArguments;
}
// We have:
// * a list of arguments, already converted to their proper types,
// in source code order. Some optional arguments might be missing.
// * a map showing which parameter each argument corresponds to. If
// this is null, then the argument to parameter mapping is one-to-one.
// * the ref kind of each argument, in source code order. That is, whether
// the argument was marked as ref, out, or value (neither).
// * a method symbol.
// * whether the call is expanded or normal form.
// We rewrite the call so that:
// * if in its expanded form, we create the params array.
// * if the call requires reordering of arguments because of named arguments, temporaries are generated as needed
// Doing this transformation can move around refness in interesting ways. For example, consider
//
// A().M(y : ref B()[C()], x : out D());
//
// This will be created as a call with receiver A(), symbol M, argument list ( B()[C()], D() ),
// name list ( y, x ) and ref list ( ref, out ). We can rewrite this into temporaries:
//
// A().M(
// seq ( ref int temp_y = ref B()[C()], out D() ),
// temp_y );
//
// Now we have a call with receiver A(), symbol M, argument list as shown, no name list,
// and ref list ( out, value ). We do not want to pass a *ref* to temp_y; the temporary
// storage is not the thing being ref'd! We want to pass the *value* of temp_y, which
// *contains* a reference.
// We attempt to minimize the number of temporaries required. Arguments which neither
// produce nor observe a side effect can be placed into their proper position without
// recourse to a temporary. For example:
//
// Where(predicate: x=>x.Length!=0, sequence: S())
//
// can be rewritten without any temporaries because the conversion from lambda to
// delegate does not produce any side effect that could be observed by S().
//
// By contrast:
//
// Foo(z: this.p, y: this.Q(), x: (object)10)
//
// The boxing of 10 can be reordered, but the fetch of this.p has to happen before the
// call to this.Q() because the call could change the value of this.p.
//
// We start by binding everything that is not obviously reorderable as a temporary, and
// then run an optimizer to remove unnecessary temporaries.
ImmutableArray<ParameterSymbol> parameters = methodOrIndexer.GetParameters();
BoundExpression[] actualArguments = new BoundExpression[parameters.Length]; // The actual arguments that will be passed; one actual argument per formal parameter.
ArrayBuilder<BoundAssignmentOperator> storesToTemps = ArrayBuilder<BoundAssignmentOperator>.GetInstance(rewrittenArguments.Length);
ArrayBuilder<RefKind> refKinds = ArrayBuilder<RefKind>.GetInstance(parameters.Length, RefKind.None);
// Step one: Store everything that is non-trivial into a temporary; record the
// stores in storesToTemps and make the actual argument a reference to the temp.
// Do not yet attempt to deal with params arrays or optional arguments.
BuildStoresToTemps(expanded, argsToParamsOpt, argumentRefKindsOpt, rewrittenArguments, actualArguments, refKinds, storesToTemps);
// all the formal arguments, except missing optionals, are now in place.
// Optimize away unnecessary temporaries.
// Necessary temporaries have their store instructions merged into the appropriate
// argument expression.
ArrayBuilder<LocalSymbol> temporariesBuilder = ArrayBuilder<LocalSymbol>.GetInstance();
OptimizeTemporaries(actualArguments, refKinds, storesToTemps, temporariesBuilder);
// Step two: If we have a params array, build the array and fill in the argument.
if (expanded)
{
actualArguments[actualArguments.Length - 1] = BuildParamsArray(syntax, methodOrIndexer, argsToParamsOpt, rewrittenArguments, parameters, actualArguments[actualArguments.Length - 1]);
}
// Step three: Now fill in the optional arguments.
InsertMissingOptionalArguments(syntax, optionalParametersMethod.Parameters, actualArguments, enableCallerInfo);
if (isComReceiver)
{
RewriteArgumentsForComCall(parameters, actualArguments, refKinds, temporariesBuilder);
}
temps = temporariesBuilder.ToImmutableAndFree();
storesToTemps.Free();
// * The refkind map is now filled out to match the arguments.
// * The list of parameter names is now null because the arguments have been reordered.
// * The args-to-params map is now null because every argument exactly matches its parameter.
// * The call is no longer in its expanded form.
argumentRefKindsOpt = GetRefKindsOrNull(refKinds);
refKinds.Free();
return actualArguments.AsImmutableOrNull();
}
public override void VisitMethod(MethodSymbol symbol)
{
_cancellationToken.ThrowIfCancellationRequested();
if (DoNotVisit(symbol)) return;
Compliance compliance = GetDeclaredOrInheritedCompliance(symbol);
// Most CLS checks don't apply to accessors.
if (symbol.IsAccessor())
{
CheckForAttributeOnAccessor(symbol);
CheckForMeaninglessOnParameter(symbol.Parameters);
CheckForMeaninglessOnReturn(symbol);
if (IsTrue(compliance))
{
CheckForAttributeWithArrayArgument(symbol);
}
return;
}
if (!VisitTypeOrMember(symbol, compliance)) return;
if (IsTrue(compliance))
{
CheckParameterCompliance(symbol.Parameters, symbol.ContainingType);
CheckTypeParameterCompliance(symbol.TypeParameters, symbol.ContainingType);
if (symbol.IsVararg)
{
this.AddDiagnostic(ErrorCode.WRN_CLS_NoVarArgs, symbol.Locations[0]);
}
}
}