////////////////////////////////////////////////////////////////////////////////
// Determine best method for overload resolution. Returns null if no best
// method, in which case two tying methods are returned for error reporting.
private CandidateFunctionMember FindBestMethod(
List <CandidateFunctionMember> list,
CType pTypeThrough,
ArgInfos args,
out CandidateFunctionMember methAmbig1,
out CandidateFunctionMember methAmbig2)
{
Debug.Assert(list.Any());
Debug.Assert(list.First().mpwi != null);
Debug.Assert(list.Count > 0);
// select the best method:
/*
* Effectively, we pick the best item from a set using a non-transitive ranking function
* So, pick the first item (candidate) and compare against next (contender), if there is
* no next, goto phase 2
* If first is better, move to next contender, if none proceed to phase 2
* If second is better, make the contender the candidate and make the item following
* contender into the new contender, if there is none, goto phase 2
* If neither, make contender+1 into candidate and contender+2 into contender, if possible,
* otherwise, if contender was last, return null, otherwise if new candidate is last,
* goto phase 2
* Phase 2: compare all items before candidate to candidate
* If candidate always better, return it, otherwise return null
*
*/
// Record two method that are ambiguous for error reporting.
CandidateFunctionMember ambig1 = null;
CandidateFunctionMember ambig2 = null;
bool ambiguous = false;
CandidateFunctionMember candidate = list[0];
for (int i = 1; i < list.Count; i++)
{
CandidateFunctionMember contender = list[i];
Debug.Assert(candidate != contender);
switch (WhichMethodIsBetter(candidate, contender, pTypeThrough, args))
{
case BetterType.Left:
ambiguous = false; // (meaning m1 is better...)
break;
case BetterType.Right:
ambiguous = false;
candidate = contender;
break;
default:
// in case of tie we don't want to bother with the contender who tied...
ambig1 = candidate;
ambig2 = contender;
i++;
if (i < list.Count)
{
contender = list[i];
candidate = contender;
}
else
{
ambiguous = true;
}
break;
}
}
if (!ambiguous)
{
// Now, compare the candidate with items previous to it...
foreach (CandidateFunctionMember contender in list)
{
if (contender == candidate)
{
// We hit our winner, so its good enough...
methAmbig1 = null;
methAmbig2 = null;
return(candidate);
}
switch (WhichMethodIsBetter(contender, candidate, pTypeThrough, args))
{
case BetterType.Right:
// meaning m2 is better
continue;
case BetterType.Same:
case BetterType.Neither:
ambig1 = candidate;
ambig2 = contender;
break;
}
break;
}
}
// an ambiguous call. Return two of the ambiguous set.
if (ambig1 != null & ambig2 != null)
{
methAmbig1 = ambig1;
methAmbig2 = ambig2;
}
else
{
// For some reason, we have an ambiguity but never had a tie.
// This can easily happen in a circular graph of candidate methods.
methAmbig1 = list.First();
methAmbig2 = list.Skip(1).First();
}
return(null);
}
private BetterType WhichMethodIsBetterTieBreaker(
CandidateFunctionMember node1,
CandidateFunctionMember node2,
CType pTypeThrough,
ArgInfos args)
{
MethPropWithInst mpwi1 = node1.mpwi;
MethPropWithInst mpwi2 = node2.mpwi;
// Same signatures. If they have different lifting numbers, the smaller number wins.
// Otherwise, if one is generic and the other isn't then the non-generic wins.
// Otherwise, if one is expanded and the other isn't then the non-expanded wins.
// Otherwise, if one has fewer modopts than the other then it wins.
if (node1.ctypeLift != node2.ctypeLift)
{
return(node1.ctypeLift < node2.ctypeLift ? BetterType.Left : BetterType.Right);
}
// Non-generic wins.
if (mpwi1.TypeArgs.Count != 0)
{
if (mpwi2.TypeArgs.Count == 0)
{
return(BetterType.Right);
}
}
else if (mpwi2.TypeArgs.Count != 0)
{
return(BetterType.Left);
}
// Non-expanded wins
if (node1.fExpanded)
{
if (!node2.fExpanded)
{
return(BetterType.Right);
}
}
else if (node2.fExpanded)
{
return(BetterType.Left);
}
// See if one's parameter types (un-instantiated) are more specific.
BetterType nT = GetGlobalSymbols().CompareTypes(
RearrangeNamedArguments(mpwi1.MethProp().Params, mpwi1, pTypeThrough, args),
RearrangeNamedArguments(mpwi2.MethProp().Params, mpwi2, pTypeThrough, args));
if (nT == BetterType.Left || nT == BetterType.Right)
{
return(nT);
}
// Fewer modopts wins.
if (mpwi1.MethProp().modOptCount != mpwi2.MethProp().modOptCount)
{
return(mpwi1.MethProp().modOptCount < mpwi2.MethProp().modOptCount ? BetterType.Left : BetterType.Right);
}
// Bona-fide tie.
return(BetterType.Neither);
}
////////////////////////////////////////////////////////////////////////////////
// Determine which method is better for the purposes of overload resolution.
// Better means: as least as good in all params, and better in at least one param.
// Better w/r to a param means is an ordering, from best down:
// 1) same type as argument
// 2) implicit conversion from argument to formal type
// Because of user defined conversion opers this relation is not transitive.
//
// If there is a tie because of identical signatures, the tie may be broken by the
// following rules:
// 1) If one is generic and the other isn't, the non-generic wins.
// 2) Otherwise if one is expanded (params) and the other isn't, the non-expanded wins.
// 3) Otherwise if one has more specific parameter types (at the declaration) it wins:
// This occurs if at least on parameter type is more specific and no parameter type is
// less specific.
//* A type parameter is less specific than a non-type parameter.
//* A constructed type is more specific than another constructed type if at least
// one type argument is more specific and no type argument is less specific than
// the corresponding type args in the other.
// 4) Otherwise if one has more modopts than the other does, the smaller number of modopts wins.
//
// Returns Left if m1 is better, Right if m2 is better, or Neither/Same
private BetterType WhichMethodIsBetter(
CandidateFunctionMember node1,
CandidateFunctionMember node2,
CType pTypeThrough,
ArgInfos args)
{
MethPropWithInst mpwi1 = node1.mpwi;
MethPropWithInst mpwi2 = node2.mpwi;
// Substitutions should have already been done on these!
TypeArray pta1 = RearrangeNamedArguments(node1.@params, mpwi1, pTypeThrough, args);
TypeArray pta2 = RearrangeNamedArguments(node2.@params, mpwi2, pTypeThrough, args);
// If the parameter types for both candidate methods are identical,
// use the tie breaking rules.
if (pta1 == pta2)
{
return(WhichMethodIsBetterTieBreaker(node1, node2, pTypeThrough, args));
}
// Otherwise, do a parameter-by-parameter comparison:
//
// Given an argument list A with a set of argument expressions {E1, ... En} and
// two applicable function members Mp and Mq with parameter types {P1,... Pn} and
// {Q1, ... Qn}, Mp is defined to be a better function member than Mq if:
//* for each argument the implicit conversion from Ex to Qx is not better than
// the implicit conversion from Ex to Px.
//* for at least one argument, the conversion from Ex to Px is better than the
// conversion from Ex to Qx.
BetterType betterMethod = BetterType.Neither;
int carg = args.carg;
for (int i = 0; i < carg; i++)
{
Expr arg = args.fHasExprs ? args.prgexpr[i] : null;
CType p1 = pta1[i];
CType p2 = pta2[i];
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// RUNTIME BINDER ONLY CHANGE
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
//
// We need to consider conversions from the actual runtime type
// since we could have private interfaces that we are converting
CType argType = arg?.RuntimeObjectActualType ?? args.types[i];
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// END RUNTIME BINDER ONLY CHANGE
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
BetterType betterConversion = WhichConversionIsBetter(argType, p1, p2);
if (betterMethod == BetterType.Right)
{
if (betterConversion == BetterType.Left)
{
betterMethod = BetterType.Neither;
break;
}
}
else if (betterMethod == BetterType.Left)
{
if (betterConversion == BetterType.Right)
{
betterMethod = BetterType.Neither;
break;
}
}
else
{
Debug.Assert(betterMethod == BetterType.Neither);
if (betterConversion == BetterType.Right || betterConversion == BetterType.Left)
{
betterMethod = betterConversion;
}
}
}
// We may have different sizes if we had optional parameters. If thats the case,
// the one with fewer parameters wins (ie less optional parameters) unless it is
// expanded. If so, the one with more parameters wins (ie option beats expanded).
if (pta1.Count != pta2.Count && betterMethod == BetterType.Neither)
{
if (node1.fExpanded)
{
if (!node2.fExpanded)
{
return(BetterType.Right);
}
}
else if (node2.fExpanded)
{
return(BetterType.Left);
}
// Here, if both methods needed to use optionals to fill in the signatures,
// then we are ambiguous. Otherwise, take the one that didn't need any
// optionals.
if (pta1.Count == carg)
{
return(BetterType.Left);
}
if (pta2.Count == carg)
{
return(BetterType.Right);
}
return(BetterType.Neither);
}
return(betterMethod);
}
////////////////////////////////////////////////////////////////////////////////
// Determine best method for overload resolution. Returns null if no best
// method, in which case two tying methods are returned for error reporting.
protected CandidateFunctionMember FindBestMethod(
List<CandidateFunctionMember> list,
CType pTypeThrough,
ArgInfos args,
out CandidateFunctionMember methAmbig1,
out CandidateFunctionMember methAmbig2)
{
Debug.Assert(list.Any());
Debug.Assert(list.First().mpwi != null);
Debug.Assert(list.Count > 0);
// select the best method:
/*
Effectively, we pick the best item from a set using a non-transitive ranking function
So, pick the first item (candidate) and compare against next (contender), if there is
no next, goto phase 2
If first is better, move to next contender, if none proceed to phase 2
If second is better, make the contender the candidate and make the item following
contender into the new contender, if there is none, goto phase 2
If neither, make contender+1 into candidate and contender+2 into contender, if possible,
otherwise, if contender was last, return null, otherwise if new candidate is last,
goto phase 2
Phase 2: compare all items before candidate to candidate
If candidate always better, return it, otherwise return null
*/
// Record two method that are ambiguous for error reporting.
CandidateFunctionMember ambig1 = null;
CandidateFunctionMember ambig2 = null;
bool ambiguous = false;
CandidateFunctionMember candidate = list[0];
for (int i = 1; i < list.Count; i++)
{
CandidateFunctionMember contender = list[i];
Debug.Assert(candidate != contender);
BetterType result = WhichMethodIsBetter(candidate, contender, pTypeThrough, args);
if (result == BetterType.Left)
{
ambiguous = false;
continue; // (meaning m1 is better...)
}
else if (result == BetterType.Right)
{
ambiguous = false;
candidate = contender;
}
else
{
// in case of tie we don't want to bother with the contender who tied...
ambig1 = candidate;
ambig2 = contender;
i++;
if (i < list.Count)
{
contender = list[i];
candidate = contender;
}
else
{
ambiguous = true;
}
}
}
if (ambiguous)
goto AMBIG;
// Now, compare the candidate with items previous to it...
foreach (CandidateFunctionMember contender in list)
{
if (contender == candidate)
{
// We hit our winner, so its good enough...
methAmbig1 = null;
methAmbig2 = null;
return candidate;
}
BetterType result = WhichMethodIsBetter(contender, candidate, pTypeThrough, args);
if (result == BetterType.Right)
{ // meaning m2 is better
continue;
}
else if (result == BetterType.Same || result == BetterType.Neither)
{
ambig1 = candidate;
ambig2 = contender;
}
break;
}
AMBIG:
// an ambig call. Return two of the ambiguous set.
if (ambig1 != null && ambig2 != null)
{
methAmbig1 = ambig1;
methAmbig2 = ambig2;
}
else
{
// For some reason, we have an ambiguity but never had a tie.
// This can easily happen in a circular graph of candidate methods.
methAmbig1 = list.First();
methAmbig2 = list.Skip(1).First();
}
return null;
}
protected BetterType WhichMethodIsBetterTieBreaker(
CandidateFunctionMember node1,
CandidateFunctionMember node2,
CType pTypeThrough,
ArgInfos args)
{
MethPropWithInst mpwi1 = node1.mpwi;
MethPropWithInst mpwi2 = node2.mpwi;
// Same signatures. If they have different lifting numbers, the smaller number wins.
// Otherwise, if one is generic and the other isn't then the non-generic wins.
// Otherwise, if one is expanded and the other isn't then the non-expanded wins.
// Otherwise, if one has fewer modopts than the other then it wins.
if (node1.ctypeLift != node2.ctypeLift)
{
return node1.ctypeLift < node2.ctypeLift ? BetterType.Left : BetterType.Right;
}
// Non-generic wins.
if (mpwi1.TypeArgs.size != 0)
{
if (mpwi2.TypeArgs.size == 0)
{
return BetterType.Right;
}
}
else if (mpwi2.TypeArgs.size != 0)
{
return BetterType.Left;
}
// Non-expanded wins
if (node1.fExpanded)
{
if (!node2.fExpanded)
{
return BetterType.Right;
}
}
else if (node2.fExpanded)
{
return BetterType.Left;
}
// See if one's parameter types (un-instantiated) are more specific.
BetterType nT = GetGlobalSymbols().CompareTypes(
RearrangeNamedArguments(mpwi1.MethProp().Params, mpwi1, pTypeThrough, args),
RearrangeNamedArguments(mpwi2.MethProp().Params, mpwi2, pTypeThrough, args));
if (nT == BetterType.Left || nT == BetterType.Right)
{
return nT;
}
// Fewer modopts wins.
if (mpwi1.MethProp().modOptCount != mpwi2.MethProp().modOptCount)
{
return mpwi1.MethProp().modOptCount < mpwi2.MethProp().modOptCount ? BetterType.Left : BetterType.Right;
}
// Bona-fide tie.
return BetterType.Neither;
}
////////////////////////////////////////////////////////////////////////////////
// Determine which method is better for the purposes of overload resolution.
// Better means: as least as good in all params, and better in at least one param.
// Better w/r to a param means is an ordering, from best down:
// 1) same type as argument
// 2) implicit conversion from argument to formal type
// Because of user defined conversion opers this relation is not transitive.
//
// If there is a tie because of identical signatures, the tie may be broken by the
// following rules:
// 1) If one is generic and the other isn't, the non-generic wins.
// 2) Otherwise if one is expanded (params) and the other isn't, the non-expanded wins.
// 3) Otherwise if one has more specific parameter types (at the declaration) it wins:
// This occurs if at least on parameter type is more specific and no parameter type is
// less specific.
//* A type parameter is less specific than a non-type parameter.
//* A constructed type is more specific than another constructed type if at least
// one type argument is more specific and no type argument is less specific than
// the corresponding type args in the other.
// 4) Otherwise if one has more modopts than the other does, the smaller number of modopts wins.
//
// Returns Left if m1 is better, Right if m2 is better, or Neither/Same
protected BetterType WhichMethodIsBetter(
CandidateFunctionMember node1,
CandidateFunctionMember node2,
CType pTypeThrough,
ArgInfos args)
{
MethPropWithInst mpwi1 = node1.mpwi;
MethPropWithInst mpwi2 = node2.mpwi;
// Substitutions should have already been done on these!
TypeArray pta1 = RearrangeNamedArguments(node1.@params, mpwi1, pTypeThrough, args);
TypeArray pta2 = RearrangeNamedArguments(node2.@params, mpwi2, pTypeThrough, args);
// If the parameter types for both candidate methods are identical,
// use the tie breaking rules.
if (pta1 == pta2)
{
return WhichMethodIsBetterTieBreaker(node1, node2, pTypeThrough, args);
}
// Otherwise, do a parameter-by-parameter comparison:
//
// Given an argument list A with a set of argument expressions {E1, ... En} and
// two applicable function members Mp and Mq with parameter types {P1,... Pn} and
// {Q1, ... Qn}, Mp is defined to be a better function member than Mq if:
//* for each argument the implicit conversion from Ex to Qx is not better than
// the implicit conversion from Ex to Px.
//* for at least one argument, the conversion from Ex to Px is better than the
// conversion from Ex to Qx.
BetterType betterMethod = BetterType.Neither;
CType type1 = pTypeThrough != null ? pTypeThrough : mpwi1.GetType();
CType type2 = pTypeThrough != null ? pTypeThrough : mpwi2.GetType();
MethodOrPropertySymbol methProp1 = GroupToArgsBinder.FindMostDerivedMethod(GetSymbolLoader(), mpwi1.MethProp(), type1);
MethodOrPropertySymbol methProp2 = GroupToArgsBinder.FindMostDerivedMethod(GetSymbolLoader(), mpwi2.MethProp(), type2);
List<Name> names1 = methProp1.ParameterNames;
List<Name> names2 = methProp2.ParameterNames;
for (int i = 0; i < args.carg; i++)
{
EXPR arg = args.fHasExprs ? args.prgexpr[i] : null;
CType argType = args.types.Item(i);
CType p1 = pta1.Item(i);
CType p2 = pta2.Item(i);
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// RUNTIME BINDER ONLY CHANGE
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
//
// We need to consider conversions from the actual runtime type
// since we could have private interfaces that we are converting
if (arg.RuntimeObjectActualType != null)
{
argType = arg.RuntimeObjectActualType;
}
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// END RUNTIME BINDER ONLY CHANGE
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
BetterType betterConversion = WhichConversionIsBetter(arg, argType, p1, p2);
if (betterMethod == BetterType.Right && betterConversion == BetterType.Left)
{
betterMethod = BetterType.Neither;
break;
}
else if (betterMethod == BetterType.Left && betterConversion == BetterType.Right)
{
betterMethod = BetterType.Neither;
break;
}
else if (betterMethod == BetterType.Neither)
{
if (betterConversion == BetterType.Right || betterConversion == BetterType.Left)
{
betterMethod = betterConversion;
}
}
}
// We may have different sizes if we had optional parameters. If thats the case,
// the one with fewer parameters wins (ie less optional parameters) unless it is
// expanded. If so, the one with more parameters wins (ie option beats expanded).
if (pta1.size != pta2.size && betterMethod == BetterType.Neither)
{
if (node1.fExpanded && !node2.fExpanded)
{
return BetterType.Right;
}
else if (node2.fExpanded && !node1.fExpanded)
{
return BetterType.Left;
}
// Here, if both methods needed to use optionals to fill in the signatures,
// then we are ambiguous. Otherwise, take the one that didn't need any
// optionals.
if (pta1.size == args.carg)
{
return BetterType.Left;
}
else if (pta2.size == args.carg)
{
return BetterType.Right;
}
return BetterType.Neither;
}
return betterMethod;
}
