/// <summary>
/// Gets the better conversion (C# 4.0 spec, §7.5.3.3)
/// </summary>
/// <returns>0 = neither is better; 1 = t1 is better; 2 = t2 is better</returns>
public int BetterConversion(ResolveResult resolveResult, IType t1, IType t2)
{
LambdaResolveResult lambda = resolveResult as LambdaResolveResult;
if (lambda != null)
{
if (!lambda.IsAnonymousMethod)
{
t1 = UnpackExpressionTreeType(t1);
t2 = UnpackExpressionTreeType(t2);
}
IMethod m1 = t1.GetDelegateInvokeMethod();
IMethod m2 = t2.GetDelegateInvokeMethod();
if (m1 == null || m2 == null)
{
return(0);
}
int r = BetterConversionTarget(t1, t2);
if (r != 0)
{
return(r);
}
if (m1.Parameters.Count != m2.Parameters.Count)
{
return(0);
}
IType[] parameterTypes = new IType[m1.Parameters.Count];
for (int i = 0; i < parameterTypes.Length; i++)
{
parameterTypes[i] = m1.Parameters[i].Type;
if (!parameterTypes[i].Equals(m2.Parameters[i].Type))
{
return(0);
}
}
if (lambda.HasParameterList && parameterTypes.Length != lambda.Parameters.Count)
{
return(0);
}
IType ret1 = m1.ReturnType;
IType ret2 = m2.ReturnType;
if (ret1.Kind == TypeKind.Void && ret2.Kind != TypeKind.Void)
{
return(2);
}
if (ret1.Kind != TypeKind.Void && ret2.Kind == TypeKind.Void)
{
return(1);
}
IType inferredRet = lambda.GetInferredReturnType(parameterTypes);
r = BetterConversion(inferredRet, ret1, ret2);
if (r == 0 && lambda.IsAsync)
{
ret1 = UnpackTask(ret1);
ret2 = UnpackTask(ret2);
inferredRet = UnpackTask(inferredRet);
if (ret1 != null && ret2 != null && inferredRet != null)
{
r = BetterConversion(inferredRet, ret1, ret2);
}
}
return(r);
}
else
{
return(BetterConversion(resolveResult.Type, t1, t2));
}
}
void MakeOutputTypeInference(ResolveResult e, IType t)
{
Log.WriteLine(" MakeOutputTypeInference from " + e + " to " + t);
// If E is an anonymous function with inferred return type U (§7.5.2.12) and T is a delegate type or expression
// tree type with return type Tb, then a lower-bound inference (§7.5.2.9) is made from U to Tb.
LambdaResolveResult lrr = e as LambdaResolveResult;
if (lrr != null)
{
IMethod m = GetDelegateOrExpressionTreeSignature(t);
if (m != null)
{
IType inferredReturnType;
if (lrr.IsImplicitlyTyped)
{
if (m.Parameters.Count != lrr.Parameters.Count)
{
return; // cannot infer due to mismatched parameter lists
}
TypeParameterSubstitution substitution = GetSubstitutionForFixedTPs();
IType[] inferredParameterTypes = new IType[m.Parameters.Count];
for (int i = 0; i < inferredParameterTypes.Length; i++)
{
IType parameterType = m.Parameters[i].Type;
inferredParameterTypes[i] = parameterType.AcceptVisitor(substitution);
}
inferredReturnType = lrr.GetInferredReturnType(inferredParameterTypes);
}
else
{
inferredReturnType = lrr.GetInferredReturnType(null);
}
MakeLowerBoundInference(inferredReturnType, m.ReturnType);
return;
}
}
// Otherwise, if E is a method group and T is a delegate type or expression tree type
// with parameter types T1…Tk and return type Tb, and overload resolution
// of E with the types T1…Tk yields a single method with return type U, then a lower-bound
// inference is made from U to Tb.
MethodGroupResolveResult mgrr = e as MethodGroupResolveResult;
if (mgrr != null)
{
IMethod m = GetDelegateOrExpressionTreeSignature(t);
if (m != null)
{
ResolveResult[] args = new ResolveResult[m.Parameters.Count];
TypeParameterSubstitution substitution = GetSubstitutionForFixedTPs();
for (int i = 0; i < args.Length; i++)
{
IParameter param = m.Parameters[i];
IType parameterType = param.Type.AcceptVisitor(substitution);
if ((param.IsRef || param.IsOut) && parameterType.Kind == TypeKind.ByReference)
{
parameterType = ((ByReferenceType)parameterType).ElementType;
args[i] = new ByReferenceResolveResult(parameterType, param.IsOut);
}
else
{
args[i] = new ResolveResult(parameterType);
}
}
var or = mgrr.PerformOverloadResolution(compilation,
args,
allowExtensionMethods: false,
allowExpandingParams: false);
if (or.FoundApplicableCandidate && or.BestCandidateAmbiguousWith == null)
{
IType returnType = or.BestCandidate.ReturnType;
MakeLowerBoundInference(returnType, m.ReturnType);
}
}
return;
}
// Otherwise, if E is an expression with type U, then a lower-bound inference is made from U to T.
if (IsValidType(e.Type))
{
MakeLowerBoundInference(e.Type, t);
}
}
