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Allow suppressing nullability warnings in more ref scenarios #74498

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Sep 11, 2024
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34 changes: 28 additions & 6 deletions src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
Original file line number Diff line number Diff line change
Expand Up @@ -5772,6 +5772,11 @@ void makeAndAdjustReceiverSlot(BoundExpression receiver)

if (isRef)
{
Debug.Assert(node is not BoundConditionalOperator { WasTargetTyped: true }, """
Unexpected ref target typed conditional operator.
Should not do type inference below in this case.
""");

TypeWithAnnotations consequenceLValue;
TypeWithAnnotations alternativeLValue;

Expand All @@ -5780,20 +5785,28 @@ void makeAndAdjustReceiverSlot(BoundExpression receiver)
(alternativeLValue, alternativeRValue) = visitConditionalRefOperand(alternativeState, originalAlternative);
Join(ref this.State, ref consequenceState);

var lValueAnnotation = consequenceLValue.NullableAnnotation.EnsureCompatible(alternativeLValue.NullableAnnotation);
var rValueState = consequenceRValue.State.Join(alternativeRValue.State);

TypeSymbol? refResultType = node.Type?.SetUnknownNullabilityForReferenceTypes();
if (IsNullabilityMismatch(consequenceLValue, alternativeLValue))
{
// l-value types must match
ReportNullabilityMismatchInAssignment(node.Syntax, consequenceLValue, alternativeLValue);
// If there is a mismatch between the operands, use type inference to determine the target type.
BoundExpression consequencePlaceholder = CreatePlaceholderIfNecessary(originalConsequence, consequenceLValue);
BoundExpression alternativePlaceholder = CreatePlaceholderIfNecessary(originalAlternative, alternativeLValue);
var discardedUseSiteInfo = CompoundUseSiteInfo<AssemblySymbol>.Discarded;
refResultType = BestTypeInferrer.InferBestTypeForConditionalOperator(consequencePlaceholder, alternativePlaceholder, _conversions, out _, ref discardedUseSiteInfo);

// Report warning for each operand that is not convertible to the target type.
var refResultTypeWithAnnotations = TypeWithAnnotations.Create(refResultType, lValueAnnotation);
reportMismatchIfNecessary(originalConsequence, consequenceLValue, refResultTypeWithAnnotations);
reportMismatchIfNecessary(originalAlternative, alternativeLValue, refResultTypeWithAnnotations);
}
else if (!node.HasErrors)
{
refResultType = consequenceRValue.Type!.MergeEquivalentTypes(alternativeRValue.Type, VarianceKind.None);
}

var lValueAnnotation = consequenceLValue.NullableAnnotation.EnsureCompatible(alternativeLValue.NullableAnnotation);
var rValueState = consequenceRValue.State.Join(alternativeRValue.State);

SetResult(node, TypeWithState.Create(refResultType, rValueState), TypeWithAnnotations.Create(refResultType, lValueAnnotation));
return null;
}
Expand Down Expand Up @@ -5957,6 +5970,14 @@ void addConvertArmsAsCompletion(
TypeWithAnnotations lValueType = VisitLvalueWithAnnotations(operand);
return (lValueType, ResultType);
}

void reportMismatchIfNecessary(BoundExpression node, TypeWithAnnotations source, TypeWithAnnotations destination)
{
if (!node.IsSuppressed && IsNullabilityMismatch(source, destination))
{
ReportNullabilityMismatchInAssignment(node.Syntax, source, destination);
}
}
}

private TypeWithState ConvertConditionalOperandOrSwitchExpressionArmResult(
Expand Down Expand Up @@ -10890,7 +10911,8 @@ public override void VisitForEachIterationVariables(BoundForEachStatement node)
if (iterationVariable.IsRef)
{
// foreach (ref DestinationType variable in collection)
if (IsNullabilityMismatch(sourceType, destinationType))
if (node.Expression is not BoundConversion { Operand.IsSuppressed: true } &&
IsNullabilityMismatch(sourceType, destinationType))
{
var foreachSyntax = (ForEachStatementSyntax)node.Syntax;
ReportNullabilityMismatchInAssignment(foreachSyntax.Type, sourceType, destinationType);
Expand Down
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