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Fix handling of variant casting in the managed type system #91788

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merged 1 commit into from
Sep 13, 2023
Merged

Fix handling of variant casting in the managed type system #91788

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29 changes: 20 additions & 9 deletions src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -391,7 +391,9 @@ private static bool CanCastToClassOrInterface(this TypeDesc thisType, TypeDesc o

private static bool CanCastToInterface(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protect)
{
if (!otherType.HasVariance)
// Interfaces that don't have variance can still behave variantly when arrays are involved.
bool arrayCovariance = thisType.IsSzArray && otherType.HasInstantiation;
if (!otherType.HasVariance && !arrayCovariance)
{
return thisType.CanCastToNonVariantInterface(otherType);
}
Expand All @@ -404,7 +406,7 @@ private static bool CanCastToInterface(this TypeDesc thisType, TypeDesc otherTyp

foreach (var interfaceType in thisType.RuntimeInterfaces)
{
if (interfaceType.CanCastByVarianceToInterfaceOrDelegate(otherType, protect))
if (interfaceType.CanCastByVarianceToInterfaceOrDelegate(otherType, protect, arrayCovariance))
{
return true;
}
Expand Down Expand Up @@ -432,7 +434,7 @@ private static bool CanCastToNonVariantInterface(this TypeDesc thisType, TypeDes
return false;
}

private static bool CanCastByVarianceToInterfaceOrDelegate(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protectInput)
private static bool CanCastByVarianceToInterfaceOrDelegate(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protectInput, bool arrayCovariance = false)
{
if (thisType == otherType)
{
Expand Down Expand Up @@ -467,23 +469,24 @@ private static bool CanCastByVarianceToInterfaceOrDelegate(this TypeDesc thisTyp

if (!arg.IsEquivalentTo(targetArg))
{
GenericParameterDesc openArgType = (GenericParameterDesc)instantiationOpen[i];
GenericVariance variance = arrayCovariance
? GenericVariance.Covariant : ((GenericParameterDesc)instantiationOpen[i]).Variance;

switch (openArgType.Variance)
switch (variance)
{
case GenericVariance.Covariant:
if (!arg.IsBoxedAndCanCastTo(targetArg, protect))
if (!arg.IsBoxedAndCanCastTo(targetArg, protect, arrayCovariance))
return false;
break;

case GenericVariance.Contravariant:
if (!targetArg.IsBoxedAndCanCastTo(arg, protect))
if (!targetArg.IsBoxedAndCanCastTo(arg, protect, arrayCovariance))
return false;
break;

default:
// non-variant
Debug.Assert(openArgType.Variance == GenericVariance.None);
Debug.Assert(variance == GenericVariance.None);
return false;
}
}
Expand Down Expand Up @@ -548,7 +551,7 @@ private static bool CanCastToClass(this TypeDesc thisType, TypeDesc otherType, S
return false;
}

private static bool IsBoxedAndCanCastTo(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protect)
private static bool IsBoxedAndCanCastTo(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protect, bool arrayCovariance)
{
TypeDesc fromUnderlyingType = thisType.UnderlyingType;

Expand All @@ -564,6 +567,14 @@ private static bool IsBoxedAndCanCastTo(this TypeDesc thisType, TypeDesc otherTy
return genericVariableFromParam.CanCastToInternal(otherType, protect);
}
}
else if (arrayCovariance && fromUnderlyingType.IsPrimitive)
{
TypeDesc toUnderlyingType = otherType.UnderlyingType;
if (GetNormalizedIntegralArrayElementType(fromUnderlyingType) == GetNormalizedIntegralArrayElementType(toUnderlyingType))
{
return true;
}
}

return false;
}
Expand Down
18 changes: 18 additions & 0 deletions src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CastingTests.cs
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Expand Up @@ -95,18 +95,36 @@ public void TestSameSizeArrayTypeCasting()
public void TestArrayInterfaceCasting()
{
TypeDesc intType = _context.GetWellKnownType(WellKnownType.Int32);
TypeDesc byteType = _context.GetWellKnownType(WellKnownType.Byte);
TypeDesc objectType = _context.GetWellKnownType(WellKnownType.Object);
TypeDesc stringType = _context.GetWellKnownType(WellKnownType.String);
TypeDesc intBasedEnumType = _testModule.GetType("Casting", "IntBasedEnum");
MetadataType iListType = _context.SystemModule.GetType("System.Collections", "IList");
MetadataType iListOfTType = _context.SystemModule.GetType("System.Collections.Generic", "IList`1");

InstantiatedType iListOfIntType = iListOfTType.MakeInstantiatedType(intType);
InstantiatedType iListOfObjectType = iListOfTType.MakeInstantiatedType(objectType);
InstantiatedType iListOfStringType = iListOfTType.MakeInstantiatedType(stringType);
TypeDesc intSzArrayType = intType.MakeArrayType();
TypeDesc byteSzArrayType = byteType.MakeArrayType();
TypeDesc objectSzArrayType = objectType.MakeArrayType();
TypeDesc stringSzArrayType = stringType.MakeArrayType();
TypeDesc intArrayType = intType.MakeArrayType(1);
TypeDesc intBasedEnumSzArrayType = intBasedEnumType.MakeArrayType();

Assert.True(intSzArrayType.CanCastTo(iListOfIntType));
Assert.True(intSzArrayType.CanCastTo(iListType));

Assert.False(intArrayType.CanCastTo(iListOfIntType));
Assert.True(intArrayType.CanCastTo(iListType));

Assert.True(intBasedEnumSzArrayType.CanCastTo(iListOfIntType));
Assert.False(byteSzArrayType.CanCastTo(iListOfIntType));

Assert.True(stringSzArrayType.CanCastTo(iListOfObjectType));
Assert.True(stringSzArrayType.CanCastTo(iListOfStringType));
Assert.True(objectSzArrayType.CanCastTo(iListOfObjectType));
Assert.False(objectSzArrayType.CanCastTo(iListOfStringType));
}

[Fact]
Expand Down
1 change: 0 additions & 1 deletion src/libraries/System.Linq/tests/ToArrayTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -358,7 +358,6 @@ private enum Enum1
}

[Fact]
[ActiveIssue("https://github.com/dotnet/runtime/issues/85146", typeof(PlatformDetection), nameof(PlatformDetection.IsNativeAot))]
public void ToArray_Cast()
{
Enum0[] source = { Enum0.First, Enum0.Second, Enum0.Third };
Expand Down
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