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Merged
merged 2 commits into from
Feb 4, 2020
Merged

Fix logic in compareTypesForCast #31681

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c3925a0
Fix logic in compareTypesForCast
AndyAyersMS Feb 3, 2020
140f35f
fix typos
AndyAyersMS Feb 3, 2020
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31 changes: 22 additions & 9 deletions src/coreclr/src/tools/Common/JitInterface/CorInfoImpl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1757,16 +1757,29 @@ private TypeCompareState compareTypesForCast(CORINFO_CLASS_STRUCT_* fromClass, C
{
result = TypeCompareState.Must;
}
// For negative results, the unknown type parameter in
// fromClass might match some instantiated interface,
// either directly or via variance.
// We have __Canon parameter(s) in fromClass, somewhere.
//
// However, CanCastTo will report failure in such cases since
// __Canon won't match the instantiated type on the
// interface (which can't be __Canon since we screened out
// canonical subtypes for toClass above). So only report
// failure if the interface is not instantiated.
else if (!toType.HasInstantiation)
// In CanCastTo, these __Canon(s) won't match the interface or
// instantiated types on the interface, so CanCastTo may
// return false negatives.
//
// Only report MustNot if the fromClass is not __Canon
// and the interface is not instantiated; then there is
// no way for the fromClass __Canon(s) to confuse things.
//
// __Canon -> IBar May
// IFoo<__Canon> -> IFoo<string> May
// IFoo<__Canon> -> IBar MustNot
//
else if (fromType.IsCanonicalDefinitionType(CanonicalFormKind.Any))
{
result = TypeCompareState.May;
}
else if (toType.HasInstantiation)
{
result = TypeCompareState.May;
}
else
{
result = TypeCompareState.MustNot;
}
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31 changes: 22 additions & 9 deletions src/coreclr/src/vm/jitinterface.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4495,16 +4495,29 @@ TypeCompareState CEEInfo::compareTypesForCast(
{
result = TypeCompareState::Must;
}
// For negative results, the unknown type parameter in
// fromClass might match some instantiated interface,
// either directly or via variance.
// We have __Canon parameter(s) in fromClass, somewhere.
//
// However, CanCastTo will report failure in such cases since
// __Canon won't match the instantiated type on the
// interface (which can't be __Canon since we screened out
// canonical subtypes for toClass above). So only report
// failure if the interface is not instantiated.
else if (!toHnd.HasInstantiation())
// In CanCastTo, these __Canon(s) won't match the interface or
// instantiated types on the interface, so CanCastTo may
// return false negatives.
//
// Only report MustNot if the fromClass is not __Canon
// and the interface is not instantiated; then there is
// no way for the fromClass __Canon(s) to confuse things.
//
// __Canon -> IBar May
// IFoo<__Canon> -> IFoo<string> May
// IFoo<__Canon> -> IBar MustNot
//
else if (fromHnd == TypeHandle(g_pCanonMethodTableClass))
{
result = TypeCompareState::May;
}
else if (toHnd.HasInstantiation())
{
result = TypeCompareState::May;
}
else
{
result = TypeCompareState::MustNot;
}
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122 changes: 122 additions & 0 deletions src/coreclr/tests/src/JIT/opt/Casts/shared2.cs
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@@ -0,0 +1,122 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.Runtime.CompilerServices;

interface IBar {}
interface IFoo<T> {}
class C : IBar {}
class C<T> : IFoo<T> {}
struct S {}
struct SBar : IBar {}

// More tests for shared types passing through compareTypesForCast

class X
{
static int _errors;

static void IsTrue(bool expression, [CallerLineNumber] int line = 0, [CallerFilePath] string file = "")
{
if (!expression)
{
Console.WriteLine($"{file}:L{line} test failed (expected: true).");
_errors++;
}
}

static void IsFalse(bool expression, [CallerLineNumber] int line = 0, [CallerFilePath] string file = "")
{
if (expression)
{
Console.WriteLine($"{file}:L{line} test failed (expected: false).");
_errors++;
}
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool A1<T>()
{
return typeof(IFoo<string>).IsAssignableFrom(typeof(T));
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool A2<T>()
{
return typeof(IBar).IsAssignableFrom(typeof(T));
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool I1<T>(T t)
{
return t is IFoo<string>;
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool I2<T>(T t)
{
return t is IBar;
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool C1<T>(T t)
{
return (t as IFoo<string>) != null;
}

[MethodImpl(MethodImplOptions.NoInlining)]
static bool C2<T>(T t)
{
return (t as IBar) != null;
}

public static int Main()
{
var c = new C();
var ci = new C<int>();
var cs = new C<string>();
var s = new S();
var sb = new SBar();

IsTrue(A1<IFoo<string>>());
IsFalse(A1<IFoo<int>>());
IsFalse(A1<IBar>());
IsFalse(A1<S>());
IsFalse(A1<SBar>());

IsTrue(I1(cs));
IsFalse(I1(ci));
IsFalse(I1(c));
IsFalse(I1(s));
IsFalse(I1(sb));

IsTrue(C1(cs));
IsFalse(C1(ci));
IsFalse(C1(c));
IsFalse(C1(s));
IsFalse(C1(sb));

IsFalse(A2<IFoo<string>>());
IsFalse(A2<IFoo<int>>());
IsTrue(A2<IBar>());
IsFalse(A2<S>());
IsTrue(A2<SBar>());

IsFalse(I2(cs));
IsFalse(I2(ci));
IsTrue(I2(c));
IsFalse(I2(s));
IsTrue(I2(sb));

IsFalse(C2(cs));
IsFalse(C2(ci));
IsTrue(C2(c));
IsFalse(C2(s));
IsTrue(C2(sb));

if (_errors == 0) Console.WriteLine("Passed");
return _errors > 0 ? -1 : 100;
}
}
12 changes: 12 additions & 0 deletions src/coreclr/tests/src/JIT/opt/Casts/shared2.csproj
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@@ -0,0 +1,12 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
</PropertyGroup>
<PropertyGroup>
<DebugType>PdbOnly</DebugType>
<Optimize>True</Optimize>
</PropertyGroup>
<ItemGroup>
<Compile Include="shared2.cs" />
</ItemGroup>
</Project>