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Fix ref safe context of assignments to be their RHS #80633

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merged 5 commits into from
Nov 3, 2025
Merged

Fix ref safe context of assignments to be their RHS #80633

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90ab5b4
Fix ref safe context of assignments to be their RHS
jjonescz Oct 10, 2025
8252ac8
Update more tests
jjonescz Oct 10, 2025
f7e706a
Fix null-coalescing and compound assignments
jjonescz Oct 13, 2025
4eb427d
Add more tests
jjonescz Oct 13, 2025
0b3d823
Update a test name
jjonescz Oct 31, 2025
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21 changes: 12 additions & 9 deletions src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3894,7 +3894,8 @@ internal SafeContext GetRefEscape(BoundExpression expr, SafeContext localScopeDe
break;
}

return GetRefEscape(assignment.Left, localScopeDepth);
// The result of a ref assignment is its right-hand side.
return GetRefEscape(assignment.Right, localScopeDepth);

case BoundKind.Conversion:
Debug.Assert(expr is BoundConversion conversion &&
Expand Down Expand Up @@ -4228,9 +4229,10 @@ internal bool CheckRefEscape(SyntaxNode node, BoundExpression expr, SafeContext
break;
}

// The result of a ref assignment is its right-hand side.
return CheckRefEscape(
node,
assignment.Left,
assignment.Right,
escapeFrom,
escapeTo,
checkingReceiver: false,
Expand Down Expand Up @@ -4615,14 +4617,13 @@ internal SafeContext GetValEscape(BoundExpression expr, SafeContext localScopeDe
return GetValEscape(conversion.Operand, localScopeDepth);

case BoundKind.AssignmentOperator:
// https://github.com/dotnet/roslyn/issues/73549:
// We do not have a test that demonstrates that the statement below makes a difference.
// If 'localScopeDepth' is always returned, not a single test fails.
// Same for the 'case BoundKind.NullCoalescingAssignmentOperator:' below.
// The result of an assignment is its right-hand side.
return GetValEscape(((BoundAssignmentOperator)expr).Right, localScopeDepth);

case BoundKind.NullCoalescingAssignmentOperator:
return GetValEscape(((BoundNullCoalescingAssignmentOperator)expr).RightOperand, localScopeDepth);
var nullCoalescingAssignment = (BoundNullCoalescingAssignmentOperator)expr;
return GetValEscape(nullCoalescingAssignment.LeftOperand, localScopeDepth)
.Intersect(GetValEscape(nullCoalescingAssignment.RightOperand, localScopeDepth));

case BoundKind.IncrementOperator:
var increment = (BoundIncrementOperator)expr;
Expand Down Expand Up @@ -5376,11 +5377,13 @@ internal bool CheckValEscape(SyntaxNode node, BoundExpression expr, SafeContext

case BoundKind.AssignmentOperator:
var assignment = (BoundAssignmentOperator)expr;
return CheckValEscape(node, assignment.Left, escapeFrom, escapeTo, checkingReceiver: false, diagnostics: diagnostics);
// The result of an assignment is its right-hand side.
return CheckValEscape(node, assignment.Right, escapeFrom, escapeTo, checkingReceiver: false, diagnostics: diagnostics);

case BoundKind.NullCoalescingAssignmentOperator:
var nullCoalescingAssignment = (BoundNullCoalescingAssignmentOperator)expr;
return CheckValEscape(node, nullCoalescingAssignment.LeftOperand, escapeFrom, escapeTo, checkingReceiver: false, diagnostics: diagnostics);
return CheckValEscape(node, nullCoalescingAssignment.LeftOperand, escapeFrom, escapeTo, checkingReceiver: false, diagnostics: diagnostics) &&
CheckValEscape(node, nullCoalescingAssignment.RightOperand, escapeFrom, escapeTo, checkingReceiver: false, diagnostics: diagnostics);

case BoundKind.IncrementOperator:
var increment = (BoundIncrementOperator)expr;
Expand Down
88 changes: 88 additions & 0 deletions src/Compilers/CSharp/Test/Emit3/RefStructInterfacesTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -28614,6 +28614,94 @@ static T F<T>() where T : allows ref struct
comp.VerifyEmitDiagnostics();
}

[Fact]
public void NullCoalescingAssignment_06()
{
var comp = CreateCompilation("""
static class C
{
static T M1<T>(T c1, scoped T c2) where T : allows ref struct
{
return X(c1 ??= c2);
}
static T M2<T>(T c1, scoped T c2) where T : allows ref struct
{
return X(c1 ??= c1);
}
static T M3<T>(T c1, scoped T c2) where T : allows ref struct
{
return X(c2 ??= c2);
}
static T M4<T>(T c1, scoped T c2) where T : allows ref struct
{
return X(c2 ??= c1);
}
static T X<T>(T c) where T : allows ref struct => c;
}
""", targetFramework: s_targetFrameworkSupportingByRefLikeGenerics);

comp.VerifyDiagnostics(
// (5,18): error CS8352: Cannot use variable 'scoped T c2' in this context because it may expose referenced variables outside of their declaration scope
// return X(c1 ??= c2);
Diagnostic(ErrorCode.ERR_EscapeVariable, "c1 ??= c2").WithArguments("scoped T c2").WithLocation(5, 18),
// (5,16): error CS8347: Cannot use a result of 'C.X<T>(T)' in this context because it may expose variables referenced by parameter 'c' outside of their declaration scope
// return X(c1 ??= c2);
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c1 ??= c2)").WithArguments("C.X<T>(T)", "c").WithLocation(5, 16),
// (13,18): error CS8352: Cannot use variable 'scoped T c2' in this context because it may expose referenced variables outside of their declaration scope
// return X(c2 ??= c2);
Diagnostic(ErrorCode.ERR_EscapeVariable, "c2 ??= c2").WithArguments("scoped T c2").WithLocation(13, 18),
// (13,16): error CS8347: Cannot use a result of 'C.X<T>(T)' in this context because it may expose variables referenced by parameter 'c' outside of their declaration scope
// return X(c2 ??= c2);
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c2 ??= c2)").WithArguments("C.X<T>(T)", "c").WithLocation(13, 16),
// (17,18): error CS8352: Cannot use variable 'scoped T c2' in this context because it may expose referenced variables outside of their declaration scope
// return X(c2 ??= c1);
Diagnostic(ErrorCode.ERR_EscapeVariable, "c2 ??= c1").WithArguments("scoped T c2").WithLocation(17, 18),
// (17,16): error CS8347: Cannot use a result of 'C.X<T>(T)' in this context because it may expose variables referenced by parameter 'c' outside of their declaration scope
// return X(c2 ??= c1);
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c2 ??= c1)").WithArguments("C.X<T>(T)", "c").WithLocation(17, 16));
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79054")]
public void NullCoalescingAssignment_07()
{
var comp = CreateCompilation("""
static class C
{
static T M1<T>(T c1, scoped T c2) where T : allows ref struct
{
var c3 = (c1 ??= c2);
return c3; // 1
}
static T M2<T>(T c1, scoped T c2) where T : allows ref struct
{
var c3 = (c1 ??= c1);
return c3; // 2
}
static T M3<T>(T c1, scoped T c2) where T : allows ref struct
{
var c3 = (c2 ??= c2);
return c3; // 3
}
static T M4<T>(T c1, scoped T c2) where T : allows ref struct
{
var c3 = (c2 ??= c1);
return c3; // 4
}
}
""", targetFramework: s_targetFrameworkSupportingByRefLikeGenerics);

comp.VerifyDiagnostics(
// (6,16): error CS8352: Cannot use variable 'c3' in this context because it may expose referenced variables outside of their declaration scope
// return c3; // 1
Diagnostic(ErrorCode.ERR_EscapeVariable, "c3").WithArguments("c3").WithLocation(6, 16),
// (16,16): error CS8352: Cannot use variable 'c3' in this context because it may expose referenced variables outside of their declaration scope
// return c3; // 3
Diagnostic(ErrorCode.ERR_EscapeVariable, "c3").WithArguments("c3").WithLocation(16, 16),
// (21,16): error CS8352: Cannot use variable 'c3' in this context because it may expose referenced variables outside of their declaration scope
// return c3; // 4
Diagnostic(ErrorCode.ERR_EscapeVariable, "c3").WithArguments("c3").WithLocation(21, 16));
}

[Theory]
[CombinatorialData]
public void ObjectCreation_01(bool addStructConstraint)
Expand Down
34 changes: 21 additions & 13 deletions src/Compilers/CSharp/Test/Emit3/Semantics/ExtensionOperatorsTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -24616,9 +24616,18 @@ static class Extensions
// (8,23): error CS8352: Cannot use variable 'scoped C c1' in this context because it may expose referenced variables outside of their declaration scope
// return Y(c += c1);
Diagnostic(ErrorCode.ERR_EscapeVariable, "c1").WithArguments("scoped C c1").WithLocation(8, 23),
// (12,16): error CS8347: Cannot use a result of 'C.Y(C)' in this context because it may expose variables referenced by parameter 'left' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "Y(c = X(c, c1))").WithArguments("C.Y(C)", "left").WithLocation(12, 16),
// (12,22): error CS8347: Cannot use a result of 'C.X(C, C)' in this context because it may expose variables referenced by parameter 'right' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c, c1)").WithArguments("C.X(C, C)", "right").WithLocation(12, 22),
// (12,22): error CS8347: Cannot use a result of 'C.X(C, C)' in this context because it may expose variables referenced by parameter 'right' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c, c1)").WithArguments("C.X(C, C)", "right").WithLocation(12, 22),
// (12,27): error CS8352: Cannot use variable 'scoped C c1' in this context because it may expose referenced variables outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeVariable, "c1").WithArguments("scoped C c1").WithLocation(12, 27),
// (12,27): error CS8352: Cannot use variable 'scoped C c1' in this context because it may expose referenced variables outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeVariable, "c1").WithArguments("scoped C c1").WithLocation(12, 27)
Expand Down Expand Up @@ -24817,9 +24826,12 @@ static class Extensions
// (12,16): error CS8347: Cannot use a result of 'C.Y(C)' in this context because it may expose variables referenced by parameter 'left' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "Y(c = X(c, c1))").WithArguments("C.Y(C)", "left").WithLocation(12, 16),
// (12,18): error CS8352: Cannot use variable 'scoped C c' in this context because it may expose referenced variables outside of their declaration scope
// (12,22): error CS8347: Cannot use a result of 'C.X(C, C)' in this context because it may expose variables referenced by parameter 'left' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c, c1)").WithArguments("C.X(C, C)", "left").WithLocation(12, 22),
// (12,24): error CS8352: Cannot use variable 'scoped C c' in this context because it may expose referenced variables outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeVariable, "c = X(c, c1)").WithArguments("scoped C c").WithLocation(12, 18)
Diagnostic(ErrorCode.ERR_EscapeVariable, "c").WithArguments("scoped C c").WithLocation(12, 24)
);
}

Expand Down Expand Up @@ -24866,16 +24878,19 @@ static class Extensions
// (12,16): error CS8347: Cannot use a result of 'C.Y(C)' in this context because it may expose variables referenced by parameter 'left' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "Y(c = X(c, c1))").WithArguments("C.Y(C)", "left").WithLocation(12, 16),
// (12,18): error CS8352: Cannot use variable 'scoped C c' in this context because it may expose referenced variables outside of their declaration scope
// (12,22): error CS8347: Cannot use a result of 'C.X(C, scoped C)' in this context because it may expose variables referenced by parameter 'left' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeVariable, "c = X(c, c1)").WithArguments("scoped C c").WithLocation(12, 18)
Diagnostic(ErrorCode.ERR_EscapeCall, "X(c, c1)").WithArguments("C.X(C, scoped C)", "left").WithLocation(12, 22),
// (12,24): error CS8352: Cannot use variable 'scoped C c' in this context because it may expose referenced variables outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeVariable, "c").WithArguments("scoped C c").WithLocation(12, 24)
);
}

/// <summary>
/// This is a clone of Microsoft.CodeAnalysis.CSharp.UnitTests.Semantics.RefEscapingTests.UserDefinedBinaryOperator_RefStruct_Compound_ScopedTarget_04
/// </summary>
[Fact]
[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79054")]
public void CompoundAssignment_089_RefSafety()
{
var source = """
Expand All @@ -24902,14 +24917,7 @@ static class Extensions
}
}
""";
CreateCompilation(source).VerifyDiagnostics(
// (12,16): error CS8347: Cannot use a result of 'C.Y(C)' in this context because it may expose variables referenced by parameter 'left' outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeCall, "Y(c = X(c, c1))").WithArguments("C.Y(C)", "left").WithLocation(12, 16),
// (12,18): error CS8352: Cannot use variable 'scoped C c' in this context because it may expose referenced variables outside of their declaration scope
// return Y(c = X(c, c1));
Diagnostic(ErrorCode.ERR_EscapeVariable, "c = X(c, c1)").WithArguments("scoped C c").WithLocation(12, 18)
);
CreateCompilation(source).VerifyDiagnostics();
}

/// <summary>
Expand Down
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