Learn from bool constants and conditional accesses inside ==/!= #52425
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| // : y.ToString(); // 2 | ||
| Diagnostic(ErrorCode.ERR_UseDefViolation, "y").WithArguments("y").WithLocation(12, 15) | ||
| ); | ||
| } |
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Does this change include:
if (e is string s == false) return;
s.ToString(); // ok? From the title I thought that should be covered.
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I expect it does (comparing to bool constants should propagate conditional state). I'll add some tests. Thanks!
| || (expr is BoundConversion | ||
| { | ||
| ConversionKind: ConversionKind.ExplicitNullable or ConversionKind.ImplicitNullable, | ||
| } conv && conv.Operand.Type.IsNonNullableValueType()); |
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&& conv.Operand.Type.IsNonNullableValueType() [](start = 27, length = 45)
When is this part not true? #Resolved
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One test where this is not true is EqualsCondAccess_14. Conversion input is an int?, result type is a long?, and the conversion kind is ImplicitNullable. Further discussion in #52425 (comment)
#Resolved
| @@ -2235,20 +2240,106 @@ private void VisitBinaryOperatorChildren(BoundBinaryOperator node) | |||
| protected virtual void VisitBinaryOperatorChildren(ArrayBuilder<BoundBinaryOperator> stack) | |||
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Consider nullable-enabling this method. #Resolved
| } | ||
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| static bool isEquals(BoundBinaryOperator binary) | ||
| => binary.OperatorKind.Operator() == BinaryOperatorKind.Equal; |
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It's not in the spec, but should we also consider lifted nullable relational operators? ie, >, >=, etc? #Closed
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Perhaps, although I think we'll have to reason out the implications of the fact that:
(int?)null == (int?)nullreturnstrue, but(int?)null >= (int?)nullreturnsfalse.
https://github.com/dotnet/csharplang/blob/main/spec/expressions.md#lifted-operators
I'd like to file it as a "stretch goal" in dotnet/csharplang#4465. #Closed
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I'd like to file it as a "stretch goal" in dotnet/csharplang#4465.
Fine with me.
In reply to: 610945102 [](ancestors = 610945102)
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| struct S | ||
| { | ||
| public static bool operator ==(S left, S right) => false; |
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Would be good to have an example with reference types instead of struct types.
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Have added test EqualsCondAccess_18 for this scenario.
| || (expr is BoundConversion | ||
| { | ||
| ConversionKind: ConversionKind.ExplicitNullable or ConversionKind.ImplicitNullable, | ||
| } conv && conv.Operand.Type!.IsNonNullableValueType()); |
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!. [](start = 51, length = 2)
Why is this safe?
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The ExplicitNullable and ImplicitNullable conversions are only defined on operands with types, so if we get a conversion node with one of these kinds whose operand has no type, it means the conversion is malformed.
https://github.com/dotnet/csharplang/blob/main/spec/conversions.md#implicit-nullable-conversions
https://github.com/dotnet/csharplang/blob/main/spec/conversions.md#explicit-nullable-conversions
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Have expanded a bit on the test EqualsCondAccess_12 to show that the null literal for example is not subject to this conversion (null being the most common typeless expression that we might think would be subject to this conversion).
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Done review pass (commit 14) |
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I believe I've addressed all your feedback @333fred. Please let me know if you have any more. |
Test plan: #51463
Specification: https://github.com/dotnet/csharplang/blob/main/proposals/improved-definite-assignment.md#-relational-equality-operator-expressions