Flow analysis of with-expressions #44644
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Changes records to generate init-only properties instead of get-only, and modifies the `with` expression to treat arguments as assignments to the left-hand side, with the safety rules of object initializers (meaning init-only assignments are allowed). Also changes records to generate a Clone method and a copy constructor. The clone calls the copy constructor and the copy constructor does a memberwise copy of the instance fields of the other type. This change also tries to simplify and reuse more pieces of binding and lowering from other initializer-based forms. The with-expression is now bound as though it were an assignment to a field or member access on a call to the Clone method.
src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.DebugVerifier.cs
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…hesizedRecordClone.cs Co-authored-by: Jared Parsons <jaredpparsons@gmail.com>
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After dotnet/csharplang#3527 has been merged, please work with @agocke to draft spec language for definite assignment of with expressions to add to the records spec. |
| B b = new B(""hello"", null); | ||
| if (flag) | ||
| { | ||
| b.X.ToString(); // PROTOTYPE(records) |
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// PROTOTYPE(records) [](start = 28, length = 21)
Please replace PROTOTYPE with link to issue.
Note, I agree this should work as we map constructor parameters to properties (just like we do for tuples or Nullable<T>).
| // due to limitations of object initializer analysis. | ||
| // Tracking in https://github.com/dotnet/roslyn/issues/44759 | ||
| comp.VerifyDiagnostics(); | ||
| } |
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} [](start = 8, length = 1)
The following nullability scenarios should already work because of the sharing of logic, but may be worth capturing:
x with { P1 = (other = null), P2 = other.M() } // possible dereferenceb with { X = M(out s), Y = s }
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| data class B(string? X) | ||
| { | ||
| public B? Clone() => new B(X); |
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It sounds like some upcoming spec changes are probably going to make this necessary to define in metadata if we want to test this scenario.
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I think I will squash this PR when merging. @agocke |
Fixes #44672
Related to #40726
/cc @agocke @dotnet/roslyn-compiler