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[Fact] |
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public void UserDefinedBinaryOperator_RefStruct_Compound_ScopedTarget_04() |
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{ |
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var source = """ |
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public ref struct C |
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{ |
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public static C operator +(scoped C left, C right) => right; |
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public static C X(scoped C left, C right) => right; |
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public static C Y(C left) => left; |
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public C M1(scoped C c, C c1) |
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{ |
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return Y(c += c1); |
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} |
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public C M2(scoped C c, C c1) |
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{ |
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return Y(c = X(c, c1)); |
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} |
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} |
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"""; |
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CreateCompilation(source).VerifyDiagnostics( |
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// (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 |
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// return Y(c = X(c, c1)); |
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Diagnostic(ErrorCode.ERR_EscapeCall, "Y(c = X(c, c1))").WithArguments("C.Y(C)", "left").WithLocation(12, 16), |
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// (12,18): error CS8352: Cannot use variable 'scoped C c' in this context because it may expose referenced variables outside of their declaration scope |
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// return Y(c = X(c, c1)); |
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Diagnostic(ErrorCode.ERR_EscapeVariable, "c = X(c, c1)").WithArguments("scoped C c").WithLocation(12, 18) |
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); |
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} |
The error in the test above is unexpected. First, both M1 and M2 result in equivalent IL code, hence both should report equivalent diagnostics. Second, the assignment returns its right-hand side, so the return expression is equivalent to Y(X(c, c1)) which is ref safe.
See also #78987 (comment).