Bug 8387 - Mono MCS doesn't allow implicit double to enum conversion, but MS CSC does
Summary: Mono MCS doesn't allow implicit double to enum conversion, but MS CSC does
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: unspecified
Hardware: PC Windows
: --- normal
Target Milestone: ---
Assignee: Marek Safar
Depends on:
Reported: 2012-11-13 19:18 UTC by Brett van Swelm
Modified: 2012-11-14 02:48 UTC (History)
1 user (show)

Is this bug a regression?: ---
Last known good build:

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Description Brett van Swelm 2012-11-13 19:18:36 UTC
Mono MCS doesn't allow implicit double to enum conversion, but MS CSC does.

With "D:\Applications\Mono-2.11.4\bin" and
"C:\Windows\Microsoft.NET\Framework\v4.0.30319" in the path on my Windows 7

===== ConvertDouble =====
using System;

public class Outer {
    public Outer(Inner inner) {}
    public enum Inner { ONE, TWO }

public class ConvertDouble {
    public static void Main(String[] args) {
        new Outer(0.0);
===== end =====

Section "6.1.3 Implicit enumeration conversions" of the C# language
specification states "An implicit enumeration conversion permits the
decimal-integer-literal 0 to be converted to any enum-type", which seems to
exclude implicit conversions to enums from floating point numbers. It seems
like MCS is correct and CSC is too permissive, however if compatibility
with CSC is a goal this may be worth fixing.

$ csc ConvertDouble.cs
Microsoft (R) Visual C# Compiler version 4.0.30319.17929
for Microsoft (R) .NET Framework 4.5
Copyright (C) Microsoft Corporation. All rights reserved.

$ mcs ConvertDouble.cs
ConvertDouble.cs(10,9): error CS1502: The best overloaded method match for
`Outer.Outer(Outer.Inner)' has some invalid arguments
ConvertDouble.cs(4,12): (Location of the symbol related to previous error)
ConvertDouble.cs(10,19): error CS1503: Argument `#1' cannot convert `double'
expression to type `Outer.Inner'
Compilation failed: 2 error(s), 0 warnings


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Comment 1 Brett van Swelm 2012-11-13 19:22:59 UTC
Some more examples of differences (accepted by CSC but not MCS):

    new Outer(0.0f); // "float" literal
    new Outer(0.0m); // "decimal" literal
    new Outer(0.0e47); // "double" using scientific notation
    new Outer(0.0 / 42.0);
Comment 2 Marek Safar 2012-11-14 02:48:59 UTC
This is one of the cases where we are standard compatible but not csc compatible. Please fix your code to work with mcs