Bug 17647 - Mono C# compiler incorrectly emits CS0695 for concrete instances of generic types
Summary: Mono C# compiler incorrectly emits CS0695 for concrete instances of generic t...
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 3.2.x
Hardware: All All
: --- normal
Target Milestone: ---
Assignee: Marek Safar
Depends on:
Reported: 2014-02-06 17:53 UTC by Richard Cook
Modified: 2014-02-25 13:17 UTC (History)
4 users (show)

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

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Description Richard Cook 2014-02-06 17:53:32 UTC
Here's a minimal repro case:

===== Test.cs =====
class A<T>
    public interface IB { }

class C { }
class D { }

class E : A<C>.IB, A<D>.IB
===== End of Test.cs =====

Here's the output from running against Mono master:

$ mcs --version
Mono C# compiler version
$ mcs Test.cs /target:library
Test.cs(11,7): error CS0695: `E' cannot implement both `A<C>.IB' and `A<D>.IB' because they may unify for some type parameter substitutions
Compilation failed: 1 error(s), 0 warnings

Here's the output from running against Mono 2.10.9:

$ mcs --version
Mono C# compiler version
$ mcs Test.cs /target:library

This also compiles as expected using csc.exe. It looks like the compiler is incorrectly treating A<C> and A<D> as generic types instead of concrete types.

Thanks, Richard.

Richard Cook | Principal engineer
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Comment 1 Marek Safar 2014-02-17 05:16:11 UTC
Fixed in master
Comment 2 Richard Cook 2014-02-17 12:25:19 UTC
Thank you. I found the commit: https://github.com/mono/mono/commit/3f08ba83cc73218377a3b10929f87e1335e5bd63