Bug 37444 - Locking on generic type parameter results in compiler error
Summary: Locking on generic type parameter results in compiler error
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 4.0.0
Hardware: PC Linux
: --- normal
Target Milestone: ---
Assignee: Marek Safar
Depends on:
Reported: 2016-01-06 12:07 UTC by Tomasz Malinowski
Modified: 2016-08-01 15:37 UTC (History)
1 user (show)

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

sample code (375 bytes, text/plain)
2016-01-06 12:07 UTC, Tomasz Malinowski

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Description Tomasz Malinowski 2016-01-06 12:07:06 UTC
Created attachment 14465 [details]
sample code

Locking on non-constrained generic type parameter results in the following compiler error: "`TKey' is not a reference type as required by the lock statement (CS0185)" (see attached code sample).

This seems to actually be The Right Thing (see https://msdn.microsoft.com/en-us/library/aa479858.aspx#bestpractices_topic6), but Microsoft compiler raises neither error nor warning in this situation, leading to some code failing to build on Mono despite building on .NET.
Comment 1 Marek Safar 2016-01-11 12:52:31 UTC
The spec is not very strict here (yet) but I think we are doing right think. I'll see if the wording can be fixes to disallow this explicitly.
Comment 2 Marek Safar 2016-08-01 15:37:55 UTC
The spec forbids this code so csc just violates the spec and we won't follow in this case as it does not make sense to mis-compile this code.