Bug 17519 - Incorrect error CS0165 "Use of unassigned local variable" for identically named type and local variable
Summary: Incorrect error CS0165 "Use of unassigned local variable" for identically nam...
Status: RESOLVED FIXED
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 3.2.x
Hardware: All All
: --- normal
Target Milestone: ---
Assignee: Marek Safar
URL:
Depends on:
Blocks:
 
Reported: 2014-01-30 14:45 UTC by Richard Cook
Modified: 2014-02-25 13:17 UTC (History)
4 users (show)

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

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Status:
RESOLVED FIXED

Description Richard Cook 2014-01-30 14:45:45 UTC
When a method defines a local variable named identically to a class and attempts to invoke a static method on the class, mcs incorrectly reports error CS0165 "Use of unassigned local variable". Here's a simple repro case:

===== Test.cs =====

public class A
{
    public static A Get() { return null; }
}

public class Test
{
    void M()
    {
        A A = A.Get();
    }
}

===== End of Test.cs =====

===== Sample command lines =====

# From Visual Studio 2013 command prompt:
$ csc /target:library Test.cs
Microsoft (R) Visual C# Compiler version 12.0.21005.1
Copyright (C) Microsoft Corporation. All rights reserved.

[No errors]

# From Mono 2.10.9 command prompt:
$ mcs /target:library Test.cs

[No errors]

# From Mono 3.2.3 command prompt:
$ mcs /target:library Test.cs
Class1.cs(10,15): error CS0165: Use of unassigned local variable `A'
Compilation failed: 1 error(s), 0 warnings

===== End of sample command lines =====

Thus, this source file is compiled by csc and mcs version 2.10.9. mcs 3.x fails to compile this code. This looks like a regression between the 2.x and 3.x series of the mcs compiler.

Thanks, Richard.

Richard Cook | Principal engineer
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Comment 1 Marek Safar 2014-01-30 14:53:24 UTC
Already fixed in master and Mono 3.2.7
Comment 2 Richard Cook 2014-01-30 14:57:50 UTC
Could you provide the commit hash for the fix?
Comment 3 Marek Safar 2014-01-30 15:00:27 UTC
I don't think there was single commit. It was probably fixes as part of flow-analysis rewrite which is ~10 commits