c# - C# Visual Studio 2012 does not produce a helpful compilation error when failing to return a value, while VS 2010 does

Question

Steps to reproduce: Compile this piece of code:

    public string SomeMethod()
    {
        return;
    }

Visual Studio 2012 produce this unhelpful compilation error:

    Could not copy the file "<insert path of executable>" because it was not found.

Visual Studio 2010 produces this helpful compilation error:

    An object of a type convertible to 'string' is required

Visual Studio Versions:

• VS 2012: Version 11.0.50727.1
• VS 2010: Version 10.0.40219.1

We upgraded to JetBrains ReSharper 7.0.1 C# Edition at the same time as upgrading to VS 2012, but reproducing this while suspending ReSharper produces the same results.