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Unexpected compiler warning for "<T extends ...>" return type


Unexpected compiler warning for "<T extends ...>" return type

By : user2953896
Date : November 21 2020, 07:31 AM
will help you The generic method in Example is supposed to work where T can be any type extending Example, but you have tried to implement it in ExampleImpl in such a way that it always returns an ExampleImpl. This may be ok if ExampleImpl is the only class implementing Example, but if there are others you can get a ClassCastException at runtime.
In the following example, we instantiate a new ExampleImpl, cast it to the base interface and then call the generic method init() with T equal to ExampleImpl2. This is supposed to return an ExampleImpl2, but since you returned this, it throws a ClassCastException. This is why your code must generate a warning.
code :
public class StackOverflowQuestion {

    interface Example {

        <T extends Example> T init();
    }

    static class ExampleImpl implements Example {

        @Override
        public ExampleImpl init() {
            return this;
        }
    }

    static class ExampleImpl2 implements Example {

        @Override
        public <T extends Example> T init() {
            return null;
        }
    }

    public static void main(String[] args) {
        ExampleImpl2 e2 = ((Example) new ExampleImpl()).<ExampleImpl2>init();
    }
}


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"Unchecked generic array creation for varargs parameter of type Matcher <? extends String> []" warning u

"Unchecked generic array creation for varargs parameter of type Matcher <? extends String> []" warning u


By : Sn8wm8n
Date : March 29 2020, 07:55 AM
may help you . If this is Java 7+, then the library you're using can annotate the method with @SafeVarargs. However, this is not under your control.
Otherwise there is no way to avoid an unchecked warning with this method, because the method fundamentally requires an array of a parameterized type, and it is impossible to obtain a non-null value of this type without an unchecked operation somewhere (either in your method or some other method that you call).
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By : Pravin
Date : March 29 2020, 07:55 AM
I wish did fix the issue. C does not have an implicit conversion from const-qualified pointer types to non-const-qualified ones, so you should add an explicit one, i.e. a cast. Then the warning will go away:
code :
unsigned char* getBeginning(const unsigned char * Packet)
{
                    return (unsigned char *)Packet+3;
}
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By : Dave 'Medium' Wensle
Date : March 29 2020, 07:55 AM
it helps some times Closure Compiler does not have any "hint" mechanism to modify the Control Flow Analysis. You are stuck with disabling the warning group altogether, @suppress annotations or modifying the code.
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By : Ajeet Sirohi
Date : March 29 2020, 07:55 AM
wish helps you Figured out the issue: I have some of my source files accidentally listed under "Copy Bundle Resources" in Build Phases. Fixed by removing those files from "Copy Bundle Resources".
Can I enable the "Function doesn't return a value on all code paths" warning for "Value Type" functi

Can I enable the "Function doesn't return a value on all code paths" warning for "Value Type" functi


By : user2698692
Date : March 29 2020, 07:55 AM
may help you . Under the Project Properties > Compile, there's a section called "Warning configurations". In there, you can set if you want these type of condition as warning, error or none.
In this case, the condition "Function returning intrinsic value type without return value" may be set to "None". It would also be possible to disable it with #Disable Warning BC42353
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