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turansky

06/04/2021, 6:39 PM
Is it legal to declare same public 
typealias
in different modules? Like this one:
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package react

typealias FC<P> = FunctionalComponent<P>
z

Zach Klippenstein (he/him) [MOD]

06/04/2021, 7:04 PM
In the same package as well?
t

turansky

06/04/2021, 7:31 PM
Yes
It works, but it doesn't look legal :(
a

andylamax

06/04/2021, 10:21 PM
should not be legal
t

turansky

06/04/2021, 11:19 PM
k

kqr

06/05/2021, 1:09 PM
if it is same same is it a problem?
t

turansky

06/05/2021, 1:32 PM
Looks like bomb for me
d

dmitriy.novozhilov

06/06/2021, 7:21 PM
This is common problem from JVM world. Imagine that you have such module structure and classes in it (pure java):
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// MODULE: lib1
public class A {
    public void foo() {}
}

// MODULE: lib2
public class A {
    public void bar() {}
}

// MODULE: app (depends on lib1 and lib 2)
public class Main {
    public static void test(A a) {
        a.foo(); // (1)
        a.bar(); // (2)
    }
}
Which line (
(1)
or 
(2)
) will be assumed as compile error? What happend on runtime if we comment errornous line?
Answer is simple: classpath order. JVM, java and kotlin lives in assumption that for each fully qualified name can be found only one class (or none). So on jmv (and javac, and kotlinc) problem of different classes with same fqn is resolved very simple: some fqn is resolved to first class which was found on classpath of compilation session/runtime So even if we comment line 
(1)
and it will be compiled successfully (because compilation classpath was 
lib2.jar;lib1.jar
) there is no guarantee that this code won't throw 
NoSuchMethodError
at runtime (where classpath can be 
lib1.jar;lib2.jar
)
Unfortunately, there is no way to protect users from such kind of errors. Even if compiler will check that there are no clashes between names from compiled module and from dependencies or even between just names in dependencies (such check will cost a lot of performance), then there is no guarantee that on runtime there will be same versions of dependencies
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