dart - Why can I assign List<dynamic> to a List<String>? -

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i getting confused around how type checking works dart. shown, assigning general list<dynamic> list<string> ok. means can assign content in list, not string. why that?

void main() {   list<string> a;   = [1];                 // pass   = new list<int>();     // fail   = 1;                   // fail   = new list<string>();  // pass   a.add(1);                // fail }

the dynamic type special. means "turn off type checking this, know i'm doing".

in example, assign list<dynamic> instance list<string> variable. static type checker sees: list list, that's ok, , type parameter dynamic, i'll not check @ all, programmer must know doing.

whenever use dynamic type, or part of type, taking full responsibility typing being correct. system let whatever want.

even without dynamic, dart type system isn't safe. means can create programs no static type warnings still fail type error @ runtime. languages have problem, actually, contain parameterized types either co- or contra-variant subtyping. or casts.


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