Dart Functions - The forEach() and map() functions in Dart. 

Dart automatically infers the data type. It knows that the list contains integers. So item will be of type int. Should show it when you hover over item.

​@@JohanJurrius ok but if I try to add some DataType then it is give error, I write list.forEach(int item) => print(item). then it is giving error. and can't I change the variable name in the print like list.forEach(int item) => print(MyItem) ?

@@heavenlife5619 You are missing extra set of parenthesis around (int item) => print(item), forEach takes in a function as an argument, here it is the anonymous function (int item) => print(item). Second, the 'item' is the variable you are passing on to the right side of your anon function. Sometimes you may pass two different items, (int i, int j) = i + j; Therefore variable name(s) on right side, where you are processing them, should match to the variable name(s) on the left side of anon function where you are passing them. final numbers = [1, 2, 6, 7]; numbers.forEach((int element) => print(element)); //works. Third, as sir has explained, dart does the inference automatically so that while coding we ourselves dont type wrong types down the stream as well as it reduces unnecessary typing which reduces time wasted on typing boilerplate code, and that time you can spend on optimising it, or writing new code.

Let me know if this answers your question: stackoverflow.com/questions/52345694/dart-iterablee-vs-liste-always-use-iterable

@@JohanJurrius I guess i got it. list is a child class of iterable, like num has int and double, we can use num but its better to use int when we only need int. Also iterable is computed as needed.