Dart: how many string objects are allocated when using the * operator in an assignment?

In the following code, I would expect 3 total string allocations to be made:

String str  = "abc";
String str2 = str*2; //"abcabc"

• 1 when creating str


• another when creating a copy of str to concatenate with itself


• a third to hold the concatenation of str with itself (str2)

Are there fewer or more allocations made in this example? I know that strings are immutable in Dart but I'm unsure how these operations work under the hood because of this property.