This type already contains a property with the name "{0}" (AJTERR10059)

A property in a type was declared, although one with the same name already exists.

test: string := "";
test: string := "";/*
^^^^ A property with this name was already defined */

testFunction ||: void { }
testFunction ||: void { }/*
^^^^^^^^^^^^ A property with this name was already defined */

Use distinct names for every property.