prefer_const_constructors

Use 'const' with the constructor to improve performance.

The analyzer produces this diagnostic when an invocation of a const constructor isn't either preceded by const or in a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more.

The following code produces this diagnostic because the invocation of the const constructor is neither prefixed by const nor in a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more:

class C {
  const C();
}
​
C c = C();

If the context can be made a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more, then do so:

class C {
  const C();
}
​
const C c = C();

If the context can't be made a constant contextConstant contextA region of code where the const keyword is implied and everything within that region must be a constant. Learn more, then add const before the constructor invocation:

class C {
  const C();
}
​
C c = const C();