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>>> Named parameter.
f(  {  optional  =  null  }  ) {}
<<< 3.7
f({optional = null}) {}
>>> Named parameter with old separator.
### This syntax is no longer supported by new versions of Dart, but we want to
### support formatting older versions if possible.
f(  {  optional  :  1  +  2  }  ) {}
<<< 3.7
f({optional: 1 + 2}) {}
>>> Optional positional parameter.
f(  [  optional  =  1  +  2  ]  ) {}
<<< 3.7
f([optional = 1 + 2]) {}
>>> Split on positional default.
doStuff([parameter = veryLongDefaultValueThatSplits, another =
veryLongDefaultValue, third = alsoQuiteLongDefaultValue]) {}
<<< 3.7
doStuff([
  parameter =
      veryLongDefaultValueThatSplits,
  another = veryLongDefaultValue,
  third = alsoQuiteLongDefaultValue,
]) {}
>>> Split on named default.
doStuff({parameter = veryLongDefaultValueThatSplits, another =
veryLongDefaultValue, third = alsoAQuiteLongDefaultValue}) {}
<<< 3.7
doStuff({
  parameter =
      veryLongDefaultValueThatSplits,
  another = veryLongDefaultValue,
  third = alsoAQuiteLongDefaultValue,
}) {}
>>> Prefer block-like splitting for collection default values.
function([param = [element, element, element, element]]) { body; }
<<< 3.7
function([
  param = [
    element,
    element,
    element,
    element,
  ],
]) {
  body;
}
>>> Function typed parameter with default value.
f([callback() = constantFunction]) {}
<<< 3.7
f([callback() = constantFunction]) {}
>>> Split in function typed parameter parameter list with default value.
f([callback(SomeLongType longParameter, AnotherType anotherParameter) = constantFunction]) {}
<<< 3.7
f([
  callback(
        SomeLongType longParameter,
        AnotherType anotherParameter,
      ) =
      constantFunction,
]) {}
<<< 3.13
f([
  callback(
    SomeLongType longParameter,
    AnotherType anotherParameter,
  ) = constantFunction,
]) {}
>>> Split in function typed parameter default value.
f([callback(SomeType parameter) = const CallableClass(someLongConstantArgument, anotherConstantArgument)]) {}
<<< 3.7
f([
  callback(
    SomeType parameter,
  ) = const CallableClass(
    someLongConstantArgument,
    anotherConstantArgument,
  ),
]) {}