Exponentiation should have a different prioritisation for solidity version bellow 0.8.0

[Janther]

originally Solidity's exponentiation had left associativity which was fixed at 0.8.0.

If I set the compiler bellow 0.8.0 I expect the output of a ** b ** c to resemble the following:

{
  "leftOperand": {
    "leftOperand": "a",
    "operator": "**",
    "rightOperand": "b"
  },
  "operator": "**",
  "rightOperand": "c"
}

Instead I the parser returns something like:

{
  "leftOperand": "a",
  "operator": "**",
  "rightOperand": {
    "leftOperand": "b",
    "operator": "**",
    "rightOperand": "c"
  }
}

This is just a simplification of the actual result but it helps as a guide.

UPDATE:
With further testing 0.5.8 works as expected while 0.7.0 has this bug. Will need to investigate further to figure out in which versions this doesn't work properly.

[Xanewok]

@OmarTawfik this is probably correct:

We currently define the 0.6.0 as the version that changed this:

slang/crates/solidity/inputs/language/src/definition.rs

Lines 3359 to 3374 in 0630345

	PrecedenceExpression(
	name = ExponentiationExpression,
	operators = [
	// Before '0.6.0', it was left-associative:
	PrecedenceOperator(
	model = BinaryLeftAssociative,
	enabled = Till("0.6.0"),
	fields = (operator = Required(AsteriskAsterisk))
	),
	// In '0.6.0', it became right-associative:
	PrecedenceOperator(
	model = BinaryRightAssociative,
	enabled = From("0.6.0"),
	fields = (operator = Required(AsteriskAsterisk))
	)
	]

However, looking at the commits upstream, it seems that 0.8.0 is only the version that changed the associativity itself: ethereum/solidity@13e7012.

What has changed in 0.6.0 are the type semantics, where the type of the base is used for the result, rather than the operand's: ethereum/solidity@33f7f96.