Narrow types after cast in generator based Handlers

[staabm]

as discussed in #4595 (review)

see

phpstan-src/src/Analyser/LegacyTypeSpecifier.php

Lines 198 to 221 in d7482af

	} elseif ($expr instanceof Expr\Cast\Bool_) {
	return $this->specifyTypesInCondition(
	$scope,
	new Node\Expr\BinaryOp\Equal($expr->expr, new ConstFetch(new Name\FullyQualified('true'))),
	$context,
	)->setRootExpr($expr);
	} elseif ($expr instanceof Expr\Cast\String_) {
	return $this->specifyTypesInCondition(
	$scope,
	new Node\Expr\BinaryOp\NotEqual($expr->expr, new Node\Scalar\String_('')),
	$context,
	)->setRootExpr($expr);
	} elseif ($expr instanceof Expr\Cast\Int_) {
	return $this->specifyTypesInCondition(
	$scope,
	new Node\Expr\BinaryOp\NotEqual($expr->expr, new Node\Scalar\LNumber(0)),
	$context,
	)->setRootExpr($expr);
	} elseif ($expr instanceof Expr\Cast\Double) {
	return $this->specifyTypesInCondition(
	$scope,
	new Node\Expr\BinaryOp\NotEqual($expr->expr, new Node\Scalar\DNumber(0.0)),
	$context,
	)->setRootExpr($expr);