Method bindOptionalChain

internal/binder/binder.go:2363–2388

(node *ast.Node, trueTarget *ast.FlowLabel, falseTarget *ast.FlowLabel)

}

func (b *Binder) bindOptionalChain(node *ast.Node, trueTarget *ast.FlowLabel, falseTarget *ast.FlowLabel) {
	// For an optional chain, we emulate the behavior of a logical expression:
	//
	// a?.b         -> a && a.b
	// a?.b.c       -> a && a.b.c
	// a?.b?.c      -> a && a.b && a.b.c
	// a?.[x = 1]   -> a && a[x = 1]
	//
	// To do this we descend through the chain until we reach the root of a chain (the expression with a `?.`)
	// and build it's CFA graph as if it were the first condition (`a && ...`). Then we bind the rest
	// of the node as part of the "true" branch, and continue to do so as we ascend back up to the outermost
	// chain node. We then treat the entire node as the right side of the expression.
	var preChainLabel *ast.FlowLabel
	if ast.IsOptionalChainRoot(node) {
		preChainLabel = b.createBranchLabel()
	}
	b.bindOptionalExpression(node.Expression(), core.IfElse(preChainLabel != nil, preChainLabel, trueTarget), falseTarget)
	if preChainLabel != nil {
		b.currentFlow = b.finishFlowLabel(preChainLabel)
	}
	b.doWithConditionalBranches((*Binder).bindOptionalChainRest, node, trueTarget, falseTarget)
	if ast.IsOutermostOptionalChain(node) {
		b.addAntecedent(trueTarget, b.createFlowCondition(ast.FlowFlagsTrueCondition, b.currentFlow, node))
		b.addAntecedent(falseTarget, b.createFlowCondition(ast.FlowFlagsFalseCondition, b.currentFlow, node))
	}
}

func (b *Binder) bindOptionalExpression(node *ast.Node, trueTarget *ast.FlowLabel, falseTarget *ast.FlowLabel) {
	b.doWithConditionalBranches((*Binder).bind, node, trueTarget, falseTarget)