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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
/*
Common protocols for AST nodes and values. These allow us
to do more capabilities-based programming, currently
implemented on top of existentials.
*/
// MARK: - AST parent/child
public protocol _ASTNode: _ASTPrintable {
var location: SourceLocation { get }
}
extension _ASTNode {
var startPosition: Source.Position { location.start }
var endPosition: Source.Position { location.end }
}
protocol _ASTParent: _ASTNode {
var children: [AST.Node] { get }
}
extension AST.Concatenation: _ASTParent {}
extension AST.Alternation: _ASTParent {}
extension AST.Group: _ASTParent {
var children: [AST.Node] { [child] }
}
extension AST.Quantification: _ASTParent {
var children: [AST.Node] { [child] }
}
extension AST.AbsentFunction: _ASTParent {
public var children: [AST.Node] {
switch kind {
case .repeater(let a), .stopper(let a): return [a]
case .expression(let a, _, let c): return [a, c]
case .clearer: return []
}
}
}
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