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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 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
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#if swift(>=6)
@_spi(RawSyntax) internal import SwiftSyntax
#else
@_spi(RawSyntax) import SwiftSyntax
#endif
/// A type that can be used to make sure that a loop in the parser makes process.
///
/// See `TokenConsumer.hasProgressed` for details.
struct LoopProgressCondition {
var currentToken: Lexer.Lexeme?
init() {}
/// Implementation of the above `evaluate` methods.
fileprivate mutating func evaluate(_ currentToken: Lexer.Lexeme) -> Bool {
defer {
self.currentToken = currentToken
}
guard let previousToken = self.currentToken else {
return true
}
let hasMadeProgress = currentToken.cursor.hasProgressed(comparedTo: previousToken.cursor)
assert(hasMadeProgress, "Loop should always make progress")
return hasMadeProgress
}
}
// Implementing the extension separately on `Parser` and `Parser.Lookahead` is
// ~1.5% faster than implementing it on `TokenConsumer`.
extension Parser {
/// Check that the token consumer has made progress since `hasProgress` was
/// called the last time with this `loopProgress`.
///
/// In assert builds, this traps if the loop has not made any parser progress
/// in between two iterations, ie. it checks if the parser's `currentToken`
/// has changed in between two calls to `evaluate`.
/// In non-assert builds, `evaluate()` returns `false` if the loop has not made
/// progress, thus aborting the loop.
@inline(__always)
func hasProgressed(_ loopProgress: inout LoopProgressCondition) -> Bool {
return loopProgress.evaluate(self.currentToken)
}
}
extension Parser.Lookahead {
/// Check that the token consumer has made progress since `hasProgress` was
/// called the last time with this `loopProgress`.
///
/// In assert builds, this traps if the loop has not made any parser progress
/// in between two iterations, ie. it checks if the parser's `currentToken`
/// has changed in between two calls to `evaluate`.
/// In non-assert builds, `evaluate()` returns `false` if the loop has not made
/// progress, thus aborting the loop.
@inline(__always)
func hasProgressed(_ loopProgress: inout LoopProgressCondition) -> Bool {
return loopProgress.evaluate(self.currentToken)
}
}
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