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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 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
//
//===----------------------------------------------------------------------===//
import Foundation
import SwiftSyntax
/// Redundant labels are forbidden in case patterns.
///
/// In practice, *all* case pattern labels should be redundant.
///
/// Lint: Using a label in a case statement yields a lint error unless the label does not match the
/// binding identifier.
///
/// Format: Redundant labels in case patterns are removed.
@_spi(Rules)
public final class NoLabelsInCasePatterns: SyntaxFormatRule {
public override func visit(_ node: SwitchCaseLabelSyntax) -> SwitchCaseLabelSyntax {
var newCaseItems: [SwitchCaseItemSyntax] = []
for item in node.caseItems {
guard
var exprPattern = item.pattern.as(ExpressionPatternSyntax.self),
var funcCall = exprPattern.expression.as(FunctionCallExprSyntax.self)
else {
newCaseItems.append(item)
continue
}
// Search function call argument list for violations
var newArguments = LabeledExprListSyntax()
for argument in funcCall.arguments {
guard
let label = argument.label,
let unresolvedPat = argument.expression.as(PatternExprSyntax.self),
let valueBinding = unresolvedPat.pattern.as(ValueBindingPatternSyntax.self)
else {
newArguments.append(argument)
continue
}
// Remove label if it's the same as the value identifier
let name = valueBinding.pattern.trimmedDescription
guard name == label.text else {
newArguments.append(argument)
continue
}
diagnose(.removeRedundantLabel(name: name), on: label)
var newArgument = argument
newArgument.label = nil
newArgument.colon = nil
newArguments.append(newArgument)
}
var newItem = item
funcCall.arguments = newArguments
exprPattern.expression = ExprSyntax(funcCall)
newItem.pattern = PatternSyntax(exprPattern)
newCaseItems.append(newItem)
}
var result = node
result.caseItems = SwitchCaseItemListSyntax(newCaseItems)
return result
}
}
extension Finding.Message {
fileprivate static func removeRedundantLabel(name: String) -> Finding.Message {
"remove the label '\(name)' from this 'case' pattern"
}
}
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