Merge pull request #765 from harlanhaskins/hhaskins/retro-activity

Add lint warning for retroactive conformances

Author: allevato

Documentation/RuleDocumentation.md

@@ -14,6 +14,7 @@ Here's the list of available rules:
 - [AlwaysUseLiteralForEmptyCollectionInit](#AlwaysUseLiteralForEmptyCollectionInit)
 - [AlwaysUseLowerCamelCase](#AlwaysUseLowerCamelCase)
 - [AmbiguousTrailingClosureOverload](#AmbiguousTrailingClosureOverload)
+- [AvoidRetroactiveConformances](#AvoidRetroactiveConformances)
 - [BeginDocumentationCommentWithOneLineSummary](#BeginDocumentationCommentWithOneLineSummary)
 - [DoNotUseSemicolons](#DoNotUseSemicolons)
 - [DontRepeatTypeInStaticProperties](#DontRepeatTypeInStaticProperties)
@@ -93,6 +94,14 @@ Lint: If two overloaded functions with one closure parameter appear in the same
 
 `AmbiguousTrailingClosureOverload` is a linter-only rule.
 
+### AvoidRetroactiveConformances
+
+`@retroactive` conformances are forbidden.
+
+Lint: Using `@retroactive` results in a lint error.
+
+`AvoidRetroactiveConformances` is a linter-only rule.
+
 ### BeginDocumentationCommentWithOneLineSummary
 
 All documentation comments must begin with a one-line summary of the declaration.

Sources/SwiftFormat/CMakeLists.txt

@@ -57,6 +57,7 @@ add_library(SwiftFormat
   Rules/AlwaysUseLiteralForEmptyCollectionInit.swift
   Rules/AlwaysUseLowerCamelCase.swift
   Rules/AmbiguousTrailingClosureOverload.swift
+  Rules/AvoidRetroactiveConformances.swift
   Rules/BeginDocumentationCommentWithOneLineSummary.swift
   Rules/DoNotUseSemicolons.swift
   Rules/DontRepeatTypeInStaticProperties.swift

Sources/SwiftFormat/Core/Pipelines+Generated.swift

@@ -64,6 +64,14 @@ class LintPipeline: SyntaxVisitor {
     onVisitPost(rule: TypeNamesShouldBeCapitalized.self, for: node)
   }
 
+  override func visit(_ node: AttributeSyntax) -> SyntaxVisitorContinueKind {
+    visitIfEnabled(AvoidRetroactiveConformances.visit, for: node)
+    return .visitChildren
+  }
+  override func visitPost(_ node: AttributeSyntax) {
+    onVisitPost(rule: AvoidRetroactiveConformances.self, for: node)
+  }
+
   override func visit(_ node: ClassDeclSyntax) -> SyntaxVisitorContinueKind {
     visitIfEnabled(AllPublicDeclarationsHaveDocumentation.visit, for: node)
     visitIfEnabled(AlwaysUseLowerCamelCase.visit, for: node)
@@ -193,12 +201,14 @@ class LintPipeline: SyntaxVisitor {
   }
 
   override func visit(_ node: ExtensionDeclSyntax) -> SyntaxVisitorContinueKind {
+    visitIfEnabled(AvoidRetroactiveConformances.visit, for: node)
     visitIfEnabled(DontRepeatTypeInStaticProperties.visit, for: node)
     visitIfEnabled(NoAccessLevelOnExtensionDeclaration.visit, for: node)
     visitIfEnabled(UseTripleSlashForDocumentationComments.visit, for: node)
     return .visitChildren
   }
   override func visitPost(_ node: ExtensionDeclSyntax) {
+    onVisitPost(rule: AvoidRetroactiveConformances.self, for: node)
     onVisitPost(rule: DontRepeatTypeInStaticProperties.self, for: node)
     onVisitPost(rule: NoAccessLevelOnExtensionDeclaration.self, for: node)
     onVisitPost(rule: UseTripleSlashForDocumentationComments.self, for: node)

Sources/SwiftFormat/Core/RuleNameCache+Generated.swift

@@ -19,6 +19,7 @@ public let ruleNameCache: [ObjectIdentifier: String] = [
   ObjectIdentifier(AlwaysUseLiteralForEmptyCollectionInit.self): "AlwaysUseLiteralForEmptyCollectionInit",
   ObjectIdentifier(AlwaysUseLowerCamelCase.self): "AlwaysUseLowerCamelCase",
   ObjectIdentifier(AmbiguousTrailingClosureOverload.self): "AmbiguousTrailingClosureOverload",
+  ObjectIdentifier(AvoidRetroactiveConformances.self): "AvoidRetroactiveConformances",
   ObjectIdentifier(BeginDocumentationCommentWithOneLineSummary.self): "BeginDocumentationCommentWithOneLineSummary",
   ObjectIdentifier(DoNotUseSemicolons.self): "DoNotUseSemicolons",
   ObjectIdentifier(DontRepeatTypeInStaticProperties.self): "DontRepeatTypeInStaticProperties",

Sources/SwiftFormat/Core/RuleRegistry+Generated.swift

@@ -18,6 +18,7 @@
     "AlwaysUseLiteralForEmptyCollectionInit": false,
     "AlwaysUseLowerCamelCase": true,
     "AmbiguousTrailingClosureOverload": true,
+    "AvoidRetroactiveConformances": true,
     "BeginDocumentationCommentWithOneLineSummary": false,
     "DoNotUseSemicolons": true,
     "DontRepeatTypeInStaticProperties": true,

Sources/SwiftFormat/Rules/AvoidRetroactiveConformances.swift

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2024 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 SwiftSyntax
+
+/// `@retroactive` conformances are forbidden.
+///
+/// Lint: Using `@retroactive` results in a lint error.
+@_spi(Rules)
+public final class AvoidRetroactiveConformances: SyntaxLintRule {
+  public override func visit(_ node: ExtensionDeclSyntax) -> SyntaxVisitorContinueKind {
+    if let inheritanceClause = node.inheritanceClause {
+      walk(inheritanceClause)
+    }
+    return .skipChildren
+  }
+  public override func visit(_ type: AttributeSyntax) -> SyntaxVisitorContinueKind {
+    if let identifier = type.attributeName.as(IdentifierTypeSyntax.self) {
+      if identifier.name.text == "retroactive" {
+        diagnose(.doNotUseRetroactive, on: type)
+      }
+    }
+    return .skipChildren
+  }
+}
+
+extension Finding.Message {
+  fileprivate static let doNotUseRetroactive: Finding.Message = "do not declare retroactive conformances"
+}

Tests/SwiftFormatTests/Rules/AvoidRetroactiveConformancesTests.swift

@@ -0,0 +1,17 @@
+import _SwiftFormatTestSupport
+
+@_spi(Rules) import SwiftFormat
+
+final class AvoidRetroactiveConformancesTests: LintOrFormatRuleTestCase {
+  func testRetroactiveConformanceIsDiagnosed() {
+    assertLint(
+      AvoidRetroactiveConformances.self,
+      """
+      extension Int: 1️⃣@retroactive Identifiable {}
+      """,
+      findings: [
+        FindingSpec("1️⃣", message: "do not declare retroactive conformances"),
+      ]
+    )
+  }
+}