Apply minor changes to the syntactic sugar rewrite (#3915)

* Improve docstrings for `StringView+SwiftSyntax.swift`
* Move changelog entry to correct section & reword
* Change parameter type from `Int` to `ByteCount`
* Move AbsolutePosition / ByteCount conversion to internal API
* Only warn once if syntax tree cannot be parsed
* Move Syntactic Sugar examples to a dedicated file
* Change SyntacticSugarRuleVisitor from SyntaxAnyVisitor to SyntaxVisitor
* Add `SugaredType` enum to help with the implement `SyntacticSugarRule`

CHANGELOG.md

@@ -23,6 +23,11 @@
   [JP Simard](https://github.com/jpsim)
   [#3628](https://github.com/realm/SwiftLint/issues/3628)
 
+* Improved the `syntactic_sugar` rule's detection accuracy and fixed some
+  corrections leading to invalid code.  
+  [Paul Taykalo](https://github.com/PaulTaykalo)
+  [#3866](https://github.com/realm/SwiftLint/issues/3866)
+
 ## 0.47.0: Smart Appliance
 
 #### Breaking
@@ -133,9 +138,6 @@
 #### Experimental
 
 * None.
-* Fix incorrect autocorrection in `syntactic_sugar` rule 
-  [Paul Taykalo](https://github.com/PaulTaykalo)
-  [#3866](https://github.com/realm/SwiftLint/issues/3866)
 
 #### Enhancements
 

Source/SwiftLintFramework/Extensions/ByteCount+SwiftSyntax.swift

@@ -0,0 +1,11 @@
+import SourceKittenFramework
+import SwiftSyntax
+
+extension ByteCount {
+    /// Converts a SwiftSyntax `AbsolutePosition` to a SourceKitten `ByteCount`.
+    ///
+    /// - parameter position: The SwiftSyntax position to convert.
+    init(_ position: AbsolutePosition) {
+        self.init(position.utf8Offset)
+    }
+}

Source/SwiftLintFramework/Extensions/StringView+SwiftSyntax.swift

@@ -3,23 +3,25 @@ import SourceKittenFramework
 import SwiftSyntax
 
 extension StringView {
-    /// Converts two absolute positions from SwiftSyntax  to valid NSRange if possible
-    /// - Parameters:
-    ///   - start: starting poisiition
-    ///   - end: end position
-    /// - Returns: NSRange or nil in case of empty string
+    /// Converts two absolute positions from SwiftSyntax to a valid `NSRange` if possible.
+    ///
+    /// - parameter start: Starting position.
+    /// - parameter end:   End position.
+    ///
+    /// - returns: `NSRange` or nil in case of empty string.
     func NSRange(start: AbsolutePosition, end: AbsolutePosition) -> NSRange? {
-        precondition(end.utf8Offset >= start.utf8Offset, "End position should be beigger than start position")
-        return NSRange(start: start, length: end.utf8Offset - start.utf8Offset)
+        precondition(end >= start, "End position should be bigger than the start position")
+        return NSRange(start: start, length: ByteCount(end.utf8Offset - start.utf8Offset))
     }
 
-    /// Converts absolute position with length from SwiftSyntax  to valid NSRange if possible
-    /// - Parameters:
-    ///   - start: starting position
-    ///   - length: length in bytes
-    /// - Returns: NSRange or nil in case of empty string
-    private func NSRange(start: AbsolutePosition, length: Int) -> NSRange? {
-        let byteRange = ByteRange(location: ByteCount(start.utf8Offset), length: ByteCount(length))
+    /// Converts absolute position with length from SwiftSyntax to a valid `NSRange` if possible.
+    ///
+    /// - parameter start:  Starting position.
+    /// - parameter length: Length in bytes.
+    ///
+    /// - returns: `NSRange` or nil in case of empty string.
+    private func NSRange(start: AbsolutePosition, length: ByteCount) -> NSRange? {
+        let byteRange = ByteRange(location: ByteCount(start), length: length)
         return byteRangeToNSRange(byteRange)
     }
 }

Source/SwiftLintFramework/Extensions/SwiftLintFile+Cache.swift

@@ -5,6 +5,14 @@ import SwiftSyntax
 import SwiftSyntaxParser
 #endif
 
+private let warnSyntaxParserFailureOnceImpl: Void = {
+    queuedPrintError("Could not parse the syntax tree for at least one file. Results may be invalid.")
+}()
+
+private func warnSyntaxParserFailureOnce() {
+    _ = warnSyntaxParserFailureOnceImpl
+}
+
 private typealias FileCacheKey = UUID
 private var responseCache = Cache({ file -> [String: SourceKitRepresentable]? in
     do {
@@ -28,8 +36,13 @@ private var structureDictionaryCache = Cache({ file in
     return structureCache.get(file).map { SourceKittenDictionary($0.dictionary) }
 })
 
-private var syntaxTreeCache = Cache({ file in
-    return try? SyntaxParser.parse(source: file.contents)
+private var syntaxTreeCache = Cache({ file -> SourceFileSyntax? in
+    do {
+        return try SyntaxParser.parse(source: file.contents)
+    } catch {
+        warnSyntaxParserFailureOnce()
+        return nil
+    }
 })
 
 private var commandsCache = Cache({ file -> [Command] in

Source/SwiftLintFramework/Rules/Idiomatic/ForceCastRule.swift

@@ -1,14 +1,6 @@
 import SourceKittenFramework
 import SwiftSyntax
 
-private let warnSyntaxParserFailureOnceImpl: Void = {
-    queuedPrintError("The force_cast rule is disabled because the Swift Syntax tree could not be parsed")
-}()
-
-private func warnSyntaxParserFailureOnce() {
-    _ = warnSyntaxParserFailureOnceImpl
-}
-
 public struct ForceCastRule: ConfigurationProviderRule, AutomaticTestableRule {
     public var configuration = SeverityConfiguration(.error)
 
@@ -26,16 +18,14 @@ public struct ForceCastRule: ConfigurationProviderRule, AutomaticTestableRule {
     )
 
     public func validate(file: SwiftLintFile) -> [StyleViolation] {
-        guard let tree = file.syntaxTree else {
-            warnSyntaxParserFailureOnce()
-            return []
-        }
+        guard let tree = file.syntaxTree else { return [] }
+
         let visitor = ForceCastRuleVisitor()
         visitor.walk(tree)
         return visitor.positions.map { position in
             StyleViolation(ruleDescription: Self.description,
                            severity: configuration.severity,
-                           location: Location(file: file, byteOffset: ByteCount(position.utf8Offset)))
+                           location: Location(file: file, byteOffset: ByteCount(position)))
         }
     }
 }