Fix redundantInit rule: preserve .init with trailing closure on collection types for Swift < 6.4 (#2396)

Co-authored-by: calda <1811727+calda@users.noreply.github.com>

Sources/Rules/RedundantInit.swift

@@ -46,6 +46,14 @@ public extension FormatRule {
             if [.startOfScope("#if"), .keyword("#elseif")].contains(formatter.tokens[lineStart]) {
                 return
             }
+            // In Swift < 6.4, trailing closure syntax is not allowed after array/dictionary
+            // literals (e.g. `[String] { "foo" }`). This was fixed in SE-0508 for Swift 6.4+.
+            if formatter.tokens[openParenOrOpenBraceIndex] == .startOfScope("{"),
+               prevToken == .endOfScope("]"),
+               formatter.options.swiftVersion < "6.4"
+            {
+                return
+            }
             var j = dotIndex
             while let prevIndex = formatter.index(
                 of: prevToken, before: j

Tests/Rules/RedundantInitTests.swift

@@ -295,4 +295,42 @@ final class RedundantInitTests: XCTestCase {
         """
         testFormatting(for: input, output, rule: .redundantInit, exclude: [.propertyTypes])
     }
+
+    func testPreserveInitOnCollectionTypeWithTrailingClosureBeforeSwift64() {
+        let input = """
+        [String].init { "foo" }
+        [String: Int].init { ("key", 1) }
+        [[String]].init { ["foo"] }
+        """
+        let options = FormatOptions(swiftVersion: "6.3")
+        testFormatting(for: input, rule: .redundantInit, options: options)
+    }
+
+    func testRemoveInitOnCollectionTypeWithTrailingClosureInSwift64() {
+        let input = """
+        [String].init { "foo" }
+        [String: Int].init { ("key", 1) }
+        [[String]].init { ["foo"] }
+        """
+        let output = """
+        [String] { "foo" }
+        [String: Int] { ("key", 1) }
+        [[String]] { ["foo"] }
+        """
+        let options = FormatOptions(swiftVersion: "6.4")
+        testFormatting(for: input, output, rule: .redundantInit, options: options)
+    }
+
+    func testRemoveInitOnCollectionTypeWithParensUnaffectedBySwiftVersion() {
+        let input = """
+        let array = [String].init()
+        let dictionary = [String: Int].init()
+        """
+        let output = """
+        let array = [String]()
+        let dictionary = [String: Int]()
+        """
+        let options = FormatOptions(swiftVersion: "6.3")
+        testFormatting(for: input, output, rule: .redundantInit, options: options, exclude: [.propertyTypes])
+    }
 }