Fix indenting dot-prefixed expressions inside #elseif

Sources/Tokenizer.swift

@@ -1492,12 +1492,17 @@ public func tokenize(_ source: String) -> [Token] {
                 if prevNonSpaceToken.isLvalue {
                     var lineStart = index(of: .linebreak, before: prevNonSpaceIndex) ?? 0
                     lineStart = index(of: .nonSpaceOrComment, after: lineStart) ?? lineStart
-                    if [.startOfScope("#if"), .keyword("#elseif")].contains(tokens[lineStart]),
-                       let prevIndex = index(of: .nonSpaceOrCommentOrLinebreak, before: lineStart)
-                    {
+                    switch tokens[lineStart] {
+                    case .keyword("#elseif"), .keyword("#else"):
+                        lineStart = index(of: .startOfScope, before: lineStart) ?? lineStart
+                        fallthrough
+                    case .startOfScope("#if"):
+                        guard let prevIndex = index(of: .nonSpaceOrCommentOrLinebreak, before: lineStart) else {
+                            fallthrough
+                        }
                         prevNonSpaceIndex = prevIndex
                         continue
-                    } else {
+                    default:
                         _type = .infix
                     }
                 } else if prevNonSpaceToken.isAttribute ||

Tests/RulesTests+Indentation.swift

@@ -2902,6 +2902,23 @@ class IndentTests: RulesTests {
         testFormatting(for: input, rule: FormatRules.indent)
     }
 
+    func testNoIndentDotExpressionInsideIfdef() {
+        let input = """
+        let current: Platform = {
+            #if os(macOS)
+                .mac
+            #elseif os(Linux)
+                .linux
+            #elseif os(Windows)
+                .windows
+            #else
+                fatalError("Unknown OS not supported")
+            #endif
+        }()
+        """
+        testFormatting(for: input, rule: FormatRules.indent)
+    }
+
     // indent #if/#else/#elseif/#endif (mode: noindent)
 
     func testIfEndifNoIndenting() {
@@ -3070,6 +3087,10 @@ class IndentTests: RulesTests {
         func myFunc() -> String {
             #if DEBUG
             .init("foo")
+            #elseif PROD
+            .init("bar")
+            #else
+            .init("baz")
             #endif
         }
         """