lint: add SwiftLint rule against Int for epoch milliseconds (#8181)

.swiftlint.yml

@@ -109,6 +109,23 @@ custom_rules:
     message: "Use Bundle.revenueCatUI instead of Bundle.module for Compose Resources compatibility"
     severity: error
 
+  no_int_epoch_milliseconds:
+    name: "No Int for epoch milliseconds"
+    message: "Epoch milliseconds (~1.7e12) overflow `Int` on 32-bit platforms (e.g. arm64_32 Apple Watches), crashing at runtime. Use `Int64` instead."
+    severity: error
+    included:
+      - "Sources/.*\\.swift"
+      - "RevenueCatUI/.*\\.swift"
+      - "AdapterSDKs/RevenueCatAdMob/Sources/.*\\.swift"
+    excluded_match_kinds:
+      - comment
+      - doccomment
+      - doccomment.field
+      - string
+    # Matches, within a single line: Int(<...since...> * 1000), Int(1000 * <...since...>),
+    # Int(<...since...>) * 1000 and 1000 * Int(<...since...>). One level of nested parentheses is supported.
+    regex: '\bInt\((?:[^()\n]|\([^()\n]*\)|\()*timeIntervalSince(?:1970|ReferenceDate|Now)\b(?:[^()\n]|\([^()\n]*\))*\*\s*1_?000\b|\bInt\((?:[^()\n]|\([^()\n]*\)|\()*\b1_?000\s*\*\s*(?:[^()\n]|\([^()\n]*\))*timeIntervalSince(?:1970|ReferenceDate|Now)\b|\bInt\((?:[^()\n]|\([^()\n]*\))*timeIntervalSince(?:1970|ReferenceDate|Now)\b(?:[^()\n]|\([^()\n]*\))*\)\s*\*\s*1_?000\b|\b1_?000\s*\*\s*Int\((?:[^()\n]|\([^()\n]*\))*timeIntervalSince(?:1970|ReferenceDate|Now)\b'
+
   no_new_public_enums:
     name: "No new public enums in consumer-facing APIs"
     message: "Adding a new `public enum` to the SDK's consumer-facing surface (including `@_spi(Experimental)`) is not allowed. Adding a case to an existing `public enum` is a source-breaking change for any consumer with an exhaustive `switch`. Use a struct with static constants instead."

Tests/SwiftLintCustomRules/Fixtures/no_int_epoch_milliseconds.swift.fixture

@@ -0,0 +1,34 @@
+import Foundation
+
+let date = Date()
+
+// Int(... * 1000)
+let purchaseDate = date.map { Int($0.timeIntervalSince1970 * 1000) } // violation
+let expirationDate = Int(date.timeIntervalSince1970 * 1000) // violation
+let underscored = Int(date.timeIntervalSince1970 * 1_000) // violation
+let nested = Int((date.timeIntervalSince1970 * 1000).rounded()) // violation
+let fromNow = Int(Date().timeIntervalSince1970 * 1000) // violation
+let wrapped = Int(max(0, date.timeIntervalSince1970 * 1000)) // violation
+let safePurchaseDate = date.map { Int64($0.timeIntervalSince1970 * 1000) }
+let safeRounded = Int64((date.timeIntervalSince1970 * 1000).rounded())
+
+// Int(...) * 1000
+let convertedFirst = Int(date.timeIntervalSince1970) * 1000 // violation
+let leadingMultiplier = 1000 * Int(date.timeIntervalSince1970) // violation
+let safeConvertedFirst = Int64(date.timeIntervalSince1970) * 1000
+
+// Reversed operands
+let reversed = Int(1000 * date.timeIntervalSince1970) // violation
+let reversedNested = Int((1_000 * date.timeIntervalSinceReferenceDate).rounded()) // violation
+let safeReversed = Int64(1000 * date.timeIntervalSince1970)
+
+// Not epoch milliseconds
+let seconds = Int(date.timeIntervalSince1970)
+let smallDuration = Int(duration * 1000)
+let unrelatedReversed = Int(1000 * duration)
+let otherCall = Int(1) + foo(date.timeIntervalSince1970 * 1000)
+let separateInt = Int(5); let millis = Double(date.timeIntervalSince1970 * 1000)
+
+// Comments are ignored
+// let commented = Int(date.timeIntervalSince1970 * 1000)
+let trailingComment = Int(1) // timeIntervalSince1970 * 1000