Make our time types transparent (#2374)

Motivation:

Our time types are trivial, and they should be fully transparent. This
produces minor performance improvements in code handling time types, but
is mostly useful in terms of allowing the compiler to observe that these
functions have no side effects, thereby eliding some ARC traffic.

Modifications:

Make our time types inlinable.

Result:

Better performance.

Sources/NIOCore/EventLoop.swift

@@ -445,7 +445,8 @@ public struct TimeAmount: Hashable, Sendable {
     /// The nanoseconds representation of the `TimeAmount`.
     public let nanoseconds: Int64
 
-    private init(_ nanoseconds: Int64) {
+    /* private but */ @inlinable
+    init(_ nanoseconds: Int64) {
         self.nanoseconds = nanoseconds
     }
 
@@ -454,6 +455,7 @@ public struct TimeAmount: Hashable, Sendable {
     /// - parameters:
     ///     - amount: the amount of nanoseconds this `TimeAmount` represents.
     /// - returns: the `TimeAmount` for the given amount.
+    @inlinable
     public static func nanoseconds(_ amount: Int64) -> TimeAmount {
         return TimeAmount(amount)
     }
@@ -463,6 +465,7 @@ public struct TimeAmount: Hashable, Sendable {
     /// - parameters:
     ///     - amount: the amount of microseconds this `TimeAmount` represents.
     /// - returns: the `TimeAmount` for the given amount.
+    @inlinable
     public static func microseconds(_ amount: Int64) -> TimeAmount {
         return TimeAmount(amount * 1000)
     }
@@ -472,6 +475,7 @@ public struct TimeAmount: Hashable, Sendable {
     /// - parameters:
     ///     - amount: the amount of milliseconds this `TimeAmount` represents.
     /// - returns: the `TimeAmount` for the given amount.
+    @inlinable
     public static func milliseconds(_ amount: Int64) -> TimeAmount {
         return TimeAmount(amount * (1000 * 1000))
     }
@@ -481,6 +485,7 @@ public struct TimeAmount: Hashable, Sendable {
     /// - parameters:
     ///     - amount: the amount of seconds this `TimeAmount` represents.
     /// - returns: the `TimeAmount` for the given amount.
+    @inlinable
     public static func seconds(_ amount: Int64) -> TimeAmount {
         return TimeAmount(amount * (1000 * 1000 * 1000))
     }
@@ -490,6 +495,7 @@ public struct TimeAmount: Hashable, Sendable {
     /// - parameters:
     ///     - amount: the amount of minutes this `TimeAmount` represents.
     /// - returns: the `TimeAmount` for the given amount.
+    @inlinable
     public static func minutes(_ amount: Int64) -> TimeAmount {
         return TimeAmount(amount * (1000 * 1000 * 1000 * 60))
     }
@@ -499,12 +505,14 @@ public struct TimeAmount: Hashable, Sendable {
     /// - parameters:
     ///     - amount: the amount of hours this `TimeAmount` represents.
     /// - returns: the `TimeAmount` for the given amount.
+    @inlinable
     public static func hours(_ amount: Int64) -> TimeAmount {
         return TimeAmount(amount * (1000 * 1000 * 1000 * 60 * 60))
     }
 }
 
 extension TimeAmount: Comparable {
+    @inlinable
     public static func < (lhs: TimeAmount, rhs: TimeAmount) -> Bool {
         return lhs.nanoseconds < rhs.nanoseconds
     }
@@ -512,30 +520,37 @@ extension TimeAmount: Comparable {
 
 extension TimeAmount: AdditiveArithmetic {
     /// The zero value for `TimeAmount`.
+    @inlinable
     public static var zero: TimeAmount {
         return TimeAmount.nanoseconds(0)
     }
 
+    @inlinable
     public static func + (lhs: TimeAmount, rhs: TimeAmount) -> TimeAmount {
         return TimeAmount(lhs.nanoseconds + rhs.nanoseconds)
     }
 
+    @inlinable
     public static func +=(lhs: inout TimeAmount, rhs: TimeAmount) {
         lhs = lhs + rhs
     }
 
+    @inlinable
     public static func - (lhs: TimeAmount, rhs: TimeAmount) -> TimeAmount {
         return TimeAmount(lhs.nanoseconds - rhs.nanoseconds)
     }
 
+    @inlinable
     public static func -=(lhs: inout TimeAmount, rhs: TimeAmount) {
         lhs = lhs - rhs
     }
 
+    @inlinable
     public static func * <T: BinaryInteger>(lhs: T, rhs: TimeAmount) -> TimeAmount {
         return TimeAmount(Int64(lhs) * rhs.nanoseconds)
     }
 
+    @inlinable
     public static func * <T: BinaryInteger>(lhs: TimeAmount, rhs: T) -> TimeAmount {
         return TimeAmount(lhs.nanoseconds * Int64(rhs))
     }
@@ -563,13 +578,14 @@ public struct NIODeadline: Equatable, Hashable, Sendable {
     public typealias Value = UInt64
 
     // This really should be an UInt63 but we model it as Int64 with >=0 assert
-    private var _uptimeNanoseconds: Int64 {
+    /* private but */ @usableFromInline var _uptimeNanoseconds: Int64 {
         didSet {
             assert(self._uptimeNanoseconds >= 0)
         }
     }
 
     /// The nanoseconds since boot representation of the `NIODeadline`.
+    @inlinable
     public var uptimeNanoseconds: UInt64 {
         return .init(self._uptimeNanoseconds)
     }
@@ -577,7 +593,7 @@ public struct NIODeadline: Equatable, Hashable, Sendable {
     public static let distantPast = NIODeadline(0)
     public static let distantFuture = NIODeadline(.init(Int64.max))
 
-    private init(_ nanoseconds: Int64) {
+    /* private but */ @inlinable init(_ nanoseconds: Int64) {
         precondition(nanoseconds >= 0)
         self._uptimeNanoseconds = nanoseconds
     }
@@ -593,8 +609,8 @@ public struct NIODeadline: Equatable, Hashable, Sendable {
     /// we make that call here, directly from NIO.
     ///
     /// - TODO: Investigate optimizing the call to `DispatchTime.now()` away on other platforms too.
-    @inline(__always)
+    @inlinable
-    private static func timeNow() -> UInt64 {
+    static func timeNow() -> UInt64 {
 #if os(Linux)
         var ts = timespec()
         clock_gettime(CLOCK_MONOTONIC, &ts)
@@ -607,38 +623,55 @@ public struct NIODeadline: Equatable, Hashable, Sendable {
 #endif // os(Linux)
     }
 
+    @inlinable
     public static func now() -> NIODeadline {
         return NIODeadline.uptimeNanoseconds(timeNow())
     }
 
+    @inlinable
     public static func uptimeNanoseconds(_ nanoseconds: UInt64) -> NIODeadline {
         return NIODeadline(Int64(min(UInt64(Int64.max), nanoseconds)))
     }
+
+    @inlinable
+    public static func == (lhs: NIODeadline, rhs: NIODeadline) -> Bool {
+        return lhs.uptimeNanoseconds == rhs.uptimeNanoseconds
+    }
+
+    @inlinable
+    public func hash(into hasher: inout Hasher) {
+        hasher.combine(self.uptimeNanoseconds)
+    }
 }
 
 extension NIODeadline: Comparable {
+    @inlinable
     public static func < (lhs: NIODeadline, rhs: NIODeadline) -> Bool {
         return lhs.uptimeNanoseconds < rhs.uptimeNanoseconds
     }
 
+    @inlinable
     public static func > (lhs: NIODeadline, rhs: NIODeadline) -> Bool {
         return lhs.uptimeNanoseconds > rhs.uptimeNanoseconds
     }
 }
 
 extension NIODeadline: CustomStringConvertible {
+    @inlinable
     public var description: String {
         return self.uptimeNanoseconds.description
     }
 }
 
 extension NIODeadline {
+    @inlinable
     public static func - (lhs: NIODeadline, rhs: NIODeadline) -> TimeAmount {
         // This won't ever crash, NIODeadlines are guaranteed to be within 0 ..< 2^63-1 nanoseconds so the result can
         // definitely be stored in a TimeAmount (which is an Int64).
         return .nanoseconds(Int64(lhs.uptimeNanoseconds) - Int64(rhs.uptimeNanoseconds))
     }
 
+    @inlinable
     public static func + (lhs: NIODeadline, rhs: TimeAmount) -> NIODeadline {
         let partial: Int64
         let overflow: Bool
@@ -653,6 +686,7 @@ extension NIODeadline {
         return NIODeadline(partial)
     }
 
+    @inlinable
     public static func - (lhs: NIODeadline, rhs: TimeAmount) -> NIODeadline {
         if rhs.nanoseconds < 0 {
             // The addition won't crash because the worst that could happen is `UInt64(Int64.max) + UInt64(Int64.max)`