From da392cd9e836cf7955e9217d7e06b7a411dab107 Mon Sep 17 00:00:00 2001
From: Mike McQuaid <mike@mikemcquaid.com>
Date: Thu, 4 Apr 2019 08:34:25 +0100
Subject: [PATCH] xcode_requirement: require macOS 10.14.4 for Xcode 10.2.

See discussion in https://github.com/Homebrew/brew/pull/5940.
---
 .../requirements/xcode_requirement.rb         | 24 +++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/Library/Homebrew/requirements/xcode_requirement.rb b/Library/Homebrew/requirements/xcode_requirement.rb
index 045a88822e..248e362fe3 100644
--- a/Library/Homebrew/requirements/xcode_requirement.rb
+++ b/Library/Homebrew/requirements/xcode_requirement.rb
@@ -13,6 +13,7 @@ class XcodeRequirement < Requirement
   def xcode_installed_version
     return false unless MacOS::Xcode.installed?
     return true unless @version
+    return true if xcode_swift_compatability?
 
     MacOS::Xcode.version >= @version
   end
@@ -20,16 +21,24 @@ class XcodeRequirement < Requirement
   def message
     version = " #{@version}" if @version
     message = <<~EOS
-      A full installation of Xcode.app#{version} is required to compile this software.
-      Installing just the Command Line Tools is not sufficient.
+      A full installation of Xcode.app#{version} is required to compile
+      this software. Installing just the Command Line Tools is not sufficient.
     EOS
+    unless xcode_swift_compatability?
+      message += <<~EOS
+
+        Xcode >=10.2 requires macOS >=10.14.4 to build many formulae.
+      EOS
+    end
     if @version && Version.new(MacOS::Xcode.latest_version) < Version.new(@version)
       message + <<~EOS
+
         Xcode#{version} cannot be installed on macOS #{MacOS.version}.
         You must upgrade your version of macOS.
       EOS
     else
       message + <<~EOS
+
         Xcode can be installed from the App Store.
       EOS
     end
@@ -38,4 +47,15 @@ class XcodeRequirement < Requirement
   def inspect
     "#<#{self.class.name}: #{tags.inspect} version=#{@version.inspect}>"
   end
+
+  private
+
+  # TODO: when 10.14.4 and 10.2 have been around for long enough remove this
+  # method in favour of requiring 10.14.4 and 10.2.
+  def xcode_swift_compatability?
+    return true if MacOS::Xcode.version < "10.2"
+    return true if MacOS::Xcode.version >= "10.14.4"
+
+    MacOS.version < "10.14"
+  end
 end