MacOSVersion: enable strong typing

Library/Homebrew/ast_constants.rb

@@ -52,4 +52,4 @@ FORMULA_COMPONENT_PRECEDENCE_LIST = T.let([
   [{ name: :caveats, type: :method_definition }],
   [{ name: :plist_options, type: :method_call }, { name: :plist, type: :method_definition }],
   [{ name: :test, type: :block_call }],
-].freeze, T::Array[[{ name: Symbol, type: Symbol }]])
+].freeze, T::Array[T::Array[{ name: Symbol, type: Symbol }]])

Library/Homebrew/cask/dsl.rb

@@ -486,7 +486,7 @@ module Cask
     def add_implicit_macos_dependency
       return if (cask_depends_on = @depends_on).present? && cask_depends_on.macos.present?
 
-      depends_on macos: ">= :#{MacOSVersion::SYMBOLS.key MacOSVersion::SYMBOLS.values.min}"
+      depends_on macos: ">= #{MacOSVersion.new(HOMEBREW_MACOS_OLDEST_ALLOWED).to_sym.inspect}"
     end
 
     # Declare conflicts that keep a cask from installing or working correctly.

Library/Homebrew/cask/dsl/depends_on.rb

@@ -52,16 +52,17 @@ module Cask
         raise "Only a single 'depends_on macos' is allowed." if defined?(@macos)
 
         # workaround for https://github.com/sorbet/sorbet/issues/6860
-        first_arg = args.first&.to_s
+        first_arg = args.first
+        first_arg_s = first_arg&.to_s
 
         begin
           @macos = if args.count > 1
             MacOSRequirement.new([args], comparator: "==")
-          elsif MacOSVersion::SYMBOLS.key?(args.first)
+          elsif first_arg.is_a?(Symbol) && MacOSVersion::SYMBOLS.key?(first_arg)
             MacOSRequirement.new([args.first], comparator: "==")
-          elsif (md = /^\s*(?<comparator><|>|[=<>]=)\s*:(?<version>\S+)\s*$/.match(first_arg))
+          elsif (md = /^\s*(?<comparator><|>|[=<>]=)\s*:(?<version>\S+)\s*$/.match(first_arg_s))
             MacOSRequirement.new([T.must(md[:version]).to_sym], comparator: md[:comparator])
-          elsif (md = /^\s*(?<comparator><|>|[=<>]=)\s*(?<version>\S+)\s*$/.match(first_arg))
+          elsif (md = /^\s*(?<comparator><|>|[=<>]=)\s*(?<version>\S+)\s*$/.match(first_arg_s))
             MacOSRequirement.new([md[:version]], comparator: md[:comparator])
           # This is not duplicate of the first case: see `args.first` and a different comparator.
           else # rubocop:disable Lint/DuplicateBranch

Library/Homebrew/macos_version.rb

@@ -1,4 +1,4 @@
-# typed: true # rubocop:todo Sorbet/StrictSigil
+# typed: strong
 # frozen_string_literal: true
 
 require "version"
@@ -10,6 +10,7 @@ class MacOSVersion < Version
     sig { returns(T.nilable(T.any(String, Symbol))) }
     attr_reader :version
 
+    sig { params(version: T.nilable(T.any(String, Symbol))).void }
     def initialize(version)
       @version = version
       super "unknown or unsupported macOS version: #{version.inspect}"
@@ -18,7 +19,7 @@ class MacOSVersion < Version
 
   # NOTE: When removing symbols here, ensure that they are added
   #       to `DEPRECATED_MACOS_VERSIONS` in `MacOSRequirement`.
-  SYMBOLS = {
+  SYMBOLS = T.let({
     tahoe:       "26",
     sequoia:     "15",
     sonoma:      "14",
@@ -30,7 +31,7 @@ class MacOSVersion < Version
     high_sierra: "10.13",
     sierra:      "10.12",
     el_capitan:  "10.11",
-  }.freeze
+  }.freeze, T::Hash[Symbol, String])
 
   sig { params(macos_version: MacOSVersion).returns(Version) }
   def self.kernel_major_version(macos_version)
@@ -57,7 +58,9 @@ class MacOSVersion < Version
 
     super(T.must(version))
 
-    @comparison_cache = {}
+    @comparison_cache = T.let({}, T::Hash[T.untyped, T.nilable(Integer)])
+    @pretty_name = T.let(nil, T.nilable(String))
+    @sym = T.let(nil, T.nilable(Symbol))
   end
 
   sig { override.params(other: T.untyped).returns(T.nilable(Integer)) }
@@ -95,7 +98,7 @@ class MacOSVersion < Version
 
   sig { returns(Symbol) }
   def to_sym
-    return @sym if defined?(@sym)
+    return @sym if @sym
 
     sym = SYMBOLS.invert.fetch(strip_patch.to_s, :dunno)
 
@@ -106,7 +109,7 @@ class MacOSVersion < Version
 
   sig { returns(String) }
   def pretty_name
-    return @pretty_name if defined?(@pretty_name)
+    return @pretty_name if @pretty_name
 
     pretty_name = to_sym.to_s.split("_").map(&:capitalize).join(" ").freeze
 
@@ -154,5 +157,7 @@ class MacOSVersion < Version
   # Represents the absence of a version.
   #
   # NOTE: Constructor needs to called with an arbitrary macOS-like version which is then set to `nil`.
-  NULL = MacOSVersion.new("10.0").tap { |v| v.instance_variable_set(:@version, nil) }.freeze
+  NULL = T.let(MacOSVersion.new("10.0").tap do |v|
+    T.let(v, MacOSVersion).instance_variable_set(:@version, nil)
+  end.freeze, MacOSVersion)
 end