Only use HOMEBREW_TAP_PATH_REGEX once inside Tap class.

Library/Homebrew/cask/lib/hbc/cask_loader.rb

@@ -97,14 +97,14 @@ module Hbc
 
     class FromTapPathLoader < FromPathLoader
       def self.can_load?(ref)
-        File.expand_path(ref).match?(HOMEBREW_TAP_PATH_REGEX) && super
+        super && !Tap.from_path(ref).nil?
       end
 
       attr_reader :tap
 
-      def initialize(tap_path)
-        @tap = Tap.from_path(File.expand_path(tap_path))
-        super tap_path
+      def initialize(path)
+        @tap = Tap.from_path(path)
+        super(path)
       end
 
       private

Library/Homebrew/exceptions.rb

@@ -181,8 +181,7 @@ class TapFormulaAmbiguityError < RuntimeError
     @name = name
     @paths = paths
     @formulae = paths.map do |path|
-      match = path.to_s.match(HOMEBREW_TAP_PATH_REGEX)
-      "#{Tap.fetch(match[:user], match[:repo])}/#{path.basename(".rb")}"
+      "#{Tap.from_path(path).name}/#{path.basename(".rb")}"
     end
 
     super <<~EOS

Library/Homebrew/formula.rb

@@ -179,8 +179,8 @@ class Formula
 
     @tap = if path == Formulary.core_path(name)
       CoreTap.instance
-    elsif match = path.to_s.match(HOMEBREW_TAP_PATH_REGEX)
-      Tap.fetch(match[:user], match[:repo])
+    else
+      Tap.from_path(path)
     end
 
     @full_name = full_name_with_optional_tap(name)

Library/Homebrew/tap.rb

@@ -39,7 +39,7 @@ class Tap
   end
 
   def self.from_path(path)
-    match = path.to_s.match(HOMEBREW_TAP_PATH_REGEX)
+    match = File.expand_path(path).match(HOMEBREW_TAP_PATH_REGEX)
     raise "Invalid tap path '#{path}'" unless match
     fetch(match[:user], match[:repo])
   rescue