Handle TapFormulaAmbiguityError in diagnostics.

Library/Homebrew/diagnostic.rb

@@ -841,7 +841,13 @@ module Homebrew
             Formulary::FromAPILoader,
             Formulary::FromNameLoader,
           ].any? do |loader_class|
-            if (loader = loader_class.try_new(keg.name, warn: false))
+            loader = begin
+              loader_class.try_new(keg.name, warn: false)
+            rescue TapFormulaAmbiguityError => e
+              e.loaders.first
+            end
+
+            if loader
               # If we know the tap, ignore all other taps.
               next false if tap && loader.tap != tap
 

Library/Homebrew/exceptions.rb

@@ -259,11 +259,12 @@ end
 
 # Raised when a formula with the same name is found in multiple taps.
 class TapFormulaAmbiguityError < RuntimeError
-  attr_reader :name, :taps
+  attr_reader :name, :taps, :loaders
 
-  def initialize(name, taps)
+  def initialize(name, loaders)
     @name = name
-    @taps = taps
+    @loaders = loaders
+    @taps = loaders.map(&:tap)
 
     formulae = taps.map { |tap| "#{tap}/#{name}" }
     formula_list = formulae.map { |f| "\n       * #{f}" }.join

Library/Homebrew/formulary.rb

@@ -772,7 +772,7 @@ module Formulary
       when 1
         loaders.first
       when 2..Float::INFINITY
-        raise TapFormulaAmbiguityError.new(name, loaders.map(&:tap))
+        raise TapFormulaAmbiguityError.new(name, loaders)
       end
     end
   end