retire support for no_checksum stanza

doc/CASK_LANGUAGE_REFERENCE.md

@@ -95,8 +95,7 @@ Each Cask must declare one or more *artifacts* (i.e. something to install)
 
 ## Legacy Stanzas
 
-The following stanzas may be seen in current use but are deprecated
-and slated for retirement.
+The following stanzas are no longer in use.
 
 | name               | multiple occurrences allowed? | meaning     |
 | ------------------ |------------------------------ | ----------- |
@@ -169,8 +168,8 @@ And the following methods may be useful for interpolation:
 
 ## Checksum Stanza Details
 
-Older Casks may still use `no_checksum` stanzas.  This is OK, but new
-Casks and updates should adopt `sha256 :no_check`.
+Casks should no longer use `no_checksum` stanzas.  That form has
+been superseded by `sha256 :no_check`.
 
 
 ## URL Stanza Details

lib/cask/dsl.rb

@@ -140,10 +140,6 @@ def hash_name(hash_type)
     end
 
     def sha256(sha2=nil)
-      # @@@ todo remove this after deleting support for legacy no_checksum stanza
-      if @sums == :no_check
-        raise CaskInvalidError.new(self.title, "'no_checksum' stanza conflicts with 'sha256'")
-      end
       if sha2 == :no_check
         @sums = sha2
       else
@@ -152,14 +148,6 @@ def sha256(sha2=nil)
       end
     end
 
-    # @@@ todo remove support for no_checksum stanza
-    def no_checksum
-      unless @sums.nil? or @sums.empty?
-        raise CaskInvalidError.new(self.title, "'no_checksum' stanza conflicts with '#{hash_name(@sums.first.hash_type)}'")
-      end
-      @sums = :no_check
-    end
-
     def method_missing(method, *args)
       poo = <<-EOPOO.undent
         Unexpected method '#{method}' called on #{self}.

test/cask/dsl_test.rb

@@ -109,20 +109,4 @@ def caveats; <<-EOS.undent
     }.must_raise(CaskInvalidError)
     err.message.must_include "'version' stanza may only appear once"
   end
-
-  # @@@ todo this test can be removed when support for no_checksum is dropped
-  it "prevents defining conflicting checksums (first order)" do
-    err = lambda {
-      invalid_cask = Cask.load('invalid/invalid-checksum-conflict1')
-    }.must_raise(CaskInvalidError)
-    err.message.must_include "'no_checksum' stanza conflicts with"
-  end
-
-  # @@@ todo this test can be removed when support for no_checksum is dropped
-  it "prevents defining conflicting checksums (second order)" do
-    err = lambda {
-      invalid_cask = Cask.load('invalid/invalid-checksum-conflict2')
-    }.must_raise(CaskInvalidError)
-    err.message.must_include "'no_checksum' stanza conflicts with"
-  end
 end