Move #eval to base class

Code is identical across sub-classes.

src/spectator/expectations/block_expectation_partial.cr

@@ -21,11 +21,5 @@ module Spectator::Expectations
     protected def initialize(@block : -> ReturnType)
       super(@block.to_s)
     end
-
-    # Evaluates the expectation and returns it.
-    private def eval(matcher, negated = false) : Expectation
-      matched = matcher.match?(self)
-      Expectation.new(matched, negated, self, matcher)
-    end
   end
 end

src/spectator/expectations/expectation_partial.cr

@@ -40,7 +40,10 @@ module Spectator::Expectations
     end
 
     # Evaluates the expectation and returns it.
-    private abstract def eval(matcher, negated = false) : Expectation
+    private def eval(matcher, negated = false)
+      matched = matcher.match?(self)
+      Expectation.new(matched, negated, self, matcher)
+    end
 
     # Reports an expectation to the current harness.
     private def report(expectation : Expectation)

src/spectator/expectations/value_expectation_partial.cr

@@ -20,11 +20,5 @@ module Spectator::Expectations
     protected def initialize(@actual : ActualType)
       super(@actual.to_s)
     end
-
-    # Evaluates the expectation and returns it.
-    private def eval(matcher, negated = false) : Expectation
-      matched = matcher.match?(self)
-      Expectation.new(matched, negated, self, matcher)
-    end
   end
 end