Abstract Matcher#label getter

There's no need to store a value for this.
Some matchers have a static label.

src/spectator/matchers/empty_matcher.cr

@@ -4,9 +4,9 @@ module Spectator::Matchers
   # Matcher that tests whether a collection is empty.
   # The values are checked with the `empty?` method.
   struct EmptyMatcher < Matcher
-    # Creates the matcher.
-    def initialize
-      super("empty?")
+    # Textual representation of what the matcher expects.
+    def label
+      "empty?"
     end
 
     # Determines whether the matcher is satisfied with the partial given to it.

src/spectator/matchers/matcher.cr

@@ -8,11 +8,7 @@ module Spectator::Matchers
     # Textual representation of what the matcher expects.
     # This shouldn't be used in the conditional logic,
     # but for verbose output to help the end-user.
-    getter label : String
-
-    # Creates the base of the matcher.
-    def initialize(@label)
-    end
+    abstract def label : String
 
     # Determines whether the matcher is satisfied with the value given to it.
     # True is returned if the match was successful, false otherwise.

src/spectator/matchers/nil_matcher.cr

@@ -4,9 +4,9 @@ module Spectator::Matchers
   # Common matcher that tests whether a value is nil.
   # The `Object#nil?` method is used for this.
   struct NilMatcher < Matcher
-    # Creates the matcher.
-    def initialize
-      super("nil?")
+    # Textual representation of what the matcher expects.
+    def label
+      "nil?"
     end
 
     # Determines whether the matcher is satisfied with the partial given to it.

src/spectator/matchers/predicate_matcher.cr

@@ -5,10 +5,10 @@ module Spectator::Matchers
   # The `ExpectedType` type param should be a `NamedTuple`.
   # Each key in the tuple is a predicate (without the '?') to test.
   struct PredicateMatcher(ExpectedType) < Matcher
-    # Creates the matcher.
+    # Textual representation of what the matcher expects.
     # Constructs the label from the type parameters.
-    def initialize
-      super({{ExpectedType.keys.splat.stringify}})
+    def label
+      {{ExpectedType.keys.splat.stringify}}
     end
 
     # Determines whether the matcher is satisfied with the value given to it.

src/spectator/matchers/type_matcher.cr

@@ -4,10 +4,10 @@ module Spectator::Matchers
   # Matcher that tests a value is of a specified type.
   # The values are compared with the `Object#is_a?` method.
   struct TypeMatcher(Expected) < Matcher
-    # Creates the type matcher.
-    # The `Expected` type param will be used to populate the underlying label.
-    def initialize
-      super(Expected.to_s)
+    # Textual representation of what the matcher expects.
+    # The `Expected` type param will be used to populate the label.
+    def label
+      Expected.to_s
     end
 
     # Determines whether the matcher is satisfied with the value given to it.

src/spectator/matchers/value_matcher.cr

@@ -5,6 +5,11 @@ module Spectator::Matchers
   # Matchers of this type expect that a SUT applies to the value in some way.
   # Sub-types must implement `Matcher#match?`, `Matcher#message`, and `Matcher#negated_message`.
   abstract struct ValueMatcher(ExpectedType) < Matcher
+    # Textual representation of what the matcher expects.
+    # This shouldn't be used in the conditional logic,
+    # but for verbose output to help the end-user.
+    getter label
+
     # Expected value.
     # Sub-types may use this value to test the expectation and generate message strings.
     getter expected
@@ -12,15 +17,14 @@ module Spectator::Matchers
     # Creates the value matcher.
     # The label should be a string representation of the expectation.
     # The expected value is stored for later use.
-    def initialize(label : String, @expected : ExpectedType)
-      super(label)
+    def initialize(@label : String, @expected : ExpectedType)
     end
 
     # Creates the value matcher.
     # The label is generated by calling `#to_s` on the expected value.
     # The expected value is stored for later use.
-    def initialize(@expected : ExpectedType)
-      super(@expected.to_s)
+    def initialize(expected : ExpectedType)
+      initialize(expected.to_s, expected)
     end
   end
 end