Switch to structs to reduce memory allocations

src/spectator/expectations/expectation.cr

@@ -20,7 +20,7 @@ module Spectator::Expectations
     end
 
     # Information regarding the outcome of an expectation.
-    class Result
+    struct Result
       # Indicates whether the expectation was satisifed or not.
       getter? successful : Bool
 

src/spectator/expectations/expectation_partial.cr

@@ -4,7 +4,7 @@ module Spectator::Expectations
   # The part of the expectation this class covers is the actual value.
   # This can also cover a block's behavior.
   # Sub-types of this class are returned by the `DSL::ExampleDSL.expect` call.
-  abstract class ExpectationPartial
+  abstract struct ExpectationPartial
     # User-friendly string displayed for the actual expression being tested.
     # For instance, in the expectation:
     # ```

src/spectator/expectations/value_expectation.cr

@@ -1,7 +1,7 @@
 require "./expectation"
 
 module Spectator::Expectations
-  class ValueExpectation(ActualType, ExpectedType)
+  struct ValueExpectation(ActualType, ExpectedType)
     include Expectation
 
     def initialize(@partial : ValueExpectationPartial(ActualType),

src/spectator/expectations/value_expectation_partial.cr

@@ -1,7 +1,7 @@
 require "./expectation_partial"
 
 module Spectator::Expectations
-  class ValueExpectationPartial(ActualType) < ExpectationPartial
+  struct ValueExpectationPartial(ActualType) < ExpectationPartial
     getter actual
 
     protected def initialize(label : String, @actual : ActualType)

src/spectator/matchers/equality_matcher.cr

@@ -1,7 +1,7 @@
 require "./value_matcher"
 
 module Spectator::Matchers
-  class EqualityMatcher(ExpectedType) < ValueMatcher(ExpectedType)
+  struct EqualityMatcher(ExpectedType) < ValueMatcher(ExpectedType)
     def match?(partial : Expectations::ValueExpectationPartial(ActualType)) : Bool forall ActualType
       partial.actual == expected
     end

src/spectator/matchers/matcher.cr

@@ -1,5 +1,5 @@
 module Spectator::Matchers
-  abstract class Matcher
+  abstract struct Matcher
     private getter label : String
 
     private def initialize(@label)

src/spectator/matchers/value_matcher.cr

@@ -1,7 +1,7 @@
 require "./matcher"
 
 module Spectator::Matchers
-  abstract class ValueMatcher(ExpectedType) < Matcher
+  abstract struct ValueMatcher(ExpectedType) < Matcher
     private getter expected
 
     def initialize(label : String, @expected : ExpectedType)