Bubble up matcher description

The last run matcher's description is used if one wasn't provided by the 
user.
Only applies to examples that actually run and have expectations.

src/spectator/example.cr

@@ -6,6 +6,9 @@ module Spectator
   # Concrete types must implement the `#run_impl` method.
   abstract class Example < ExampleComponent
     @finished = false
+    @description : String? = nil
+
+    protected setter description
 
     # Indicates whether the example has already been run.
     def finished? : Bool
@@ -23,11 +26,13 @@ module Spectator
       @test_wrapper.source
     end
 
-    def description : String | Symbol?
-      @test_wrapper.description
+    def description : String | Symbol
+      @description || @test_wrapper.description
     end
 
     def symbolic? : Bool
+      return false unless @test_wrapper.description?
+
       description = @test_wrapper.description
       description.starts_with?('#') || description.starts_with?('.')
     end

src/spectator/expectations/expectation.cr

@@ -44,6 +44,10 @@ module Spectator::Expectations
       values?.not_nil!
     end
 
+    def description
+      @match_data.description
+    end
+
     # Creates the JSON representation of the expectation.
     def to_json(json : ::JSON::Builder)
       json.object do

src/spectator/harness.cr

@@ -46,6 +46,7 @@ module Spectator
     # Reports the outcome of an expectation.
     # An exception will be raised when a failing result is given.
     def report_expectation(expectation : Expectations::Expectation) : Nil
+      @example.description = expectation.description unless @example.test_wrapper.description?
       @reporter.report(expectation)
     end