Parameterless initializer that generates the label

src/spectator/dsl/matcher_dsl.cr

@@ -423,7 +423,7 @@ module Spectator::DSL
     macro method_missing(call)
       {% if call.name.starts_with?("be_") %}
       {% method_name = call.name[3..-1] %} # Remove `be_` prefix.
-      ::Spectator::Matchers::PredicateMatcher(NamedTuple({{method_name}}: Nil)).new({{method_name.stringify}})
+      ::Spectator::Matchers::PredicateMatcher(NamedTuple({{method_name}}: Nil)).new
       {% else %}
       {% raise "Undefined local variable or method '#{call}'" %}
       {% end %}

src/spectator/matchers/predicate_matcher.cr

@@ -5,6 +5,12 @@ 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.
+    # Constructs the label from the type parameters.
+    def initialize
+      super({{ExpectedType.keys.splat.stringify}})
+    end
+
     # Determines whether the matcher is satisfied with the value given to it.
     # True is returned if the match was successful, false otherwise.
     def match?(partial)