Handle case with typeless block

Fixes syntax:
`stub method(&block)`

To stub a block with args, use:
`stub method(&block : Type -> Type)`

Addresses https://github.com/icy-arctic-fox/spectator/issues/42

spec/issues/github_issue_42_spec.cr

@@ -0,0 +1,43 @@
+require "../spec_helper"
+
+abstract class SdkInterface
+  abstract def register_hook(name, &block)
+end
+
+class Example
+  def initialize(@sdk : Sdk)
+  end
+
+  def configure
+    @sdk.register_hook("name") do
+      nil
+    end
+  end
+end
+
+class Sdk < SdkInterface
+  def initialize
+  end
+
+  def register_hook(name, &block)
+    nil
+  end
+end
+
+Spectator.describe Example do
+  mock Sdk do
+    stub register_hook(name, &block)
+  end
+
+  describe "#configure" do
+    it "registers a block on configure" do
+      sdk = Sdk.new
+      example_class = Example.new(sdk)
+      allow(sdk).to receive(register_hook())
+
+      example_class.configure
+
+      expect(sdk).to have_received(register_hook()).with("name")
+    end
+  end
+end

src/spectator/mocks/stubs.cr

@@ -7,11 +7,13 @@ module Spectator::Mocks
         params = nil
         args = nil
         body = nil
+        block_arg = nil
         if definition.is_a?(Call) # stub foo { :bar }
           receiver = definition.receiver.id
           named = false
           name = definition.name.id
           params = definition.args
+          block_arg = definition.block_arg
           if params.last.is_a?(Call)
             body = params.last.block
             params[-1] = params.last.name
@@ -100,28 +102,54 @@ module Spectator::Mocks
         end
       end
 
-      def {{receiver}}{{name}}({{params.splat}}){% if return_type.is_a?(ArrayLiteral) %} : {{return_type.type}}{% elsif return_type != :undefined %} : {{return_type.id}}{% elsif definition.is_a?(TypeDeclaration) %} : {{definition.type}}{% end %}
-        if (%harness = ::Spectator::Harness.current?)
-          %args = ::Spectator::Mocks::GenericArguments.create({{args.splat}})
-          %call = ::Spectator::Mocks::MethodCall.new({{name.symbolize}}, %args)
-          %harness.mocks.record_call(self, %call)
-          if (%stub = %harness.mocks.find_stub(self, %call))
-            return %stub.call!(%args) { {{fallback}} { |*%ya| yield *%ya } }
-          end
+      {% if block_arg.is_a?(Call) %}
+        def {{receiver}}{{name}}({{params.splat}}){% if return_type.is_a?(ArrayLiteral) %} : {{return_type.type}}{% elsif return_type != :undefined %} : {{return_type.id}}{% elsif definition.is_a?(TypeDeclaration) %} : {{definition.type}}{% end %}
+          if (%harness = ::Spectator::Harness.current?)
+            %args = ::Spectator::Mocks::GenericArguments.create({{args.splat}})
+            %call = ::Spectator::Mocks::MethodCall.new({{name.symbolize}}, %args)
+            %harness.mocks.record_call(self, %call)
+            if (%stub = %harness.mocks.find_stub(self, %call))
+              return %stub.call!(%args) { {{fallback}} { yield } }
+            end
 
-          {% if body && !body.is_a?(Nop) || return_type.is_a?(ArrayLiteral) %}
-            %method({{args.splat}}) { |*%ya| yield *%ya }
-          {% else %}
+            {% if body && !body.is_a?(Nop) || return_type.is_a?(ArrayLiteral) %}
+              %method({{args.splat}}) { yield }
+            {% else %}
+              {{fallback}} do
+                yield
+              end
+            {% end %}
+          else
+            {{fallback}} do
+              yield
+            end
+          end
+        end
+
+      {% else %}
+        def {{receiver}}{{name}}({{params.splat}}){% if return_type.is_a?(ArrayLiteral) %} : {{return_type.type}}{% elsif return_type != :undefined %} : {{return_type.id}}{% elsif definition.is_a?(TypeDeclaration) %} : {{definition.type}}{% end %}
+          if (%harness = ::Spectator::Harness.current?)
+            %args = ::Spectator::Mocks::GenericArguments.create({{args.splat}})
+            %call = ::Spectator::Mocks::MethodCall.new({{name.symbolize}}, %args)
+            %harness.mocks.record_call(self, %call)
+            if (%stub = %harness.mocks.find_stub(self, %call))
+              return %stub.call!(%args) { {{fallback}} { |*%ya| yield *%ya } }
+            end
+
+            {% if body && !body.is_a?(Nop) || return_type.is_a?(ArrayLiteral) %}
+              %method({{args.splat}}) { |*%ya| yield *%ya }
+            {% else %}
+              {{fallback}} do |*%yield_args|
+                yield *%yield_args
+              end
+            {% end %}
+          else
             {{fallback}} do |*%yield_args|
               yield *%yield_args
             end
-          {% end %}
-        else
-          {{fallback}} do |*%yield_args|
-            yield *%yield_args
           end
         end
-      end
+      {% end %}
     end
   end
 end