Providers are auto-guessed when adding services.

src/service.cr

@@ -70,6 +70,10 @@ begin
 			service.consumes.each do |token|
 				provider = providers[token.token]?
 
+				if provider.nil?
+					provider = service.get_default_provider token.token
+				end
+
 				if provider.nil?
 					STDERR.puts "This service consumes a “#{token.token}” token, but you have not specified what other service is supposed to provide it."
 					STDERR.puts "Use the `service add #{args[1]} #{token.token}=<provider>` syntax to specify it."

src/service/environment.cr

@@ -67,6 +67,12 @@ class Environment
 		_def
 	end
 
+	def get_provider(token)
+		Service.all.find do |service|
+			service.environment == self && service.provides? token
+		end.try &.id
+	end
+
 	def to_s
 		"#{name} (#{type.to_s.downcase})"
 	end

src/service/service.cr

@@ -56,7 +56,7 @@ class Service
 		end
 
 		specs.sections.select(&.name.==("consumes")).each do |section|
-			@providers[section.name] = section.content["from"].as_s
+			@providers[section.options[0]] = section.content["from"].as_s
 		end
 	end
 
@@ -103,6 +103,12 @@ class Service
 		@reference.consumes
 	end
 
+	def provides?(token)
+		provides.any? do |provider|
+			provider.token == token
+		end
+	end
+
 	private def build_environment
 		env = {} of String => String
 
@@ -369,6 +375,10 @@ class Service
 
 		tree
 	end
+
+	def get_default_provider(token) : String?
+		@environment.get_provider(token) || Environment.root.get_provider(token)
+	end
 end