add Connection#last_inserted_id

extract QueryMethods modules and use it in Database and Connection
"add" finalize methods, but they cause GC warnings

spec/std/db/dummy_driver.cr

@@ -12,6 +12,10 @@ class DummyDriver < DB::Driver
       @last_statement = DummyStatement.new(self, query.split.map { |r| r.split ',' })
     end
 
+    def last_insert_id : Int64
+      0
+    end
+
     def perform_close
     end
   end

src/db/connection.cr

@@ -18,8 +18,17 @@ module DB
       @closed
     end
 
+    # # :nodoc:
+    # def finalize
+    #   close unless closed?
+    # end
+
     abstract def prepare(query) : Statement
 
+    include QueryMethods
+
+    abstract def last_insert_id : Int64
+
     protected abstract def perform_close
   end
 end

src/db/database.cr

@@ -31,39 +31,6 @@ module DB
       connection.prepare(query)
     end
 
-    def query(query, *args)
-      prepare(query).query(*args)
-    end
-
-    def query(query, *args)
-      # CHECK prepare(query).query(*args, &block)
-      query(query, *args).tap do |rs|
-        begin
-          yield rs
-        ensure
-          rs.close
-        end
-      end
-    end
-
-    def exec(query, *args)
-      prepare(query).exec(*args)
-    end
-
-    def scalar(query, *args)
-      prepare(query).scalar(*args)
-    end
-
-    def scalar(t, query, *args)
-      prepare(query).scalar(t, *args)
-    end
-
-    def scalar?(query, *args)
-      prepare(query).scalar?(*args)
-    end
-
-    def scalar?(t, query, *args)
-      prepare(query).scalar?(t, *args)
-    end
+    include QueryMethods
   end
 end

src/db/db.cr

@@ -24,6 +24,7 @@ module DB
   end
 end
 
+require "./query_methods"
 require "./database"
 require "./driver"
 require "./connection"

src/db/query_methods.cr

@@ -0,0 +1,38 @@
+module DB
+  module QueryMethods
+    def query(query, *args)
+      prepare(query).query(*args)
+    end
+
+    def query(query, *args)
+      # CHECK prepare(query).query(*args, &block)
+      query(query, *args).tap do |rs|
+        begin
+          yield rs
+        ensure
+          rs.close
+        end
+      end
+    end
+
+    def exec(query, *args)
+      prepare(query).exec(*args)
+    end
+
+    def scalar(query, *args)
+      prepare(query).scalar(*args)
+    end
+
+    def scalar(t, query, *args)
+      prepare(query).scalar(t, *args)
+    end
+
+    def scalar?(query, *args)
+      prepare(query).scalar?(*args)
+    end
+
+    def scalar?(t, query, *args)
+      prepare(query).scalar?(t, *args)
+    end
+  end
+end

src/db/statement.cr

@@ -24,7 +24,7 @@ module DB
         end
       end
 
-      raise "unreachable"
+      raise "no results"
     end
 
     def scalar?(*args)
@@ -39,7 +39,7 @@ module DB
         end
       end
 
-      raise "unreachable"
+      raise "no results"
     end
 
     def query(*args)
@@ -92,6 +92,11 @@ module DB
       @closed
     end
 
+    # # :nodoc:
+    # def finalize
+    #   close unless closed?
+    # end
+
     # 1-based positional arguments
     protected def begin_parameters
     end