avoid messing with finalize cycle in Disposable.

ensure statements are closed when connection is closed

spec/result_set_spec.cr

@@ -1,5 +1,8 @@
 require "./spec_helper"
 
+class DummyException < Exception
+end
+
 describe DB::ResultSet do
   it "should enumerate records using each" do
     nums = [] of Int32
@@ -15,4 +18,28 @@ describe DB::ResultSet do
 
     nums.should eq([3, 4, 1, 2])
   end
+
+  it "should close ResultSet after query" do
+    with_dummy do |db|
+      the_rs = uninitialized DB::ResultSet
+      db.query "3,4 1,2" do |rs|
+        the_rs = rs
+      end
+      the_rs.closed?.should be_true
+    end
+  end
+
+  it "should close ResultSet after query even with exception" do
+    with_dummy do |db|
+      the_rs = uninitialized DB::ResultSet
+      begin
+        db.query "3,4 1,2" do |rs|
+          the_rs = rs
+          raise DummyException.new
+        end
+      rescue DummyException
+      end
+      the_rs.closed?.should be_true
+    end
+  end
 end

spec/statement_spec.cr

@@ -65,6 +65,15 @@ describe DB::Statement do
     end
   end
 
+  it "closing connection should close statement" do
+    stmt = uninitialized DB::Statement
+    with_dummy do |db|
+      stmt = db.prepare "3,4 1,2"
+      stmt.query
+    end
+    stmt.closed?.should be_true
+  end
+
   it "query with block should not close statement" do
     with_dummy do |db|
       stmt = db.prepare "3,4 1,2"

src/db/connection.cr

@@ -40,6 +40,9 @@ module DB
     abstract def build_statement(query) : Statement
 
     protected def do_close
+      @statements_cache.each do |_, stmt|
+        stmt.close
+      end
       @statements_cache.clear
     end
   end

src/db/disposable.cr

@@ -17,11 +17,6 @@ module DB
       @closed
     end
 
-    # :nodoc:
-    def finalize
-      close
-    end
-
     # Implementors overrides this method to perform resource cleanup
     protected abstract def do_close
   end