Query[Measure[A]] on right hand side of === and <> (provided that A is compatible with left side)

Author: max-l

src/main/scala/org/squeryl/dsl/TypedExpression.scala

@@ -117,6 +117,12 @@ trait TypedExpression[A1,T1] extends ExpressionNode {
   def ===[A2,T2](b: TypedExpression[A2,T2])(implicit ev: CanCompare[T1, T2]) = new EqualityExpression(this, b)
   def <>[A2,T2](b: TypedExpression[A2,T2])(implicit ev: CanCompare[T1, T2]) = new BinaryOperatorNodeLogicalBoolean(this, b, "<>")
 
+  def ===[A2,T2](q: Query[Measures[A2]])(implicit tef: TypedExpressionFactory[A2,T2], ev: CanCompare[T1, T2]) = 
+    new BinaryOperatorNodeLogicalBoolean(this, q.copy(false).ast, "=")
+
+  def <>[A2,T2](q: Query[Measures[A2]])(implicit tef: TypedExpressionFactory[A2,T2], ev: CanCompare[T1, T2]) = 
+    new BinaryOperatorNodeLogicalBoolean(this, q.copy(false).ast, "=")
+  
   def gt[A2,T2](b: TypedExpression[A2,T2])(implicit ev: CanCompare[T1, T2]) = new BinaryOperatorNodeLogicalBoolean(this, b, ">")
   def lt[A2,T2](b: TypedExpression[A2,T2])(implicit ev: CanCompare[T1, T2]) = new BinaryOperatorNodeLogicalBoolean(this, b, "<")
   def gte[A2,T2](b: TypedExpression[A2,T2])(implicit ev: CanCompare[T1, T2]) = new BinaryOperatorNodeLogicalBoolean(this, b, ">=")

src/test/scala/org/squeryl/test/schooldb/SchoolDb.scala

@@ -378,6 +378,21 @@ abstract class SchoolDbTestRun extends SchoolDbTestBase {
     val se = stringKeyedEntities.insert(new StringKeyedEntity("123", Tempo.Largo))
   }
 
+  test("EqualCountInSubQuery", SingleTestRun){
+    val testInstance = sharedTestInstance; import testInstance._
+
+    val q =
+      from(courses)(c =>
+        where (          
+          //new org.squeryl.dsl.ast.BinaryOperatorNodeLogicalBoolean(1, from(courseSubscriptions)(cs => compute(countDistinct(cs.courseId))).ast, "=")
+          1 === from(courseSubscriptions)(cs => where(c.id === cs.courseId) compute(countDistinct(cs.courseId)))
+        )
+        select(c)
+     ).toList
+     
+     assert(q.size == 4)
+  }
+
   test("CountSignatures"){
     val testInstance = sharedTestInstance; import testInstance._
     val q =