Fix compiling quote in file with no splices

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/PostTyper.scala

@@ -203,7 +203,9 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
               // might be a type constructor.
               Checking.checkInstantiable(tree.tpe, nu.pos)
               withNoCheckNews(nu :: Nil)(super.transform(tree))
-            case _ =>
+            case meth =>
+              if (meth.symbol.name.eq(nme.QUOTE) && meth.symbol.owner.eq(defn.OpsPackageClass))
+                ctx.compilationUnit.containsQuotesOrSplices = true
               super.transform(tree)
           }
         case tree: TypeApply =>

tests/pos/quote-no-splices.scala

@@ -0,0 +1,9 @@
+class Foo {
+  def foo: Unit = {
+    val expr ='{
+      val a = 3
+      println("foo")
+      2 + a
+    }
+  }
+}