Fix #1786: support use package object in fun call

Author: liufengyun

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -363,12 +363,12 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         tree.withType(ownType)
     }
 
-    checkValue(tree1, pt)
+    checkValue(adaptPackageObject(tree1, pt), pt)
   }
 
   private def typedSelect(tree: untpd.Select, pt: Type, qual: Tree)(implicit ctx: Context): Select =
     healNonvariant(
-      checkValue(assignType(cpy.Select(tree)(qual, tree.name), qual), pt),
+      checkValue(adaptPackageObject(assignType(cpy.Select(tree)(qual, tree.name), qual), pt), pt),
       pt)
 
   /** Let `tree = p.n` where `p: T`. If tree's type is an unsafe instantiation
@@ -389,6 +389,15 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
       }
     else tree
 
+  /** Adapt e.g. `scala.meta { ... }` to `scala.meta.package { ... }` */
+  private def adaptPackageObject[T <: Tree](tree: T, pt: Type)(implicit ctx: Context): T = tree.tpe match {
+    case tp: NamedType if tp.symbol.is(Package) && pt.isInstanceOf[ApplyingProto] =>
+      val pkgObj = tp.symbol.moduleClass.denot.asInstanceOf[PackageClassDenotation].packageObj
+      if (pkgObj.exists) tree.withType(pkgObj.valRef).asInstanceOf[T] else tree
+    case _ =>
+      tree
+  }
+
   def typedSelect(tree: untpd.Select, pt: Type)(implicit ctx: Context): Tree = track("typedSelect") {
     def typeSelectOnTerm(implicit ctx: Context): Tree = {
       val qual1 = typedExpr(tree.qualifier, selectionProto(tree.name, pt, this))

tests/neg/i1786.scala

@@ -0,0 +1,17 @@
+package scala
+
+package object meta {
+  def apply(x: Int): Int = x * x
+}
+
+class Test {
+  def f(a: Any): Any = f(meta)         // error
+  def g(a: Any): Any = f(scala.meta)   // error
+
+  meta { 5 + 4 }
+
+  scala.meta { 3 }
+
+  val m1 = meta         // error
+  val m2 = scala.meta   // error
+}

tests/pos/i1786.scala

@@ -0,0 +1,18 @@
+package scala
+
+package object meta {
+  def apply(x: Int): Int = x * x
+}
+
+class Test {
+  meta { 5 + 4  }
+
+  scala.meta { 3 }
+
+  scala.meta.`package` { 3 }
+
+  // val m1 = meta         // error
+  // val m2 = scala.meta   // error
+  val m3 = scala.meta.`package`
+  val m4 = meta.`package`
+}