Include top-level symbols from same file in outer ambiguity error

Author: lrytz

spec/02-identifiers-names-and-scopes.md

@@ -17,11 +17,14 @@ which are collectively called _bindings_.
 Bindings of each kind are assigned a precedence which determines
 whether one binding can shadow another:
 
-1. Definitions and declarations in lexical scope that are not [top-level](09-top-level-definitions.html)
-   have the highest precedence.
-1. Definitions and declarations that are either inherited,
-   or made available by a package clause and also defined in the same compilation unit as the reference to them,
-   have the next highest precedence.
+<!-- Not in the spec since Scala 2 only warns (scala/scala#10339)
+1. Definitions and declarations that are local, or made available by a package clause and also
+   defined in the same compilation unit as the reference to them, have the highest precedence.
+1. Definitions and declarations that are inherited have the next highest precedence.
+-->
+1. Definitions and declarations that are local, inherited, or made
+   available by a package clause and also defined in the same compilation unit
+   as the reference to them, have the highest precedence.
 1. Explicit imports have the next highest precedence.
 1. Wildcard imports have the next highest precedence.
 1. Bindings made available by a package clause,

src/compiler/scala/tools/nsc/typechecker/Contexts.scala

@@ -1612,7 +1612,7 @@ trait Contexts { self: Analyzer =>
         val wasFoundInSuper = foundInSuper
         val foundCompetingSymbol: () => Boolean =
           if (foreignDefined) () => !foreignDefined
-          else () => !defSym.isTopLevel && !defSym.owner.isPackageObjectOrClass && !foundInSuper && !foreignDefined
+          else () => !defSym.owner.isPackageObjectOrClass && !foundInSuper && !foreignDefined
         while ((cx ne NoContext) && cx.depth >= symbolDepth) cx = cx.outer
         if (wasFoundInSuper)
           while ((cx ne NoContext) && (cx.owner eq cx0.owner)) cx = cx.outer

test/files/jvm/protectedacc.scala

@@ -47,7 +47,7 @@ package p {
     abstract class PolyA[a] {
       protected def m(x: a): Unit;
 
-      class B {
+      class BB {
 
         trait Node {
           def s: String = "";
@@ -134,7 +134,7 @@ package p {
 
     abstract class X[T] extends PolyA[T] {
 
-      trait Inner extends B {
+      trait Inner extends BB {
         def self: T;
         def self2: Node;
         def getB: Inner;

test/files/neg/t11921b.check

@@ -29,6 +29,13 @@ Such references are ambiguous in Scala 3. To continue using the inherited symbol
 Or use `-Wconf:msg=legacy-binding:s` to silence this warning.
         println(y)  // error
                 ^
+t11921b.scala:65: warning: reference to global is ambiguous;
+it is both defined in the enclosing package <empty> and inherited in the enclosing object D as value global (defined in class C)
+In Scala 2, symbols inherited from a superclass shadow symbols defined in an outer scope.
+Such references are ambiguous in Scala 3. To continue using the inherited symbol, write `this.global`.
+Or use `-Wconf:msg=legacy-binding:s` to silence this warning.
+  println(global)    // error
+          ^
 t11921b.scala:75: warning: reference to x is ambiguous;
 it is both defined in the enclosing object Uhu and inherited in the enclosing class C as value x (defined in class A, inherited through parent class B)
 In Scala 2, symbols inherited from a superclass shadow symbols defined in an outer scope.
@@ -50,5 +57,5 @@ Such references are ambiguous in Scala 3. To continue using the inherited symbol
 Or use `-Wconf:msg=legacy-binding:s` to silence this warning.
     def v = t(lo) // error
               ^
-7 warnings
+8 warnings
 1 error

test/files/neg/t11921b.scala

@@ -62,7 +62,7 @@ class C {
   val global = 42
 }
 object D extends C {
-  println(global)    // OK, since global is defined in package (https://github.com/scala/scala/pull/10220/files#r1109773904)
+  println(global)    // error
 }
 
 object test5 {
@@ -136,3 +136,10 @@ object test10 {
     def v = t(lo) // error
   }
 }
+
+package scala {
+  trait P { trait Option[+A] }
+  class C extends P {
+    def t = new Option[String] {} // OK, competing scala.Option is not defined in the same compilation unit
+  }
+}