Merge pull request #1624 from adriaanm/paulp-issue/5330-2.10.x

SI-5330, SI-6014 deal with existential self-type

1 files changed, 15 insertions, 3 deletions

diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index de6c6285ca..6df6ed4417 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -325,6 +325,18 @@ trait Types extends api.Types { self: SymbolTable =>
     }
   }
 
+  /** Same as a call to narrow unless existentials are visible
+   *  after widening the type. In that case, narrow from the widened
+   *  type instead of the proxy. This gives buried existentials a
+   *  chance to make peace with the other types. See SI-5330.
+   */
+  private def narrowForFindMember(tp: Type): Type = {
+    val w = tp.widen
+    // Only narrow on widened type when we have to -- narrow is expensive unless the target is a singleton type.
+    if ((tp ne w) && containsExistential(w)) w.narrow
+    else tp.narrow
+  }
+
   /** The base class for all types */
   abstract class Type extends TypeApiImpl with Annotatable[Type] {
     /** Types for which asSeenFrom always is the identity, no matter what
@@ -1079,7 +1091,7 @@ trait Types extends api.Types { self: SymbolTable =>
                          (other ne sym) &&
                          ((other.owner eq sym.owner) ||
                           (flags & PRIVATE) != 0 || {
-                             if (self eq null) self = this.narrow
+                             if (self eq null) self = narrowForFindMember(this)
                              if (symtpe eq null) symtpe = self.memberType(sym)
                              !(self.memberType(other) matches symtpe)
                           })}) {
@@ -1161,7 +1173,7 @@ trait Types extends api.Types { self: SymbolTable =>
                   if ((member ne sym) &&
                     ((member.owner eq sym.owner) ||
                       (flags & PRIVATE) != 0 || {
-                        if (self eq null) self = this.narrow
+                        if (self eq null) self = narrowForFindMember(this)
                         if (membertpe eq null) membertpe = self.memberType(member)
                         !(membertpe matches self.memberType(sym))
                       })) {
@@ -1176,7 +1188,7 @@ trait Types extends api.Types { self: SymbolTable =>
                     (other ne sym) &&
                       ((other.owner eq sym.owner) ||
                         (flags & PRIVATE) != 0 || {
-                          if (self eq null) self = this.narrow
+                          if (self eq null) self = narrowForFindMember(this)
                           if (symtpe eq null) symtpe = self.memberType(sym)
                           !(self.memberType(other) matches symtpe)
                              })}) {