From 221b6c62bdddc909252a00321b110bb77b8860c1 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sun, 5 Apr 2020 11:09:57 +0200
Subject: [PATCH 1/2] Fix #8661: Avoid inaccessible cast targets in erasure

---
 .../dotty/tools/dotc/transform/Erasure.scala  | 31 +++++++++----------
 tests/run/i8661.check                         |  1 +
 tests/run/i8661/B.java                        |  4 +++
 tests/run/i8661/C.java                        |  4 +++
 tests/run/i8661/Test.scala                    |  6 ++++
 5 files changed, 29 insertions(+), 17 deletions(-)
 create mode 100644 tests/run/i8661.check
 create mode 100644 tests/run/i8661/B.java
 create mode 100644 tests/run/i8661/C.java
 create mode 100644 tests/run/i8661/Test.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/Erasure.scala b/compiler/src/dotty/tools/dotc/transform/Erasure.scala
index b824dd839554..7f02bb5e2a9e 100644
--- a/compiler/src/dotty/tools/dotc/transform/Erasure.scala
+++ b/compiler/src/dotty/tools/dotc/transform/Erasure.scala
@@ -639,28 +639,21 @@ object Erasure {
 
       val qual1 = typed(tree.qualifier, AnySelectionProto)
 
-      def mapOwner(sym: Symbol): Symbol = {
-        // PolyFunction apply Selects will not have a symbol, so deduce the owner
-        // from the typed qual.
-        def polyOwner: Symbol =
-          if (sym.exists || tree.name != nme.apply) NoSymbol
-          else {
-            val owner = qual1.tpe.widen.typeSymbol
-            if (defn.isFunctionClass(owner)) owner else NoSymbol
-          }
-
-        polyOwner orElse {
+      def mapOwner(sym: Symbol): Symbol =
+        if !sym.exists && tree.name == nme.apply then
+          // PolyFunction apply Selects will not have a symbol, so deduce the owner
+          // from the typed qual.
+          val owner = qual1.tpe.widen.typeSymbol
+          if defn.isFunctionClass(owner) then owner else NoSymbol
+        else
           val owner = sym.maybeOwner
-          if (defn.specialErasure.contains(owner)) {
+          if defn.specialErasure.contains(owner) then
             assert(sym.isConstructor, s"${sym.showLocated}")
             defn.specialErasure(owner)
-          }
-          else if (defn.isSyntheticFunctionClass(owner))
+          else if defn.isSyntheticFunctionClass(owner)
             defn.erasedFunctionClass(owner)
           else
             owner
-        }
-      }
 
       val origSym = tree.symbol
 
@@ -710,7 +703,11 @@ object Erasure {
           if (qual1.tpe.derivesFrom(sym.owner) || qual1.isInstanceOf[Super])
             select(qual1, sym)
           else
-            recur(cast(qual1, sym.owner.typeRef))
+            val castTarget = // Avoid inaccessible cast targets, see i8661
+              if sym.owner.isAccessibleFrom(qual1.tpe)(using preErasureCtx)
+              then sym.owner
+              else erasure(tree.qualifier.typeOpt.widen).classSymbol
+            recur(cast(qual1, castTarget.typeRef))
         }
       }
 
diff --git a/tests/run/i8661.check b/tests/run/i8661.check
new file mode 100644
index 000000000000..45b983be36b7
--- /dev/null
+++ b/tests/run/i8661.check
@@ -0,0 +1 @@
+hi
diff --git a/tests/run/i8661/B.java b/tests/run/i8661/B.java
new file mode 100644
index 000000000000..f83b1b0f67bb
--- /dev/null
+++ b/tests/run/i8661/B.java
@@ -0,0 +1,4 @@
+package pk;
+class B {
+    public void hi() { System.out.println("hi"); }
+}
diff --git a/tests/run/i8661/C.java b/tests/run/i8661/C.java
new file mode 100644
index 000000000000..88d14102ce3f
--- /dev/null
+++ b/tests/run/i8661/C.java
@@ -0,0 +1,4 @@
+package pk;
+public class C extends B {
+    public C() {}
+}
diff --git a/tests/run/i8661/Test.scala b/tests/run/i8661/Test.scala
new file mode 100644
index 000000000000..eaf9bc1e8aa7
--- /dev/null
+++ b/tests/run/i8661/Test.scala
@@ -0,0 +1,6 @@
+import pk.C
+object Test {
+  def main(args: Array[String]): Unit = {
+    identity(new C).hi()
+  }
+}

From 82e5d963097807651d83446983c55ad6a60d29f8 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sun, 5 Apr 2020 11:16:03 +0200
Subject: [PATCH 2/2] Small optimization

---
 compiler/src/dotty/tools/dotc/transform/Erasure.scala | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/transform/Erasure.scala b/compiler/src/dotty/tools/dotc/transform/Erasure.scala
index 7f02bb5e2a9e..c66b4159b04f 100644
--- a/compiler/src/dotty/tools/dotc/transform/Erasure.scala
+++ b/compiler/src/dotty/tools/dotc/transform/Erasure.scala
@@ -705,9 +705,9 @@ object Erasure {
           else
             val castTarget = // Avoid inaccessible cast targets, see i8661
               if sym.owner.isAccessibleFrom(qual1.tpe)(using preErasureCtx)
-              then sym.owner
-              else erasure(tree.qualifier.typeOpt.widen).classSymbol
-            recur(cast(qual1, castTarget.typeRef))
+              then sym.owner.typeRef
+              else erasure(tree.qualifier.typeOpt.widen)
+            recur(cast(qual1, castTarget))
         }
       }