Merge pull request #4639 from dotty-staging/fix-#4430

Fix #4430: Disallow access to Java bridge methods before erasure

Author: allanrenucci

compiler/src/dotty/tools/dotc/core/Denotations.scala

@@ -488,6 +488,7 @@ object Denotations {
               (!sym2.isAsConcrete(sym1) ||
                 precedes(sym1.owner, sym2.owner) ||
                 accessBoundary(sym2).isProperlyContainedIn(accessBoundary(sym1)) ||
+                sym2.is(Bridge) && !sym1.is(Bridge) ||
                 sym1.is(Method) && !sym2.is(Method)) ||
               sym1.info.isErroneous)
 

compiler/test/dotty/tools/backend/jvm/DottyBytecodeTests.scala

@@ -264,4 +264,27 @@ class TestBCode extends DottyBytecodeTest {
       }
     }
   }
+
+  // See #4430
+  @Test def javaBridgesAreNotVisible = {
+    val source =
+      """
+        |class Test {
+        |  def test = (new java.lang.StringBuilder()).append(Array[Char](), 0, 0)
+        |}
+      """.stripMargin
+
+    checkBCode(source) { dir =>
+      // We check the method call signature to make sure we don't call a Java bridge
+      val clsIn = dir.lookupName("Test.class", directory = false).input
+      val clsNode = loadClassNode(clsIn)
+      val testMethod = getMethod(clsNode, "test")
+      val instructions = instructionsFromMethod(testMethod)
+      val containsExpectedCall = instructions.exists {
+        case Invoke(_, "java/lang/StringBuilder", "append", "([CII)Ljava/lang/StringBuilder;", _) => true
+        case _ => false
+      }
+      assertTrue(containsExpectedCall)
+    }
+  }
 }

tests/pickling/i4430.scala

@@ -0,0 +1,7 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    val sb = new java.lang.StringBuilder()
+    sb.append(Array[Char](), 0, 0)
+    sb.length
+  }
+}

tests/run/i4430.scala

@@ -0,0 +1,7 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    val sb = new java.lang.StringBuilder()
+    sb.append(Array[Char](), 0, 0)
+    sb.length
+  }
+}