From aef8d7cf78f52f41f26d7d0e26fb311806219218 Mon Sep 17 00:00:00 2001
From: Guillaume Martres <smarter@ubuntu.com>
Date: Fri, 23 Apr 2021 15:32:47 +0200
Subject: [PATCH] Correct generic signature for intersection involving Array

We can't just check the class symbol since both `Array[Int]` and
`Array[String]` have the same symbol but different erasure.

Fixes #12204.
---
 .../src/dotty/tools/dotc/transform/GenericSignatures.scala   | 4 ++--
 tests/run/i12204/A_1.scala                                   | 3 +++
 tests/run/i12204/B_2.java                                    | 5 +++++
 tests/run/i12204/Test_3.scala                                | 5 +++++
 4 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 tests/run/i12204/A_1.scala
 create mode 100644 tests/run/i12204/B_2.java
 create mode 100644 tests/run/i12204/Test_3.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala b/compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala
index e2977a03e804..4348bee27ff5 100644
--- a/compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala
+++ b/compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala
@@ -131,10 +131,10 @@ object GenericSignatures {
      */
     def splitIntersection(parents: List[Type])(using Context): (List[Type], List[Type]) =
       val erasedParents = parents.map(erasure)
-      val erasedCls = erasedGlb(erasedParents).classSymbol
+      val erasedTp = erasedGlb(erasedParents)
       parents.zip(erasedParents)
         .partitionMap((parent, erasedParent) =>
-          if erasedParent.classSymbol eq erasedCls then
+          if erasedParent =:= erasedTp then
             Left(parent)
           else
             Right(parent))
diff --git a/tests/run/i12204/A_1.scala b/tests/run/i12204/A_1.scala
new file mode 100644
index 000000000000..95b519fa066a
--- /dev/null
+++ b/tests/run/i12204/A_1.scala
@@ -0,0 +1,3 @@
+object A {
+  def intARRAY_131(x: Array[String] with Array[Int]): Unit = {}
+}
diff --git a/tests/run/i12204/B_2.java b/tests/run/i12204/B_2.java
new file mode 100644
index 000000000000..283e63a8974b
--- /dev/null
+++ b/tests/run/i12204/B_2.java
@@ -0,0 +1,5 @@
+public class B_2 {
+  public static void test() {
+    A.intARRAY_131(null); // shouldn't throw a NoSuchMethodError
+  }
+}
diff --git a/tests/run/i12204/Test_3.scala b/tests/run/i12204/Test_3.scala
new file mode 100644
index 000000000000..51ec04559ca7
--- /dev/null
+++ b/tests/run/i12204/Test_3.scala
@@ -0,0 +1,5 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    B_2.test()
+  }
+}