SI-9630 Fix spurious warning related to same-named case accessors

Hash consing of trees within pattern match analysis was broken, and
considered `x1.foo#1` to be the same tree as `x1.foo#2`, even though
the two `foo`-s referred to different symbols.

The hash consing was based on `Tree#correspondsStructure`, but the
predicate in that function cannot veto correspondance, it can only
supplement the default structural comparison.

I've instead created a custom tree comparison method for use in
the pattern matcher that handles the tree shapes that we use.

2 files changed, 17 insertions, 0 deletions

diff --git a/test/files/pos/t9630/t9630a.scala b/test/files/pos/t9630/t9630a.scala
new file mode 100644
index 0000000000..c76ecd2ff2
--- /dev/null
+++ b/test/files/pos/t9630/t9630a.scala
@@ -0,0 +1,9 @@
+
+sealed trait Base
+final case class Base_1(sameName: Some[Any]) extends Base
+final case class Base_2(sameName: Nested) extends Base
+
+sealed trait Nested
+final case class Nested_1(x: Any) extends Nested
+final case class Nested_2(y: Any) extends Nested
+
diff --git a/test/files/pos/t9630/t9630b.scala b/test/files/pos/t9630/t9630b.scala
new file mode 100644
index 0000000000..3e1787ec52
--- /dev/null
+++ b/test/files/pos/t9630/t9630b.scala
@@ -0,0 +1,8 @@
+
+class Test {
+  def test(b: Base): Unit = b match {
+    case Base_1(Some(_)) =>
+    case Base_2(Nested_1(_)) =>
+    case Base_2(Nested_2(_)) =>
+  }
+}