From 6bea14bf843f705ad252adfc3ef5f8bd945b1c4d Mon Sep 17 00:00:00 2001
From: Dale Wijnand <dale.wijnand@gmail.com>
Date: Wed, 19 Jul 2023 14:48:25 +0100
Subject: [PATCH] Avoid over widening in SpaceEngine

---
 .../src/dotty/tools/dotc/transform/patmat/Space.scala    | 8 +++++++-
 tests/patmat/i17184.scala                                | 9 +++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 tests/patmat/i17184.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
index c45cb1379a56..45c1444879db 100644
--- a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -578,7 +578,13 @@ object SpaceEngine {
           if (arity > 0)
             productSelectorTypes(resTp, unappSym.srcPos)
           else {
-            val getTp = resTp.select(nme.get).finalResultType.widenTermRefExpr
+            val getTp = resTp.select(nme.get).finalResultType match
+              case tp: TermRef if !tp.isOverloaded =>
+                // Like widenTermRefExpr, except not recursively.
+                // For example, in i17184 widen Option[foo.type]#get
+                // to Option[foo.type] instead of Option[Int].
+                tp.underlying.widenExpr
+              case tp => tp
             if (argLen == 1) getTp :: Nil
             else productSelectorTypes(getTp, unappSym.srcPos)
           }
diff --git a/tests/patmat/i17184.scala b/tests/patmat/i17184.scala
new file mode 100644
index 000000000000..9c04ade63510
--- /dev/null
+++ b/tests/patmat/i17184.scala
@@ -0,0 +1,9 @@
+class Foo
+trait Bar:
+  val foo : Int
+  val f : Option[foo.type] = Some(foo)
+
+  def g : Boolean =
+    f match
+      case None => false
+      case Some(_) => true