From 751cc2ffd0f2bac65ccc79565deb20f64b08cbd5 Mon Sep 17 00:00:00 2001
From: Matt Bovel <matthieu@bovel.net>
Date: Wed, 1 May 2024 12:02:40 +0200
Subject: [PATCH] Add warning for synchronized calls in value classes

Co-Authored-By: Yoonjae Jeon <18438185+nox213@users.noreply.github.com>
---
 compiler/src/dotty/tools/dotc/typer/RefChecks.scala |  4 +++-
 tests/warn/i17493.check                             | 11 +++++++++++
 tests/warn/i17493.scala                             |  4 ++++
 3 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 tests/warn/i17493.check
 create mode 100644 tests/warn/i17493.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
index cdfd137e5661..09ed2d91a788 100644
--- a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -1239,7 +1239,9 @@ object RefChecks {
   def checkAnyRefMethodCall(tree: Tree)(using Context) =
     if tree.symbol.exists
        && defn.topClasses.contains(tree.symbol.owner)
-       && (!ctx.owner.enclosingClass.exists || ctx.owner.enclosingClass.isPackageObject) then
+       && (!ctx.owner.enclosingClass.exists
+           || ctx.owner.enclosingClass.isPackageObject
+           || ctx.owner.enclosingClass.isValueClass) then
       report.warning(UnqualifiedCallToAnyRefMethod(tree, tree.symbol), tree)
 
 }
diff --git a/tests/warn/i17493.check b/tests/warn/i17493.check
new file mode 100644
index 000000000000..af5a0b8ad115
--- /dev/null
+++ b/tests/warn/i17493.check
@@ -0,0 +1,11 @@
+-- [E181] Potential Issue Warning: tests/warn/i17493.scala:3:11 --------------------------------------------------------
+3 |   def g = synchronized { println("hello, world") } // warn
+  |           ^^^^^^^^^^^^
+  |           Suspicious top-level unqualified call to synchronized
+  |---------------------------------------------------------------------------------------------------------------------
+  | Explanation (enabled by `-explain`)
+  |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  | Top-level unqualified calls to AnyRef or Any methods such as synchronized are
+  | resolved to calls on Predef or on imported methods. This might not be what
+  | you intended.
+   ---------------------------------------------------------------------------------------------------------------------
diff --git a/tests/warn/i17493.scala b/tests/warn/i17493.scala
new file mode 100644
index 000000000000..74f2039b81b5
--- /dev/null
+++ b/tests/warn/i17493.scala
@@ -0,0 +1,4 @@
+//> using options -explain
+ class A(val s: String) extends AnyVal {
+   def g = synchronized { println("hello, world") } // warn
+ }