Backport "Disallow overloading from breaking stable patterns" to LTS (#…

…19163) Backports #18327 to the LTS branch. PR submitted by the release tooling. [skip ci]
scala · Dec 8, 2023 · 0e01547 · 0e01547
2 parents 96af022 + c43d387
commit 0e01547
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -668,7 +668,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     if ctx.mode.is(Mode.Pattern)
        && !tree.isType
        && !pt.isInstanceOf[ApplyingProto]
-       && !tree.tpe.isStable
+       && !tree.tpe.match
+        case tp: NamedType => tp.denot.hasAltWith(_.symbol.isStableMember && tp.prefix.isStable || tp.info.isStable)
+        case tp            => tp.isStable
        && !isWildcardArg(tree)
     then
       report.error(StableIdentPattern(tree, pt), tree.srcPos)

diff --git a/tests/pos/i18247.scala b/tests/pos/i18247.scala
@@ -0,0 +1,10 @@
+sealed trait Op
+object Op {
+  case object `==` extends Op
+}
+
+def t1(a: Op): true = {
+  a match {
+    case Op.`==` => true // was: won't compile
+  }
+}