From 2b9a62bfdde75d21b352351af05f5ea92bf5906c Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Fri, 25 Aug 2023 10:52:12 +0200
Subject: [PATCH] Propagate constant in result of inline match

Fixes #13161
---
 compiler/src/dotty/tools/dotc/inlines/Inliner.scala | 8 ++++++--
 tests/pos/i13161.scala                              | 8 ++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 tests/pos/i13161.scala

diff --git a/compiler/src/dotty/tools/dotc/inlines/Inliner.scala b/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
index c6465c7d5f51..1fb6e785dd43 100644
--- a/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/inlines/Inliner.scala
@@ -877,8 +877,12 @@ class Inliner(val call: tpd.Tree)(using Context):
                 }
               case _ => rhs0
             }
-            val (usedBindings, rhs2) = dropUnusedDefs(caseBindings, rhs1)
-            val rhs = seq(usedBindings, rhs2)
+            val rhs2 = rhs1 match {
+              case Typed(expr, tpt) if rhs1.span.isSynthetic => constToLiteral(expr)
+              case _ => constToLiteral(rhs1)
+            }
+            val (usedBindings, rhs3) = dropUnusedDefs(caseBindings, rhs2)
+            val rhs = seq(usedBindings, rhs3)
             inlining.println(i"""--- reduce:
                                 |$tree
                                 |--- to:
diff --git a/tests/pos/i13161.scala b/tests/pos/i13161.scala
new file mode 100644
index 000000000000..4c6b2c4c32d0
--- /dev/null
+++ b/tests/pos/i13161.scala
@@ -0,0 +1,8 @@
+transparent inline def f: String =
+  inline 10 match
+    case _ =>
+      inline Some["foo"]("foo") match
+        case Some(x) => x
+
+def test =
+  inline val failMsg = f