From c0e93f1a57185ffebc0acdd61a54512e688976eb Mon Sep 17 00:00:00 2001
From: Dale Wijnand <dale.wijnand@gmail.com>
Date: Mon, 4 Dec 2023 16:29:08 +0000
Subject: [PATCH] Disable match anaylsis in inlined trees

---
 .../tools/dotc/transform/PatternMatcher.scala      | 14 +++++++++++---
 tests/pos/i19157.scala                             | 11 +++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 tests/pos/i19157.scala

diff --git a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
index f6d15b65b9f6..a73bd0841957 100644
--- a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -35,6 +35,13 @@ class PatternMatcher extends MiniPhase {
 
   override def runsAfter: Set[String] = Set(ElimRepeated.name)
 
+  private val InInlinedCode = new util.Property.Key[Boolean]
+  private def inInlinedCode(using Context) = ctx.property(InInlinedCode).getOrElse(false)
+
+  override def prepareForInlined(tree: Inlined)(using Context): Context =
+    if inInlinedCode then ctx
+    else ctx.fresh.setProperty(InInlinedCode, true)
+
   override def transformMatch(tree: Match)(using Context): Tree =
     if (tree.isInstanceOf[InlineMatch]) tree
     else {
@@ -46,9 +53,10 @@ class PatternMatcher extends MiniPhase {
         case rt => tree.tpe
       val translated = new Translator(matchType, this).translateMatch(tree)
 
-      // check exhaustivity and unreachability
-      SpaceEngine.checkExhaustivity(tree)
-      SpaceEngine.checkRedundancy(tree)
+      if !inInlinedCode then
+        // check exhaustivity and unreachability
+        SpaceEngine.checkExhaustivity(tree)
+        SpaceEngine.checkRedundancy(tree)
 
       translated.ensureConforms(matchType)
     }
diff --git a/tests/pos/i19157.scala b/tests/pos/i19157.scala
new file mode 100644
index 000000000000..019403adba73
--- /dev/null
+++ b/tests/pos/i19157.scala
@@ -0,0 +1,11 @@
+//> using options -Werror
+
+class Test:
+  inline def count(inline x: Boolean) = x match
+    case true => 1
+    case false => 0
+
+  assert(count(true) == 1)
+  assert(count(false) == 0)
+  var x = true
+  assert(count(x) == 1)