From 484b8086ef1d5f66219d5865b1f3f5bf1712aa89 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Thu, 14 Mar 2024 17:20:51 +0100
Subject: [PATCH] Avoid spurious val binding in quote pattern

Fixes #19947

[Cherry-picked 96afd7a4dfd177f8db99d5216d95278759cc37a3]
---
 compiler/src/dotty/tools/dotc/typer/Typer.scala | 6 +++---
 tests/pos-macros/i19947/Macro_1.scala           | 9 +++++++++
 tests/pos-macros/i19947/Test_2.scala            | 1 +
 3 files changed, 13 insertions(+), 3 deletions(-)
 create mode 100644 tests/pos-macros/i19947/Macro_1.scala
 create mode 100644 tests/pos-macros/i19947/Test_2.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 9539422d94cf..7637bb3d5e2a 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2935,8 +2935,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   /** Translate infix operation expression `l op r` to
    *
    *    l.op(r)   			        if `op` is left-associative
-   *    { val x = l; r.op(x) }  if `op` is right-associative call-by-value and `l` is impure
-   *    r.op(l)                 if `op` is right-associative call-by-name or `l` is pure
+   *    { val x = l; r.op(x) }  if `op` is right-associative call-by-value and `l` is impure, and not in a quote pattern
+   *    r.op(l)                 if `op` is right-associative call-by-name, or `l` is pure, or in a quote pattern
    *
    *  Translate infix type    `l op r` to `op[l, r]`
    *  Translate infix pattern `l op r` to `op(l, r)`
@@ -2953,7 +2953,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         typedUnApply(cpy.Apply(tree)(op, l :: r :: Nil), pt)
       else {
         val app = typedApply(desugar.binop(l, op, r), pt)
-        if op.name.isRightAssocOperatorName then
+        if op.name.isRightAssocOperatorName && !ctx.mode.is(Mode.QuotedPattern) then
           val defs = new mutable.ListBuffer[Tree]
           def lift(app: Tree): Tree = (app: @unchecked) match
             case Apply(fn, args) =>
diff --git a/tests/pos-macros/i19947/Macro_1.scala b/tests/pos-macros/i19947/Macro_1.scala
new file mode 100644
index 000000000000..dc9ae46eb55f
--- /dev/null
+++ b/tests/pos-macros/i19947/Macro_1.scala
@@ -0,0 +1,9 @@
+import scala.quoted.*
+
+inline def expandMacro(inline from: Tuple): Any =
+  ${ expandMacroImpl }
+
+def expandMacroImpl(using Quotes): Expr[?] =
+  '{ 1 *: EmptyTuple } match
+    case '{ ($hd: Int) *: ($tl: Tuple) } => '{ ??? }
+    case x => throw new MatchError(x.show)
diff --git a/tests/pos-macros/i19947/Test_2.scala b/tests/pos-macros/i19947/Test_2.scala
new file mode 100644
index 000000000000..85c0dc845dc4
--- /dev/null
+++ b/tests/pos-macros/i19947/Test_2.scala
@@ -0,0 +1 @@
+def test: Any = expandMacro