From 96bfb69c933148ad0561e589a444fab1308d7951 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Wed, 8 Feb 2023 11:58:53 +0100
Subject: [PATCH] Handle pickled forward references in pickled expressions

To compute forward references it was assumed that the owner of that
symbol can be found in the TASTy. This is not always the case with TASTy
expressions of pickled quotes. The owner might be outside the quote, in
this case the context already has the owner of the referenced symbol.
These are local symbols defined at the top-level of the TASTy.

Fixes #16843
---
 .../tools/dotc/core/tasty/TreeUnpickler.scala  |  6 +++++-
 tests/pos-macros/i16843a/Macro_1.scala         | 13 +++++++++++++
 tests/pos-macros/i16843a/Test_2.scala          |  1 +
 tests/pos-macros/i16843b/Macro_1.scala         | 18 ++++++++++++++++++
 tests/pos-macros/i16843b/Test_2.scala          |  1 +
 5 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos-macros/i16843a/Macro_1.scala
 create mode 100644 tests/pos-macros/i16843a/Test_2.scala
 create mode 100644 tests/pos-macros/i16843b/Macro_1.scala
 create mode 100644 tests/pos-macros/i16843b/Test_2.scala

diff --git a/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala b/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
index 91290b4ddd41..dfe04dbe6d2b 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
@@ -74,6 +74,9 @@ class TreeUnpickler(reader: TastyReader,
    */
   private val typeAtAddr = new mutable.HashMap[Addr, Type]
 
+  /** If this is a pickled quote, the owner of the quote, otherwise NoSymbol. */
+  private var rootOwner: Symbol = NoSymbol
+
   /** The root symbol denotation which are defined by the Tasty file associated with this
    *  TreeUnpickler. Set by `enterTopLevel`.
    */
@@ -106,6 +109,7 @@ class TreeUnpickler(reader: TastyReader,
 
   /** The unpickled trees */
   def unpickle(mode: UnpickleMode)(using Context): List[Tree] = {
+    if mode != UnpickleMode.TopLevel then rootOwner = ctx.owner
     assert(roots != null, "unpickle without previous enterTopLevel")
     val rdr = new TreeReader(reader)
     mode match {
@@ -1635,7 +1639,7 @@ class TreeUnpickler(reader: TastyReader,
             pickling.println(i"no owner for $addr among $cs%, %")
             throw ex
         }
-      try search(children, NoSymbol)
+      try search(children, rootOwner)
       catch {
         case ex: TreeWithoutOwner =>
           pickling.println(s"ownerTree = $ownerTree")
diff --git a/tests/pos-macros/i16843a/Macro_1.scala b/tests/pos-macros/i16843a/Macro_1.scala
new file mode 100644
index 000000000000..98c1505910e6
--- /dev/null
+++ b/tests/pos-macros/i16843a/Macro_1.scala
@@ -0,0 +1,13 @@
+import scala.quoted.*
+
+case class Foo(x: Int)
+
+inline def foo = ${ fooImpl }
+
+def fooImpl(using Quotes) =
+  val tmp = '{
+    1 match
+      case x @ (y: Int) => 0
+  }
+
+  '{}
diff --git a/tests/pos-macros/i16843a/Test_2.scala b/tests/pos-macros/i16843a/Test_2.scala
new file mode 100644
index 000000000000..25406428d0cf
--- /dev/null
+++ b/tests/pos-macros/i16843a/Test_2.scala
@@ -0,0 +1 @@
+val x = foo
diff --git a/tests/pos-macros/i16843b/Macro_1.scala b/tests/pos-macros/i16843b/Macro_1.scala
new file mode 100644
index 000000000000..631bde56f1f1
--- /dev/null
+++ b/tests/pos-macros/i16843b/Macro_1.scala
@@ -0,0 +1,18 @@
+import scala.quoted.*
+
+inline def foo: Int = ${ fooImpl }
+
+def fooImpl(using Quotes): Expr[Int] =
+  '{
+    val b = ${
+      val a = '{
+        (1: Int) match
+          case x @ (y: Int) => 0
+      }
+      a
+    }
+
+    (1: Int) match
+      case x @ (y: Int) => 0
+  }
+
diff --git a/tests/pos-macros/i16843b/Test_2.scala b/tests/pos-macros/i16843b/Test_2.scala
new file mode 100644
index 000000000000..54c769c9618f
--- /dev/null
+++ b/tests/pos-macros/i16843b/Test_2.scala
@@ -0,0 +1 @@
+def test = foo