From 789145cfbb078b30b6c3242627af29c95950fb25 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Wed, 18 Oct 2023 10:01:24 +0200
Subject: [PATCH 1/2] Keep qualifier of Ident when selecting setter

We already keep the qualifier as a typed splice if the prefix is an
explicit Select.

Fixes #18713
---
 .../src/dotty/tools/dotc/typer/Typer.scala     | 14 +++++++++++++-
 tests/pos/i18713.scala                         | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i18713.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 9f6bf8c7dee5..ac90664ddddf 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1119,7 +1119,19 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           case Apply(fn, _) if fn.symbol.is(ExtensionMethod) =>
             def toSetter(fn: Tree): untpd.Tree = fn match
               case fn @ Ident(name: TermName) =>
-                untpd.cpy.Ident(fn)(name.setterName)
+                // We need to make sure that the prefix of this extension getter is
+                // retained when we transform it into a setter. Otherwise, we could
+                // end up resoving an unrelated setter from another extension. We
+                // transform the `Ident` into a `Select` to ensure that the prefix
+                // is retained with a `TypedSplice` (see `case Select` bellow).
+                // See tests/pos/i18713.scala for an example.
+                fn.tpe match
+                  case TermRef(qual: TermRef, _) =>
+                    toSetter(ref(qual).select(fn.symbol).withSpan(fn.span))
+                  case TermRef(qual: ThisType, _) =>
+                    toSetter(This(qual.cls).select(fn.symbol).withSpan(fn.span))
+                  case TermRef(NoPrefix, _) =>
+                    untpd.cpy.Ident(fn)(name.setterName)
               case fn @ Select(qual, name: TermName) =>
                 untpd.cpy.Select(fn)(untpd.TypedSplice(qual), name.setterName)
               case fn @ TypeApply(fn1, targs) =>
diff --git a/tests/pos/i18713.scala b/tests/pos/i18713.scala
new file mode 100644
index 000000000000..0c406aa09d2e
--- /dev/null
+++ b/tests/pos/i18713.scala
@@ -0,0 +1,18 @@
+import language.experimental.relaxedExtensionImports
+
+class A
+object AA:
+  extension (a: A)
+    def f = ???
+    def f_=(x: String) = ???
+
+object BB:
+  extension (b: Long)
+    def f = ???
+    def f_=(x: String) = ???
+
+def test(a: A) =
+  import AA.*
+  import BB.*
+  a.f
+  a.f = "aa"

From e0f036cd744bfc7e034000bc3fef94e18ce2a2b8 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Mon, 13 Nov 2023 18:26:52 +0100
Subject: [PATCH 2/2] Update compiler/src/dotty/tools/dotc/typer/Typer.scala

---
 compiler/src/dotty/tools/dotc/typer/Typer.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index ac90664ddddf..bd83fbd864e0 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1121,7 +1121,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
               case fn @ Ident(name: TermName) =>
                 // We need to make sure that the prefix of this extension getter is
                 // retained when we transform it into a setter. Otherwise, we could
-                // end up resoving an unrelated setter from another extension. We
+                // end up resolving an unrelated setter from another extension. We
                 // transform the `Ident` into a `Select` to ensure that the prefix
                 // is retained with a `TypedSplice` (see `case Select` bellow).
                 // See tests/pos/i18713.scala for an example.