Merge pull request #15752 from dotty-staging/backport-15619

Backport #15619: Always expand inline accessor names

Author: Kordyjan

compiler/src/dotty/tools/dotc/typer/PrepareInlineable.scala

@@ -54,7 +54,7 @@ object PrepareInlineable {
     abstract class MakeInlineableMap(val inlineSym: Symbol) extends TreeMap with Insert {
       def accessorNameOf(name: TermName, site: Symbol)(using Context): TermName =
         val accName = InlineAccessorName(name)
-        if site.is(Trait) then accName.expandedName(site) else accName
+        if site.isExtensibleClass then accName.expandedName(site) else accName
 
       /** A definition needs an accessor if it is private, protected, or qualified private
        *  and it is not part of the tree that gets inlined. The latter test is implemented

tests/neg/i15323.scala

@@ -0,0 +1,23 @@
+import scala.reflect.TypeTest
+
+class ForSyntax[E](using E: TypeTest[E | Any, E]):
+  extension [A](aOrE: E | A)
+    inline def flatMap[B](f: A => E | B): E | B =
+      aOrE match
+        case e: E => ???
+        case _ => ???
+
+
+class UnhappyCase[E](using E: TypeTest[E | Any, E]) extends ForSyntax[E]:
+  extension [A](aOrE: E | A)
+    inline def fold[B](inline fe: E => B, inline fa: A => B): B =
+      aOrE match
+        case e: E => ???
+        case _ => ???
+
+class A:
+  private val a = 1
+  inline def foo() = a
+class B extends A:
+  private val a = 2
+  inline def bar() = a

tests/pos/i15612.scala

@@ -1,2 +1,2 @@
-Select(Typed(Apply(Select(New(TypeIdent("StringContextOps")), "<init>"), List(Apply(Select(Select(Select(Ident("_root_"), "scala"), "StringContext"), "apply"), List(Typed(Repeated(List(Literal(StringConstant("Hello World ")), Literal(StringConstant("!"))), Inferred()), Inferred()))))), TypeIdent("StringContextOps")), "inline$sc")
+Select(Typed(Apply(Select(New(TypeIdent("StringContextOps")), "<init>"), List(Apply(Select(Select(Select(Ident("_root_"), "scala"), "StringContext"), "apply"), List(Typed(Repeated(List(Literal(StringConstant("Hello World ")), Literal(StringConstant("!"))), Inferred()), Inferred()))))), TypeIdent("StringContextOps")), "Macro$StringContextOps$$inline$sc")
 Typed(Repeated(List(Literal(IntConstant(1))), Inferred()), Inferred())