From b0556ee3c2cdf5182ec4318dacf6864fa26b0906 Mon Sep 17 00:00:00 2001
From: Dale Wijnand <dale.wijnand@gmail.com>
Date: Fri, 11 Feb 2022 18:12:16 +0000
Subject: [PATCH 1/2] Fix backend assertion when using an exported enum

An exported enum is a <static> final method of the enum object.  When
selecting an inner enum case from it, that method will be the prefix.
The method doesn't have a type symbol, we have to widen to method type
and reach for its result type before we can get a handle on the type
symbol to key off of.

I wonder whether this widening and going to the result type is something
that should happen during Erasure's denotation transformation though...

Co-authored-by: Seth Tisue <seth@tisue.net>
---
 .../tools/backend/jvm/BCodeBodyBuilder.scala    |  2 +-
 tests/pos/i13490.scala                          | 17 +++++++++++++++++
 tests/run/i13490.min.scala                      | 13 +++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i13490.scala
 create mode 100644 tests/run/i13490.min.scala

diff --git a/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala b/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
index 96ae4e8a00af..6516d32b6518 100644
--- a/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
@@ -390,7 +390,7 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
           def genLoadQualUnlessElidable(): Unit = { if (!qualSafeToElide) { genLoadQualifier(tree) } }
 
           // receiverClass is used in the bytecode to access the field. using sym.owner may lead to IllegalAccessError
-          def receiverClass = qualifier.tpe.typeSymbol
+          def receiverClass = qualifier.tpe.widenTermRefExpr.finalResultType.typeSymbol
           if (sym.is(Module)) {
             genLoadQualUnlessElidable()
             genLoadModule(tree)
diff --git a/tests/pos/i13490.scala b/tests/pos/i13490.scala
new file mode 100644
index 000000000000..c8f3213e0649
--- /dev/null
+++ b/tests/pos/i13490.scala
@@ -0,0 +1,17 @@
+object MyApi {
+  enum MyEnum(a: Int) {
+    case A extends MyEnum(1)
+  }
+  case class Foo(a: MyEnum)
+}
+
+object Test {
+  export MyApi.*
+  import MyEnum.*
+  Foo(MyEnum.A) match {
+    case Foo(a) =>
+      a match {
+        case A =>
+      }
+  }
+}
diff --git a/tests/run/i13490.min.scala b/tests/run/i13490.min.scala
new file mode 100644
index 000000000000..4f9c19764a5d
--- /dev/null
+++ b/tests/run/i13490.min.scala
@@ -0,0 +1,13 @@
+object MyTypes:
+  enum MyEnum:
+    case Foo
+    case Bar
+
+object MyApi:
+  export MyTypes.*
+
+object MyUse:
+  import MyApi.MyEnum.Foo
+  def foo = Foo
+
+@main def Test = assert(MyUse.foo.toString == "Foo")

From 64c04d5ecbd25d51a54dd33f7ba61ae904a00f5d Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sat, 12 Feb 2022 19:52:59 +0100
Subject: [PATCH 2/2] Alternative fix based on tpd.desugarIdent

---
 compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala | 2 +-
 compiler/src/dotty/tools/dotc/ast/tpd.scala                 | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala b/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
index 6516d32b6518..96ae4e8a00af 100644
--- a/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
@@ -390,7 +390,7 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
           def genLoadQualUnlessElidable(): Unit = { if (!qualSafeToElide) { genLoadQualifier(tree) } }
 
           // receiverClass is used in the bytecode to access the field. using sym.owner may lead to IllegalAccessError
-          def receiverClass = qualifier.tpe.widenTermRefExpr.finalResultType.typeSymbol
+          def receiverClass = qualifier.tpe.typeSymbol
           if (sym.is(Module)) {
             genLoadQualUnlessElidable()
             genLoadModule(tree)
diff --git a/compiler/src/dotty/tools/dotc/ast/tpd.scala b/compiler/src/dotty/tools/dotc/ast/tpd.scala
index 98ea6e0c5c44..396d85a8c58a 100644
--- a/compiler/src/dotty/tools/dotc/ast/tpd.scala
+++ b/compiler/src/dotty/tools/dotc/ast/tpd.scala
@@ -1383,7 +1383,11 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   /** Recover identifier prefix (e.g. this) if it exists */
   def desugarIdentPrefix(tree: Ident)(using Context): Tree = tree.tpe match {
     case TermRef(prefix: TermRef, _) =>
-      ref(prefix)
+      prefix.info match
+        case mt: MethodType if mt.paramInfos.isEmpty && mt.resultType.typeSymbol.is(Module) =>
+          ref(mt.resultType.typeSymbol.sourceModule)
+        case _ =>
+          ref(prefix)
     case TermRef(prefix: ThisType, _) =>
       This(prefix.cls)
     case _ =>