From 61f29368fecf620585c8bb26bb83c746cbbe6571 Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Wed, 5 Dec 2012 10:18:53 +0100
Subject: SI-4859 Don't rewrite CC().CC2() to new CC2

Where CC and CC2 are case classes. Attempting to do so leads to
a "no legal prefix" error.

Now, we restrict this optimization (living in RefChecks ?!) to
case class applies with a "safe to inline" qualifier.
---
 .../scala/tools/nsc/typechecker/RefChecks.scala         |  9 ++++++---
 test/files/pos/t4859.scala                              | 17 +++++++++++++++++
 test/pending/pos/t4859.scala                            | 15 ---------------
 3 files changed, 23 insertions(+), 18 deletions(-)
 create mode 100644 test/files/pos/t4859.scala
 delete mode 100644 test/pending/pos/t4859.scala

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index e88447c46d..f0ced1a8d4 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -1389,9 +1389,12 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
         case TypeApply(fun, targs) =>
           isClassTypeAccessible(fun)
         case Select(module, apply) =>
-          // Fixes SI-5626. Classes in refinement types cannot be constructed with `new`. In this case,
-          // the companion class is actually not a ClassSymbol, but a reference to an abstract type.
-          module.symbol.companionClass.isClass
+          ( // SI-4859 `CaseClass1().InnerCaseClass2()` must not be rewritten to `new InnerCaseClass2()`
+            treeInfo.isExprSafeToInline(module) &&
+            // SI-5626 Classes in refinement types cannot be constructed with `new`. In this case,
+            // the companion class is actually not a ClassSymbol, but a reference to an abstract type.
+            module.symbol.companionClass.isClass
+          )
       }
 
       val doTransform =
diff --git a/test/files/pos/t4859.scala b/test/files/pos/t4859.scala
new file mode 100644
index 0000000000..284a39b7ab
--- /dev/null
+++ b/test/files/pos/t4859.scala
@@ -0,0 +1,17 @@
+object O {
+  // error: C is not a legal prefix for a constructor
+  C().CC()
+  // but this works.
+  D().DD()
+}
+
+case class C() {
+  case class CC()
+}
+
+case class D() {
+  class DD()
+  object DD {
+    def apply() = new DD()
+  }
+}
diff --git a/test/pending/pos/t4859.scala b/test/pending/pos/t4859.scala
deleted file mode 100644
index ec5abd966d..0000000000
--- a/test/pending/pos/t4859.scala
+++ /dev/null
@@ -1,15 +0,0 @@
-object O {
-  C().CC()
-  D().DD()
-}
-
-case class C() {
-  case class CC()
-}
-
-case class D() {
-  class DD()
-  object DD {
-    def apply() = new DD()
-  }
-}
-- 
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