From 7babdab9ace07884ce844af923c93e0dcd49f7ea Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Wed, 9 Jan 2013 14:53:08 +0100
Subject: SI-6891 Fix value class + tailrec crasher.

rhs.substituteSymbols(old, new) leaves us with:

    def loop#12225(x#12226: A#15491): scala#21.this.Unit#1615 =
      loop#12225(x#12226)

In which the TermSymbol x#12226 has a stale info, pointing at
the A#7274, the class type parameter, rather than A#15491,
the corresponding type parameter of the synthetic backing
method.

I've improved `TreeSymSubstituter` to substitute not
only `Tree#{tpe, symbol}`, but also `DefTree#sym.info`.

The `pos` test that triggered the new code path are
listed here: https://gist.github.com/4575687

AFAICS, no special treatment of Function, Return, or Import
is needed in TreeSymSubstutor.
---
 src/reflect/scala/reflect/internal/Trees.scala | 16 ++++++++++++++++
 test/files/pos/t6891.flags                     |  1 +
 test/files/pos/t6891.scala                     | 26 ++++++++++++++++++++++++++
 test/pending/pos/t6891.flags                   |  1 -
 test/pending/pos/t6891.scala                   | 19 -------------------
 5 files changed, 43 insertions(+), 20 deletions(-)
 create mode 100644 test/files/pos/t6891.flags
 create mode 100644 test/files/pos/t6891.scala
 delete mode 100644 test/pending/pos/t6891.flags
 delete mode 100644 test/pending/pos/t6891.scala

diff --git a/src/reflect/scala/reflect/internal/Trees.scala b/src/reflect/scala/reflect/internal/Trees.scala
index 62998ef6cb..a528a9ced8 100644
--- a/src/reflect/scala/reflect/internal/Trees.scala
+++ b/src/reflect/scala/reflect/internal/Trees.scala
@@ -1439,6 +1439,22 @@ trait Trees extends api.Trees { self: SymbolTable =>
       if (tree.tpe ne null) tree.tpe = symSubst(tree.tpe)
       if (tree.hasSymbol) {
         subst(from, to)
+        tree match {
+          case _: DefTree =>
+            val newInfo = symSubst(tree.symbol.info)
+            if (!(newInfo =:= tree.symbol.info)) {
+              debuglog(sm"""
+                |TreeSymSubstituter: updated info of symbol ${tree.symbol}
+                |  Old: ${showRaw(tree.symbol.info, printTypes = true, printIds = true)}
+                |  New: ${showRaw(newInfo, printTypes = true, printIds = true)}""")
+              tree.symbol updateInfo newInfo
+            }
+          case _          =>
+            // no special handling is required for Function or Import nodes here.
+            // as they don't have interesting infos attached to their symbols.
+            // Subsitution of the referenced symbol of Return nodes is handled
+            // in .ChangeOwnerTraverser
+        }
         tree match {
           case Ident(name0) if tree.symbol != NoSymbol =>
             treeCopy.Ident(tree, tree.symbol.name)
diff --git a/test/files/pos/t6891.flags b/test/files/pos/t6891.flags
new file mode 100644
index 0000000000..fe048006aa
--- /dev/null
+++ b/test/files/pos/t6891.flags
@@ -0,0 +1 @@
+-Ycheck:extmethods -Xfatal-warnings
\ No newline at end of file
diff --git a/test/files/pos/t6891.scala b/test/files/pos/t6891.scala
new file mode 100644
index 0000000000..bed2d0d777
--- /dev/null
+++ b/test/files/pos/t6891.scala
@@ -0,0 +1,26 @@
+object O {
+  implicit class Foo[A](val value: String) extends AnyVal {
+    def bippy() = {
+      @annotation.tailrec def loop(x: A): Unit = loop(x)
+      ()
+    }
+
+    def boppy() = {
+      @annotation.tailrec def loop(x: value.type): Unit = loop(x)
+      ()
+    }
+
+    def beppy[C](c: => C) = {
+      () => c
+      @annotation.tailrec def loop(x: value.type): Unit = loop(x)
+        () => c
+      ()
+    }
+  }
+  // uncaught exception during compilation: Types$TypeError("type mismatch;
+  //  found   : A(in method bippy$extension)
+  //  required: A(in class Foo)") @ scala.tools.nsc.typechecker.Contexts$Context.issueCommon(Contexts.scala:396)
+  // error: scala.reflect.internal.Types$TypeError: type mismatch;
+  //  found   : A(in method bippy$extension)
+  //  required: A(in class Foo)
+}
diff --git a/test/pending/pos/t6891.flags b/test/pending/pos/t6891.flags
deleted file mode 100644
index fe048006aa..0000000000
--- a/test/pending/pos/t6891.flags
+++ /dev/null
@@ -1 +0,0 @@
--Ycheck:extmethods -Xfatal-warnings
\ No newline at end of file
diff --git a/test/pending/pos/t6891.scala b/test/pending/pos/t6891.scala
deleted file mode 100644
index bf79c2d293..0000000000
--- a/test/pending/pos/t6891.scala
+++ /dev/null
@@ -1,19 +0,0 @@
-object O {
-  implicit class Foo[A](val value: String) extends AnyVal {
-    def bippy() = {
-      @annotation.tailrec def loop(x: A): Unit = loop(x)
-      ()
-    }
-
-    def boppy() = {
-      @annotation.tailrec def loop(x: value.type): Unit = loop(x)
-      ()
-    }
-  }
-  // uncaught exception during compilation: Types$TypeError("type mismatch;
-  //  found   : A(in method bippy$extension)
-  //  required: A(in class Foo)") @ scala.tools.nsc.typechecker.Contexts$Context.issueCommon(Contexts.scala:396)
-  // error: scala.reflect.internal.Types$TypeError: type mismatch;
-  //  found   : A(in method bippy$extension)
-  //  required: A(in class Foo)
-}
-- 
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