From 394b645dd2d44ff68597527c6c690c73653f1bcb Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Fri, 9 May 2014 18:55:10 +0200
Subject: Fix of pos/t2429

This was a hard nut to crack. The problem exemplified by t2429 is that in a situation like

     val x: T = foo(...)

where `foo` needs implicit parameters the expected result type `T` is propagated into the
typechecking of foo(...) and consequently also into the implicit parameter search. This
is often necessary, for instance to instantiate type parameters. But it can lead to overconstrained
searches if in fact the right expansion is

     val x: T = viewToT(foo(...)(implicit params))

where `viewToT` is some implicit conversion. The fix handles that case by re-hecking the
application foo(...) with an empty result type, if the implicit parameter search fails.
But the re-checking is very subtle as is explained in the comment to `TyperState#tryWithFallback`.
---
 tests/pending/pos/t2429.scala | 25 -------------------------
 tests/pos/t2429.scala         | 25 +++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 25 deletions(-)
 delete mode 100755 tests/pending/pos/t2429.scala
 create mode 100755 tests/pos/t2429.scala

(limited to 'tests')

diff --git a/tests/pending/pos/t2429.scala b/tests/pending/pos/t2429.scala
deleted file mode 100755
index 4cda3bde1..000000000
--- a/tests/pending/pos/t2429.scala
+++ /dev/null
@@ -1,25 +0,0 @@
-object Msg {
-  trait T
-
-  trait TSeq
-
-  object TSeq {
-    implicit def fromSeq(s: Seq[T]): TSeq = sys.error("stub")
-  }
-
-  def render: Unit = {
-    val msgs: TSeq = (List[(Any, Any)]().flatMap {
-      case (a, b) => {
-        a match {
-          case _ => b match {
-            case _ => sys.error("stub")
-          }
-        }
-      }
-    } /*: Seq[T] Adding this type annotation avoids the compile error.*/)
-  }
-}
-object Oops {
- implicit def someImplicit(s: Seq[_]): String = sys.error("stub")
- def item: String = Nil map { case e: Any => e }
-}
diff --git a/tests/pos/t2429.scala b/tests/pos/t2429.scala
new file mode 100755
index 000000000..4cda3bde1
--- /dev/null
+++ b/tests/pos/t2429.scala
@@ -0,0 +1,25 @@
+object Msg {
+  trait T
+
+  trait TSeq
+
+  object TSeq {
+    implicit def fromSeq(s: Seq[T]): TSeq = sys.error("stub")
+  }
+
+  def render: Unit = {
+    val msgs: TSeq = (List[(Any, Any)]().flatMap {
+      case (a, b) => {
+        a match {
+          case _ => b match {
+            case _ => sys.error("stub")
+          }
+        }
+      }
+    } /*: Seq[T] Adding this type annotation avoids the compile error.*/)
+  }
+}
+object Oops {
+ implicit def someImplicit(s: Seq[_]): String = sys.error("stub")
+ def item: String = Nil map { case e: Any => e }
+}
-- 
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