From 77d1c83ff67894bf87d37bfb8982d818fdc88f73 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Mon, 17 Mar 2014 15:53:21 +0100
Subject: Fix of t0625 - compare method types

Method type comparison via <:< yielded false if the signatures of the two method types differed.
This is too strict, because methods can have the same parametyers but different result types and still
be in a subtype relationship. We now onyl demand that the sighatures have the same parameters.
---
 src/dotty/tools/dotc/core/TypeComparer.scala | 8 ++++++--
 tests/pending/pos/t0625.scala                | 8 --------
 tests/pos/t0625.scala                        | 8 ++++++++
 3 files changed, 14 insertions(+), 10 deletions(-)
 delete mode 100644 tests/pending/pos/t0625.scala
 create mode 100644 tests/pos/t0625.scala

diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala
index cfb9477c3..612b78f79 100644
--- a/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -201,7 +201,11 @@ class TypeComparer(initctx: Context) extends DotClass {
   def isNonBottomSubType(tp1: Type, tp2: Type): Boolean =
     !(tp2 isRef NothingClass) && isSubType(tp1, tp2)
 
-  def isSubType(tp1: Type, tp2: Type): Boolean = /*>|>*/ ctx.traceIndented(s"isSubType ${tp1.show} <:< ${tp2.show}", subtyping) /*<|<*/ {
+  private def traceInfo(tp1: Type, tp2: Type) =
+    s"${tp1.show} <:< ${tp2.show}" +
+    (if (ctx.settings.verbose.value) s"${tp1.getClass} ${tp2.getClass}" else "")
+
+  def isSubType(tp1: Type, tp2: Type): Boolean = /*>|>*/ ctx.traceIndented(s"isSubType ${traceInfo(tp1, tp2)}", subtyping) /*<|<*/ {
     if (tp2 eq NoType) false
     else if (tp1 eq tp2) true
     else {
@@ -467,7 +471,7 @@ class TypeComparer(initctx: Context) extends DotClass {
     case tp2 @ MethodType(_, formals2) =>
       def compareMethod = tp1 match {
         case tp1 @ MethodType(_, formals1) =>
-          tp1.signature == tp2.signature &&
+          (tp1.signature sameParams tp2.signature) &&
             (if (Config.newMatch) subsumeParams(formals1, formals2, tp1.isJava, tp2.isJava)
              else matchingParams(formals1, formals2, tp1.isJava, tp2.isJava)) &&
             tp1.isImplicit == tp2.isImplicit && // needed?
diff --git a/tests/pending/pos/t0625.scala b/tests/pending/pos/t0625.scala
deleted file mode 100644
index 561454259..000000000
--- a/tests/pending/pos/t0625.scala
+++ /dev/null
@@ -1,8 +0,0 @@
-object Test {
-  def idMap[C[_],T](m: { def map[U](f: T => U): C[U] }): C[T] = m.map(t => t)
-
-  def main(args: Array[String]): Unit = {
-    idMap(Some(5))
-    idMap(Responder.constant(5))
-  }
-}
diff --git a/tests/pos/t0625.scala b/tests/pos/t0625.scala
new file mode 100644
index 000000000..561454259
--- /dev/null
+++ b/tests/pos/t0625.scala
@@ -0,0 +1,8 @@
+object Test {
+  def idMap[C[_],T](m: { def map[U](f: T => U): C[U] }): C[T] = m.map(t => t)
+
+  def main(args: Array[String]): Unit = {
+    idMap(Some(5))
+    idMap(Responder.constant(5))
+  }
+}
-- 
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