Merge pull request #4808 from retronym/ticket/9527

SI-9527 Fix NPE in ambiguous implicit error generation

5 files changed, 31 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
index c9d3b3da96..b7c72f5373 100644
--- a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
@@ -1250,13 +1250,14 @@ trait ContextErrors {
           )
         }
 
-        def treeTypeArgs(annotatedTree: Tree) = annotatedTree match {
+        def treeTypeArgs(annotatedTree: Tree): List[String] = annotatedTree match {
           case TypeApply(_, args) => args.map(_.toString)
+          case Block(_, Function(_, treeInfo.Applied(_, targs, _))) => targs.map(_.toString) // eta expansion, see neg/t9527b.scala
           case _ => Nil
         }
 
         context.issueAmbiguousError(AmbiguousImplicitTypeError(tree,
-          (tree1.symbol, tree2.symbol) match {
+          (info1.sym, info2.sym) match {
             case (ImplicitAmbiguousMsg(msg), _) => msg.format(treeTypeArgs(tree1))
             case (_, ImplicitAmbiguousMsg(msg)) => msg.format(treeTypeArgs(tree2))
             case (_, _) if isView => viewMsg
diff --git a/test/files/neg/t9527a.check b/test/files/neg/t9527a.check
new file mode 100644
index 0000000000..e756518bed
--- /dev/null
+++ b/test/files/neg/t9527a.check
@@ -0,0 +1,7 @@
+t9527a.scala:5: error: ambiguous implicit values:
+ both method f in class C of type (x: Int)String
+ and method g in class C of type (x: Int)String
+ match expected type Int => String
+    implicitly[Int => String]
+              ^
+one error found
diff --git a/test/files/neg/t9527a.scala b/test/files/neg/t9527a.scala
new file mode 100644
index 0000000000..35c58fc9a6
--- /dev/null
+++ b/test/files/neg/t9527a.scala
@@ -0,0 +1,8 @@
+class C {
+  implicit def f(x: Int): String = "f was here"
+  implicit def g(x: Int): String = "f was here"
+  def test: Unit = {
+    implicitly[Int => String]
+  }
+}
+
diff --git a/test/files/neg/t9527b.check b/test/files/neg/t9527b.check
new file mode 100644
index 0000000000..4529ec83ea
--- /dev/null
+++ b/test/files/neg/t9527b.check
@@ -0,0 +1,4 @@
+t9527b.scala:6: error: msg A=Nothing
+    implicitly[Int => String]
+              ^
+one error found
diff --git a/test/files/neg/t9527b.scala b/test/files/neg/t9527b.scala
new file mode 100644
index 0000000000..b40a4dca9e
--- /dev/null
+++ b/test/files/neg/t9527b.scala
@@ -0,0 +1,9 @@
+class C {
+  @annotation.implicitAmbiguous("msg A=${A}")
+  implicit def f[A](x: Int): String = "f was here"
+  implicit def g(x: Int): String = "f was here"
+  def test: Unit = {
+    implicitly[Int => String]
+  }
+}
+