Some work on error messages, somewhat based on ...

Some work on error messages, somewhat based on ideas in #3092. No
review.

7 files changed, 72 insertions, 21 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
index 081be78c8b..99c85f72f1 100644
--- a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala
@@ -145,11 +145,15 @@ trait TypeDiagnostics {
   def alternativesString(tree: Tree) =
     alternatives(tree) map (x => "  " + methodTypeErrorString(x)) mkString ("", " <and>\n", "\n")
 
-  def missingParameterTypeError(fun: Tree, vparam: ValDef) = {
-    val suffix = if (vparam.mods.isSynthetic) " for expanded function "+fun else ""
-
-    inferError(vparam.pos, "missing parameter type" + suffix)
-    ErrorType
+  def missingParameterTypeMsg(fun: Tree, vparam: ValDef) = {
+    val suffix =
+      if (!vparam.mods.isSynthetic) ""
+      else " for expanded function" + (fun match {
+        case Function(_, Match(_, _)) => "\n(see SLS 8.5, \"Pattern Matching Anonymous Functions\")"
+        case _                        => " " + fun
+      })
+
+    "missing parameter type" + suffix
   }
 
   def treeSymTypeMsg(tree: Tree): String = {
@@ -170,6 +174,22 @@ trait TypeDiagnostics {
     else defaultMessage
   }
 
+  def notEnoughArgumentsMsg(fun: Tree, missing: List[Symbol]): String = {
+    val suffix = {
+      if (missing.isEmpty) ""
+      else {
+        val keep = missing take 3 map (_.name)
+        ".\nUnspecified value parameter%s %s".format(
+          if (missing.tail.isEmpty) "" else "s",
+          if (missing drop 3 nonEmpty) (keep :+ "...").mkString(", ")
+          else keep.mkString("", ", ", ".")
+        )
+      }
+    }
+
+    "not enough arguments for " + treeSymTypeMsg(fun) + suffix
+  }
+
   def applyErrorMsg(tree: Tree, msg: String, argtpes: List[Type], pt: Type) = {
     def asParams(xs: List[Any]) = xs.mkString("(", ", ", ")")
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 0ead1f6eee..155883299a 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -2036,11 +2036,7 @@ trait Typers { self: Analyzer =>
                     }
                   case _ =>
                 }
-                error(
-                  vparam.pos,
-                  "missing parameter type"+
-                  (if (vparam.mods.isSynthetic) " for expanded function "+fun
-                   else ""))
+                error(vparam.pos, missingParameterTypeMsg(fun, vparam))
                 ErrorType
               }
             if (!vparam.tpt.pos.isDefined) vparam.tpt setPos vparam.pos.focus
@@ -2390,16 +2386,7 @@ trait Typers { self: Analyzer =>
                   if (!(context.diagnostic contains note)) context.diagnostic = note :: context.diagnostic
                   doTypedApply(tree, if (blockIsEmpty) fun else fun1, allArgs, mode, pt)
                 } else {
-                  tryTupleApply.getOrElse {
-                    val suffix =
-                      if (missing.isEmpty) ""
-                      else {
-                        val missingStr = missing.take(3).map(_.name).mkString(", ") + (if (missing.length > 3) ", ..." else ".")
-                        val sOpt = if (missing.length > 1) "s" else ""
-                        ".\nUnspecified value parameter"+ sOpt +" "+ missingStr
-                      }
-                    errorTree(tree, "not enough arguments for "+treeSymTypeMsg(fun) + suffix)
-                  }
+                  tryTupleApply getOrElse errorTree(tree, notEnoughArgumentsMsg(fun, missing))
                 }
               }
             }
diff --git a/test/files/neg/predef-masking.check b/test/files/neg/predef-masking.check
new file mode 100644
index 0000000000..79e4dece8a
--- /dev/null
+++ b/test/files/neg/predef-masking.check
@@ -0,0 +1,4 @@
+predef-masking.scala:7: error: value + is not a member of type parameter T
+  def f[T](x: T) = x + 5
+                     ^
+one error found
diff --git a/test/files/neg/predef-masking.scala b/test/files/neg/predef-masking.scala
new file mode 100644
index 0000000000..67b69aa169
--- /dev/null
+++ b/test/files/neg/predef-masking.scala
@@ -0,0 +1,21 @@
+// Testing predef masking
+import Predef.{ any2stringadd => _, _ }
+
+object StringPlusConfusion {
+  // Would love to do something about this error message, but by the
+  // time we get our hands on it the context is lost.
+  def f[T](x: T) = x + 5
+
+  // After we block out any2stringadd, the error is:
+  //
+  // work/a.scala:7: error: value + is not a member of type parameter T
+  //   def f[T](x: T) = x + 5
+  //                      ^
+  // Normally, it is:
+  //
+  // work/a.scala:7: error: type mismatch;
+  //  found   : Int(5)
+  //  required: String
+  //   def f[T](x: T) = x + 5
+  //                        ^
+}
diff --git a/test/files/neg/type-diagnostics.check b/test/files/neg/type-diagnostics.check
index 33e07f3816..62d580a788 100644
--- a/test/files/neg/type-diagnostics.check
+++ b/test/files/neg/type-diagnostics.check
@@ -13,4 +13,8 @@ type-diagnostics.scala:17: error: type mismatch;
  required: java.lang.String
   def f2[String](s: String) = strings(List(s))
                                            ^
-three errors found
+type-diagnostics.scala:21: error: missing parameter type for expanded function
+(see SLS 8.5, "Pattern Matching Anonymous Functions")
+  val f = { case 5 => 10 }
+          ^
+four errors found
diff --git a/test/files/neg/type-diagnostics.scala b/test/files/neg/type-diagnostics.scala
index fdc0978138..fcc49812f4 100644
--- a/test/files/neg/type-diagnostics.scala
+++ b/test/files/neg/type-diagnostics.scala
@@ -16,3 +16,7 @@ object TParamConfusion {
 
   def f2[String](s: String) = strings(List(s))
 }
+
+object PartialInfer {
+  val f = { case 5 => 10 }
+}
\ No newline at end of file
diff --git a/test/pending/neg/type-diagnostics.scala b/test/pending/neg/type-diagnostics.scala
new file mode 100644
index 0000000000..7f9a151dcd
--- /dev/null
+++ b/test/pending/neg/type-diagnostics.scala
@@ -0,0 +1,11 @@
+object TooManyParens {
+  def f = Map(1 -> 2).keySet()
+  //
+  // Confusion reigns!
+  //
+  // work/a.scala:27: error: not enough arguments for method apply: (elem: Int)Boolean in trait SetLike.
+  // Unspecified value parameter elem.
+  //   def f = Map(1 -> 2).keySet()
+  //                             ^
+
+}