Better pattern matcher error message.

For the common case when someone hasn't quite grokked
the significance of lower case in a pattern match.  I'd
like to make all the unreachables errors, not warnings,
but there may be a bug or two to clear out first.

class A {
  def badEquals(x: Any, y: Any) = x match {
    case y => true
    case _ => false
  }
}

a.scala:3: warning: patterns after a variable pattern cannot match (SLS 8.1.1)
If you intended to match against parameter y of method badEquals, you must use backticks, like: case `y` =>
    case y => true
         ^
a.scala:4: warning: unreachable code due to variable pattern 'y' on line 3
    case _ => false
              ^
two warnings found

8 files changed, 84 insertions, 12 deletions

diff --git a/test/files/neg/macro-invalidsig-context-bounds.check b/test/files/neg/macro-invalidsig-context-bounds.check
index 894eabc442..6c9482e537 100644
--- a/test/files/neg/macro-invalidsig-context-bounds.check
+++ b/test/files/neg/macro-invalidsig-context-bounds.check
@@ -1,4 +1,4 @@
-Impls_1.scala:5: error: macro implementations cannot have implicit parameters other than AbsTypeTag evidences

-  def foo[U: c.AbsTypeTag: Numeric](c: Ctx) = {

-      ^

-one error found

+Impls_1.scala:5: error: macro implementations cannot have implicit parameters other than AbsTypeTag evidences
+  def foo[U: c.AbsTypeTag: Numeric](c: Ctx) = {
+      ^
+one error found
diff --git a/test/files/neg/macro-invalidsig-implicit-params.check b/test/files/neg/macro-invalidsig-implicit-params.check
index 029b8a4634..98b3167b7a 100644
--- a/test/files/neg/macro-invalidsig-implicit-params.check
+++ b/test/files/neg/macro-invalidsig-implicit-params.check
@@ -1,4 +1,4 @@
-Impls_Macros_1.scala:5: error: macro implementations cannot have implicit parameters other than AbsTypeTag evidences

-  def foo_targs[T, U: c.AbsTypeTag](c: Ctx)(implicit x: c.Expr[Int]) = {

-                                                     ^

-one error found

+Impls_Macros_1.scala:5: error: macro implementations cannot have implicit parameters other than AbsTypeTag evidences
+  def foo_targs[T, U: c.AbsTypeTag](c: Ctx)(implicit x: c.Expr[Int]) = {
+                                                     ^
+one error found
diff --git a/test/files/neg/newpat_unreachable.check b/test/files/neg/newpat_unreachable.check
new file mode 100644
index 0000000000..08453cac19
--- /dev/null
+++ b/test/files/neg/newpat_unreachable.check
@@ -0,0 +1,27 @@
+newpat_unreachable.scala:6: error: patterns after a variable pattern cannot match (SLS 8.1.1)
+If you intended to match against parameter b of method contrivedExample, you must use backticks, like: case `b` =>
+      case b => println("matched b")
+           ^
+newpat_unreachable.scala:7: error: unreachable code due to variable pattern 'b' on line 6
+If you intended to match against parameter c of method contrivedExample, you must use backticks, like: case `c` =>
+      case c => println("matched c")
+                       ^
+newpat_unreachable.scala:8: error: unreachable code due to variable pattern 'b' on line 6
+If you intended to match against value d in class A, you must use backticks, like: case `d` =>
+      case d => println("matched d")
+                       ^
+newpat_unreachable.scala:9: error: unreachable code due to variable pattern 'b' on line 6
+      case _ => println("matched neither")
+                       ^
+newpat_unreachable.scala:22: error: patterns after a variable pattern cannot match (SLS 8.1.1)
+If you intended to match against parameter b of method g, you must use backticks, like: case `b` =>
+          case b => 1
+               ^
+newpat_unreachable.scala:23: error: unreachable code due to variable pattern 'b' on line 22
+If you intended to match against parameter c of method h, you must use backticks, like: case `c` =>
+          case c => 2
+                    ^
+newpat_unreachable.scala:24: error: unreachable code due to variable pattern 'b' on line 22
+          case _ => 3
+                    ^
+7 errors found
diff --git a/test/files/neg/newpat_unreachable.flags b/test/files/neg/newpat_unreachable.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/newpat_unreachable.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/newpat_unreachable.scala b/test/files/neg/newpat_unreachable.scala
new file mode 100644
index 0000000000..c9cc85cec6
--- /dev/null
+++ b/test/files/neg/newpat_unreachable.scala
@@ -0,0 +1,29 @@
+object Test {
+  class A {
+    val d = 55
+
+    def contrivedExample[A, B, C](a: A, b: B, c: C): Unit = a match {
+      case b => println("matched b")
+      case c => println("matched c")
+      case d => println("matched d")
+      case _ => println("matched neither")
+    }
+
+    def correctExample[A, B, C](a: A, b: B, c: C): Unit = a match {
+      case `b` => println("matched b")
+      case `c` => println("matched c")
+      case `d` => println("matched d")
+      case _ => println("matched neither")
+    }
+
+    def f[A](a: A) = {
+      def g[B](b: B) = {
+        def h[C](c: C) = a match {
+          case b => 1
+          case c => 2
+          case _ => 3
+        }
+      }
+    }
+  }
+}
diff --git a/test/files/neg/pat_unreachable.check b/test/files/neg/pat_unreachable.check
index 4e1463d591..c5706b7fad 100644
--- a/test/files/neg/pat_unreachable.check
+++ b/test/files/neg/pat_unreachable.check
@@ -4,4 +4,10 @@ pat_unreachable.scala:5: error: unreachable code
 pat_unreachable.scala:9: error: unreachable code
     case Seq(x, y) => List(x, y)
                           ^
-two errors found
+pat_unreachable.scala:23: error: unreachable code
+    case c => println("matched c")
+                     ^
+pat_unreachable.scala:24: error: unreachable code
+    case _ => println("matched neither")
+                     ^
+four errors found
diff --git a/test/files/neg/pat_unreachable.scala b/test/files/neg/pat_unreachable.scala
index fc0fd41920..1f402e5212 100644
--- a/test/files/neg/pat_unreachable.scala
+++ b/test/files/neg/pat_unreachable.scala
@@ -8,7 +8,7 @@ object Test extends App {
     case Seq(x, y, _*) => x::y::Nil
     case Seq(x, y) => List(x, y)
   }
-  
+
   def not_unreachable(xs:Seq[Char]) = xs match {
     case Seq(x, y, _*) => x::y::Nil
     case Seq(x) => List(x)
@@ -17,4 +17,10 @@ object Test extends App {
     case Seq(x, y) => x::y::Nil
     case Seq(x, y, z, _*) => List(x,y)
   }
+
+  def contrivedExample[A, B, C](a: A, b: B, c: C): Unit = a match {
+    case b => println("matched b")
+    case c => println("matched c")
+    case _ => println("matched neither")
+  }
 }
diff --git a/test/files/neg/t6048.check b/test/files/neg/t6048.check
index 051f41877e..5bdf2eca88 100644
--- a/test/files/neg/t6048.check
+++ b/test/files/neg/t6048.check
@@ -4,7 +4,10 @@ t6048.scala:3: error: unreachable code
 t6048.scala:8: error: unreachable code
     case _ if false => x // unreachable
                        ^
-t6048.scala:14: error: unreachable code
+t6048.scala:13: error: patterns after a variable pattern cannot match (SLS 8.1.1)
+    case _ => x
+         ^
+t6048.scala:14: error: unreachable code due to variable pattern on line 13
     case 5 if true  => x // unreachable
                        ^
-three errors found
+four errors found