When a CHECK-NEXT fails because there was no match on the next line, include
the non-matching next line in the diagnostic to make the problem more obvious.

llvm-svn: 205725
diff --git a/llvm/utils/FileCheck/FileCheck.cpp b/llvm/utils/FileCheck/FileCheck.cpp
index a1f4be9..a124377 100644
--- a/llvm/utils/FileCheck/FileCheck.cpp
+++ b/llvm/utils/FileCheck/FileCheck.cpp
@@ -965,7 +965,8 @@
 
 /// CountNumNewlinesBetween - Count the number of newlines in the specified
 /// range.
-static unsigned CountNumNewlinesBetween(StringRef Range) {
+static unsigned CountNumNewlinesBetween(StringRef Range,
+                                        const char *&FirstNewLine) {
   unsigned NumNewLines = 0;
   while (1) {
     // Scan for newline.
@@ -980,6 +981,9 @@
         (Range[0] != Range[1]))
       Range = Range.substr(1);
     Range = Range.substr(1);
+
+    if (NumNewLines == 1)
+      FirstNewLine = Range.begin();
   }
 }
 
@@ -1039,7 +1043,8 @@
              SMLoc::getFromPointer(Buffer.data())))->getBufferStart() &&
          "CHECK-NEXT can't be the first check in a file");
 
-  unsigned NumNewLines = CountNumNewlinesBetween(Buffer);
+  const char *FirstNewLine = 0;
+  unsigned NumNewLines = CountNumNewlinesBetween(Buffer, FirstNewLine);
 
   if (NumNewLines == 0) {
     SM.PrintMessage(Loc, SourceMgr::DK_Error, Prefix +
@@ -1058,6 +1063,8 @@
                     SourceMgr::DK_Note, "'next' match was here");
     SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
                     "previous match ended here");
+    SM.PrintMessage(SMLoc::getFromPointer(FirstNewLine), SourceMgr::DK_Note,
+                    "non-matching line after previous match is here");
     return true;
   }