Fixed a crasher in the scanner when unicode esc...

Fixed a crasher in the scanner when unicode escape sequences offered up
EOF before completion. Also made the repl a little more robust against
crashers in scalac. Treat it like a hostile witness! Closes #4584, no
review.

3 files changed, 32 insertions, 17 deletions

diff --git a/src/compiler/scala/tools/nsc/interpreter/IMain.scala b/src/compiler/scala/tools/nsc/interpreter/IMain.scala
index 0ef82351b1..517e6ee6d0 100644
--- a/src/compiler/scala/tools/nsc/interpreter/IMain.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/IMain.scala
@@ -362,16 +362,14 @@ class IMain(val settings: Settings, protected val out: PrintWriter) extends Impo
     // warning about serially defining companions.  It'd be easy
     // enough to just redefine them together but that may not always
     // be what people want so I'm waiting until I can do it better.
-    if (!settings.nowarnings.value) {
-      for {
-        name   <- req.definedNames filterNot (x => req.definedNames contains x.companionName)
-        oldReq <- definedNameMap get name.companionName
-        newSym <- req.definedSymbols get name
-        oldSym <- oldReq.definedSymbols get name.companionName
-      } {
-        printMessage("warning: previously defined %s is not a companion to %s.".format(oldSym, newSym))
-        printMessage("Companions must be defined together; you may wish to use :paste mode for this.")
-      }
+    for {
+      name   <- req.definedNames filterNot (x => req.definedNames contains x.companionName)
+      oldReq <- definedNameMap get name.companionName
+      newSym <- req.definedSymbols get name
+      oldSym <- oldReq.definedSymbols get name.companionName
+    } {
+      replwarn("warning: previously defined %s is not a companion to %s.".format(oldSym, newSym))
+      replwarn("Companions must be defined together; you may wish to use :paste mode for this.")
     }
 
     // Updating the defined name map
@@ -404,12 +402,20 @@ class IMain(val settings: Settings, protected val out: PrintWriter) extends Impo
     }
   }
 
+  private[nsc] def replwarn(msg: => String): Unit =
+    if (!settings.nowarnings.value)
+      printMessage(msg)
+
   def isParseable(line: String): Boolean = {
     beSilentDuring {
-      parse(line) match {
+      try parse(line) match {
         case Some(xs) => xs.nonEmpty  // parses as-is
         case None     => true         // incomplete
       }
+      catch { case x: Exception =>    // crashed the compiler
+        replwarn("Exception in isParseable(\"" + line + "\"): " + x)
+        false
+      }
     }
   }
 
diff --git a/src/compiler/scala/tools/nsc/util/CharArrayReader.scala b/src/compiler/scala/tools/nsc/util/CharArrayReader.scala
index c79ac91f49..aee87d8ad9 100644
--- a/src/compiler/scala/tools/nsc/util/CharArrayReader.scala
+++ b/src/compiler/scala/tools/nsc/util/CharArrayReader.scala
@@ -15,7 +15,7 @@ abstract class CharArrayReader { self =>
   def decodeUni: Boolean = true
 
   /** An error routine to call on bad unicode escapes \\uxxxx. */
-  protected def error(offset: Int, msg: String)
+  protected def error(offset: Int, msg: String): Unit
 
   /** the last read character */
   var ch: Char = _
@@ -68,10 +68,19 @@ abstract class CharArrayReader { self =>
       (charOffset - p) % 2 == 0
     }
     def udigit: Int = {
-      val d = digit2int(buf(charOffset), 16)
-      if (d >= 0) charOffset += 1
-      else error(charOffset, "error in unicode escape")
-      d
+      if (charOffset >= buf.length) {
+        // Since the positioning code is very insistent about throwing exceptions,
+        // we have to decrement the position so our error message can be seen, since
+        // we are one past EOF.  This happens with e.g. val x = \ u 1 <EOF>
+        error(charOffset - 1, "incomplete unicode escape")
+        SU
+      }
+      else {
+        val d = digit2int(buf(charOffset), 16)
+        if (d >= 0) charOffset += 1
+        else error(charOffset, "error in unicode escape")
+        d
+      }
     }
     if (charOffset < buf.length && buf(charOffset) == 'u' && decodeUni && evenSlashPrefix) {
       do charOffset += 1
diff --git a/src/compiler/scala/tools/nsc/util/SourceFile.scala b/src/compiler/scala/tools/nsc/util/SourceFile.scala
index f875ff549f..97aa08b183 100644
--- a/src/compiler/scala/tools/nsc/util/SourceFile.scala
+++ b/src/compiler/scala/tools/nsc/util/SourceFile.scala
@@ -22,7 +22,7 @@ abstract class SourceFile {
   def isSelfContained: Boolean
   def length : Int
   def position(offset: Int) : Position = {
-    assert(offset < length)
+    assert(offset < length, file + ": " + offset + " >= " + length)
     new OffsetPosition(this, offset)
   }
   def position(line: Int, column: Int) : Position = new OffsetPosition(this, lineToOffset(line) + column)