handle trailing escapes

build.sbt

@@ -94,7 +94,7 @@ val mimaFilterSettings = Seq(
     ProblemFilters.exclude[MissingClassProblem]("scala.reflect.runtime.JavaMirrors$JavaMirror$typeTagCache$"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.reflect.api.TypeTags.TypeTagImpl"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.reflect.api.Universe.TypeTagImpl"),
-    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.StringContext.processUnicode")
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.StringContext.processUnicode"),
     ProblemFilters.exclude[MissingClassProblem]("scala.StringContext$InvalidUnicodeEscapeException")
   ),
 )

src/compiler/scala/tools/nsc/ast/parser/Scanners.scala

@@ -907,41 +907,49 @@ trait Scanners extends ScannersCommon {
           syntaxError(start, s"octal escape literals are unsupported: use $alt instead")
           putChar(oct.toChar)
         } else {
-          ch match {
-            case 'b'  => putChar('\b')
-            case 't'  => putChar('\t')
-            case 'n'  => putChar('\n')
-            case 'f'  => putChar('\f')
-            case 'r'  => putChar('\r')
-            case '\"' => putChar('\"')
-            case '\'' => putChar('\'')
-            case '\\' => putChar('\\')
-            case 'u'  => getUEscape()
-            case _    => invalidEscape()
+          if (ch == 'u') {
+            if (getUEscape()) nextChar()
+          }
+          else {
+            ch match {
+              case 'b'  => putChar('\b')
+              case 't'  => putChar('\t')
+              case 'n'  => putChar('\n')
+              case 'f'  => putChar('\f')
+              case 'r'  => putChar('\r')
+              case '\"' => putChar('\"')
+              case '\'' => putChar('\'')
+              case '\\' => putChar('\\')
+              case _    => invalidEscape()
+            }
+            nextChar()
           }
-          nextChar()
         }
       } else  {
         putChar(ch)
         nextChar()
       }
 
-    private def getUEscape(): Unit = {
+    private def getUEscape(): Boolean = {
       while (ch == 'u') nextChar()
       var codepoint = 0
       var digitsRead = 0
-      while(digitsRead < 4){
+      while (digitsRead < 4) {
         if (digitsRead > 0) nextChar()
         val digit = digit2int(ch, 16)
         digitsRead += 1
         if (digit >= 0) {
           codepoint = codepoint << 4
           codepoint += digit
         }
-        else invalidUnicodeEscape(digitsRead)
+        else {
+          invalidUnicodeEscape(digitsRead)
+          return false
+        }
       }
       val found = codepoint.asInstanceOf[Char]
       putChar(found)
+      true
     }
 
 
@@ -951,7 +959,7 @@ trait Scanners extends ScannersCommon {
     }
 
     protected def invalidUnicodeEscape(n: Int): Unit = {
-      syntaxError(charOffset -n, "invalid unicode escape")
+      syntaxError(charOffset - n, "invalid unicode escape")
       putChar(ch)
     }
 

src/library/scala/StringContext.scala

@@ -344,6 +344,8 @@ object StringContext {
           val digitsRead = dindex
           (codepoint.asInstanceOf[Char], usRead + digitsRead)
         }
+        else if (dindex + uindex >= len)
+          throw new InvalidUnicodeEscapeException(src, startindex, dindex + uindex)
         else {
           val ch = src(dindex + uindex)
           val e = ch.asDigit

test/files/neg/t3220-1.check

@@ -4,4 +4,22 @@ t3220-1.scala:2: error: invalid unicode escape
 t3220-1.scala:3: error: invalid unicode escape at index 6 of foo \unope that's wrong
   val badtriple = """foo \unope that's wrong"""
                   ^
-two errors found
+t3220-1.scala:4: error: invalid unicode escape
+  val caretPos = "foo \u12x3 pos @ x"
+                        ^
+t3220-1.scala:5: error: invalid unicode escape
+  val caretPos2 = "foo \uuuuuuu12x3 pos @ x"
+                               ^
+t3220-1.scala:6: error: invalid unicode escape
+  val carPosTerm = "foo \u123"
+                          ^
+t3220-1.scala:7: error: invalid unicode escape
+  val halfAnEscape = "foo \u12"
+                            ^
+t3220-1.scala:8: error: invalid unicode escape
+  val halfAnEscapeChar = '\u45'
+                            ^
+t3220-1.scala:9: error: invalid unicode escape
+  val `half An Identifier\u45` = "nope"
+                           ^
+8 errors found

test/files/neg/t3220-1.scala

@@ -1,4 +1,10 @@
 object Example {
   val badsingle = "foo \unope that's wrong"
   val badtriple = """foo \unope that's wrong""" 
+  val caretPos = "foo \u12x3 pos @ x"
+  val caretPos2 = "foo \uuuuuuu12x3 pos @ x"
+  val carPosTerm = "foo \u123"
+  val halfAnEscape = "foo \u12"
+  val halfAnEscapeChar = '\u45'
+  val `half An Identifier\u45` = "nope"
 }

test/files/neg/t3220-2.check

@@ -1,13 +1,16 @@
 t3220-2.scala:2: error: invalid unicode escape at index 6 of foo \unope that's wrong
   val badInters1 = s"foo \unope that's wrong"
                            ^
-t3220-2.scala:3: error: invalid unicode escape at index 6 of foo \unope that's wrong
+t3220-2.scala:3: error: invalid unicode escape at index 8 of foo \u12
+  val badIntersEnd1 = s"foo \u12"
+                                ^
+t3220-2.scala:4: error: invalid unicode escape at index 6 of foo \unope that's wrong
   val badInterRaw1 = raw"foo \unope that's wrong"
                                ^
-t3220-2.scala:4: error: invalid unicode escape at index 6 of foo \unope that's wrong
+t3220-2.scala:6: error: invalid unicode escape at index 6 of foo \unope that's wrong
   val badInters3 = s"""foo \unope that's wrong"""
                              ^
-t3220-2.scala:5: error: invalid unicode escape at index 6 of foo \unope that's wrong
+t3220-2.scala:7: error: invalid unicode escape at index 6 of foo \unope that's wrong
   val badInterRaw3 = raw"""foo \unope that's wrong"""
                                  ^
-four errors found
+5 errors found

test/files/neg/t3220-2.scala

@@ -1,6 +1,8 @@
 object Example {
   val badInters1 = s"foo \unope that's wrong"
+  val badIntersEnd1 = s"foo \u12"
   val badInterRaw1 = raw"foo \unope that's wrong"
+  val badInterRawEnd1 = raw"foo \u12"
   val badInters3 = s"""foo \unope that's wrong""" 
   val badInterRaw3 = raw"""foo \unope that's wrong"""
 }