SI-6810 Disallow EOL in char literal

It's clear that char literals are one-lined like normal
string literals.

By the same token, pun intended, char literals accept
unicode escapes the same as string literals, including
`\u000A`.

This commit adds the usual exclusions (CR, NL, SU).

The spec is outdated in outlawing chars that are not
"printable", in particular, the ASCII control codes.
The original intention may have been that the ordinary
string escapes are required, such as "\b\n". Note that
some common escapes are absent, such as "\a".

3 files changed, 49 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala b/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala
index 92833d647b..d5cb0d6a3b 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala
@@ -515,7 +515,7 @@ trait Scanners extends ScannersCommon {
               charLitOr(getIdentRest)
             else if (isOperatorPart(ch) && (ch != '\\'))
               charLitOr(getOperatorRest)
-            else {
+            else if (!isAtEnd && (ch != SU && ch != CR && ch != LF || isUnicodeEscape)) {
               getLitChar()
               if (ch == '\'') {
                 nextChar()
@@ -525,6 +525,8 @@ trait Scanners extends ScannersCommon {
                 syntaxError("unclosed character literal")
               }
             }
+            else
+              syntaxError("unclosed character literal")
           }
           fetchSingleQuote()
         case '.' =>
@@ -690,7 +692,7 @@ trait Scanners extends ScannersCommon {
 
     private def unclosedStringLit(): Unit = syntaxError("unclosed string literal")
 
-    private def getRawStringLit(): Unit = {
+    @tailrec private def getRawStringLit(): Unit = {
       if (ch == '\"') {
         nextRawChar()
         if (isTripleQuote()) {
@@ -707,7 +709,7 @@ trait Scanners extends ScannersCommon {
       }
     }
 
-    @scala.annotation.tailrec private def getStringPart(multiLine: Boolean): Unit = {
+    @tailrec private def getStringPart(multiLine: Boolean): Unit = {
       def finishStringPart() = {
         setStrVal()
         token = STRINGPART
diff --git a/test/files/neg/t6810.check b/test/files/neg/t6810.check
new file mode 100644
index 0000000000..8b0e6715aa
--- /dev/null
+++ b/test/files/neg/t6810.check
@@ -0,0 +1,22 @@
+t6810.scala:4: error: unclosed character literal
+  val y = '
+          ^
+t6810.scala:5: error: unclosed character literal
+'                     // but not embedded EOL sequences not represented as escapes
+^
+t6810.scala:9: error: unclosed string literal
+  val Y = "
+          ^
+t6810.scala:10: error: unclosed string literal
+"                     // obviously not
+^
+t6810.scala:20: error: unclosed quoted identifier
+  val `
+      ^
+t6810.scala:21: error: unclosed quoted identifier
+` = EOL               // not raw string literals aka triple-quoted, multiline strings
+^
+t6810.scala:22: error: '=' expected but '}' found.
+}
+^
+7 errors found
diff --git a/test/files/neg/t6810.scala b/test/files/neg/t6810.scala
new file mode 100644
index 0000000000..a9d8813389
--- /dev/null
+++ b/test/files/neg/t6810.scala
@@ -0,0 +1,22 @@
+
+trait t6810 {
+  val x = '\u000A'    // char literals accept arbitrary unicode escapes
+  val y = '
+'                     // but not embedded EOL sequences not represented as escapes
+  val z = '\n'        // normally, expect this escape
+
+  val X = "\u000A"    // it's the same as ordinary string literals
+  val Y = "
+"                     // obviously not
+  val Z = "\n"        // normally, expect this escape
+
+  val A = """
+"""                   // which is what these are for
+  val B = s"""
+"""                   // or the same for interpolated strings
+
+  import scala.compat.Platform.EOL
+  val `\u000A` = EOL  // backquoted identifiers are arbitrary string literals
+  val `
+` = EOL               // not raw string literals aka triple-quoted, multiline strings
+}