From ebe6f1ce8d9a9915fcbfd6f7773360e656989248 Mon Sep 17 00:00:00 2001
From: Jendrik Wenke <jendrikwenke@gmail.com>
Date: Mon, 12 Mar 2018 14:48:21 +0100
Subject: [PATCH 1/2] fix escaping backslash for char and string show

---
 library/src/dotty/Show.scala       | 46 +++++++++++++-----------------
 library/test/dotty/ShowTests.scala |  4 ++-
 2 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/library/src/dotty/Show.scala b/library/src/dotty/Show.scala
index 0a1bfd89d8a0..f57d6c0e0ac8 100644
--- a/library/src/dotty/Show.scala
+++ b/library/src/dotty/Show.scala
@@ -20,25 +20,28 @@ object Show extends LowPrioShow {
       ev.show(v)
   }
 
+  /** Adds escaping backslashes in a string so that it could be put in source code.
+    * For example, a newline character is shown as '\n' (without the quotes).
+    * Chars that don't have to be escaped are simply converted to a string.
+    * @param c the char to be escaped
+    * @return a string describing how to escape the give char in source code.
+    */
+  private def escapeChar(c: Char): String = c match {
+    case '\b' => "\\b"
+    case '\t' => "\\t"
+    case '\n' => "\\n"
+    case '\f' => "\\f"
+    case '\r' => "\\r"
+    case '\'' => "\\'"
+    case '\"' => "\\\""
+    case '\\' => "\\\\"
+    case c    => c.toString
+  }
+
   implicit val stringShow: Show[String] = new Show[String] {
     // From 2.12 spec, `charEscapeSeq`:
     // ‘\‘ (‘b‘ | ‘t‘ | ‘n‘ | ‘f‘ | ‘r‘ | ‘"‘ | ‘'‘ | ‘\‘)
-    def show(str: String) = {
-      val sb = new StringBuilder
-      sb.append("\"")
-      str.foreach {
-        case '\b' => sb.append("\\b")
-        case '\t' => sb.append("\\t")
-        case '\n' => sb.append("\\n")
-        case '\f' => sb.append("\\f")
-        case '\r' => sb.append("\\r")
-        case '\'' => sb.append("\\'")
-        case '\"' => sb.append("\\\"")
-        case c => sb.append(c)
-      }
-      sb.append("\"")
-      sb.toString
-    }
+    def show(str: String) = str.flatMap(escapeChar).mkString("\"", "", "\"")
   }
 
   implicit val floatShow: Show[Float] = new Show[Float] {
@@ -46,16 +49,7 @@ object Show extends LowPrioShow {
   }
 
   implicit val charShow: Show[Char] = new Show[Char] {
-    def show(c: Char) = "'" + (c match {
-      case '\b' => "\\b"
-      case '\t' => "\\t"
-      case '\n' => "\\n"
-      case '\f' => "\\f"
-      case '\r' => "\\r"
-      case '\'' => "\\'"
-      case '\"' => "\\\""
-      case c    => c
-    }) + "'"
+    def show(c: Char) = s"'${escapeChar(c)}'"
   }
 
   implicit def showList[T](implicit st: Show[T]): Show[List[T]] = new Show[List[T]] {
diff --git a/library/test/dotty/ShowTests.scala b/library/test/dotty/ShowTests.scala
index d114f62881a2..b7f41b2866a0 100644
--- a/library/test/dotty/ShowTests.scala
+++ b/library/test/dotty/ShowTests.scala
@@ -7,10 +7,11 @@ class ShowTests {
   import Show._
 
   @Test def showString = {
+    assertEquals(""""\\"""", "\\".show)
     assertEquals("\"\\thello world!\"", "\thello world!".show)
     assertEquals("\"\\nhello world!\"", "\nhello world!".show)
     assertEquals("\"\\rhello world!\"", "\rhello world!".show)
-    assertEquals("\"\\b\\t\\n\\f\\r\\\'\\\"\"", "\b\t\n\f\r\'\"".show)
+    assertEquals(""""\b\t\n\f\r\'\"\\"""", "\b\t\n\f\r\'\"\\".show)
   }
 
   @Test def showFloat = {
@@ -31,6 +32,7 @@ class ShowTests {
     assertEquals("'\\r'", '\r'.show)
     assertEquals("'\\''", '\''.show)
     assertEquals("'\\\"'", '\"'.show)
+    assertEquals("'\\\\'", '\\'.show)
   }
 
   @Test def showCar = {

From 07d2bb6749786e7ec99c055d3318248f56a98378 Mon Sep 17 00:00:00 2001
From: Jendrik Wenke <jendrikwenke@gmail.com>
Date: Mon, 12 Mar 2018 17:14:12 +0100
Subject: [PATCH 2/2] move comment to escapeChar

---
 library/src/dotty/Show.scala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/library/src/dotty/Show.scala b/library/src/dotty/Show.scala
index f57d6c0e0ac8..42f7953cd528 100644
--- a/library/src/dotty/Show.scala
+++ b/library/src/dotty/Show.scala
@@ -27,6 +27,8 @@ object Show extends LowPrioShow {
     * @return a string describing how to escape the give char in source code.
     */
   private def escapeChar(c: Char): String = c match {
+    // From 2.12 spec, `charEscapeSeq`:
+    // ‘\‘ (‘b‘ | ‘t‘ | ‘n‘ | ‘f‘ | ‘r‘ | ‘"‘ | ‘'‘ | ‘\‘)
     case '\b' => "\\b"
     case '\t' => "\\t"
     case '\n' => "\\n"
@@ -39,8 +41,6 @@ object Show extends LowPrioShow {
   }
 
   implicit val stringShow: Show[String] = new Show[String] {
-    // From 2.12 spec, `charEscapeSeq`:
-    // ‘\‘ (‘b‘ | ‘t‘ | ‘n‘ | ‘f‘ | ‘r‘ | ‘"‘ | ‘'‘ | ‘\‘)
     def show(str: String) = str.flatMap(escapeChar).mkString("\"", "", "\"")
   }