Use skylark-preferred quote char for string literal

We currently have no need to discern between strings quoted with ' or ". While it could be
nice for something one day (and may have been in the past), it's yagni now. Removing the
distinction simplifies string concatenation.

--
PiperOrigin-RevId: 148273400
MOS_MIGRATED_REVID=148273400
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java b/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
index b5cbc92..5135dd3 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
@@ -840,16 +840,6 @@
   }
 
   /**
-   * Returns the character in the input buffer at the given position.
-   *
-   * @param at the position to get the character at.
-   * @return the character at the given position.
-   */
-  public char charAt(int at) {
-    return buffer[at];
-  }
-
-  /**
    * Returns the string at the current line, minus the new line.
    *
    * @param line the line from which to retrieve the String, 1-based
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
index e499907..fd97117 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
@@ -606,9 +606,8 @@
   private StringLiteral parseStringLiteral() {
     Preconditions.checkState(token.kind == TokenKind.STRING);
     int end = token.right;
-    char quoteChar = lexer.charAt(token.left);
     StringLiteral literal =
-        setLocation(new StringLiteral((String) token.value, quoteChar), token.left, end);
+        setLocation(new StringLiteral((String) token.value), token.left, end);
 
     nextToken();
     if (token.kind == TokenKind.STRING) {
@@ -957,9 +956,7 @@
       if (expr instanceof StringLiteral && secondary instanceof StringLiteral) {
         StringLiteral left = (StringLiteral) expr;
         StringLiteral right = (StringLiteral) secondary;
-        if (left.getQuoteChar() == right.getQuoteChar()) {
-          return new StringLiteral(left.getValue() + right.getValue(), left.getQuoteChar());
-        }
+        return new StringLiteral(left.getValue() + right.getValue());
       }
     }
     return new BinaryOperatorExpression(operator, expr, secondary);
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/StringLiteral.java b/src/main/java/com/google/devtools/build/lib/syntax/StringLiteral.java
index b2526a0..640d007 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/StringLiteral.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/StringLiteral.java
@@ -18,16 +18,13 @@
  */
 public final class StringLiteral extends Literal<String> {
 
-  private final char quoteChar;
-
-  public StringLiteral(String value, char quoteChar) {
+  public StringLiteral(String value) {
     super(value);
-    this.quoteChar = quoteChar;
   }
 
   @Override
   public String toString() {
-    return quoteChar + value.replace(Character.toString(quoteChar), "\\" + quoteChar) + quoteChar;
+    return Printer.repr(value);
   }
 
   @Override
@@ -35,16 +32,6 @@
     visitor.visit(this);
   }
 
-  /**
-   * Gets the quote character that was used for this string.  For example, if
-   * the string was 'hello, world!', then this method returns '\''.
-   *
-   * @return the character used to quote the string.
-   */
-  public char getQuoteChar() {
-    return quoteChar;
-  }
-
   @Override
   void validate(ValidationEnvironment env) throws EvalException {
   }