JDK-8325078 (Better escaping of single and double quotes in javac annotation toString() results) changed some logic for quoting strings that is also used by Pretty when pretty-printing AST nodes. The new logic distinguishes between char and string contexts, to escape " but not ' in string contexts, and vice versa for char contexts.

The modified Convert.quote function is used by Pretty here [1], and the new behaviour means that when pretty-printing char literals the wrong quoting happens.

I don't know if this results in any user-visible issues, I think pretty-printing is mainly used for debugging. But it would still be nice to clear this up so the pretty printed output was valid Java source.

Demo:

import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.tree.TreeMaker;
import com.sun.tools.javac.util.Context;

import java.nio.charset.StandardCharsets;
import java.util.List;

public class T {
  public static void main(String[] args) {
    var context = new Context();
    new JavacFileManager(context, true, StandardCharsets.UTF_8);
    var make = TreeMaker.instance(context);
    for (var l : List .of('\'', '\"', "\"", "\'")) {
      System.err.printf("%s -> %s\n", l, make.Literal(l));
    }
  }
}

/google/data/ro/projects/java-platform/linux-amd64/jdk-22-latest/bin/java --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED T
' -> '\''
" -> '\"'
" -> "\""
' -> "\'"

' -> '''
" -> '\"'
" -> "\""
' -> "'"

The case of a character literal for a single quote shows the pretty printed output is ''', which is incorrect.

[1] https://github.com/openjdk/jdk/blob/2461263aac35b25e2a48b6fc84da49e4b553dbc3/src/jdk.compiler/share/classes/com/sun/tools/javac/tree/Pretty.java#L1470