JDK 21 String Template Bug

Bad00Main.java

import java.util.function.*;

class JDBC {
  void transaction(Consumer<ConnectionW> f) {
    f.accept(new ConnectionW());
  }
  <T> T transaction(Function<ConnectionW, T> f) {
    return f.apply(new ConnectionW());
  }
}

class ConnectionW {
  SQL prepare() {
    return new SQL();
  }
}

class SQL implements StringTemplate.Processor<PreparedStatementW, RuntimeException> {
  public PreparedStatementW process(StringTemplate template) throws RuntimeException {
    System.out.println(template.fragments());
    return new PreparedStatementW();
  }
}

class PreparedStatementW {
  void execute() {
    System.out.println("Here I am!");
  }
}

void main() {
  var jdbc = new JDBC();
  jdbc.transaction(conn -> {
    var name = "a";
    var age = 100;
    conn.prepare()."""
      insert into "test_user" ("name", "age") values (\{name}, \{age})"""
      .execute();
  });
}

/*
> javac --source 21 --enable-preview Bad00Main.java
Picked up JAVA_TOOL_OPTIONS: -Duser.language=en
Bad00Main.java:36: error: processor type cannot be a raw type: prepare
    conn.prepare()."""
                ^
Note: Bad00Main.java uses preview features of Java SE 21.
Note: Recompile with -Xlint:preview for details.
1 error
*/

Bad05Main.java

import java.util.function.*;

class JDBC {
  void transaction(Consumer<ConnectionW> f) {
    f.accept(new ConnectionW());
  }
  <T> T transaction(Function<ConnectionW, T> f) {
    return f.apply(new ConnectionW());
  }
}

class ConnectionW {
  SQL prepare() {
    return new SQL();
  }
}

class SQL implements StringTemplate.Processor<PreparedStatementW, RuntimeException> {
  public PreparedStatementW process(StringTemplate template) throws RuntimeException {
    System.out.println(template.fragments());
    return new PreparedStatementW();
  }
}

class PreparedStatementW {
  void execute() {
    System.out.println("Here I am!");
  }
}

void main() {
  var jdbc = new JDBC();
  jdbc.transaction(conn -> {
    var name = "a";
    var age = 100;
    var sql = conn.prepare();
    sql."""
      insert into "test_user" ("name", "age") values (\{name}, \{age})"""
      .execute();
  });
}

/*
> javac --source 21 --enable-preview Bad05Main.java
Picked up JAVA_TOOL_OPTIONS: -Duser.language=en
Bad05Main.java:37: error: processor type cannot be a raw type: prepare
    sql."""
    ^
Note: Bad05Main.java uses preview features of Java SE 21.
Note: Recompile with -Xlint:preview for details.
1 error
*/

javac-version.txt

> java -version
Picked up JAVA_TOOL_OPTIONS: -Duser.language=en
openjdk version "21.0.1" 2023-10-17
OpenJDK Runtime Environment (build 21.0.1+12-29)
OpenJDK 64-Bit Server VM (build 21.0.1+12-29, mixed mode, sharing)

> javac -version
Picked up JAVA_TOOL_OPTIONS: -Duser.language=en
javac 21.0.1

OK01Main.java

import java.util.function.*;

class JDBC {
  void transaction(Consumer<ConnectionW> f) {
    f.accept(new ConnectionW());
  }
/*
 * <T> T transaction(Function<ConnectionW, T> f) {
 *     return f.apply(new ConnectionW());
 *   }
 */
}

class ConnectionW {
  SQL prepare() {
    return new SQL();
  }
}

class SQL implements StringTemplate.Processor<PreparedStatementW, RuntimeException> {
  public PreparedStatementW process(StringTemplate template) throws RuntimeException {
    System.out.println(template.fragments());
    return new PreparedStatementW();
  }
}

class PreparedStatementW {
  void execute() {
    System.out.println("Here I am!");
  }
}

void main() {
  var jdbc = new JDBC();
  jdbc.transaction(conn -> {
    var name = "a";
    var age = 100;
    conn.prepare()."""
      insert into "test_user" ("name", "age") values (\{name}, \{age})"""
      .execute();
  });
}

OK02Main.java

import java.util.function.*;

class JDBC {
  void transaction(Consumer<ConnectionW> f) {
    f.accept(new ConnectionW());
  }
  <T> T transaction(Function<ConnectionW, T> f) {
    return f.apply(new ConnectionW());
  }
}

class ConnectionW {
  SQL prepare() {
    return new SQL();
  }
}

class SQL implements StringTemplate.Processor<PreparedStatementW, RuntimeException> {
  public PreparedStatementW process(StringTemplate template) throws RuntimeException {
    System.out.println(template.fragments());
    return new PreparedStatementW();
  }
}

class PreparedStatementW {
  void execute() {
    System.out.println("Here I am!");
  }
}

void main() {
  var jdbc = new JDBC();
  jdbc.transaction((ConnectionW conn) -> {
    var name = "a";
    var age = 100;
    conn.prepare()."""
      insert into "test_user" ("name", "age") values (\{name}, \{age})"""
      .execute();
  });
}

OK03Main.java

import java.util.function.*;

class JDBC {
  void transaction(Consumer<ConnectionW> f) {
    f.accept(new ConnectionW());
  }
  <T> T transaction(Function<ConnectionW, T> f) {
    return f.apply(new ConnectionW());
  }
}

class ConnectionW {
  SQL prepare() {
    return new SQL();
  }
}

class SQL implements StringTemplate.Processor<PreparedStatementW, RuntimeException> {
  public PreparedStatementW process(StringTemplate template) throws RuntimeException {
    System.out.println(template.fragments());
    return new PreparedStatementW();
  }
}

class PreparedStatementW {
  void execute() {
    System.out.println("Here I am!");
  }
}

void main() {
  var jdbc = new JDBC();
  jdbc.transaction((Consumer<ConnectionW>) conn -> {
    var name = "a";
    var age = 100;
    conn.prepare()."""
      insert into "test_user" ("name", "age") values (\{name}, \{age})"""
      .execute();
  });
}

OK04Main.java

import java.util.function.*;

class JDBC {
  void transaction(Consumer<ConnectionW> f) {
    f.accept(new ConnectionW());
  }
  <T> T transaction(Function<ConnectionW, T> f) {
    return f.apply(new ConnectionW());
  }
}

class ConnectionW {
  SQL prepare() {
    return new SQL();
  }
}

class SQL implements StringTemplate.Processor<PreparedStatementW, RuntimeException> {
  public PreparedStatementW process(StringTemplate template) throws RuntimeException {
    System.out.println(template.fragments());
    return new PreparedStatementW();
  }
}

class PreparedStatementW {
  void execute() {
    System.out.println("Here I am!");
  }
}

void main() {
  var jdbc = new JDBC();
  jdbc.transaction(conn -> {
    var name = "a";
    var age = 100;
    SQL sql = conn.prepare();
    sql."""
      insert into "test_user" ("name", "age") values (\{name}, \{age})"""
      .execute();
  });
}