ADDITIONAL SYSTEM INFORMATION :
> java -version
openjdk version "21" 2023-09-19
OpenJDK Runtime Environment (build 21+35-2513)
OpenJDK 64-Bit Server VM (build 21+35-2513, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
This code is fine:

===
  // we are happy if this cooLoginID/password combo can simply bind correctly
        try (var ignored = new AutoCloseableInitialLdapContext(bindEnvironment, connCtls)) {
            res = true;
        } catch (NamingException e) {
            log.warn("canBind(username: {}, usernameWithDomain: {}, password: {}) suffered exception while binding: {}", username, usernameWithDomain, password, e.toString());
            res = false;
        }
===

THIS code results in runtime error:

===
        // we are happy if this cooLoginID/password combo can simply bind correctly
        try (var _ = new AutoCloseableInitialLdapContext(bindEnvironment, connCtls)) {
            res = true;
        } catch (NamingException e) {
            log.warn("canBind(username: {}, usernameWithDomain: {}, password: {}) suffered exception while binding: {}", username, usernameWithDomain, password, e.toString());
            res = false;
        }
===

ONLY change: relace 'ignored' with '_'.

In the first case, javap.exe -verbose -p -l -c .\MY.class, shows the LocalVariableTable with 'ignored'

===
     LocalVariableTable:
        Start Length Slot Name Signature
          226 8 7 res Z
          223 33 8 ignored Ltce/ad/AutoCloseableInitialLdapContext;
          256 3 7 res Z
          261 37 8 e Ljavax/naming/NamingException;
            0 335 0 this Ltce/ad/EnergexActiveDirectoryAuthenticationManager;
            0 335 1 username Ljava/lang/String;
            0 335 2 usernameWithDomain Ljava/lang/String;
            0 335 3 password Ljava/lang/String;
           69 266 4 principal Ljava/lang/String;
           90 245 5 bindEnvironment Ljava/util/Hashtable;
          208 127 6 I
          298 37 7 res Z
===

In teh latter case:

===
      LocalVariableTable:
        Start Length Slot Name Signature
          226 8 7 res Z
          223 33 8 Ltce/ad/AutoCloseableInitialLdapContext;
          256 3 7 res Z
          261 37 8 e Ljavax/naming/NamingException;
            0 335 0 this Ltce/ad/EnergexActiveDirectoryAuthenticationManager;
            0 335 1 username Ljava/lang/String;
            0 335 2 usernameWithDomain Ljava/lang/String;
            0 335 3 password Ljava/lang/String;
           69 266 4 principal Ljava/lang/String;
           90 245 5 bindEnvironment Ljava/util/Hashtable;
          208 127 6 I
          298 37 7 res Z
===

NOt sure if this is significant?


CUSTOMER SUBMITTED WORKAROUND :
don't use _ in try with resources...