RFR: 8359493: Refactor how aggregated mandatory warnings are handled in the compiler

[Maurizio Cimadamore]

On Fri, 13 Jun 2025 21:25:54 GMT, Archie Cobbs <acobbs at openjdk.org> wrote:

> The compiler's handling of the aggregation of mandatory warnings into "notes" at the end of compilation can be refactored to simplify the code.
> 
> The `JCDiagnostic` class supports flags that alter how warnings are handled, e.g., `MANDATORY`, `NON_DEFERRABLE`, etc. So instead of having to log aggregated mandatory warnings through a separate channel (the `MandatoryWarningHandler`), these warnings could instead be logged just like any other warning, but with an `AGGREGATED` flag added. The actual aggregation can then be handled "behind the scenes" by the logging subsystem.
> 
> This will also make it easier to implement `@SuppressAnnotations` support for parser/tokenizer warnings which require aggregated mandatory warning notes such as warnings for preview features.

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java line 1:

> 1: /*

The changes in this class are really really good! Lot of complex, coupled, stateful code disappears :-)

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java line 248:

> 246:             }
> 247:         }
> 248:         Optional.ofNullable(warningKey)

I think I'd prefer a regular `if (warningKey != null) { log.mandatoryWarning(...) }`, as it seems generally "flatter".

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/25810#discussion_r2161163126
PR Review Comment: https://git.openjdk.org/jdk/pull/25810#discussion_r2161161816