RFR: 8129418: JShell: better highlighting of errors in imports on demand

[Jan Lahoda]

On Thu, 2 May 2024 23:42:38 GMT, Nizar Benalla <duke at openjdk.org> wrote:

> When Type-Import-on-Demand fails, we now point the position of the first incorrect PackageOrTypeName which clearly isn't package, a class,or an interface.
> 
> old behavior:
> 
> |  Welcome to JShell -- Version 22.0.1
> |  For an introduction type: /help intro
> 
> jshell> import unknown.*;
> |  Error:
> |  package unknown does not exist
> |  import unknown.*;
> |  ^
> 
> New behavior:
> 
> |  Welcome to JShell -- Version 23-internal
> |  For an introduction type: /help intro
> 
> jshell> import unknown.*;
> |  Error:
> |  package unknown does not exist
> |  import unknown.*;
> |         ^-----^
> 
> 
> 
> jshell> import unknown.unknown.unknown.*;
> |  Error:
> |  package unknown.unknown.unknown does not exist
> |  import unknown.unknown.unknown.*;
> |         ^---------------------^

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Check.java line 4428:

> 4426:                 if (tsym.kind == PCK && tsym.members().isEmpty() &&
> 4427:                     !(Feature.IMPORT_ON_DEMAND_OBSERVABLE_PACKAGES.allowedInSource(source) && tsym.exists())) {
> 4428:                     log.error(DiagnosticFlag.RESOLVE_ERROR, imp.qualid.selected.pos, Errors.DoesntExist(tsym));

I would suggest to use `.pos()`, instead of `.pos`. The former returns a `DiagnosticPosition`, with start/end/preferred positions, while the later just an integer. I.e. in JShell, the former will do:

jshell> import unknown.unknown.unknown.*;
|  Error:
|  package unknown.unknown.unknown does not exist
|  import unknown.unknown.unknown.*;
|         ^---------------------^


while the latter will do:

jshell> import unknown.unknown.unknown.*;
|  Error:
|  package unknown.unknown.unknown does not exist
|  import unknown.unknown.unknown.*;
|                        ^

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

PR Review Comment: https://git.openjdk.org/jdk/pull/19073#discussion_r1588861114