Most specific method in diagnostic generation for overload resolution

[Vicente Romero]

Hi Bernard,

[1] is a link to the fix for the bug you reported. I used your email to 
mark it as contributed by you. Finally we made some minor adjustments to 
the code in order to avoid cloning the key set.

Thanks!
Vicente

[1] http://hg.openjdk.java.net/jdk10/master/rev/2e947e1bd907

On 09/20/2017 10:56 AM, B. Blaser wrote:
> Hi,
>
> Related to [1], I wrote a specialized map to store only the most
> specific candidates during the diagnostic generation for overload
> resolution, here under.
>
> It's then used in "Resolve.InapplicableSymbolsError.mapCandidates()"
> when non-applicable methods are collected to generate the diagnostic.
>
> What do you think?
> Bernard
>
> [1] http://mail.openjdk.java.net/pipermail/compiler-dev/2017-September/011062.html
>
> diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Resolve.java
> b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Resolve.java
> --- a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Resolve.java
> +++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Resolve.java
> @@ -59,6 +59,7 @@
>   import java.util.HashSet;
>   import java.util.Iterator;
>   import java.util.LinkedHashMap;
> +import java.util.LinkedList;
>   import java.util.Map;
>   import java.util.Set;
>   import java.util.function.BiFunction;
> @@ -3995,14 +3996,29 @@
>           }
>           //where
>               private Map<Symbol, JCDiagnostic> mapCandidates() {
> -                Map<Symbol, JCDiagnostic> candidates = new LinkedHashMap<>();
> +                MostSpecificMap candidates = new MostSpecificMap();
>                   for (Candidate c : resolveContext.candidates) {
>                       if (c.isApplicable()) continue;
> -                    candidates.put(c.sym, c.details);
> +                    candidates.put(c);
>                   }
>                   return candidates;
>               }
>
> +            @SuppressWarnings("serial")
> +            private class MostSpecificMap extends
> LinkedHashMap<Symbol, JCDiagnostic> {
> +                private void put(Candidate c) {
> +                    new LinkedList<>(keySet()).stream()
> +                            .filter( s -> !s.equals(c.sym) )
> +                            .filter( s -> c.sym.overrides(s,
> (TypeSymbol)s.owner, types, false) )
> +                            .forEach( s -> remove(s) );
> +
> +                    if (!keySet().stream()
> +                            .filter( s -> !s.equals(c.sym) )
> +                            .anyMatch( s -> s.overrides(c.sym,
> (TypeSymbol)c.sym.owner, types, false) ))
> +                        put(c.sym, c.details);
> +                }
> +            }
> +
>               Map<Symbol, JCDiagnostic> filterCandidates(Map<Symbol,
> JCDiagnostic> candidatesMap) {
>                   Map<Symbol, JCDiagnostic> candidates = new LinkedHashMap<>();
>                   for (Map.Entry<Symbol, JCDiagnostic> _entry :
> candidatesMap.entrySet()) {